I have a 94 Z28 with the following mods:
Forged 383 stroker kit
10.8:1 Compression Ratio
COMP CAMS XFI 268 218/224 & .565/.570 113 LSA
58 MM Throttle Body
2.02 Intake valves, 1.60 exhaust swirl polished
Titanium retainers
ported and polished heads
1.5 Roller Rockers
Ported and polished intake
Accel 300+ ignition system/coil/opti
3.42:1 gears
PCMforLess mail order tune
255 lph fuel pump
42# lucas injectors
optispark II conversion
Electric Water Pump
Descreened MAF
Cold Air Intake
Accel Adjustable Fuel Pressure Regulator
Cloyes Double Roller
!EGR !AIR
Long Tube Pacesetter
Off Road Y with No Cats
BFG Drag Radials 315/30/18
107 octane

The problem is that with an auto and stock stall i was only putting down 13.11 1/4 mile times at 108 MPH.
Since then my A4 took a dump and i did an M6 swap. With the 6 speed my fastest time was a 13.400 @ 106.

Whats the deal????
In my opinion i think the cam is a little on the small side for a 383. I overestimated the cam i chose. I also think the mail order tune isn't quite right. I still only have the LT1 knock sensor as well, but i requested that it be desensitized by PCMforLess.

I realize my gears and stock stall were hurting me, but even with those i'd probably only be pulling 12.8 at best...


Any input would be nice. I haven't had it on a real Dyno yet so i have no horsepower or torque numbers. I'd estimate somewhere around 330-340 RWHP--pretty disappointing.


thanks guys

 

Somethings wrong. You should get it on the dyno. It should make 400rwhp through the m6 easy; if the heads were ported correctly.

 

Get a scanner go through the basics first o2 readings plugs misfires and knock and timing pull. Second check the fuel and third if you havent tuned the car then get a tune.. Oh last make sure you have no leaks anywhere exhaust injectors and so on.. real easy to do just takes some time.... last check you rockers for being to tight.

 

What was the 60' and DA?

MPH is way low, a dynotune will help for sure but it is probably pulling a lot of timing. You cant really desensitive a knock sensor by mail order tune...it is something that needs to be done in small steps, datalogging after every change.

 

The specs on the cam match the 466 xfi and all the lift on the xfi cams are with 1.6 rockers. Some 1.6's and a dyno tune may help.

 

the first thing that i would do is either a leak down test (best option) or a compression test. this will tell you if everything is sealed up, (valve seats, piston rings, gaskets, ect.) then, i would ask who put the motor together & who did the machining? is it someone who build's high end engines on a regular basis, or a garage mechanic? next would be a scanner or datalog, this would also be very important.

 

why the 107 octane?

 

The times in my sig are with a 156k mi LT1 convertible with a stock A4 trans and bolt ons on street tires...

I think that says it all. Something is very wrong.

 

Thanks for the insight fellas... Does anyone think this cam is a bit on the weak side for a 383? It seems small to me. I built the engine by the way. I chose this cam because the car is my DD. Its a little milder than i expected. Compared to the HotCam it has about the same duration with a little more lift. We have a 200 Hp dyno at school and a 5 gas analyzer. The car was running about 13.5:1 AFR during the run. The only reason i had it on the dyno was for emissions testing in my fuels class. We also have a leakdown tester and the engine is sealed up great. Would the LT4 knock sensor make a big difference on its own or should i just wait til i get a tuner to desensitize the knock sensor?

Again thanks for the help. I thought these numbers were kinda weak for what i've read about 383 LT1s.

 

I'd say that cam is on the small side for an NA application, especially a 383. That cam is very similar to the one I have for my 355 turbo app. I'd try switching it out, but if your AFR's are accurate, I'd say your tune is off. They say the power is in the tune, and they are right. You may want to invest some money in a dyno tune.

 

mail-order tune
1.5 rockers
stock gears

 

Obviously something is wrong. Is it throwing any codes? Go over your ignition, check plugs and look for burnt wires. Get it on a dyno and see where the afr is.

 

Those XFI cams can create valve train control issues. The rockers aren't helping. What rpm and what gear are you rolling through the traps? Are the heads all that they are cracked up to have been? 3.42s might be killing you. 107 octane is NOT needed at all!

 

With the engine idling, put a vacuum gauge on it(mityvac)....what is the reading? Is the needle steady at that value or bouncing around?

What is your RPM redline?

 

I'm thinking about going with the 306 cam. I know this question has been beat to death but does that sound like the way to go? It is my daily driver so i still want it to be well mannered in the city.

As far as the heads go; they could be better. really all i did was a little bit of pocket porting and gasket matching. I didn't want to take too much material out and make them flow like crap. I put the 2.02 intakes and 1.60 exhaust valves in. I did all the work on the heads and intake and engine.

Mail order tune-
1.5 rockers-
Stock gears-
I think that pretty much sums it up. I need to just suck it up and get a good dyno tune. The rockers and gears are on their way too...

The only code it is throwing is for the cooling fans. I think the fans are worn and are just drawing too many amps. The SES won't come on til it blows the fuse. I just got tired of wasting fuses. There is no opti code or anything like that. OBD1 so no misfire detection either.

Redline is set at 6500 rpm.

What do you mean by valve train control issues?