Tri-power Carb Tuning Tricks on My 650HP 496 Build
03-14-2010, 12:40 PM
#1
Racer
Thread Starter
Tri-power Carb Tuning Tricks on My 650HP 496 Build
It has seemed like an eternity but my engine finally made it from the dyno to engine bay. I took the time to detail everything under the hood so it looks like a restored car under there now and I am really happy with the finished product.
I can't say as much for the tuning process to get this thing to run right on the street. I always find the carb tuning on the dyno is way off from what it wants on the street. This could not be more true than with a tripower where the dyno air horn doesn't fit, the air cleaners aren't on during testing, and the air temp and carb heat are far from what happens under the hood of a running machine.
I have been through hell and back getting it right and am just about there but I learned so many interesting and valuable idiosyncrasies about this set up that I thought I would pass them on to save some other enthusiasts alot of time. There aren't many of these on the street any more and alot of myth and false information surrounds them. Hope to clarify a few points and give a reasonable blue print to making a tripower work well on the more and more common big inch (500 ci+) big blocks trolling the street. Keep in mind my car is a 69 and the 67 version tripower may exhibit some other characteristics due to a different manifold and higher hoodline.
1. Documentation errors - in anything you read from holley or chevrolet it will say the factory jetting is a 62, 63, or 64 on the center carb. Most say 62 manual and 64 auto. Most new versions of this center carb come with a 63 jet as a compromise. So it will depend on whether you have an original carb or one of the new ones holley makes now. The BIG problem is on the end carbs. ALL the documentation I have ever seen states an equivalent 76 jet size for the metering plate in the end carbs. THIS IS NOT CORRECT. What THEY MEAN is the orifice size is .076 in diameter. This corresponds to a 70 or 71 jet approximately. A 76 jet is actually .082 in area and WAY to large, period. This becomes very important if you convert the original jet plate to an aftermarket plate that uses regular jets ( I HIGHLY RECOMMEND). If you use the aftermarked jet plates, check float clearance to the plate VERY carefully as sometimes they will catch on the jets and flood everything.
2. Many people do not realize that there is an idle circuit in the end carbs. It is a fixed circuit and is not adjustable. BUT if you change to end plates that have replacable jets, MAKE SURE AND CHECK the size of the idle transfer hole in the new plate. The factory hole in the metering plate is .036. Most aftermarket plates are smaller. OPEN this hole to the factory size or you will have idle circuit problems (too lean).
3. DO NOT attempt to increase idle circuit fuel by opening the hole in the BASE PLATE of the end carbs. Trust me, I KNOW. The factory hole is .022. LEAVE IT ALONE as if you open it at all the increase in fuel flow goes up DRAMATICALLY and will over richen the off idle fuel mixture too much to control with the idle mixture screws on the center carb. Part throttle cruise will be very rich and you will wonder why.
4. If you modifiy the carbs by a good shop like AED pay particular attention to the idle transfer slot in the end carbs. I had my end carb base plates modified for thin blades and shafts to help carb flow. These are MUCH thinner than the factory blades. You will find afterward that the transfer slot in the base plate is much farther away from the blade. This is the acclerator pump for the end carbs when they come on. To smooth the transition of the end carbs activating and prevent bogs, lengthen the transfer slot with a small drill bit until it is close to the top of the new thinner blade when it is closed. The end carbs will come in more smoothly and with less of a lean spot on transition.
5. Despite this carb setup being used on a pretty hot factory motor back in the day, I had a big problem getting it enough idle fuel. 500 inches and a solid roller are a far cry from 427 cubes and a flat tappet solid cam. The air bleeds and throttle blades are fine. Just slowy open up the idle feed restrictions .001 at a time until it is right. Factory IFR is .034-.035. Mine needed about .039 to get good idle control with 1-1.5 turns on the screw. You should have no more than .040 of the idle transfer slot showing at idle speed.
6. I STRONGLY recommend you set WOT fuel mixture before anything else. The reason is because the minute you change end carb jet size the fuel flow to the end carb idle circuit will change. If you have already adjusted the center carb for what you think it wants and then jet down on the end carbs for WOT you will be back to square one on the idle circuit and may have already drilled passages you can't go back on.
