clarkkei96

First of all, thanks for reading. I have finally acquired a car I have been after for 10 years, 96 Trans Am WS6. This car has had a fair amount of work put in, rebuilt engine, trans, and rear end. Transmission has a 3000 stall and rear end 3.73. Now here comes the nuts and bolts of the problem.
Engine was crate forged internal LT1/LT4 383 stroker. 4340 crank, Holley intake, hooker headers, Borla exhaust, 58mm TB, 550 Bosch Fuel pump, and AFR 1031 heads (195 and 74cc).
This combination produced 392hp at the wheel with a tune.
Previous owner decided to have a Comp cam 306 installed. Ran rough and he had it tuned again. It produced 352 at the wheel.
It lost 40hp with a big cam. Not unheard of for stock components, but shouldn't this set up have yielded better results?
Few different theories I've been told.
1. Cam to large, heads don't support the air it needs, need a 210cc or better and. (solution- new or port heads)
2. Cam is old technology, better cams out there. Large spread with intake and exhaust. (solution- new cam, comp 302?)
3. AFR heads don't have combustion chamber needed, these are 74cc. (solution- new heads with 64cc to achieve 11to1 compression.
4. Cam possibly installed wrong, off by 1 timing chain gear cog. (solution- remove and install correctly)

I would appreciate any ideas and information! Sorry if I am not speaking technically correct, I hope everyone gets where I'm going. Valve spring are upgraded titanium and roller rockers arms top of line. Comp cam 306 = valve lift is .510"intake and .540"exhaust. Duration at .050"lift 230 intake and 244 exhaust. Duration 290 intake and 307 exhaust.

space387

Always start simple. use one of the data logging programs and record how the engine is running, lets make sure the tune is not to blame. If all checks out on the data log check your cam timing ( its a PITA but you need to). See if you can find out what happened to the prior cam, was it stock of aftermarket and can you get it back?

ACE1252

Do you have both dyno graphs for comparison? Any specs on the old cam? How high are you turning the engine with the 306?

What do you mean by the above? Surely it was not running the stock cam. If so, 392hp seems really, really, high.....too high(for the stock cam)....but can't say I know what only heads and a displacement bump would do for the engine. Generally, the heads and cam are changed together. Can't recall any numbers from a heads/displacement only engine.

clarkkei96

I do remember when the original cam was in, I don't have any spec's on it. It was a smaller cam though. Engine ran great back then, responsive and more power off the line. Don't know the tune, custom.
I was told, this smaller cam worked better with the street AFR heads because the 74cc chamber was a good fit. And the 195cc intake runner was enough to feed it.
With the bigger Comp Cam 306, I was told it needs the bigger intake to feed it, 225cc? And also the combustion chamber should be 64cc. These AFR 3310 heads were $2K back then, I believe they are still close to that if you can find them.
Would I get better results with a Comp Cam 302? Which is not as big and the intake and exhaust duration are closer.
I just want to optimize what I have. I would like to be close to the 500 mark. I drive it to work couple times a week and weekend driving. Parked winters since I live in MN. Comp cam is $300 compared to a set of better heads $1,800, and a little less work. I do have ARP bolts inside.

Heatmaker

CC 306 is a classic guys pulled numbers with that just running stock untouched heads that and the GM 847. LT4 AFR's are plenty good for big cams. I'm looking at your graph and it seems really choppy. Your engine isn't running smooth at all. Doesn't seem like it's tuned right for the 306 or your your Opti is spazzing out. What does your exhaust smell like? Does the car pop or backfire?

BALLSS

as suggested you should get some data log to confirm 1. the tune is good. 2. there are no issues caused by mechanical problems (fuel pressure, vac leaks, etc)

assuming none of the above (although tune is suspect) contact Lloyd Elliott about a cam suited for your parts and what your use intent of the car is.

FWIW I have a small cam in my 383 (218/224) and I make 380hp/395tq to the wheels so you don't need a uber big cam to make decent power. Certainly a bigger cam with the appropriate tune and supporting parts can yield more power form a 383. Just depends on your needs and use of the car.

I live in Calif. so emission testing is the line I need to stay within

clarkkei96

The 5500rpm to 6500rpm looks horrible, I was told it is struggling to be fed, thus needing a bigger intake runner, 225cc?
Same optispark was ran with both cams, same was as I can remember since before it was mine. It runs smoothish, choppy idle but gets up to RJM and sounds unbelievably great. Nothing I can smell for anything from the exhaust. Though I do smell something this week after a check engine light came on, bank 1. Ordered new AC delco o2 sensors after I checked underneath.
Does a 74cc combustion chamber seem to big to make 10-1 compression? Typically AFR is 64?

clarkkei96

I'm not 100% sure on data log, is that a program I can run from my computer to the car, to check the tune?
I was told it was tuned all day to figure it out and get it running right. After the cam swap, it was brutally horrible running. The guys at the shop got it running up to par, but lost the power. Dunno why.
The guys who tuned were not the cam installer.
Could the cam be off by 1 timing chain gear cog?

