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**Z Ya Later** · 01-25-2005, 11:20 PM

Dig into the suspension, rear-end and chassis first. You can get away with the stock rear if you're not gonna use slicks, but with that much power I'd hate to blow the rear after all that work. Good set of lower control arms and relocation brackets, panhard rod, torque arm, sub-frame connectors, springs, shocks, strong driveshaft and maybe a shock-tower brace. That'll set you up for making some real power. As far as the motor, if you're sold on NA then I'd stick with that. Unless you're already sold on the GMPP LT4 kit, I'd get the LT4 manifold and a good set of AFR LT4 heads. Cam choice isn't my strong point, but I know there's others here that can help. Good luck with your build.

And welcome to the board

**Injuneer** · 01-26-2005, 09:58 AM

You're not going to get close to 500rwHP with a 383 + LT4 conversion + HOT cam..... more like 460 flywheel HP. You'll need about 575 flywheel HP.

You'll need a healthy rework on the LT4 heads and intake, to push them close to 300cfm on the intake side, and the HOT cam is going to be swallowed up by a 383... it'll feel like the stock cam does in your current engine. You're looking at least a cam in the 24xI/25xE range for 575 flywheel HP.

Just as a point of reference, the LT4 conversion on a 350 is advertised as "425HP".... that is flywheel HP, and requires a number of parts in addition to what's in the kit.... larger throttle body, long tube headers, larger injectors, custom PCM tuning (the 425HP engine dyno setup included a $3,000 aftermarket ECU, but that isn't necessary). All that on a 383 platform might make you another 40HP over the 350ci setup.

**maxracing4** · 01-26-2005, 11:25 AM

LT4 MOD ???

Well, I am not really sold on anything yet. I would consider other options that you guys might have. Originally I had thought about a turbo kit for the car until I found out it was $5000.00 for parts and install by a local performance shop. So, I figured if I am going to spend that kind of money why not do it in the motor. To make a long story shot I am wanting to run high 10's - low 11's. I am going to use some slicks so I am planning on putting a least a set of 3.73 or possiblly even 4.10 gears in the black beast, but who knows I have not quite made up my mind on anything yet that is why I am here talking to you guys. I read about some T/A going high 10s in the Pontiac Perf. Magazine spraying 100 dry & 100 wet shot w/ 3.55 gears, slicks, headers, and a few other suspension mods in and LS1.

Thanks for the welcome guys and I look forward to talking with you and keeping you updated.

**Z Ya Later** · 01-26-2005, 01:19 PM

If you're gonna be runnin' slicks with that much power, then definitely upgrade the rear end. Either a Moser/SLP 12-bolt or a Strange 9" would work, but the Moser/SLP unit will retain the stock ABS if you want it that much lol. As for the LT4 conversion, as Fred said, I'd stay away from the kit and just get the intake from GMPP. AFR LT4 heads would be a better choice.

**maxracing4** · 01-26-2005, 03:00 PM

LT4 MOD

I was thinking the same about starting with the rear. I know I am going to need something to hold that much power assuming I can produce the power 1st. Are you saying that I need to stay away from the 383 kit or just the LT4 kit in itself? I was going to get the LT4 intake and a set of AFR Heads I found w/ 309/230 w/ 700 valve lift, 76cc combustion, 80cc exhaust, 1.6 roller rockers, and ported 100% by AFR. Any thoughts on this combination? I still think I need to start w/ the rear and work my way forward, but I am kind of itching for power if you know what I mean. The stock LT1 just isn't enough. What do you think about swaping the LT1 with a complete LT4 Corvette motor?
Tim

**Z Ya Later** · 01-26-2005, 05:01 PM

What I mean and what I think Fred is also suggesting is to stay away from the LT4 Conversion Kit if that's your power goal. A ported LT4 intake and those AFR heads should do well, I believe. Match that with the 383 kit, a good cam and some long-tubes and you should be pretty close I think. Fred and some others can give you more exact parts and numbers, but that should be a good baseplate. As for the rear, I think the Ford 9" is a little bit more complicated to install and takes away a little more power than the GM 12-bolt. I personally would go with the SLP/Moser 12-bolt, but that's my opinion. Good luck on your build-up...can't wait to see it

**Injuneer** · 01-26-2005, 05:33 PM

I agree.... there are better ways to get to the HP levels you are ultimately looking for. 575 flywheel HP is going to be borderline "street friendly".... the size of the cam is going to make it a handful at low rpm.