7. FLOAT LEVEL IS VERY, VERY IMPORTANT on this set up. Any change in float level will move the idle circuit and part throttle fuel mixture around significantly. This is because of 6 sets of barrels instead of just two. I recommend you set float level to the LOW side of acceptable for several reasons. One, the front carb gets alot of heat from the fan. If the float level is too high it will percolate on shutdown and create hardstarting problems. More importantly, you can use an increase in float level to compensate for about .5 in AFR if you need to. This comes in really handy if you are going to the track or weather changes and you need to fatten it up a bit. You can compensate for it with a two second float adjustment rather than rejetting the carbs which takes ALOT more time. Once the floats are set DO NOT change them until you have completed ALL other calibration of carb circuits.
8. I highly recommend you modify your carb air horns with weather stripping to raise the air cleaner base up about a half inch. I did another thread on this. This GREATLY improves fuel level stability and removes a very pesky problem of bowl vent interference that will send the AFR all over the place.
9. Getting the fuel lines to seat is another real pain. I recommend you get the small lines that connect to the carb bowls tight and dry and then DO NOT loosen them. Disconnect the carbs at the fuel blocks side and remove the carbs with the shorty fuel lines attached. Do not loosen the fuel line that connects the two fuel blocks together either. When you remove the carbs work from the back to front. Disconnect the back carb fuel line at the block, then the center, then the front. Pull the fuel line away from the carbs and leave it there. When you reconnect, set the front carb on then hand thread to the fuel block, THEN tighen the carb base bolts, same for center carb. Then when you put the back one on undo the front two hand tighten lines and thread it in. Then reconnect the center and front carbs lines and tighten up evenly as you go. The idea here is very small variations in the carb location on the manifold can create leaks and real aggravation in getting the lines to thread. If you do it this way it is fast and leak free.
10. Make sure you make final idle speed and mixture adjustment with air cleaner on. It changes the air flow considerably and will richen the mixture quite a bit.
11. Believe it or not most of the time the factory jetting will be VERY close to optimum with the engine in the car, even if the dyno is much richer. My final set up actually went down a main jet from factory and up one size on the ends.
12. I STRONGLY, STRONGLY recommend you don't even attempt this task without a good wideband O2 sensor setup like the portable Innovate LM2. There are just too many variables in this systems to short cut it and you will go insane trying to get it right.
13. If you are running a big inch motor like mine you will want one of the middle strength springs on the secondary vaccum pods. THe brown spring is way to stiff. I think silver or yellow is a good selection and compromise.
14. I recommend you jet the main circuit a little lean for cool weather (14.3-14.7 AFR) and power mixture about 12.5 AFR. THen when temps warm up it will be right on and if you need a little more or little less fuel then adjust it through the float level without having to get into the whole system.
Lastly, if you can believe it, with everything dialed in this monster logged 17.5 MPG cruising at 60-65 with the tripower. This really is a great system after you get it right but it takes patience and alot of time.
Good luck.
I can't say as much for the tuning process to get this thing to run right on the street. I always find the carb tuning on the dyno is way off from what it wants on the street. This could not be more true than with a tripower where the dyno air horn doesn't fit, the air cleaners aren't on during testing, and the air temp and carb heat are far from what happens under the hood of a running machine.
I have been through hell and back getting it right and am just about there but I learned so many interesting and valuable idiosyncrasies about this set up that I thought I would pass them on to save some other enthusiasts alot of time. There aren't many of these on the street any more and alot of myth and false information surrounds them. Hope to clarify a few points and give a reasonable blue print to making a tripower work well on the more and more common big inch (500 ci+) big blocks trolling the street. Keep in mind my car is a 69 and the 67 version tripower may exhibit some other characteristics due to a different manifold and higher hoodline.
1. Documentation errors - in anything you read from holley or chevrolet it will say the factory jetting is a 62, 63, or 64 on the center carb. Most say 62 manual and 64 auto. Most new versions of this center carb come with a 63 jet as a compromise. So it will depend on whether you have an original carb or one of the new ones holley makes now. The BIG problem is on the end carbs. ALL the documentation I have ever seen states an equivalent 76 jet size for the metering plate in the end carbs. THIS IS NOT CORRECT. What THEY MEAN is the orifice size is .076 in diameter. This corresponds to a 70 or 71 jet approximately. A 76 jet is actually .082 in area and WAY to large, period. This becomes very important if you convert the original jet plate to an aftermarket plate that uses regular jets ( I HIGHLY RECOMMEND). If you use the aftermarked jet plates, check float clearance to the plate VERY carefully as sometimes they will catch on the jets and flood everything.
