Mike1234

iTrader: (4)

Okay... "stoopid noob" question. I've search for hours via Google and here on LS1Tech.

I'm old school (Gen1) and I know very little about the newer engines.

I made a rash purchase today... bought an early 90's L98 long block (from a Corvette) thinking it was an early LT1... I didn't know the LT1 has the dizzy up front. I wanted a bolt-in hi-po solution for my 1974 Datsun Z-car... just a fun, light-weight street rocket.

Please tell me if I understand my findings correctly.

(1) One of the the L98's short-falls is the intake design, right? How much HP can I gain by going with a 4 bbl carb and a low rise dual plane combo like an Edelbrock Performer EPS or RPM and a vacuum secondary street carb like a Edelbrock 650?

(2) Another issue is that the head intake ports are tiny... inhibiting air flow. Will I EVER get decent performance from this engine without spending a fortune on parts, i.e. new heads and cam? Will these heads limit me to 4500 RPM or so?

Again... this is not a race car... just a fun driver that I want to shame most Mustangs with I would like to run in the mid 11's (max) in the 1/4 mile. I want a (theoretical) all-out top-end speed of at least 140. I have several differential ratios to choose from (3.15:1 - 3.90:1) and I'll probably install a TH350 unless I can find a good 200R4 for a decent price. Car will weigh approximately 2400 pounds with fuel and driver.

Sorry for the verbose post... just trying to answer most questions before they come up.

Thanks!!
P.S. Nitrous is a possible solution but will spray lots of methanol to keep things cool and avoid detonation.

EDIT... Here's the car, BTW... just wanted you guys to knows this ain't no rice ride

383astro

Did you buy the whole motor or just the TPI intake setup? From what I have heard those L98 Aluminum Heads make some good lower end torque due to high velocity. I actually had a 78 280z with a TPI 305 with a single non intercooled turbo. Motor was out of a 85 Iroc and had 160000 miles on it when I put it in. I added the older rajay turbo to it and did a few other mods to get it to run right (Injectors, MSD btm, etc) And had a shop tune it. This was 6 years ago and I ran a 11.16 @ 134 with a horrible 60 ft. The car had I believe 3.54 gears in it. It was an auto. It had a 700r4 out of a cop car in it. I made one run with turbo and a 150 shot of nitrous and slicks but broke the tranny on the line.

Mike1234

iTrader: (4)

Thanks 383. This is just the long block with aluminum heads and no TPI components... no induction system of any kind. The seller says it has only 32K miles on it... and it does look quite clean.

You're right. The stock L98 heads should make great low-end torque but I don't want the motor to gasp for air at 5500 RPM. Also... there are few options for exhaust headers that will fit an SBC mounted in a Z-car. Most of these are shorty types (high RPM) which is a total mismatch for the small intake runners on these heads. I would need very long headers to match them.

BTW, I don't want to turbo or supercharge this engine. An occasional 150 shot of nitrous isn't out of the equation though.

I didn't pay much for this motor but I really don't want to have to resell it?

Formula350

iTrader: (3)

1) Sort of. They are torque MONSTERS, but they stop making power around 5300RPM. You can probably squeeze out 5700 with some good porting and what not. I've ran a TPI car before, and let me tell you I loved it. I wouldn't goto a carb setup. I should still have the tune file I made for it (assuming yours is MAP and not MAF (89-92 = MAP)), and if so its all yours. That's only really good for a stock car running 24# injectors, 58mm TB, ported plenum and exhaust.

2) Heads can get ported, and you won't get anywhere with leaving them stock, like all cars. Can you make 11s with those heads? I don't know. Since it was a Vette motor, it'll have Alu heads, which is a huge plus, and from there you should be able to do fairly well. What the limit is, I don't know, you'd have to talk to some of the big name porters to get a good answer. I know Lloyd Elliot frequents here, someone might be able to PM you his name and you can ask him.

Top end driving or top end 1/4? My Firebird with 3.23's would do 130 on just what I mentioned above for the chip. So after work has been done (some head and intake porting, cam, etc) you'll be fine. Will you do 11s? I don't know. I would ask 87__TA what he did to his L98 to make 10s. Will you beat Mustangs? W/o a problem! I never lost to a single (non Cobra or the like) Stang in mine, 4.6 or 5.0. That's in a 3300lb Firebird, not your light weight Z The stock L98 in a Firebird ran around 14.7 in the 1/4, so I can see you easily hitting 13s on a stock motor. Now, will you be able to do 11s with SPRAY, probably. I don't know how low into 11s, but I can see 11s with out spending a fortune. I don't think you'll need methanol either, or very little if you do. I'd also rather see you run a 200R4 built up than a TH350, simply because OD is a sweet thing to have with a TPI. You'll get nice cruising gas mileage with it. A local guy built a 200R4 for a handicapped guy with a VERY high powered Grand National. I think he ran 9s with it.

You might be happy you went with the L98 instead of the LT1 simply because you don't run an Opti And TPiS (A sponsor here) makes a Mini Ram based off the LT1 intake for the L98s. Holley makes a Mini Ram too, but it's fairly different.

You won't be disappointed with the TPI

Formula350

iTrader: (3)

It's not the heads that make the torque, it's the intake and it's long runner design.

