Built LT1 Low Dyno numbers
 

Hey guys,

I'm new to the corvette world (not so new to wrenching), I've bought 2 in the last year and never been so happy/frustrated in my life!

I'm rebuilding a '94 from the ground up.

Had the motor/transmission rebuilt a few months ago. Finally found a local tuner that can tune the car and it put down 308rwhp/315tq. I'm extremely frustrated because, based on what I've read guys putting down with less mods than I've got, I KNOW I should have more with the mods I've done.

Here's the build:

LT1 motor rebuilt (master rebuild kit) by local engine builder.

Heads/intake manifold port, polished & port matched

56mm throttle body, intake over-bored to match

Comp 1.6 roller rockers

Comp beehive valve Springs

Comp cam:
210/218, .560/.555 lift, 113 LSA

Melrose LT headers, 3" X Pipe, 3" straight-thru mufflers after X pipe, 2.5" pipes from diff back.

Transmission rebuilt and bullet proofed by Sean at top gear (recommended on this site). Trans-go shift kit, FTI 3200 stall, lightweight drive shaft.

How the heck am I putting down LESS than stock #''s? !?!?!?

was it a mustang dyno? (they read low for some reason but are still useful for tuning) . if so, its number cant be compared to a dynojet

how high of an rpm was is ran until? (ie. was the run cut short)

what was your afr ratio during the run?

do you have a datalog ? (of commanded spark advance and other operating parameters? )
this will also answer if there is knock activity retarding timing and styming your gains

are you using an oem quality optispark or something other brand?

that cam seems on the smallish side (which is fine), but i too would have expected more if this was on a dynojet. i made 353 rwhp/ 355 rwtq with hotcam kit, 1 3/4 headers and mild port of lt1 heads

lastly... i would do a compression check and make sure all the cylinders are creating equalish compression. you wouldnt believe how many engine builds ive seen go wrong here.

you'll get this straightened out
good luck

I'm on my way to pick up the car and dyno/data log info now. I was wondering too if it's a Mustang dyno, I'll ask when I get there. Hope that's the case.

I think they took the car to 5900 each pull. I was only on the phone with him briefly and was half awake. I'll get more details while at the shop.

When we got the car back from the builder, we had a massive oil consumption problem, so they did a compression and leak down test. They said everything looked good. (The oil consumption went away magically).

I couldn't say what optispark the builder put on it, I do know it was $350, so hopefully OEM quality.

I'll update in a bit.

...if the builder didn't do a correct valve lash, could that be robbing me?

I know lashing is super important with mechanical lifters, not sure how much so with our hydraulic.

Stock auto LT1 usually puts down about 260rwhp, so there is a improvement.
The cam is on the small side, and it would also depend on what kind of head porting was done.

Port and polish?Without knowing the head flow you have no way to know if it actually helped or hurt.

Stall converter can skew numbers as well.Was the converter run locked or unlocked?

:iagree:

How does it run?

May be nothing wrong with it comparing online #s isnt worth it everyones will read different, some high some low some plain bs.
When you do your next mods and use the same dyno as a measure...which imo is what dynos are best for.

Have fun:cheers:

That cam is definitely holding you back by a lot I think. That's barely an upgrade. Also, did you dyno on a mustang dyno? They read lower than dynojets. For an lt1 you need at least like a 224 duration and 112 LSA for it to be worth a cam swap IMO.

I appreciate all the responses.

Spoke to the shop manager and tuner at length today and here's the deal:

They use a mustang dyno (meh) with a "calibrated load" unfortunately they couldn't say exactly what that load was. They use the same dyno to check timing on trucks used for towing. I may have been pulling a yacht while on the dyno, who knows.

AFR looks good across the RPM range, and starts to make good hp/tq around 3700-4000.

Seat of the pants is way better. Car pulls all the way to red, and feels "cleaner" if that makes sense.

As far as flow rate for the heads, the builder ported them in house on their CNC. I asked if they bench flowed before installing them, they said "No". That frustrated me for sure, but the motor was assembled at that point.