2. Many people do not realize that there is an idle circuit in the end carbs. It is a fixed circuit and is not adjustable. BUT if you change to end plates that have replacable jets, MAKE SURE AND CHECK the size of the idle transfer hole in the new plate. The factory hole in the metering plate is .036. Most aftermarket plates are smaller. OPEN this hole to the factory size or you will have idle circuit problems (too lean).
3. DO NOT attempt to increase idle circuit fuel by opening the hole in the BASE PLATE of the end carbs. Trust me, I KNOW. The factory hole is .022. LEAVE IT ALONE as if you open it at all the increase in fuel flow goes up DRAMATICALLY and will over richen the off idle fuel mixture too much to control with the idle mixture screws on the center carb. Part throttle cruise will be very rich and you will wonder why.
4. If you modifiy the carbs by a good shop like AED pay particular attention to the idle transfer slot in the end carbs. I had my end carb base plates modified for thin blades and shafts to help carb flow. These are MUCH thinner than the factory blades. You will find afterward that the transfer slot in the base plate is much farther away from the blade. This is the acclerator pump for the end carbs when they come on. To smooth the transition of the end carbs activating and prevent bogs, lengthen the transfer slot with a small drill bit until it is close to the top of the new thinner blade when it is closed. The end carbs will come in more smoothly and with less of a lean spot on transition.
5. Despite this carb setup being used on a pretty hot factory motor back in the day, I had a big problem getting it enough idle fuel. 500 inches and a solid roller are a far cry from 427 cubes and a flat tappet solid cam. The air bleeds and throttle blades are fine. Just slowy open up the idle feed restrictions .001 at a time until it is right. Factory IFR is .034-.035. Mine needed about .039 to get good idle control with 1-1.5 turns on the screw. You should have no more than .040 of the idle transfer slot showing at idle speed.
6. I STRONGLY recommend you set WOT fuel mixture before anything else. The reason is because the minute you change end carb jet size the fuel flow to the end carb idle circuit will change. If you have already adjusted the center carb for what you think it wants and then jet down on the end carbs for WOT you will be back to square one on the idle circuit and may have already drilled passages you can't go back on.
7. FLOAT LEVEL IS VERY, VERY IMPORTANT on this set up. Any change in float level will move the idle circuit and part throttle fuel mixture around significantly. This is because of 6 sets of barrels instead of just two. I recommend you set float level to the LOW side of acceptable for several reasons. One, the front carb gets alot of heat from the fan. If the float level is too high it will percolate on shutdown and create hardstarting problems. More importantly, you can use an increase in float level to compensate for about .5 in AFR if you need to. This comes in really handy if you are going to the track or weather changes and you need to fatten it up a bit. You can compensate for it with a two second float adjustment rather than rejetting the carbs which takes ALOT more time. Once the floats are set DO NOT change them until you have completed ALL other calibration of carb circuits.
8. I highly recommend you modify your carb air horns with weather stripping to raise the air cleaner base up about a half inch. I did another thread on this. This GREATLY improves fuel level stability and removes a very pesky problem of bowl vent interference that will send the AFR all over the place.
9. Getting the fuel lines to seat is another real pain. I recommend you get the small lines that connect to the carb bowls tight and dry and then DO NOT loosen them. Disconnect the carbs at the fuel blocks side and remove the carbs with the shorty fuel lines attached. Do not loosen the fuel line that connects the two fuel blocks together either. When you remove the carbs work from the back to front. Disconnect the back carb fuel line at the block, then the center, then the front. Pull the fuel line away from the carbs and leave it there. When you reconnect, set the front carb on then hand thread to the fuel block, THEN tighen the carb base bolts, same for center carb. Then when you put the back one on undo the front two hand tighten lines and thread it in. Then reconnect the center and front carbs lines and tighten up evenly as you go. The idea here is very small variations in the carb location on the manifold can create leaks and real aggravation in getting the lines to thread. If you do it this way it is fast and leak free.
10. Make sure you make final idle speed and mixture adjustment with air cleaner on. It changes the air flow considerably and will richen the mixture quite a bit.
11. Believe it or not most of the time the factory jetting will be VERY close to optimum with the engine in the car, even if the dyno is much richer. My final set up actually went down a main jet from factory and up one size on the ends.
