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Well, I got the QFT 1050 carb idle mixture set, floats, and fuel pressure. Ran it up through 7500 rpm, and it maintained 8 psi at the carb, so my pump and fuel lines seem to be sufficient. I got the idle timing set for where it likes it at 25 deg advanced. Distributor has 20 deg advance, so that puts me all in at 45 at 5000 rpm with the springs I put in it. I'll check the mixture under load when I get it down to the chassis dyno place for fine tuning. Overall I'm very happy with the outcome!
Well, I got the QFT 1050 carb idle mixture set, floats, and fuel pressure. Ran it up through 7500 rpm, and it maintained 8 psi at the carb, so my pump and fuel lines seem to be sufficient. I got the idle timing set for where it likes it at 25 deg advanced. Distributor has 20 deg advance, so that puts me all in at 45 at 5000 rpm with the springs I put in it. I'll check the mixture under load when I get it down to the chassis dyno place for fine tuning. Overall I'm very happy with the outcome!
8 psi sounds high and I'm thinking that the floats are just about at their limit. What's the fuel pressure at idle?
Being a SBC guy, I'm not familiar with spark advance for a BBC, but I'm seeing WOT timing recommendations between 35 and 38 degrees, total. 45 degrees @ WOT sounds about 7-9 degrees too much (for a SBC as well as a BBC). Does this engine have vacuum advance as well?
Last edited by 65tripleblack; Jan 26, 2018 at 11:13 AM.
8 psi sounds high and I'm thinking that the floats are just about at their limit. What's the fuel pressure at idle?
Being a SBC guy, I'm not familiar with spark advance for a BBC, but I'm seeing WOT timing recommendations between 35 and 38 degrees, total. 45 degrees @ WOT sounds about 7-9 degrees too much (for a SBC as well as a BBC). Does this engine have vacuum advance as well?
When it was getting dyno tested the tester set the pressure at 10 psi and it wasn't a problem. I just have it at 8 right now for testing later on chassis dyno under load to see how far the pressure drops. Recommended pressure for QFT is 6.5 psi, so I could go down to that and still be ok. 42 degrees is where I wanted it, so I may restrict it to that later when I get it tested again. No vacuum advance on this one.
When it was getting dyno tested the tester set the pressure at 10 psi and it wasn't a problem. I just have it at 8 right now for testing later on chassis dyno under load to see how far the pressure drops. Recommended pressure for QFT is 6.5 psi, so I could go down to that and still be ok. 42 degrees is where I wanted it, so I may restrict it to that later when I get it tested again. No vacuum advance on this one.
Exactly! IIWY, I'd set it at 6.5 at idle and as long as it doesn't drop to less than 3-4 @ 7500 then the supply will be more than enough. Running so much pressure is looking for trouble, and will gain you nothing.
Why did you want it at 42 degrees? There is such a thing as too much spark advance. The entire point of spark advance is to time the burn to achieve max cylinder pressure to occur at around 14 degrees ATDC. Too much advance will cause the piston to begin pushing the connecting rod down before ideal mechanical advantage is achieved, leading to a severe loss of torque and power. Maybe the mechanics of your engine build requires such an excessive amount of advance for smaller displacements. Inquiring minds want to know.
Last edited by 65tripleblack; Jan 26, 2018 at 05:15 PM.
Given the level of this build, I believe the OP is well aware of engine timing, and the effects of too much or too little spark advance.
Buying an LS crate engine doesn't allow one to enjoy the fun and satisfaction of designing a build combo and achieving the results (or not) you were aiming for.
Sometimes it's not the destination, but the journey...
Those old motors love timing. I'm at 42 on my '69 Camaro with a set of 492 iron heads. It goes faster each time I move it up but I have decided to stop at 42.
I have a Carter strip pump on the car which is 8 psi. I have a Barry Grant modified 750 double pumper (pre-Demon Carburetion) that is rated 1040 cfm. I have had no issues with the 8 psi on the Holley needle and seat assemblies.
Exactly! IIWY, I'd set it at 6.5 at idle and as long as it doesn't drop to less than 3-4 @ 7500 then the supply will be more than enough. Running so much pressure is looking for trouble, and will gain you nothing.
