Thank you,
To answer a few other comments: I have long tube headers (EM), no cats, stock pipes to stock resonator, then 2.75" pipes to Borlas.

Stock intake was "ported" to accomodate the installation of the 58mm BBK. Car was tuned on a Dynojet.

The AFR 195 street eliminator heads are sprung with the springs that came with the heads.

The printer did not print out the curve but gave the digital numbers on the computer screen.

Tune is very rich (smell unburned fuel) 42# injectors may be too much. Stock fuel pump (no problem).

Car runs very close (performance-wise, based on track times and straightaway speeds) to my stock 02 LS6 Z06 on the track. So the torque numbers "feel" to compare closely to the rwtq numbers of a stock Z06 (400# @ crank). Indicating to me that this build should be producing a little more more torque. I was hoping for around 450 at the wheels.

I hope this added info, though limited, will help you guys to formulate an opinion to offer related to avenues available to enhance the torque output of this build.

Again I appreciate you critique and welcome all suggestions.

 

if you port the actual runners themselves then get your tune right think youll be real happy with the changes. Dont let anyone tell you that running it rich like that is Ok or safe you can damage a motor just as easy too rich as you can lean.

 

I will also add that "most" 383's do not make 450rwtq. I would bet a few pennies that "most" LTX 383's on this forum probably make anywhere from 375-425rwtq.

 

Thanks for the suggestion. Provided this modification would get me 50-70 more ft#, dollarwise would the torque per buck (port and re-tune)increase be a viable and advisable pursuit, in your opinion?

Again, Thank you very much for contributing your experience. I really do want this to be a good motor.

 

No it wont get you anywhere near that but do it anyways your motor will be much happer.

That intake cant keep up with those heads as they are...by a longshot.

Think those expected tq #s are a little lofty being at the rear wheels.

 

My 383 lt4 with afr 195's made 419 rwtq-442 rwhp.

 

Safe to presume that you have ported your intake? Finally, would it be advisable to shave the heads to increase compression to _______..to 1...(for high torque production) please fill in the blanks. Primilary a roadcourse driven Z07 25 - 30 min. track sessions. Need to dice things up with the local GT3 Cup Porsches. This car handles like a pro prepared race car, when I run the Kumho V710 315s on the squares. Very capable in the right hands.

 

Stock gm intake.Compression is 11.8-1 runs fine on pump gas.All in the tune.Comp 232/236 @ .050 cam on a 112*.Built with driveability in mind more than absolute power.
Mine is a sunday driver now with hopefully an occasional trip to the track.

Torque curve is big and flat from 2500 rpm to 5000 rpm

 

You definatly need to have the intake manifold fully ported. I'd expect to see 10-15HP gain if it's ported by someone that knows what they are doing.

What cc are your combustion chambers now?
What pistons and how far in the hole?
What head gasket?

You can increase the compression quite a bit by milling the heads and changing the head gaskets. However it's going to decrease your piston to valve clearance so it will need to be rechecked. It's also going to screw up your pushrod/rocker geometry so that will have to be rechecked and probally new pushrods installed.

With the 280XFI you need to be around 11.5 SCR for max power in an LTX. That will put you around 8.9DCR.

If your truly 10.1 SCR now - your DCR is 7.7ish.... increasing the compression to 11.5 will be a big HP/TQ gain. Probally in the 50HP (crankshaft) range.

Will

 

Flattop Mahle Pistons is the only answer that I have immediately. Thank you very much for the detailed reply.

One question. What will the ball park price tag be for porting the runners in the intake?

It sounds like increasing the compression and replacing the pushrods is a "must do" for this engine to make power!! I personally will have to rely on the local machine shop at retail prices for this modification. Am I screwed pricewise?

I feel like I have gotted some VERY constructive advice from this group. I THANK YOU!.

 

All you need to do is measure (when the piston is at TDC)
-the distance between the top of the piston and the deck of the block
-Head gasket PN you have now
-CC size of the head, then go from there.

Bump the compression port that intake and retune I bet youll smile at the results. If you had to shave the heads its cheap and effective

Porting that intake probably 100-200 depending who does it.

 

You have a very good porting shop right south of you. Champion Racing Heads in Palm Coast, FL.

http://www.championgn1.com/contact.html


If you would rather go north give Jerry Killian in Warner Robbins, Ga a call.

http://www.killiansportingservice.com/id5.html

Either of them will be able to take care of porting your LTX intake and milling down your AFR heads.
Will

 

His porting work looks super clean.

 

I read this and Id like to see hp/tq curves alongside afr ratio.

13.2:1 is what produces max tq and is safe for a naturally aspirated motor.

If you see smoke and smell raw gas, then its prob running 11.0:1 or lower afr.

You can pick up a lot of power by optimizing afr.

Also don't forget spark advance. Our motors can require up to 36 degrees full advance(typically by 2600 rpm) to make peak power.

With good premium gas, and your slightly lowered comp ratio maybe there is some more power there too.

I think you need to ask your tuner what the afr's were and what kind of advance is it running

 

The proceedure sounds quick and very effective. Provided I trailer the car to the chosen shop, ask to port the intake, shave the heads and replace using a proper size head gasket, install new push rods (turn-key start to finish), what kind of out of pocket would I be responsible for (including dyno tune)? Ball park please.

This sounds extremely exciting and possibly the key to making the motor "come alive" as enjoyed by some of the very happy owners of truly high performance strokers. "Come alive" in my mind conceivably means a close to 10% gain in torque numbers, (with a tune).

Do the shops referenced above have the capacity to tune the finished product?

You guys are obviously very experienced with the LTX and I genuinely appreciate your suggestions and opinions. I absolutely love being a C4 owner. The styling, and raw feel is a good fit for me (over the new ones, which I like, just not as much) and the persona of being an "underdog" is very appealing. OK.... it's outright fun. I would never talk trash or put down someone elses labor of love, but can there be fun than owning a sleeper?

You guys are truly awesome and I hope to see some of you at the track, strip or cruise-in real soon. I always park with the vettes at cruise-ins

 

Is that true for E10?

 

I would think that you'd need to have a really special cam for that to work well. Let's not forget the DCR. I've ran 12:1 on the street a lot and I'm building a new engine for the Vette and am going to 11:1 for a reason. I want to go on a road trip with no concerns for gas quality and engine stress. I don't want the cam to close the intake so late that it barely idles.

There's probably only 2 percent gain to be had by going to 12:1 from 11:1 and I can live with that disappointment. The difference between 500 and 510 Horsepower isn't going to ruin my day considering I now have some leeway on gas quality.

 

He's talking about air/fuel ratio not compression.

 

Yes he is and it was a late night last night. Maybe I shouldn't post until the cobwebs are gone. Sorry for the misunderstanding.

 

yes i am. thank you for clearing this up STL94LT1 !