12. I STRONGLY, STRONGLY recommend you don't even attempt this task without a good wideband O2 sensor setup like the portable Innovate LM2. There are just too many variables in this systems to short cut it and you will go insane trying to get it right.
13. If you are running a big inch motor like mine you will want one of the middle strength springs on the secondary vaccum pods. THe brown spring is way to stiff. I think silver or yellow is a good selection and compromise.
14. I recommend you jet the main circuit a little lean for cool weather (14.3-14.7 AFR) and power mixture about 12.5 AFR. THen when temps warm up it will be right on and if you need a little more or little less fuel then adjust it through the float level without having to get into the whole system.
Lastly, if you can believe it, with everything dialed in this monster logged 17.5 MPG cruising at 60-65 with the tripower. This really is a great system after you get it right but it takes patience and alot of time.
Good luck.
The following users liked this post:
cwwhk (08-20-2016)
03-14-2010, 12:47 PM
#2
Racer
Thread Starter
One other thing I forgot. Absolutely, positively DO NOT RUN ANY type of filter in the carburetor itself, either bronze or paper. It cannot not handle the demand of a motor this strong and the motor will go lean regardless of a fuel pump the size of a basketball (trust me I KNOW). I recommend running a cannister filter at the tank. There is an easy plase to mount it right on the frame out of the way of the muffler and with easy bends and transitions. Then you won't clutter up your nice factory looking fuel lines in the engine bay with some half assed in line filter.
03-14-2010, 02:58 PM
#3
Le Mans Master
Damn good info right there!!!
Thanks for posting!
I have been doing a little tuning myself....My engine on the dyno wanted 80f/80r jetting. The AFR was in the low 12s and BSFCs were in the low 400s. In the car the engine builder told me to jet up to 82s in the front....So I had 82f/80r. The car ran great around town but I knew it was rich. I put the LM1 on it and the cruise RPM was in the 12.4-12.6 range....WOT was 11.6 or so..... I pulled the 82s out, went back to 80/80 and the cruise AFR now is 12.8-13.2, WOT is still in the mid 11s in 2nd/3rd gear but 1st is a tad lean at mid 13s....I think it needs jet extensions and maybe a bigger accelerator pump. Even though the LM1 shows its pig rich at 11.5, I am not going to lean it out anymore because I know what it made peak power at on the dyno....
Mine damn sure doesn't get 17.5 mpgs though...... I got 10.15 mpgs on my last freeway trip....
Thanks for posting!
I have been doing a little tuning myself....My engine on the dyno wanted 80f/80r jetting. The AFR was in the low 12s and BSFCs were in the low 400s. In the car the engine builder told me to jet up to 82s in the front....So I had 82f/80r. The car ran great around town but I knew it was rich. I put the LM1 on it and the cruise RPM was in the 12.4-12.6 range....WOT was 11.6 or so..... I pulled the 82s out, went back to 80/80 and the cruise AFR now is 12.8-13.2, WOT is still in the mid 11s in 2nd/3rd gear but 1st is a tad lean at mid 13s....I think it needs jet extensions and maybe a bigger accelerator pump. Even though the LM1 shows its pig rich at 11.5, I am not going to lean it out anymore because I know what it made peak power at on the dyno....
Mine damn sure doesn't get 17.5 mpgs though...... I got 10.15 mpgs on my last freeway trip....
03-14-2010, 06:13 PM
#4
Racer
Thread Starter
Damn good info right there!!!
Thanks for posting!
I have been doing a little tuning myself....My engine on the dyno wanted 80f/80r jetting. The AFR was in the low 12s and BSFCs were in the low 400s. In the car the engine builder told me to jet up to 82s in the front....So I had 82f/80r. The car ran great around town but I knew it was rich. I put the LM1 on it and the cruise RPM was in the 12.4-12.6 range....WOT was 11.6 or so..... I pulled the 82s out, went back to 80/80 and the cruise AFR now is 12.8-13.2, WOT is still in the mid 11s in 2nd/3rd gear but 1st is a tad lean at mid 13s....I think it needs jet extensions and maybe a bigger accelerator pump. Even though the LM1 shows its pig rich at 11.5, I am not going to lean it out anymore because I know what it made peak power at on the dyno....
