questions about a engine build

[94taproject]

ok everyone i am a new member but am a very experienced mechanic. i picked up a 94 ta that is in really good shape but the motor had blew the head gasket or gaskets. so i will be dropping the whole subframe down with the engine and trans. and i am going to strip the motor down because it has been sitting for two years and im worried about rust in the cylinders from the gaskets. so after all the work of pulling the motor apart to check it out im not going to put a stock motor back in lol. i want to find out what heads people are running with the lt1 motors and getting good numbers out of them. mine might be warped from overheating. i know for sure i will be doing a 383 stroker bottom end with a 10.5 to 1 comp ratio. and i want to run a big cam and probably a elderbrock lt4 intake. i will not be starting working on it till after the first of the year so i have plenty of time to figure things out and im not going to rush and cheap out on anything. i am shooting for 500 hp so im interested in hearing some setups people are running and what numbers there getting and what works well and not a nightmare. one other question is i want to know if people have removed there cats and how it works. and what are a decent header long tube or shorty.

[KW Baraka]

Originally Posted by 94taproject

.......i want to find out what heads people are running with the lt1 motors.......i know for sure i will be doing a 383 stroker bottom end with a 10.5 to 1 comp ratio. and i want to run a big cam and probably a elderbrock lt4 intake.......i am shooting for 500 hp so im interested in hearing some setups people are running and what numbers there getting and what works well......i want to know if people have removed there cats and how it works. and what are a decent header long tube or shorty.

1. Heads = Lloyd Elliot or Advanced Induction ....... click the links.

2. 10.5:1 compression ration with a "big cam" sounds like a mistake waiting to happen. My question is....."How Big Of A Cam"??? And 10.5:1 CR is a bit low, IMHO.

3. An LT4 intake is NOT an upgrade over a LT1 intake. The only reason to use a LT4 intake is because you're gonna use LT4 heads. PERIOD!!

4. 500 HP? Is this goal from the engine.....or at the wheels? If from the engine.....a couple of us have done that. If 500 HP at the wheels, my question is......"How Big Is Your Budget"?

Do searches on this forum and on Google for "Engine Quench" and "Dynamic Compression Ratio". You'll learn a lot !

KW

[justinkp]

very experienced mechanic? asking about cats?
I'm confused.

[94taproject]

The reason I asked about the cats is I don't know how easly they can be tuned out from the computer with the egr system this will be the first computer controlled performance motor I will build and I'm not sure what they can do with a obd1 system. I have messed a lot with carb motors mostly mopars and its simple just jets and timing changes to tune them. And as far as the compression ratio I don't want to run into problems with pinging from bad fuel. And there should be no problem getting around 500 at the fly my mopar smallblock is pushing 418hp and 473tq at the wheels and I'm only running 10.0:1 ratio the trick is I'm running Indy heads that i had work done to them. And the cam .580 /.578--.236 / .242 HR110 it is a roller camshaft. I don't know a lot about Chevys but I know they can make great power as far as budget heads I'm willing to go probably 3k and the intake I read some article off of google and it said the runners were bigger on the elderbrock intake that is better for aftermarket heads. So would it be better to stick with the stocker?

[KW Baraka]

Originally Posted by 94taproject

The reason I asked about the cats is I don't know how easly they can be tuned out from the computer with the egr system this will be the first computer controlled performance motor I will build and I'm not sure what they can do with a obd1 system. I have messed a lot with carb motors mostly mopars and its simple just jets and timing changes to tune them. And as far as the compression ratio I don't want to run into problems with pinging from bad fuel. And there should be no problem getting around 500 at the fly my mopar smallblock is pushing 418hp and 473tq at the wheels and I'm only running 10.0:1 ratio the trick is I'm running Indy heads that i had work done to them. And the cam .580 /.578--.236 / .242 HR110 it is a roller camshaft. I don't know a lot about Chevys but I know they can make great power as far as budget heads I'm willing to go probably 3k and the intake I read some article off of google and it said the runners were bigger on the elderbrock intake that is better for aftermarket heads. So would it be better to stick with the stocker?

First off, understand that the LT1/LT4 engines are reverse flow; the coolent leaves the radiator and flows through the heads FIRST.....and then to the engine. So running higher compression (about 1:1 to 1.3:1 more) with these engines is not much of a risk. A lot of guys (myself included) run or have ran about 12:1 compression with their LT1's (daily drivers)......on pump gas......with no issues !

The 'secret' to running higher compression though, is to have an optimal engine quench and running in an optimal dynamic compression ratio range. That's why you'll want to read up on those two items.



If you run a 236* intake cam, with good quench, you can run 12:1 CR pretty easily on pump gas. With good heads, 500HP and the crank will be achieved fairly easily.



Edelbrock sells a LT1 AND a LT4 intake with the longer runners; they're virtually identcal but they are specific to the LT1 and LT4 heads respectively. You could buy a Edlebrock LT1 intake.....but it's pretty common knowledge in LT1 circles that they only add about 5 HP (if that), and all at the top of the RPM range. A better option would be to have the stock intake ported by one of the companies I originally recommended to you.



$3k won't cut it. Hell.....you'll spend half that (at least) on a good heads/cam set-up . After that, the rest of that 3K will be sucked up by 'bolt-on' modifications like throttle body, upgraded valve train, new or freshened fuel injectors, headers, exhaust, etc.

