I have an 89 Vette that I just recently replaced the short block with a 383 but has the stock top end, LT4 hotcam (I know not the right cam), Hooker headers no cats true duals with h-pipe and flow masters. Problem is the machine shop gave me wrong numbers of cc for the heads and said I would be running about 9-9:1 compression with the 76cc L98 heads. Being that he was wrong I have no idea what the compression is now other than its a lot higher.
Ok my questions:
What would be the most the ECm could handle as far as correcting?
I know I need a different chip but would an EZ-EFI be better with still having so many changes?
Any idea what kind of timing I should be setting this at?
Idles fine but get a pop under acceleration.
Can hear run at http://www.youtube.com/watch?v=w25SE66U5aw
or 1989 vette w/LT4 hot cam.
Your help is appreciated, thanks

 

http://www.wallaceracing.com/cr_test2.php

Ask your machinist how far down in the hole the piston is
Or
get pn on the piston, length rod and ask about decking the block if so how much go from there.

That cam will work fine with the 383

Id keep the stock computer and get a good tune before driving it much. Its more than capable of handling what you have with some tweaking
mseven here is super good others will list some ones they like.

When the tune is spot on you probably wont hear the cam at all.

 

The LT4 Hot Cam isn't really optimal for the TPI Intake, as it's designed to make power up higher. Generally speaking it gives up a little bit of low end which really hurts on the TPI because right about the time it comes alive, the intake can't flow any more.

The 383 should help compensate for the loss of torque to some degree, but more airflow per rev means that you're probably gonna run out of air at an even lower RPM. It's certainly not the ideal cam, but it's mild enough that you can probably make some decent power out of it.

As far as the timing goes, set it to what the owner's manual says and then have it tuned. You have way more control over timing in the computer than you do by making global changes at the distributor. If it pings a little at wide open throttle they can back off just the wide open throttle timing, or if it needs more at wide open they can do that too without having to mess it up everywhere else.

Getting it tuned is certainly the best thing you can do for it.

 

Just a new short block? So you used the 89 heads? The 89 heads are 113's with a 58cc chamber, not 76 cc's. Summit Racing has a horse power calculator on their site. Plug in the numbers and it should give you a ball park figure.
The stock computer can handle a lot more than some give it credit for. I agree with the above, find a GOOD tuner and data log and tune for normal driving, then hit the Dyno and do a WOT tune.

 

Nathan Plemons: Yeah I read a lot of haters about the hotcam but I bought it before thinking I was going to use it with the 350, well that didnt happen. With the changes I have and the stock TPI suck a cork I know that Im losing A LOT but its what I have to work with right now and Id like to just drive before forking a couple thousand more for a decent top end. It actually started pinging at lower revs when I was trying to take it around the block, I tried setting timing a hundred times with the same results.(yes I unplug the wire) before anyone asks. I know a tune is what I need but I cant even get down the street without it popping.
Corvette40: Yeah, like I said ran out of time in my buddies garage and it had to go. All top end is stock due to it having to go.
I know they are 58cc now and not 76cc like the machine shop told me, again I didnt realize until it was to late having to get my car moving.
I have done estimates for compression calculators and all say about 11.5:1, however just an estimate.

 

If there is any truth to that, there's your problem. You've got to have a perfect setup (quench height, dynamic compression ratio) to pull off that kind of a static ratio on pump gas. It's way easier to do on an LT1 due to the reverse flow cooling.

You may end up having to back your timing off so far that you can't get any performance out of it. You could buy yourself some help with a set of thicker head gaskets.

Don't get me wrong, I love the Hot Cam. I'm not just the hot cam club president, I'm also a client. It's a great cam, just not ideal with the TPI. If you can get past the pinging issue it should do OK for you until such time as you have the money to swap the intake.

Just to verify your numbers... do you know if the block was 0 decked, do you know the head gasket thickness, and do you know if the pistons have any dish?