Mine damn sure doesn't get 17.5 mpgs though...... I got 10.15 mpgs on my last freeway trip....
Thanks for posting!
I have been doing a little tuning myself....My engine on the dyno wanted 80f/80r jetting. The AFR was in the low 12s and BSFCs were in the low 400s. In the car the engine builder told me to jet up to 82s in the front....So I had 82f/80r. The car ran great around town but I knew it was rich. I put the LM1 on it and the cruise RPM was in the 12.4-12.6 range....WOT was 11.6 or so..... I pulled the 82s out, went back to 80/80 and the cruise AFR now is 12.8-13.2, WOT is still in the mid 11s in 2nd/3rd gear but 1st is a tad lean at mid 13s....I think it needs jet extensions and maybe a bigger accelerator pump. Even though the LM1 shows its pig rich at 11.5, I am not going to lean it out anymore because I know what it made peak power at on the dyno....
Mine damn sure doesn't get 17.5 mpgs though...... I got 10.15 mpgs on my last freeway trip....
My engine makes 13 inches of vacuum at idle. By conventional wisdom it would get a 5.5 or 6.5 power valve. NOT SO. Again there is so little load on this engine under moderate acceleration that I am half throttle and accelerating like a bat out of hell but vaccum is still at 11-12 inches!!! So the power valve is not coming in and leaned out. I had to go UP to and 8.5 to get it close to right which is completely inverse to the normal cirumstance and expectation. At cruise it is pulling 21 inches. Most cars the minute you get in the gas the engine is loaded sufficiently to pull in the extra fuel and activate the valve. But at these high power levels the engine is making so much power and my car is very light at about 3400 with me in it that its nothing for this motor.
Also the air cleaner issue is really important to getting consistent jetting and A/F information. Although in your case if you are running the spacer you will not have enough room left to raise the air cleaner base. For example, in my old engine raising the air cleaner base took two full points off the AF ratio with no other change. This is because the turn of the air into the carb and float bowl atmospheric reference is dramatically changed for the better.
I love dynos, but like I said my engine dyno jetting was completely different than in the car. On the stand I was running 70's in the center and 75 outboard. In the car I am now running 62's in the center and 71's outboard. If yours was done on a chassis dyno your numbers will be alot less different than mine were and of course cam timing, cubic inches, etc. all play a big role in what it wants.
A good cruise mixture in the high 13s to low 14s will save alot of fuel and will keep the plugs and cylinder walls alot happier.
03-14-2010, 09:32 PM
#7
I'm running a modified 550cfm Holley 4412 2bbl as my middle carb on my BB tri-power setup. (See Left). I have a stout mechanical cam that produces 9 inches of vac at idle (1000rpm) - It runs like a champ - I have 71's in the middle w/ 5.0 power valve. Progressive Linkage. The electric choke is a nice add on as well. 
03-14-2010, 11:00 PM
#8
Racer
Thread Starter
I don't know how to post pics to this site or I would be happy to do so. But I think Babbah's engine takes the cake. That is one bad looking tripower.
03-14-2010, 11:10 PM
#9
Racer
Thread Starter
I'm running a modified 550cfm Holley 4412 2bbl as my middle carb on my BB tri-power setup. (See Left). I have a stout mechanical cam that produces 9 inches of vac at idle (1000rpm) - It runs like a champ - I have 71's in the middle w/ 5.0 power valve. Progressive Linkage. The electric choke is a nice add on as well.
03-14-2010, 11:43 PM
#10
Racer
Thread Starter
03-15-2010, 12:03 AM
#11
03-16-2010, 05:13 PM
#12
Racer
Thread Starter
Another interesting idiosyncracy with these units. If you are running alot of cubes and cam and have to open up the IFRs I have noticed that after a point there is more impact on the idle transfer slot than the idle discharge port. So ideally I think you would want to get close with opening up the IFR a thousanth at a time but when you note the off idle mixture is right on around 13 to one you will need to go to the Idle air bleed to get the additional richness out of the idle circuit itself. I discussed this with AED and they said the idle air bleed on the center carb is HUGE at about 82 thousands. I have and old 4781 double pumper laying around and compared them and it is quite a difference in the size of the idle air bleed. Keep in mind the larger the bleed the leaner the mixture with the same IFR. So as you open up the IFR you are fighting that big air bleed to get it richer. But the transfer slot has not such impact so it richens fast with any changes. So to get much additional richness on the idle circuit you are likely richening the transfer slot more than it wants. This would require having the idle air bleed made adjustable but that is not a big deal with a reputable carb shop.