I went "small" with the cam because I didn't know when or if I'd find a good dyno tuner, so I wanted it safely drivable till then. I was just thiyght it'd put down more torque with those specs. May be more $$$, but now that I've got a reliable tuner, I may swap later.

All said, after learning about the dyno and feeling how healthy it is after the tune. I'm less disappointed than I was. Maybe I'll head to a dynojet and do a pull to get my big d!ck numbers.

It will be more on a dynojet, but not a lot more.
The cam is the real issue, and suspect head/intake work.

I agree. When it's time, I'm just gonna go with a cam/head combo from someone reputable like trickflow, AFR, etc...

This builder did a lot of funky stuff that cost me time and $$ to diagnose and repair. Doesn't speak well to their "precision porting" claim.

Those wheel HP numbers don't look too too bad to me. To Get to the 400 RWHP area - you're going to need significantly more cam (with the resulting loss of drivability) !!! Remember - you're probably loosing 15% - 19% between the flywheel and the tires...

If the A/F looked about "right" the next question I would be asking is what about timing ??? I'll assume that since you said Opti - you're using a stock PCM - stock heads should mean that stock timing will suffice, but you probably want to verify that's what you're seeing. If you didn't datalog during the dyno run - I would suggest repeating the test while datalogging. If you see the knock count going up - you might have just found the problem. I've also heard tell that some people have seen old fuel cause tuning nightmares - the car just doesn't want to make power - so make sure that the fuel in the tank is nice and fresh.

My only 2 points of reference.

My 94 with 180k miles, it must have a tuned chip, but doesn't sound like a cam, and it has stock exhaust, etc.
290 RWhp/330 RWT - on what people told me is a "heart breaker" dyno (since it always reads lower then other dynos)
My 92 with a build 383 - who's who list of upgrades, ported heads, headers, 56mm TB, etc etc etc etc, 15k into the motor (I didn't build it), 350 rwhp/351 rwt.

Seat of the pants tells me they feel the same until about 4k rpm, then the 92 runs a bit stronger, but not startlingly so.

So my 94 that is basically stock seems really good for a "stock" car, but then the 383 I feel is really under powered with all that it has done to it. =\

In my opinion, that set up with the right cam should make 350 hp at the wheel at least.

You also need to spin it higher.
Did you change injectors? It won't need them with those #s, but you will when you start making more power, and you don't want to max out the duty cycle and be lean.

Just for reference.
I have basically what you have, with a matched H/C/I combo, and a 6 speed, and it put down 403whp. 230/230 cam and great street manners. If you were on the same dyno and had my combo, and everything else was ok, I would think it would be 390ish.

You have significantly more cam than phoenixLT1. I'm also betting that your heads are somewhat "better flowing" than phoenixLT1's.

Yes, exactly, like I said in my first post, it is mosty in the heads/cam. Just giving some real world comparison, and that if done correctly, it can still be very streetable. The cam is bigger, but not a "big" cam, it is just his cam is very small.

A couple things jumped up at me. Define "built"? Did you just rebuild to stock specs or did you bore and stroke it? Why do you get a tuner and also a builder? I'd have gotten the tuner, who undoubtedly knows builders and have him suggest a build. Right now, a possibility is your builder tells you that your tuner is an idiot and the tuner says the engine combo was wrong.

I went to LPE and after he died, went to Hitech. Those guys tuned the car on the street (LPE) and dyno (Hitech). Either case, they advised on the combo all the way from tuning to gear selection to parts.

Did this tuner do it via email or dyno?

Why a 3200 stall again?

Maybe this time you can get the tuner to suggest a combination? Having had a bad experience with TFS and their QC, I think I would suggest AFR.

How did you select him then? Also, what made you choose this tuner? Have either of them done this before? Next time, do it from one shop. That way, if there is a screw up, they cannot blame the other guy. I've seen ugly situations where the parts supplier blames the builder and vice versa. At which point, the owner gets the shaft.