I'm also not a big fan of the AFR's. Out of the box, I've seen too many actual flow bench test that indicate they do NOT flow what AFR advertises. The ones you are talking about appear to possibly be one of the 220 or 227cc "race" heads. Good for the track, but with intake runner volumes that large, it isn't going to be street friendly.... not enough velocity at low flow.

A friend of mine had virtually unlimited $$$ and wanted what I view as "unlimited" HP (he ended up at 1,125 flywheel, on an LT1 block 383 w/ Vortech supercharger). He tried the AFR's and didn't like them at all. He got close to 1,000HP with Lingenfelter LT4 CNC's. Then went to a totally reworked (valves moved, angles changed) set of Canfield LT4 heads, to get to the 1,125HP level. I'd estimate he had as least $5,000 in the Canfield heads.

I think you also need to think a little bit about how you are going to use the car. I really can't see more than 400-450rwHP on the street. You just can't hook with a street tire, and you are borderline with drag radials. My setup makes approx 500flywheelHP without the nitrous, and smokes the 315 drag radials on the street.

The approach was to build a street friendly engine that made decent HP, but could be tuned to pass NJ rolling emissions. That's how I ended up with "only" 500HP. Then, for "fun", it was setup with a 125-shot 1st stage of nitrous for the street..... ~625 flywheelHP (it ran 11.1 @ 127.7MPH at the track), and a second stage of 150HP for the track (775 flywheel HP). Yet to run it with the full (what is now) 300-shot out fo the hole at the track. Point is, even the 125-shot was sort of useless on the street..... instant tire smoke. I also drove the 30th SS I mentioned above, at the 1,000HP level, and there was absolutely nothing you could do with it to make it useable.... half throttle and it was a lost cause. Maybe OK from a 50mph roll, but how often do you really want to do 50->140mph blasts on the street (bring clean underwear when you do

)?

As far as the rear axle, Strange and Moser make 12-bolts. Moser and Currie make the 9-inch setups.

**maxracing4** · 01-26-2005, 06:31 PM

LT4 MOD

Wow, that is freaken awesome Fred. I do want it to still be street friendly so I am probably go to end up with some what similar off your set up. Like I said all I am looking for is something to go high 10s or low 11s. Is that what you ran in your 6spd? I am definitley forgetting the conversion kit. The AFR heads are the 227cc package. So, based on what what you guys are telling me I need to stick with something more of at 185 flow rate or so. Now, keep in mind that I might would consider just installing a turbo on the lt1 setup although that is not really what I want to do. I would enjoy working the motor 1st. You guys are great source of knowledge and I will be back here for more info. For now I'm out talk to you tomorrow.

**Injuneer** · 01-26-2005, 11:50 PM

A 185cc inlet runner volume would be too small. The LT4 heads are 195 out of the box. I think mine ended up around 208-210cc after porting.

I never ran my car with nitrous at the track when it was a 6-speed. I had a hard time breaking into the 11's on straight motor. My shifting was just too poor, and I cringed every time I dropped the clutch at 5,000rpm. With the TH400 its run 11.5@117 on straight motor.

**maxracing4** · 01-28-2005, 09:16 AM

Prospect LT4 MOD

Well, I wanted to see what the T/A would do so I took it to the strip and ran a 13.97 @ 99.8 MPH in the 1/4 Coastal Plains Raceway, Jacksonville, N.C., .986 reaction spinning the whole way through 1st and 2nd. Keep in mind this is all stock except the Flowmaster Muffler and it has a rebuilt LT1 30000 miles ago. I barely hit the top of 4th gear at the end of the 1/4, not like that is a concern. I think next time I'll try leaving at about 2500 to 3000 instead of 4500. Ha, Ha, Ha, it was fun though!!! I hope to have some street slicks before the next run, however I am not going to run slicks with the stock 3.23 rearend (I believe that is what it has or is it 3.42 do you know?) unless I want to be towing my car home I'm sure. Well guys I think I have made up my mind. I am going to start with the small stuff 1st, Moroso Cold Air intake, 58MM TB, Hooker Long tubes, Borla Exhaust (I'll take the flowmaster muffler off), Hurst short throw shifter, MAF, Air Foil, hypertech programmer, then maybe some NOS. Do you know if the LT4 intake will bolt up to the LT1 heads - they should right or am I wrong?