03-17-2010, 12:58 PM
#13
Drifting
Great write-up and info.
Your ability to transfer hours and hours of tuning into this concise write-up is amazing.
BTW, Alan's(ajrothm) motor is running a single 4-barrel.
Steve
Your ability to transfer hours and hours of tuning into this concise write-up is amazing.
BTW, Alan's(ajrothm) motor is running a single 4-barrel.
Steve
03-18-2010, 10:28 AM
#14
Racer
Thread Starter
Can't imagine what 632 inches in a C2 is like as I have so much power now that I am wondering if I went a little overboard. But I am gradually getting used to it. This car makes my 06 Viper seem like a dog.
03-18-2010, 10:45 AM
#15
Racer
Thread Starter
O.k. here is the final setup after some more fine tuning. On the final mileage test I got an incredible 18.13 MPG. A testament to getting the main circuit cruise mixture right on.
Idle - 950 RPMs, 13 inches vaccum. IFR enlarged from .035 to .040.
Cruise - main circuit. 62 main jets. AFR of 14.3 to 1.
Power Circuit - enlarged PVCRs from .043 to .045. AFR 12.8 to 1, 10.5 in hg valve.
WOT - 75 jets in end carburetors. 12.4 to 1 AFR.
Squirter - stock, did not change.
For those who didn't see the dyno thread, here is a brief recap of the motor, etc.
496 ci
646 sae HP at 6400 rpms.
604 sae TQ at 4000-4300 rpms.
solid roller cam 244/253, 650 lift. 110 lsa.
Patriot aluminum heads.
10.75 compression ratio.
Timing curve. 17 degrees initial. 38 degrees total mechanical advance all in by 3000 rpm. 10 degrees ported vacuum advance.
Wide ratio 4spd muncie with 3.08 gear.
Car will pull down to 1500 rpm in high gear and accelerate with no surging or bucking. Pulls to 7000rpm effortlessly.
No hard starting problems on hot soak or from timing advance.
In short, I think this is a combo alot of us like to have but rarely achieve. Great drivability and street manners with excellent fuel mileage and 10 second quarter mile capability. I take my cars on very long trips - 8000-10000 miles every september from florida to eastern oregon and back on scenic drives. It has to drive like a dream or the aggravation factors negate the fun. I think I am there on this one.
Next test. Quarter mile. I know I am going to give up some power on the top with my current exhaust but we will see how much. It is running 2.5 inch from the crossmember back which is too small. Worked fine on my stock 427 but this is a whole new animal. Will have to go to 3 inch to let her breath as intended.
Idle - 950 RPMs, 13 inches vaccum. IFR enlarged from .035 to .040.
Cruise - main circuit. 62 main jets. AFR of 14.3 to 1.
Power Circuit - enlarged PVCRs from .043 to .045. AFR 12.8 to 1, 10.5 in hg valve.
WOT - 75 jets in end carburetors. 12.4 to 1 AFR.
Squirter - stock, did not change.
For those who didn't see the dyno thread, here is a brief recap of the motor, etc.
496 ci
646 sae HP at 6400 rpms.
604 sae TQ at 4000-4300 rpms.
solid roller cam 244/253, 650 lift. 110 lsa.
Patriot aluminum heads.
10.75 compression ratio.
Timing curve. 17 degrees initial. 38 degrees total mechanical advance all in by 3000 rpm. 10 degrees ported vacuum advance.
Wide ratio 4spd muncie with 3.08 gear.
Car will pull down to 1500 rpm in high gear and accelerate with no surging or bucking. Pulls to 7000rpm effortlessly.
No hard starting problems on hot soak or from timing advance.
In short, I think this is a combo alot of us like to have but rarely achieve. Great drivability and street manners with excellent fuel mileage and 10 second quarter mile capability. I take my cars on very long trips - 8000-10000 miles every september from florida to eastern oregon and back on scenic drives. It has to drive like a dream or the aggravation factors negate the fun. I think I am there on this one.
Next test. Quarter mile. I know I am going to give up some power on the top with my current exhaust but we will see how much. It is running 2.5 inch from the crossmember back which is too small. Worked fine on my stock 427 but this is a whole new animal. Will have to go to 3 inch to let her breath as intended.