Why did you want it at 42 degrees?There is such a thing as too much spark advance. The entire point of spark advance is to time the burn to achieve max cylinder pressure to occur at around 14 degrees ATDC. Too much advance will cause the piston to begin pushing the connecting rod down before ideal mechanical advantage is achieved, leading to a severe loss of torque and power. Maybe the mechanics of your engine build requires such an excessive amount of advance for smaller displacements. Inquiring minds want to know.
You must have a lot of time on your hands to make comments that have no effect, but not enough to read my posts on this thread explaining why I wanted 42 deg.
Homed in on the best sparkplug for this engine. I finally went with NGK 7173. I moved up in heat range until the plugs looked good at idle. These have 3/4" reach, recommended by my AFR heads, a heat range of 8, and non-resistor.
Last edited by bdhulderman; Jan 27, 2018 at 10:13 AM.
You must have a lot of time on your hands to make comments that have no effect, but not enough to read my posts on this thread explaining why I wanted 42 deg.
Only looking to use you as a source of information. I like your approach to things because it's no-nonsense and tries to maximize results. Although your earlier comment about needing high ZDDP break-in oil for a roller cam cuts your credibility as an "expert".
I looked at your timing program from your earlier post and to me, an amateur compared to you, it looks "funky" (15 degrees timing steady all the way to 4000 and then a LINEAR increase to a whopping 42 degrees). You say that you developed a program to optimize the spark program. Did you verify by plugging your program's recommendation into EA PRO? It's mechanics that determine spark advance and as I stated earlier, it's all about timing the point of max cylinder pressure to the sweet spot which is AROUND 14 degrees ATDC. Did you use your rod length and crank throw in inventing your software program?
One more thing: I'm going by conventional wisdom and according to that, you are being very conservative on this engine's DCR. Why didn't you design for more DCR, closer to 8.5 - 8.7? If engine temp, spark timing, quench, and fuel mixture are optimized then 8.75 is not dangerous using 93 octane fuel. If you stated this engine's quench earlier, then I missed it.
Last edited by 65tripleblack; Jan 28, 2018 at 09:33 AM.
Only looking to use you as a source of information. I like your approach to things because it's no-nonsense and tries to maximize results. Although your earlier comment about needing high ZDDP break-in oil for a roller cam cuts your credibility as an "expert".
I looked at your timing program from your earlier post and to me, an amateur compared to you, it looks "funky" (15 degrees timing steady all the way to 4000 and then a LINEAR increase to a whopping 42 degrees). You say that you developed a program to optimize the spark program. Did you verify by plugging your program's recommendation into EA PRO? It's mechanics that determine spark advance and as I stated earlier, it's all about timing the point of max cylinder pressure to the sweet spot which is AROUND 14 degrees ATDC. Did you use your rod length and crank throw in inventing your software program?
One more thing: I'm going by conventional wisdom and according to that, you are being very conservative on this engine's DCR. Why didn't you design for more DCR, closer to 8.5 - 8.7? If engine temp, spark timing, quench, and fuel mixture are optimized then 8.75 is not dangerous using 93 octane fuel. If you stated this engine's quench earlier, then I missed it.
The results speak for themselves. I'll further validate my software when I chassis dyno it this year. I don't know why I feel I need to defend myself against you. Don't you have something you can do besides questioning my judgement without having all the information? No disrespect, but if you want to learn, watch those doing things, and take note of the results, and make your own conclusions, without disrespecting others. Wow, even Joe Inama liked your response, that should tell you something http://enginebuilderprofessional.com/
Last edited by bdhulderman; Feb 2, 2018 at 12:21 AM.