BALLSS

96 you can buy a scanner for about $200 that logs data assuming your car was not converted to OBD1. You download their viewer and can play it back with the tool hooked up to laptop. You can also view it on scanner, just small screen

KW Baraka

iTrader: (7)

More like low 9's with stock LT1 pistons.......but you're nowhere near 10:1 CR

Right here. Those 74cc heads are better suited for a supercharged or turbo-charged engine.

But with stock pistons and the 74cc of the combustion chambers, you have way less than optimal compression ratio for a NA LT1/4 engine.

THEN you put in a cam that lowers the dynamic compression versus your previous cam. Classic example of 'bigger' NOT being better!!!!!

You have one of two options:

1. Either increase the compression ratio by buying new heads or milling the current heads, or;
2. Put a cam similar to the former cam in the engine to get closer to original specs.

BTW.....anyone telling you that you need more air.....or more fuel....just kick the in the ***** and walk away!

KW

clarkkei96

Local machine shop said he could mill 20-30 thousandths, but that will only change about 5, so I'd be at 69 chamber.
I most likely need better heads, 64cc or 58cc? Intake runner at 215cc? Sound right?
To solve the current problem, I'll most likely buy a smaller cam, comp 302. Budget with the labor is $1500 currently. Local shop can do it for $600, $300 for the cam, and $500 for the tune(?). Should get me closer to 400hp at the wheels.
Any other ideas I would appreciate.

KW Baraka

iTrader: (7)

Better heads at 215cc? Really? What makes you think you need bigger runners? Hell......I have a solid roller, 398ci LT1/4......with ARF 210 heads and I've had a couple people tell me I should've gone with 195cc runners!!

Like I stated.....you don't need more air, you don't need bigger intake runners. You need more compression with your current setup OR you need less cam.

If it were my car (I know....not my car or money), I'd buy a set new set of AFR 195 heads or a set of AI ported Trick Flow heads, mill the heads to 62cc chambers, get a fresh tune.....and would be done with it. I would also sell the current heads.

BTW.....see the links below.

http://www.airflowresearch.com/195cc...cylinder-head/

http://www.advancedinduction.com/LTX/AiLTxTF195cc.php

If you decide on a cam, get something close to the cam that was in the car originally since you know that's a formula that worked.

Feel free to ignore all of the above!

KW

clarkkei96

Okay, don't need a larger intake runner, 195 is good.

When you say if it was yours, to be clear, keep cam and get better heads with a tune?
What do you think of the cams numbers, first post last sentence explains all. Too big a gap from intake to exhaust duration?

ACE1252

Any track times old vs new cam?

clarkkei96

No track times. No idea what it would do now even? Highway I hit 0-60 in about 6 seconds but that's smoking them off the line.
Original cam, no idea on numbers, car was even more stout.

ACE1252

I'm just not sure that a change to the CC306 would cause that kind of power loss. I wonder if something else is wrong.

Did the same guys that tuned the old cam tune the CC306? Do you still have the old cam? You really need to get the specs from it if possible.

clarkkei96

Same guy, dyno sheet above. He has a pretty good reputation.

If I could hook up the tires I know I would be closer to 5 second 0-60. Stock rims, no slicks though.

ACE1252

You should be well under 5 sec to 60 with a 383.

Like the others, I think the bigger intake runner needed is nonsense.

Get the specs of the old cam if possible.

Was the old setup dyno'd right before the CC306 was installed? Trying to rule out problems before the CC306 install.

ACE1252

Also, how do you know the heads have 74cc chambers? AFR's site shows the 1031 head as 65cc.

http://www.airflowresearch.com/195cc...cylinder-head/

Were they made bigger for a reason?

Puck

iTrader: (17)

Dyno looks almost identical to my dyno with a bad opti (but your's has +20hp over my old 350). Like, damn near exact...wish I had a scan of it. Made the exact same ugly dips after around 5k, and power never rose from there. Made 332 or something terrible. Replaced Opti, pulled clean to 6300 and gained +20rwhp.

Nothing wrong with the "parts", you just have a serious ignition or fueling issue. Its not going lean, so most likely opti/coil. That cam needs a lot of RPM, even on a 383 it wouldn't be peaking under 6k like yours.