Last edited by Irish69427; 03-18-2010 at 11:10 AM.
03-18-2010, 02:06 PM
#16
Drifting
Mike - you have an enviable combination on your hands. I am anxious to hear your quarter mile times.
I am finally starting to assemble my 632 for my '67 coupe. After the motor is in and running the way I want I will start on my tri-power build up on my '67 convertible.
I have printed out your settings and will see how they are going to compare to mine. I plan on installing a "larger than stock" tri-power motor that I am going to make factory stock appearing down to every nut and bolt. I will even use the factory exhaust manifolds. The exhaust, however, will be a 3" mandrel built system with an "X" pipe - similar to what I have in 2-1/2" on my '67 convertible right now.
Hey, if you ever end up in my part of Washington with your car you are welcome to put it on my DynoJet! It's probably unlikely but since you come as far as eastern Oregon you never know.
Again, thanks for the write-up!
Steve
I am finally starting to assemble my 632 for my '67 coupe. After the motor is in and running the way I want I will start on my tri-power build up on my '67 convertible.
I have printed out your settings and will see how they are going to compare to mine. I plan on installing a "larger than stock" tri-power motor that I am going to make factory stock appearing down to every nut and bolt. I will even use the factory exhaust manifolds. The exhaust, however, will be a 3" mandrel built system with an "X" pipe - similar to what I have in 2-1/2" on my '67 convertible right now.
Hey, if you ever end up in my part of Washington with your car you are welcome to put it on my DynoJet! It's probably unlikely but since you come as far as eastern Oregon you never know.
Again, thanks for the write-up!
Steve
03-20-2010, 08:28 PM
#17
Racer
Thread Starter
Mike - you have an enviable combination on your hands. I am anxious to hear your quarter mile times.
I am finally starting to assemble my 632 for my '67 coupe. After the motor is in and running the way I want I will start on my tri-power build up on my '67 convertible.
I have printed out your settings and will see how they are going to compare to mine. I plan on installing a "larger than stock" tri-power motor that I am going to make factory stock appearing down to every nut and bolt. I will even use the factory exhaust manifolds. The exhaust, however, will be a 3" mandrel built system with an "X" pipe - similar to what I have in 2-1/2" on my '67 convertible right now.
Hey, if you ever end up in my part of Washington with your car you are welcome to put it on my DynoJet! It's probably unlikely but since you come as far as eastern Oregon you never know.
Again, thanks for the write-up!
Steve
I am finally starting to assemble my 632 for my '67 coupe. After the motor is in and running the way I want I will start on my tri-power build up on my '67 convertible.
I have printed out your settings and will see how they are going to compare to mine. I plan on installing a "larger than stock" tri-power motor that I am going to make factory stock appearing down to every nut and bolt. I will even use the factory exhaust manifolds. The exhaust, however, will be a 3" mandrel built system with an "X" pipe - similar to what I have in 2-1/2" on my '67 convertible right now.
Hey, if you ever end up in my part of Washington with your car you are welcome to put it on my DynoJet! It's probably unlikely but since you come as far as eastern Oregon you never know.
Again, thanks for the write-up!
Steve
block. Will love to hear how that one turns out. I don't get as far west as puyallup anymore. Used to when I had family in seattle but now it is spokane and the tri city area but if I come west will definitely take you up on your offer.
Found out two very unsual new problems with a tripower on late model heads. They don't use the manifold bolt hole at the top of the runners. Never though much of it but the car started showing signs of lean surge and I hadn't changed anything. Low and behold I stuck my finger over these holes and they were leaking vacuum like a pig. Only one wasn't. So if you use a late model aluminum head you will need to tap these and install pipe plugs to make sure they aren't leaking. With as bad as they were I couldn't believe the car didn't run much worse, but when plugged the idle did drop about 75 rpm and was considerably smoother. Also found another leak under the back carb so make sure the base plates are perfectly flat and use new gaskets. I think removing mine so many times created that problem.
The big news is I got to the drag strip today and my exhaust system has got to go. It is really a 2 1/4" in system with the non mandrel bends included from the crossmember back and the mufflers are not top of the line. I thought it would kill top end but I had no idea how much. I could only get 117-118 mph in trap speed and was looking for 125-130. I still managed an 11.98 at 117.4 with a 1.98 60 foot. Not bad for a wide ratio muncie and 3.08 gear and T/A radials. But I must be giving up 100 hp in this system.
