Well, things that make you go hmmm...


If that's the case with mine, I have even more horsepower than I think I do now.


So, if this is true, what kind of horsepower would a true L-88 motor pull, if it was changed to make the motor happy, like you suggest? Good thoughts, and that's what I thunked about for a long time, before making mine the way I did, because a lot of people had said the air box in the L-88 was restrictive.


But, like I said, I only have sticks and rocks in my garage, and I can't afford a dyno to test everything I do. I'm extremely happy with the power I'm getting form the motor I built. I smile all the time in it!!!

 

FedEx delivered the parts today to upgrade the fuel supply line on my 454. I spent most of the time locating the new big *** filter, pressure regulator and pressure gauge and drilling the mounting holes so tomorrow I can make the change. Just out of curiosity I put the new pressure gauge between the old Mr. Gasket regulator and the carb to see what was the actual pressure in the old system. With the setting on Mr. G at "6", the pressure gauge read 2 psi with the engine idling and "fluttered" when I increased the rpms to about 4K. Maybe I can use the old regulator for a paper weight. Hope to have everything operating tomorrow. Fingers crossed. Still waiting for my wide band A/F meter to get here. That will put some real numbers behind the modifications- then back to the dyno!

 

2 psi is just a little out of range. At least you found a problem.

 

Here's how I mounted my regulator. I made a bracket from a steel "L" angle and bolted it to the head, and the regulator. I just put the one from the other side for the P/S reservoir for giggles.

 

Holley bypass regulator and Jegs fuel gauge and billet filter


USAF- You were much more creative than I was. I wanted to keep the regulator away from conducted engine heat, so I simply bolted it to the fan shroud. Plenty strong and cool. Unlike the previous setup with the Mr. Gasket regulator from the PO at 2 psi, now I get 9-10 psi. My wideband gauge finally got here and I get between 13.0 -14.0 thru the rpm range from 1500-5000 rpm. I'll let the dyno go up to redline, but it appears the restriction was in my previous fuel line. Ihope to get dyno time this week.

 

If your fuel supply is relatively steady during the pull, you are likely going to have to jet up the carb as you are pretty lean still... Ofcourse 13.0-14.0 is a broad range but... Ideally, you don't want it any leaner then 13.0 after about 4k rpms. BTW if your idle fuel pressure is 9-10, you should back that off a bit, the needle and seat won't hold that much pressure for long, but your pressure will drop some when everything gets hot so you may be ok.

Odds are, your fuel pressure is going to drop some once you start making the pull, as long as it doesnt fall below 4-5 psi, you should be good on the supply, then jet up accordingly.

Mine actually falls to 2-3 psi on the dyno, no telling how low it drops at the track (I don't have a gauge in the car), however my AFR is rock steady at 11.8-12.0 through the traps at 126-127 mph.

 

1967 L88 didn't have the PCV tube in the base. (Mechanical secondary)

1968-1969 L88 used the tube. (Vacuum secondary)

 

If the regulator is a MR Gasket throw it in the trash and get a real one
2 lbs that car would barely run bet your not getting the right reading.

 

"Ofcourse 13.0-14.0 is a broad range " That range is by manually reading the Innovate gauge, which fluctuates, depending on rpm. After downloading the Innovate software to log my data I found my laptop does not have a serial port for the Innovate cable supplied. Serial to USB adapter is ordered (one more thing to order!) so I hope to have more accurate data soon- probably after the dyno run.

 

"throw it in the trash " Already done. New reg is a Holley.

 

Attached is the printout of the dyno run with the old cast iron peanut port heads, bad filter and bad Mr Gasket regulator. With the restrictive heads this setup was able to maintain ratio in the 11s. When I had the second run done with the aluminum rect port heads, the fuel system ran out of gas, so to speak. I did not get the A/F printout for the second run. Hope they have it archived- I'd like to look at it.

 

AFR shown in dotted lines at bottom, HP at top


torque shown in top lines, HP in lower curve

Well the most recent dyno run today confirmed the AFR is OK, but the power drop off just as the HP curve starts to take off now suggests ignition, probably a weak coil. So, I have to decide what to upgrade from my old school coil, points and condenser. I have the cheap-*** Chinese HEI distributor with tach drive I bought for about $60, but when I hooked it up, the engine ran like shxt. I can replace the module, coil and magnetic pickup with USA made parts, but I like the smaller size of the stock distributor. Has anyone used the Pertronix Ignitor III conversion kit with the Pertronix 0.3 ohm coil? This would keep my stock size distributor ....... and ..... the carefully measured and installed ceramic insulator plug wires that withstand the heat from my headers. The mfgr description makes it sound like it has MSD properties. Suggestions from people who actually have the Pertronix kit requested.

 

Well, I'm glad you got your fuel supply issue resolved and your fuel curve looks pretty good.

Now for the nosing over part, honestly, it doesnt really look like ignition to me, the power curve is very smooth, then just drops.

Does it start misfiring or breaking up at the top of the pull? Do you "hear it" nose over?

I'm almost wondering if the valve spring pressure is incorrect and its floating valves, but once again, you can usually see that in the curve and hear it.