Oh, yeh guys I read something on here earlier about import cars and hondas or something. Guess what my license plate is.........VTECTHS!......My brother has a hatchback civic, built B16 Turboed out running 10-12lbs, he has about 18K in the car and boy does it fly. I know he would put me in the wind in a heart beat. That's why I haven't raced him yet. YET!!!! That is my goal just to make sure I don't get my head handed to me by an import. And one other thing I don't think I have told you about myself is that my father runs a Ford Mustang in Pro Stock class in the IHRA. I don't know if you have heard of the Rising Storm Mustang it's a purple color on the hood with a mix of lighting bolts and storming horses. If you want to watch it some time I think the IHRA comes on the speed channel here on Saturday and Sunday. Check it out it is some pretty wild stuff. 212mph @ 6.46 in the 1/4 - talk about needing a spare set underwear!!! This was testing a few weeks ago and next year the IHRA is allowing us to shorten the wing by 2" and narrow it by 2" which is going to make the car have less down force therefore going faster. Oh, it will still make for a good holeshot and reaction, but will go even faster.

Talk to you soon!!!

Tim

**Injuneer** · 01-28-2005, 09:39 AM

All T56's from 1994 and newer left the factory with 3.42 rear axle.

I would "hold up" on the 58mm throttle body. First, you need to have the holes in the intake manifold enlarged (They are only 52mm). And I have seen at least one dyno test on a relatively stock LT1 that lost 10HP with the 58mm TB.

Consider the Pro 5.0 short throw shifter.

Not sure what you mean by "MAF", but the best advice is "leave it alone"... there is nothing to be gained by altering the stock one, and the aftermarkets like the Granatelli are junk.

The Hypertech is only useful for altering the PCM when you change rear axle ratio, want to raise the rev limiter, remove the top speed limiter, etc. The "power programming" is pretty much useless. Probably the best feature performance-wise is the ability to go to a 160degF thermostat and reset the fan on/off temperatures lower. A better alternative is to go for one of the "mail order" tunes from one of the shops with a good reputation. They can do everything that the HPP can do, they can also "program out" things like EGR, AIR and after-cat O2 sensors (generally required with your long tubes), and they can lean out the overy-rich power enrichment (PE) mode target A/F ratio and net you a quick and honest 15HP. HPP can't do that.

The LT4 intake will NOT bolt up to the LT1 heads, and there is no benefit in doing it. There is an interference between the LT4 intake and the valve cover rail on the LT1 heads. One or the other would need to be machined for clearance. But its pointless, because as-cast by the factory, the LT4 intake runners/ports are no different than the LT1 intake. While the LT4 heads have 0.100" taller intake runners, the LT4 intake manifold does not... it just has more metal cast at the top of the runners (hence the interference) so that anyone wanting to improve their LT4 performance can open up the LT4 intake to match the LT4 heads. Sounds dumb, but that's the way GM did it.

You want to "bypass" the coolant that normally flows through the throttle body, alledgedly to prevent "blade icing".... that's good for a quick, and dyno proven 6HP.

Hint.... its N2O, not NOS.... unless you are looking specifically at the NOS brand.