Then.....you'll also want to make sure that other components are new or freshened up.
No sense modding your engine and keeping old and worn accessories on it.
Oh yeah.....PCM recalibration is a must when modding your LT1.

For the power you want.....and for it to be streetable and reliable, think more in line with $8-$10K.


Welcome to the realm of computerized, fuel injected hotrodding .

KW

[cocobolo95]

When you do all that KW has recommended and are ready for a tune. You can use tunercat's obd1 tuner and a cable that connects car's dlc and laptop's usb port. Available at TunerCat Cables also available at www.aldlcable.com
and www.moates.net
your 94 has a re flashable pcm that can be tuned right in the car, using tunercat's obd1 tuner and a cable to your laptop. You will need to buy the $EE definition file to read your 94 pcm. Tunercat comes with a definition file to read a 80's cutlass.

Also while at tunercat, download the trial version of DataMaster. It's a good scanning and data logging program. Trial good for 20 free scans and unlimited playback of scan files.

Another program for scanning is freescan, as mame implies, it's free forever. Get at www.andywhittaker.com

[Dynamic396]

Yes, you have a bit of $$$ to spend to pull this off, but it will be fun! I'm just a shade over $10K, and it still looks like this:





Some notes from the "vault":

Like KW said, 10.5:1 is WAY too low on an LT1/LT4 with 236 degrees on the intake side. I'd go 11.5:1 - minimum... And, yes, by all means, research and understand quench distance and dynamic compression ratio. These are key elements in a successful build.

You're going to want a fully forged bottom end. No cast cranks or hypereutectic pistons! I, personally, would use 6" rods in your application.

The camshaft you're looking at should work well. I, personally, would like to see more lift on the exhaust side, but that will ultimately depend upon which heads you use. If you're looking at using stock heads, it will take some pretty extensive porting by somebody with some experience to use all of the lift that that camshaft provides. I am very, VERY partial to AFR heads. I see guys spend big $$$ on ported stock heads all the time, and I just don't understand it. They usually end up within a few hundred bucks of a set of AFR's, which will outflow pretty much anything in the class.

The Edelbrock intakes have runners that are 1/4" longer than stock. Not a big factor... I am using it because the heads am running have LT4 sized intake ports, which are not compatible with the stock LT1 manifold. They are a very nice piece, but not a huge performance upgrade.

As far as $$$ goes, you're buying into a very, VERY fun and rewarding project, but also one where $3K will perhaps buy you the rotating assembly, the machine work and MAYBE some valvetrain parts. Building a reliable setup will definitely cost you some dough...

There are some VERY experienced builders on here, so feel free to ask questions. That's what we're here for...!

[94taproject]

When I said 3k I ment just on the heads but the 3 is factoring the rockers springs and valves oh I know to well about how all the other things add up. I knew that it flows backwards but I didn't realize that you could get away with that kind of compression in these motors

[KW Baraka]

Originally Posted by 94taproject

When I said 3k I ment just on the heads......

Oh.....OK .

Originally Posted by 94taproject

.......I knew that it flows backwards but I didn't realize that you could get away with that kind of compression in these motors

The reverse flow was for the purpose of being able to bump up that CR. A very nice upgrade over the Gen-1 small block!

KW

[Dynamic396]

Yes, the reverse flow cooling system is a HUGE benefit on the Gen 2 small blocks. Take advantage of it!

If you've truly got $3K to spend on heads, then you're in great shape! You should be able to set yourself up quite well with heads and a large portion of the rest of the top end with that kind of budget.

If I were you (opinions may vary...but I've already expressed my bias), I'd order a set of AFR 195 heads (PN 1031), which will come with decent springs and titanium retainers. These heads have 2.02"/1.60" valves (you can upgrade to 2.05" intakes) and will run unbelievably well on your 383 with that "size" of camshaft. Have them ship them with 7/16" rocker studs instead of the standard 3/8", though. Depending upon camshaft specifics, you may want to upgrade the springs, too. You can also have them machine them with any chamber size you want from 55-65 cc's.

My advice would be to plan out your bottom end specifics in specific detail and then nail down your camshaft specs. Then, either sit down with a good DCR (dynamic compression ratio) calculator yourself, or have someone help you with it, and dial in the specs for the top end (deck height, head gasket, chamber volume, etc.). It's not rocket science, but it is incredibly important and paying close attention here will make a decent setup into a great one. I'm more than willing to help and I'm sure KW (and others) will as well. Just ask...!

[95 Firehawk]

Originally Posted by 94taproject

The reason I asked about the cats is I don't know how easly they can be tuned out from the computer with the egr system

There's no real reason to delete the cats. You will get minimal gain from it. If you choose to do so, there's no tuning required for a '94; the PCM doesn't even know they're there.

Originally Posted by Dynamic396

If I were you (opinions may vary...but I've already expressed my bias), I'd order a set of AFR 195 heads (PN 1031), which will come with decent springs and titanium retainers.

Those heads were used by GM high-tech performance in a head comparison and made 516hp/478tq using an xfi280 (230/236 .576/.570) cam on a 383, which puts you right where you want to be. They also offer the same head in a competition ported, full CNC version (PN 1039) which flows over 300cfm, and comes with upgraded springs, valves, and I believe 7/16 studs too.