Well finally finished up the car today, and got it on the dyno. This is a 383, 11.4:1 compression. Heads Started off as AFR 180. They are 2.02 1.60 valves. Heads flow 294/215 @.650. Ported lt4 manifold. Kooks long tubes, with cats, 12 bolt with 4:10 gears, and 18" z06 wheels. She managed to put down 421rwhp with 390rwtq if I remember correctly. This was all on a dynojet (SAE corrected). Im waiting for the shop to shoot me the graphs. There is a problem, between 6200-6500, the car is breaking up. We believe it is ignition related, being that it has enough fuel. Car has fairly new opti, old coil, old plugs, and new wires, and a MSD Digital 6 box. I am going to swap plugs this weekend, and see what happens. What do you guys think?

 

Nice.

 

Awesome numbers! Did you get a log? How was the AFR?

 

Brad, the o2's were buggin out big time, and we decided to go open loop instead. AF was 12.5 at Wot, we tried leaner and she didnt like it..

 

Dam and it should make the most power in that RPM range too!

Usually they like lean A/F's I've seen some stuff like 13.5+ which is a bit hairy!

Good numbers!

Bret

 

wow, nice numbers.

 

Bret, we tried leaner, and the graph would just look worse. All wiggley lines up top, but we richened her up and she cleared right up. I will post the graph and tell me if we are on the money..

 

Yeah!! I just did a search and found your old post listing your mods and I was wondering if you had ever done a dyno. That's encouraging news, is it the LE2 cam? Can't wait to see how she does after the changes.

 

GREAT #'s. There are LOTS of ways to loose power and the cars that put up bad *** #'s are just the ones that have a shorter list of things that are wasting HP. If it is fuel or ignition related, I guess that will have to be fixed first but if the fuel pressure is fine and it is not ignition related, here are a few things to try . . . . .

I am sure you checked for KR at the problem point, if not, see if it is getting KR and if it is real or false. An LT4 KM might be the only thing needed

check rocker adjustment (1/8 past zero with stock type lifters and even looser on R lifters).

NGK # 4091 (R 5671-A7) spark plugs. They can handle leaner A/F and sometimes more timing before detonating. A/F and possibly the timing might be correct but if the plug is heating up, you might be getting detonation

Not sure what the timing is up there but usually you can pull some timing up top (1 degree every 200 RPM over 6000 RPM) and the #'s keep climbing. If it is like 38* at 6000 RPM and never retards any, there is usually more power in it.

Do these things and then try to add/subtract fuel up there and see what happens. Juts keep adding fuel if it keeps making power regardless of what the A/F says. The A/F is reading what is going on at the O2 sensor, NOT in the cylinders.

these heads and that cam should peak at 6500-6600 RPM so if the #'s are not peaking there, we still have work to do and there is more in it.

Still some bad *** #'s for those heavy *** wheels and 12 bolt.

I bet it is fun to drive. Congrats on the #'s.

Lloyd Elliott
972-617-5671
Eportworks.com

 

Good numbers!!

 

Good #s, but I agree w/ some of the others and think there's probably a little more in it somewhere.

 

Yea get some new plugs and hopefully get that break up fixed. This is an auto right? I think you should put some more down with that set up. LE rocks his LE2 heads on an847 in my auto went 417 so your heads you should push that preety skyward. Good luck and keep us posted.

 

He has a M6.

 

Thanks for the compliments, but they should all be going to Lloyd and Bret. They did nothing but give me what I asked for. A car with good all around power, and GREAT street manners, and the customer service is by far the best I have ever dealt with, anywhere!

Lloyd, I will make another pass and keep my eye on the KR. The car has a lt4 KM in it now, and the KR was limited to only 5° up top. I currently run the NGK 4091, but a new set is going in tomorrow. I am running roughly 35° of timing up top, but if the kr is pulling 5° then that puts me at 30°. The first pull we did, the car was really lean, 13.5 AF and the graph was all messed up, up top. We kept adding fuel, and the car kept making power. First pull she made 381 rwhp, and just kept adding fuel, and the graph reallly cleaned up, and kept making more power. Do you believe she still has more in her? Do the torque numbers look about right? I will try to post this graph up as soon as they e-mail it to me!

 

It would be interesting to see if you can detect any vacuum at wot. The problem with running cats on LT's is that they clog easily and quickly, resulting in unwanted vacuum and power loss.