**maxracing4** · 01-28-2005, 01:33 PM

LT4? MOD

I'm not quite sure what you mean by "mail order" tunes? Please Explain. In your talk about the LT4/LT1 Intake and heads I am getting the impression that you are saying don't even worry with the LT4 setup being the heads and the intake or are you saying get the intake and a set of better heads to match the intake? All I really want is to get the most horsepower for the easiest, quickest, and least expensive way I can, but I want to do it right the 1st time. That's why I am here doing this versus going out and buying a whole bunch of junk that doesn't help me like the 58mm TB you were talking about. That helps me to know these things. Although, I have been around racing motors for about the past 8 years I still don't know that much about anything. So, I said that to say this any information I can get here is better than nothing at all. Give me your opinion on where and what you think I need to start with 1st. Throw the 500hp goal out the window for now and lets talk about raw power and putting to the ground. What do I need to do???

Thanks Tim

**Injuneer** · 01-28-2005, 01:55 PM

There are 5 ways to "program" your PCM.

1 - A module like the Jet that plugs into your PCM or ALDL and alters some of the parameters thru external processing. I'd rated this 1 (low) on a scale of 1 - 5.

2 - A "programmer" like the Hypertech that loads off-the-shelf program modifications into your PCM flash memory, and allows you to alter some variable - e.g. rear axle ratio, tire diameter, fan on/off temps, etc. - and can load a "canned" performance tune. For the OBD-II cars, the Hypertech also has the capability to insert a "module" containing a custom program prepared by Hypertech for your specific mods. Id give this 2 out of 5.

3 - Send your PCM to a "mail order" tuner.... Ed Wright at FastChips is an example, pcmforless, MadZ28 are others. They tune your PCM based on your specific modifications, but they never see your car, so it all comes down to the accuracy of the dat you are able to give them, and the liklihood that they have ever seen that specific combination of mods before. I believe Ed Wright and Ion from pcmforless will tune your car on a dyno if you want, but you have to take your car to Oklahoma (Wright) or PA. You don't even have to send them your PCM.... they can preload the program into a used PCM that they stock, charge you for the core, and you send them your stock PCM back and get the core charge back = no "down time". They can also send you a flash file that you can load in your own PCM if you have the right programming software and an interface cable (see "4" below). These guys will charge $200-300 for a full custom tune, maybe 1/2 that for simple tweeks to a stock setup. And, they will generally do periodic updates when you do more mods, for a minimal charge. I'll rate this 3 to 4 out of 5, with the possibility of getting to 5 out of 5 for a real dyno tune.

4 - Program it yourself. Get the correct software for your OBD-II PCM from carputing.com It's called LT1_Edit. Get an interface cable from AKM Electronics. Load up your laptop, connect and start programming. Obviously, there is a learning curve for this. There are databases of existing "tunes" for various combinations of mods, and you might get lucky and find one to use as a starting point. I believe TunerCat is also working on an OBD-II version of their tuning software. The results of this approach can be anywhere from 2 out of 5 to 5 out of 5 if you have access to a dyno, and know what you are doing.

5 - Take the car to a shop that has the programming software, a dyno and knows how to tune. This is the best approach for more radical normally aspirated setup, nitrous or forced induction. Obviously depends on how good the tuner is, but it should rate 5 out of 5.

There is also the possibility of running aftermarket ECU's - FAST, Accel/DFI, MoTeC, Electromotive.... a new unit from Big Stuff that looks killer. But this should only be needed for the most exotic nitrous and forced induction setups. Cost ranges from $1,500 to $5,000..... or more if you get all the options on a MoTeC for example - active suspension, traction control, ground speed control, telemetry, full digital dash, 100-channel data logging, dual wide-band closed loop control, steering wheel with integrated dash and control buttons ($3,000 just for that), etc.

I have a MoTeC M48Pro that I picked up used for about 1/2-price. Makes tuning and running a 300-shot of nitrous a little easier.

**maxracing4** · 01-28-2005, 02:27 PM

LT4 MOD

Well, sounds like you know what you're doing at least. So, I guess I will just stick to the local tuner because he is about 10 miles up the road. He has tuned a supercharged mustang of a friend I know and seems to going well from what he has told me. Thanks for the explaination. I'm still planning on doing a little street driving, but I also want it to be quick on the strip. So, where in your opinion do you think I need to start? Should I leave the LT4 setup alone? Possiblly just change my springs and valves and a possible cam?

Tim

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1997 T/A 6spd LT4 MOD

1997 T/A 6spd LT4 MOD

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