I have a 3600 lb 1994 355 with professionally ported heads and matched cam combo that should see 400+ RWHP and pull hard to 6800 rpm. It is a proven combo with many dyno sheets posted out there to prove it. The cam was degreed in and is on the correct centerline. I DO NOT think the heads/cam are the problem.

But I have a problem with my set-up. The launch seems fine. With 4200 stall and TH-350 it yanks the tires 6" off the ground and carries them 5-6', but the 60' times are only a best of 1.69 seconds. Not enough power. Those times are indicative of 340 RWHP (I'm told).

I have a problem with the top end over 5000. On a typical 12.10 pass @ 111 mph, I'm in 3rd gear for 3.1 seconds and revving from 5500 to 5900 rpm (a really long time). Best of 11.87 @ 111, but times have dropped off over the last 10 runs to 12.20s in better air.

The car runs mechanically fine, no smoke, no detonation, no misses, just very lazy up top. Fuel pressure is fine, injector duty cycle is 68%. Everything ignition related has been changed (PCM, MSD billet opti, wires, plugs, MSD Digital 6, MSD coil). It is weak on stock ignition and on Digital 6 ignition.

On the dyno last week, I made 7 runs with timing between 28 & 37degrees and air fuel ratio between 12.2 and 14.0.

All the runs were within 6 ft-lbs of torque and 13 hp of each other, which the Dyno operator could not believe and felt should not happen with that much timing and fuel variance. Max of 290 tq @ 5100 and 315 RWHP @6300.

I also made 7 runs in speed density mode with the filter/CAI/MAF/elbow removed because I thought the MAF might have been a restriction. I only gained 4 tq and 13 hp.

Nothing we did to the timing or fuel changed the output more than 2-3%.

My last set-up in the car (LT4 conversion w/ hot cam) was somewhat weaker than others with the same set-up 13.20's @ 104.

The only thing the same with the last combo and this one is the wiring harness. Both engine combos "weren't all there". I think it has to be in the harness.

Could a lack of power to the ignition system hamper the hp that much? Like less than 12 volts to coil? etc.

If so, how and what can be checked?

Please, any ideas need to be brought up, mechanical, electrical, anything!!! The more stupid it sounds, the better it will help!

2 engines, same car, bitter disapointment both cases.

 

My first question is what was the AF ratio during all these runs??????? The second most important reason for running a dyno is to gather that information at each critical point during the run. Yet I see no mention of it.

The second question is what about the components of the valve train??? For example the length of the push rods???? Are the components working together like they should?????

Last, what size are the injectors and are they low or high impedance????

 

I tried to keep it brief that's why some of the info is missing.

The dyno graphs and tables are posted on the following site. I haven't been able to figure out how to post them in this box yet. http://www.cardomain.com/ride/2408556/7

The last MAF run (run #7) the AFR started at 12.6:1 @3200 and became slightly richer during the run to finish at 12.2:1 @ 6300.

The last speed density run (run #13) started at 13.0:1 @ 3200 rpm and finished at 12.7:1 @ 6300.

The dyno log I posted shows the peak TQs and peak HPs and their respsective AFRs. It also lists the degrees of timing advance. These advance values are what was programmed into the PCM. Datamaster logs however report them as being 4 degrees higher than what is programmed in (ex: 33 deg programmed reads 37 degrees in the logs).

__________________________________________________ __________
The pushrods are 0.010 shorter due to milling of the heads and decking operations. They are the proper length and provide the correct valvetrain geometry. This was checked by myself as well as the engine builder who assembled my bottom end
__________________________________________________ __________
The injectors are #42 lb/hr lucas :
135-INJ-621031-8 Delphi/Lucas 42# High Impedence Fuel Injectors
-Static Flow Rate: 42.29 lb/hr @ 43.5PSI
-Static Flow Rate: 48.83 lb/hr @ 58.0PSI
-Dynamic Flow Rate: 9.96 gm/pulse - 2.5ms pulse width and 10ms repetition rate @ 43.5PSI
-Coil Resistance: 15.9 Ohms / High Impedance / High-Z (No ECM driver modifications required)
__________________________________________________ __________


My big concern is that we couldn't get the torque to drop off even when we dropped the timing to 28 degrees. The only noticeable change by ear and seat-of-the-pants was when I set the timing to 37 degrees advanced. The bottom end from 3500 to 5000 picked up slightly, but it was still lame after 5000.

We had one Dyno operator and 3 racing mechanics in the room during the runs and they were all baffled that we couldn't move the torque curve around or pick up any TQ or HP. The engine did not miss, break up or float the valves. They believe it has to do with the cam timing. But, I was there when the cam was degreed in on the correct centerline and opening and closing events.

If it were running out of fuel, it would not have gotten richer during the run.

There was no external air restriction (MAF, filter, etc) and the throttle blades were fully open. This can be seen in the speed density runs.

But, it is only ingesting about 340 grams of air at 77 deg F which is around 770 cfm. (I don't have my formulas with me to get the exact number) the 58mm TB can flow 1050 cfm.

Air or ignition?

 

2 suggestions which amount to the same thing. Either find a desk top dyno and put in the pertinant data and see what it tells you. Or send the same information to someone like Kevin McClelland and ask his opinion at chevyhi@sourceinterlink.com. This guy know his S@#T. Maybe something is not working like it should with all the rest of the items.

 

I have input all info into Desktop dyno Sim.

Fwhp = 540 @ 6500 - 20% = approx 432 RWHP
fwtq = 503 @ 4000 - 20% = approx 402 RWTQ

That's within 5% of what other guys have seen on the dyno.

Something is keeping it from firing with all it's electrical abilities.

I'm going to get it to an oscilloscope this week some time to see what I can find out.

It may be the MSD 8.5mm superconductor wires, I've heard bad things about them over the weekend.