 

I did have the block decked and was told it was at zero, but this is coming from individuals that gave me wrong info once already. To be honest I am very disappointed with them and will never take anything back.
Unknown on head gasket other than its a felpro standard head gasket for said car. They are a 4 valve relief piston of the Speed Pro type and what I have seen could be 5-7cc. I have to get back with the machine shop and verify though.
I was actually thinking that there might be to much compression, if such a thing exists. I was TRYING to get away from it but I may end up forking over the cash to redo the top end.
My plan was AFR 195, mini ram and larger TB.....what are your thoughts?
Id like it to breath further in the RPM range and figured since it was a stroker my TQ wouldnt get sacrificed as much.

 

As Nathan suggested, start by backing the static timing off 3 degrees or more to save the motor. You don't want to beat on the pistons and rings before you get it tuned. Use premium gas (of course). If it still pings, back off another couple of degrees. You have to do what you have to do to get the thing down the street. If you hear detonation, get off the throttle quickly.

 

Based off of what you have said and some educated gusses:
Bore: 4.03in
Stroke: 3.75in
Chamber: 58.00cc
Gasket Thickness: 0.039in (a felpro for your car)
Gasket Bore: 4.080in (same felpro)
Deck Height: 0in
Piston Dish: 7cc
Piston Clearance: 0.001in
Top Ring Depth: 0.3in

That lands us at a compression ratio of 11.68:1, which could very well be too high for pump gas.

One way to lower the compression would of course be to go with a different head. The AFR 195 is nice, but I would be tempted to go with the 210 in your application. Reason being you get a nice boost in the flow numbers and the larger runner will help the 383 breath. The larger runner would theoretically give up some low end torque but the 383 should make up for it.

The heads are available with a 65 and a 75cc chamber. This would land you at 10.75 and 9.67 if you kept everything else the same. 10.75 is still high for a stock L98 but the cam is going to lower your dynamic compression ratio some so you may be able to get by with it. I'd have to yield to the engine experts on that one.

As far as the intake, the mini ram is tailored more towards high rpm power. It will give up some low rpm, but it would be much more suited to the hot cam than the TPI intake would be.

I think the combination of the hot cam, 210's, and the mini ram, would give up enough low end torque to keep you from completely blowing the tires off of it every time you hit the gas, and would really scream in the upper RPM ranges.* Might also consider going with 1.7 rockers over 1.6. The extra lift would really help you take advantage of the extra flow of the heads.

Oh, as far as the TB goes, spend the money on something else. The factory 48 will flow plenty of air for the 383. Sure the aftermarket ones are pretty, but you'd get way more bang for your buck elsewhere.

*This statement is based purely on theory and a whole lot of bench racing, I have no first hand proof to back it up. Others have done similar combos though and should be able to offer you some valuable input.

 

You need to plan out the package. If you're going to stay with the HOT Cam (.525 lift with 1.6 rockers) the AFR 195s are more than adequate and frankly the competition ported 180s are not a bad fit. Going bigger to the 210s will be non-value added. With the AFRs you can get the combustion chamber size you desire as well.

FWIW...and obviously my engine is LT4 based...I'm over 500hp with the AFR competition ported 195s. A couple other guys on this board are as well. My cam is 230/236 @ .050 and lift is .622/.624.

 

I gotta admit, I have never understood this thought process. It flies in the face of nearly every recent/new sports car...Z06, ZR1, the high end Mustangs, the ZL1 Camaro, etc. If true, it means that none of the aforementioned cars can be launched which we know to be false, even with the traction control off. Hell, my stock BMW 335i will blow the tires off from a standing start.

This isn't meant to be a dig, I truly don't get the logic of the statement combined with the concept of building more powerful engines.

 

Certainly no offense taken. It does sound kinda counter intuitive. "Let's give up power to go faster." It only works if what you gain on the top end offsets what you loose on the bottom end.

If you can manage the power to the ground then of course you'd want as much power as you can get. If you have traction issues though you may indeed actually go faster with less power. A tire with no traction isn't doing as good a job at propelling the car as one that is hooked.

You may not have thought about it in this way, but if you've ever drag raced you've put this concept in action. You don't launch at 6000rpm's on street tires, if you do you're not going anywhere. You have to launch appropriately and feather the throttle until you are sure you're not gonna break it loose. Sure the same principle works with more power, it's just harder to pull off.

Perhaps a more accurate statement is, "It may be EASIER to go faster if you give up a little low end in favor of top end."