Well, found out the other day that my PCV valve isn't enough past about 6000 rpm to keep down the pressure in the crankcase from building up and causing oil to leak through the line of least resistance. Since my max HP is over 7000, something has to be done to prevent the crankcase pressure from exceeding an acceptable level. Fortunately, there is a solution. This pump without using relief, will pump out up to 30 CFM of blowby @ 20" Hg @ 3000 rpm. I'm thinking this will do the job. And on the track at peak power, this should give me another 20-30 Hp. http://www.aerospacecomponents.com/i...acuum-Pump.pdf
The results speak for themselves. I'll further validate my software when I chassis dyno it this year. I don't know why I feel I need to defend myself against you. Don't you have something you can do besides questioning my judgement without having all the information? No disrespect, but if you want to learn, watch those doing things, and take note of the results, and make your own conclusions, without disrespecting others. Wow, even Joe Inama liked your response, that should tell you something http://enginebuilderprofessional.com/
Good luck and it will be interesting to see if you're right. I'm enjoying this so far and will wait for proof when you dyno test it. We'll see how things go when (if) you tweak the spark timing during successive pulls. I would plug your timing results, vs conventional timing which maxes @ 36-38 degrees @ WOT into EA Pro and check the results.
I still say that your DCR is conservative. Many builds are detonation free on 93 PON as high as 8.75 or more. I hate to keep bringing this up, but my 331 has 11.35 SCR and 8.6 DCR, 21 degrees static plus 16 degrees mechanical all in by 2300 plus 14 degrees vacuum, .035 quench and runs without detonation on 93 octane (E10). It's no slouch and makes 414 RWHP @ 6500. If I add more timing the power peaks sooner but lower. I found 37 max to be optimal and using popups which slows flame front and non-compact 62cc chamber. My EA Pro shows optimal spark to peak around 6500 and then drop a couple degrees lower at very high RPM.
Last edited by 65tripleblack; Feb 2, 2018 at 09:53 AM.
Good luck and it will be interesting to see if you're right. I'm enjoying this so far and will wait for proof when you dyno test it. We'll see how things go when (if) you tweak the spark timing during successive pulls. I would plug your timing results, vs conventional timing which maxes @ 36-38 degrees @ WOT into EA Pro and check the results.
I still say that your DCR is conservative. Many builds are detonation free on 93 PON as high as 8.75 or more. I hate to keep bringing this up, but my 331 has 11.35 SCR and 8.6 DCR, 21 degrees static plus 16 degrees mechanical all in by 2300 plus 14 degrees vacuum, .035 quench and runs without detonation on 93 octane (E10). It's no slouch and makes 414 RWHP @ 6500. If I add more timing the power peaks sooner but lower. I found 37 max to be optimal and using popups which slows flame front and non-compact 62cc chamber. My EA Pro shows optimal spark to peak around 6500 and then drop a couple degrees lower at very high RPM.
Ok, I think the DCR you refer to is defined differently then how I define it. I calculate it from the cylinder pressures from my software that means a lot more to me. Here I think is how you calculate it. This is using advertised lobe lift for intake valve closing:
I've got a lot more confidence in the software I developed than any other software, since I've validated it throughout the development process. That's what I used to determine the timing requirements, and it's apparently working so far. Another thing you should keep in mind is that I'm well over 100% volumetric efficiency with the heads and lift I have at the peak torque, so DCR is no longer a factor.
Oh, hears some more info:
Oh, and if you use the .05 intake valve closing number you get the following:
Last edited by bdhulderman; Feb 2, 2018 at 01:05 PM.
Well, found out the other day that my PCV valve isn't enough past about 6000 rpm to keep down the pressure in the crankcase from building up and causing oil to leak through the line of least resistance. Since my max HP is over 7000, something has to be done to prevent the crankcase pressure from exceeding an acceptable level. Fortunately, there is a solution. This pump without using relief, will pump out up to 30 CFM of blowby @ 20" Hg @ 3000 rpm. I'm thinking this will do the job. And on the track at peak power, this should give me another 20-30 Hp. http://www.aerospacecomponents.com/i...acuum-Pump.pdf
You realize the PCV isn't open at WOT. At zero intake vacuum i.e. WOT the PCV is closed. The PCV is only open at higher vacuum levels. On a newer tight motor you shouldn't have much blowby. Both the 496 BBC in the vette and the 365 sbc in my Nova both don't have much blow by at all at higher rpm levels. The 365 hits 85-8700 rpm every run at the track. It wasn't until last year I put a Moroso vacuum pump on it to free up as much power as I could. The moroso 3 vane pumps are great, limit max vacuum at 14" and don't forget you need a catch can too. Before you do anything, how bad of blowby are you talking? One problem with large stroke sbc is oil windage as there is so much moving around in a small space inside the block. This is one of the problems associated with large stroke sbc.