Its definitely weird how the power falls off so fast, yet before it was pulling to 5300 or so before it starts dropping.


Keep investigating and trouble shooting, it definitely has something going wrong but, at least you fixed one of the problems.

It looks like you were up about 15-20hp at 4800 before it signed off so, thats a good sign.

 

"Does it start misfiring or breaking up at the top of the pull? Do you "hear it" nose over?" No unusual noise, misfires or anything. It acts like the coil crashes and the engine just starts to coast due to insufficient time for the coil to re-saturate. First time it happened the technician running the dyno asked if I had a rev limiter installed. The valve springs are double coils rated for 0.6 inch lift- my cam has .540 lift maximum. Hydraulic valve lifters are the Lunati that are matched for the cam. Don't think I have valve float. This problem causes rpms to drop off- like a rev limiter. I suspect the coil is a stock coil that may be getting weak due to age. I think for about $160 I'll try the Pertronix Ignitor III kit.


One problem resolved that I did not mention- a few people said that the rectangular port heads and intake would be too much for street driving and would not have good throttle response. I find the opposite to be true. This setup has excellent low end torque and literally lifts the nose of the car even at 1000-1500 rpm.

 

On my 496 build I used an Accel coil and a http://www.breakerless.com/

It uses the existing Points wire for an easy install. If you do get a Breakerless make sure to note the compatible coils.

 

Well, I installed the Pertronix Ignitor III and the matching 0.32 ohm coil and went back to the dyno today. (Rev limiter set at 6000 rpm). The car starts and runs well under normal driving, but... WOT and max power at high rpm problem still not solved- see attached curve. I'm wondering if the stock distributor I updated does not have enough advance, since this power drop off at 5000 rpm was there from the start, even with the original set-up from the PO. The several articles by Lars and others give total advance of 36 degrees by 2500 rpm as the benchmark. Not sure which mechanical advance springs I have. Will check tomorrow and see if I can get a mark on the dampener to check with my timing light at 36 degrees. Does anyone have a dyno run curve with not enough spark advance to compare to what I am getting? The car runs well up to 5K rpm, but I would like to figure out what this problem is caused by, now that it is driving me nuts. RA

 

Personally, I do not believe its a timing/ignition problem. You would have to have some SERIOUS timing retard going on at 4800 to kill the power and roll it over like that.

Did you verify the spring pressure/installed heights on the heads?

The power curve doesnt seem to show the "flutter" you see with valve float, but the steep power drop sure shows it. Your spring pressure requirements are not based solely on the amount of lift of the cam, but more so of the intended rpm, weight of the valve train components and type of lifter. A hyd flat tappet cam has very mild requirements for spring pressure though so I wouldnt think this would be your problem with new heads and new springs unless they made a mistake on setting up the spring height.

Honestly, I'm not sure you will hit 400 rwhp with that combo, assuming everything is correct. I do think you should see a solid 350 ish though.

I don't recall the specs on your cam but the way its nosing over, I'd really look at the cam/valve train etc etc


Also, you are dynoing with the air cleaner OFF right?

And you verified the throttle linkage/cable is giving you 100% open secondaries with no slipping? (this one has gotten me before).

On my mild 454 with a 224* cam, it stops making power at 5000, it will still "pull" to 5500-5600 but its nosed over hard by then and the car is clearly slowing down.

Judging by how hard yours noses over at the end of your pull, I am wondering if they are terminating the pull as soon as they feel it nose over, and thats when it shows the big power drop....Or are they backing off the throttle or something when they feel/hear the engine nosing over. Its just crazy how your curve is clean, then peaks, and falls over that hard, that early on.

On the street does it feel like it just dies at 5000?

 

I've ran into dyno runs like this a couple of times. One was the carb going dry, but that issue has been addressed here. The other was valve float from weak springs. Usually the graph starts getting wavy as it goes into valve float, but I had one that looked just like this. Stronger valve springs fixed it.

It seem awfully odd that it would rev to 5600 before the fuel system was fixed and now won't go to 5000. Valve springs don't go away that quick in mild applications like this. Could it still be the carb going dry? The air fuel does start to head lean right before the run ends. The O2 sensor tends to run a little behind so maybe the run ends before showing it go way lean.

 

Very likely it's a mechanical problem.

Valve train related. Spring pressure or geometry.
Will

 

"On the street does it feel like it just dies at 5000? "


So today I re-checked everything possible and temporarily installed an electronic tach to give faster read-out of rpms at the high end. I re-set the valve lash on the hydraulic lifters, just in case they had changed slightly after being in the car for a couple hours running. Took the car out to a deserted stretch of road and ran a WOT run in 2nd gear. Power died on the street at about 5K rpm just like on the dyno. Can you say valve float four times fast? The feel is unmistakable. I got out the specs on the heads that Shaw City Engines in Fresno, CA set up for me and while they did use valve springs to accommodate .650 lift, they went wimpy on the pressure: 125 lbs at installed 1.9 inch closed height. Looks like this is the problem. I will upgrade to at least 150 lbs springs. Comp Cams and a couple other vendors have 1.550 diameter springs in that range. Maybe I'll get higher rate in case I want to change to a different cam later. At least now I have a target to aim at.