I had another vette I built that ran a 550 HP dynoed motor of the exact same weight and and it trapped 120 with similar gearing but it had a full 3 inch exhaust. So with another 100+ Hp at the motor this exhaust has to be just killing this motor.
Hope to get to the exhaust shop this week.
03-21-2010, 10:56 AM
#18
Le Mans Master
You own the only other vette I want in my garage - a 67 convertible big
block. Will love to hear how that one turns out. I don't get as far west as puyallup anymore. Used to when I had family in seattle but now it is spokane and the tri city area but if I come west will definitely take you up on your offer.
Found out two very unsual new problems with a tripower on late model heads. They don't use the manifold bolt hole at the top of the runners. Never though much of it but the car started showing signs of lean surge and I hadn't changed anything. Low and behold I stuck my finger over these holes and they were leaking vacuum like a pig. Only one wasn't. So if you use a late model aluminum head you will need to tap these and install pipe plugs to make sure they aren't leaking. With as bad as they were I couldn't believe the car didn't run much worse, but when plugged the idle did drop about 75 rpm and was considerably smoother. Also found another leak under the back carb so make sure the base plates are perfectly flat and use new gaskets. I think removing mine so many times created that problem.
The big news is I got to the drag strip today and my exhaust system has got to go. It is really a 2 1/4" in system with the non mandrel bends included from the crossmember back and the mufflers are not top of the line. I thought it would kill top end but I had no idea how much. I could only get 117-118 mph in trap speed and was looking for 125-130. I still managed an 11.98 at 117.4 with a 1.98 60 foot. Not bad for a wide ratio muncie and 3.08 gear and T/A radials. But I must be giving up 100 hp in this system.
I had another vette I built that ran a 550 HP dynoed motor of the exact same weight and and it trapped 120 with similar gearing but it had a full 3 inch exhaust. So with another 100+ Hp at the motor this exhaust has to be just killing this motor.
Hope to get to the exhaust shop this week.
block. Will love to hear how that one turns out. I don't get as far west as puyallup anymore. Used to when I had family in seattle but now it is spokane and the tri city area but if I come west will definitely take you up on your offer.
Found out two very unsual new problems with a tripower on late model heads. They don't use the manifold bolt hole at the top of the runners. Never though much of it but the car started showing signs of lean surge and I hadn't changed anything. Low and behold I stuck my finger over these holes and they were leaking vacuum like a pig. Only one wasn't. So if you use a late model aluminum head you will need to tap these and install pipe plugs to make sure they aren't leaking. With as bad as they were I couldn't believe the car didn't run much worse, but when plugged the idle did drop about 75 rpm and was considerably smoother. Also found another leak under the back carb so make sure the base plates are perfectly flat and use new gaskets. I think removing mine so many times created that problem.
The big news is I got to the drag strip today and my exhaust system has got to go. It is really a 2 1/4" in system with the non mandrel bends included from the crossmember back and the mufflers are not top of the line. I thought it would kill top end but I had no idea how much. I could only get 117-118 mph in trap speed and was looking for 125-130. I still managed an 11.98 at 117.4 with a 1.98 60 foot. Not bad for a wide ratio muncie and 3.08 gear and T/A radials. But I must be giving up 100 hp in this system.
I had another vette I built that ran a 550 HP dynoed motor of the exact same weight and and it trapped 120 with similar gearing but it had a full 3 inch exhaust. So with another 100+ Hp at the motor this exhaust has to be just killing this motor.
Hope to get to the exhaust shop this week.
Yeah your exhaust is killing it for sure....
You need this:
And some good flowing mufflers:
What did your car weigh with you in it? You run it on drag radials? Did you try taking the tri power air cleaner off?
03-21-2010, 09:26 PM
#20
Racer
Thread Starter
Man that is a thing of beauty. Where did you get that crossmember. Is there one available for stick? Car weighed 3500 with me in it and a full tank of gas. So should be between 3400 and 3450 with a more realistic fuel load and I have a very light battery going in it that saves another 20+ lbs. So my estimate of 3400 race weight is very close. Figure I had at least 70 lbs. to much fuel. Did not use drag radials and never have. I run just my basic street radials which in this case are BF Goodrich Radial T/As - 245/60/15.