To add, the 365sbc with large dome pistons made the best power on the dyno at 43 degrees of advance. Myself and the dyno operator were a bit surprised, the timing marks on the balancer were double checked and were right on. This is why a well thought out day at the dyno is well worth the money.
Last edited by 4 Speed Dave; Feb 2, 2018 at 12:37 PM.
You realize the PCV isn't open at WOT. At zero intake vacuum i.e. WOT the PCV is closed. The PCV is only open at higher vacuum levels. On a newer tight motor you shouldn't have much blowby. Both the 496 BBC in the vette and the 365 sbc in my Nova both don't have much blow by at all at higher rpm levels. The 365 hits 85-8700 rpm every run at the track. It wasn't until last year I put a Moroso vacuum pump on it to free up as much power as I could. The moroso 3 vane pumps are great, limit max vacuum at 14" and don't forget you need a catch can too. Before you do anything, how bad of blowby are you talking? One problem with large stroke sbc is oil windage as there is so much moving around in a small space inside the block. This is one of the problems associated with large stroke sbc.
To add, the 365sbc with large dome pistons made the best power on the dyno at 43 degrees of advance. Myself and the dyno operator were a bit surprised, the timing marks on the balancer were double checked and were right on. This is why a well thought out day at the dyno is well worth the money.
Yes, it doesn't have vacuum at WOT, but doesn't flow enough out of the crankcase when the crankcase is under pressure either.
yes, I know to everything, the reason I'm getting the pump
Last edited by bdhulderman; Feb 17, 2018 at 07:02 PM.
Ok, I think the DCR you refer to is defined differently then how I define it. I calculate it from the cylinder pressures from my software that means a lot more to me. Here I think is how you calculate it. This is using advertised lobe lift for intake valve closing:
I've got a lot more confidence in the software I developed than any other software, since I've validated it throughout the development process. That's what I used to determine the timing requirements, and it's apparently working so far. Another thing you should keep in mind is that I'm well over 100% volumetric efficiency with the heads and lift I have at the peak torque, so DCR is no longer a factor.
Oh, hears some more info:
Oh, and if you use the .05 intake valve closing number you get the following:
Yes Wallace's program uses the same reasoning as the calculator that I use:
scroll near the bottom for the program if you want to look closer. Yes P Kelley uses seat to seat valve timing as well. Using the 0.050 events are useless. Advertised, seat-to-seat, or SAE J604d is what you need. Valve is "effectively" closed when it's about .006 off the seat.
Your software early in this thread shows your DCR @ 8.07:1, while Wallace's (similar to Pat Kelly's, and both of which state an input of seat-to-seat durations) comes up with 8.10:1........virtually identical.
EA Pro shows my VE to be well over 100% with open headers, as well.
Last edited by 65tripleblack; Feb 2, 2018 at 02:48 PM.
scroll near the bottom for the program if you want to look closer. Yes P Kelley uses seat to seat valve timing as well. Using the 0.050 events are useless. Advertised, seat-to-seat, or SAE J604d is what you need. Valve is "effectively" closed when it's about .006 off the seat.
Your software early in this thread shows your DCR @ 8.07:1, while Wallace's (similar to Pat Kelly's, and both of which state an input of seat-to-seat durations) comes up with 8.10:1........virtually identical.
EA Pro shows my VE to be well over 100% with open headers, as well.
The point I was trying to make in my last reply, is that the DCR is pretty arbitrary, what really matters is the effective compression ratio, taking in account dynamic volumetric efficiency. It shows I can get away with pump gas, even as far as I need to advance the timing. There is a reason for why I do things.
Last edited by bdhulderman; Feb 2, 2018 at 09:15 PM.