I didn't know you didn't have the intake setup. I'd def go with the Mini Ram I mentioned then, since you need it all anyways. If I had the upper plenum and ECM for this MAF setup I have, I'd sell you it. Which, I still can sell you it, but you'd need the ECM, MAF, upper plenum, injectors and throttle body. Which, basically is what you'd still need for a Mini Ram + the fuel rails, which I have.

Mike1234

iTrader: (4)

Thanks Formula350.

This engine has no induction system at all. And no ECU, etc. It's just the short block and heads.

I really don't want to get all the TPI stuff. I'm going carb(s).

Regarding a port job... before I did that I'd probably just buy some new 195 CC heads. I would worry about chasing my own tail, so-to-speak, trying to make these heads do what they were never meant to do. I was hoping these would be okay as-is but I have a feeling that I'm in Dream Land... felt that way the moment I saw those specs.

I didn't want to buy a new cam either. New heads and a roller cam will put me way past my budget on this project.

I'm feeling very stoopid right now.

I chose alcohol as the added fuel for nitrous due to its huge octane rating and extreme cooling abilities. Even race fuel can't beat it for that purpose. I'm just paranoid, I guess. I don't want to melt or shatter a piston.

I agree that the 200R4 is a better transmission choice but those built to take 400 HP and 500 pound-feet of torque are pricey, aren't they? If I could find one I could afford that would be great

I'll probably stick with a low rise intake. I think it's a better match for the heads. Also, the car has a fake Ferrari body and I don't want to modify the hood to accomodate the intake. I don't know about matching the cam though... I don't know the specs.

Mike1234

iTrader: (4)

Absolutely true about long intake runners making low-end torque. But the heads play a roll in that too. A 180cc head (intake size) will have much better low-end torque and much less high RPM ability than a 215cc head. If I remember correctly what I read earlier... somewhere online, the stock aluminum L98 heads have 140cc or so? That really concerns me regarding RPM limitation.

Mike1234

iTrader: (4)

Formula350... Thanks for your offer regarding the tuning file. I'm sure I'll go with carb(s) though.

Regarding speed... I meant an all-out top-end speed of at least 140... and a quarter ET in the 11's (max) at whatever MPH.

Okay... clarified my original post

Formula350

iTrader: (3)

No prob. BTW, the L98 is still GenI I'd still stick with the EFI though heh.

Mike1234

iTrader: (4)

I assumed it was a Gen2 because I saw the roller cam/lifters

Formula350

iTrader: (3)

Roller lifters have been around for many years, just like aluminum blocks. You CAN however, run an LT1 cam in that motor. They're more centered around FI though, so I don't know how will they'd work with a carb. If I recall, my friend had a 400 with a TBI cam and it didn't run very well carbed. So if that IS the case, you might want to look into getting a roller carb cam.

1bdbrd

iTrader: (12)

Honestly I would wait to put the motor in if you can and build a good budget topend setup. Get an lt1 intake and send it to www.lt1intake.com and they will machine it to fit a Gen I SBC and will provide you more than enough intake for what you will need. Then go to ebay and pick up a set of the patriot performance SBC heads. Its around 800 bones for an assembled set of aluminum heads which is a very good deal. Then have a custom cam ground for the heads and you will be golden.

You wont ever get decent performance out of those heads nor that intake and you dont need the low end torque that engine makes. Neither do fbodies for that matter.

96lt1m6

iTrader: (31)

ok it is obvious you want to put a carb on this engine,very simple this set up is similar to the zz4 crate motor that gm sells that is sold as a carb motor
4 bolt block
good crank
cast pistons instead of the hyperutectics
i would pull the cam out,get the zz4 cam or more, get the heads ported,add 2.00 1.56,good springs,7/16arp rocker studs,1.6 roller rockers,air-gap or victor jr.,holley 750..since you would be in the motor get the rods resized w/arp bolts.
me personally i would buy the holley stealthram,24-30lb inj.,58mm tb,painless Speed Density harness,730pcm www.stealthram.com

AF cop

The heads should be a 113 casting (last 3 digits)
If they are then they are the exact same head as on the ZZ4. Good enough for over 350hp. Guys over on corvetteforum are making over 300rwhp with those heads and running 11s with them in C4 vettes. You should have no problem with them with a mild port job. They dont like cams over 550 lift though no matter how much porting you do.

1bdbrd

iTrader: (12)

But see, the problem you run into by working over the stock heads is that you are now in the same price range as a set of aftermarket heads that will make much more power. Thats why I personally dont see the point of working over the stock heads unless you do 90% of the work yourself.

Mike1234

iTrader: (4)

Arrg... my ingorance robs my wallet again.

Mike1234

iTrader: (4)

That must be $2K++... OUCH!! I could have bought low mile LT1 complete setup AND other goodies for that

Mike1234

iTrader: (4)

So this would cost (what) $1.2-1.4K plus the induction system... whatever that may be?

If I had only known what the heck I was doing

Mike1234

iTrader: (4)

Okay... a mild port job will cost... $400-600, right?

I'm looking for 300+ RW HP and 400+ RW Torque. I want a B-R-O-A-D torque band. Will the "stock" cam, a mild port job and a 150 shot of nitrous get me there?

Mike1234

iTrader: (4)

I can't do the porting myself. New assembled heads will cost $800++. Will the stock cam take advantage of the better air flow... my guess is no. So... heads and cam will cost $1.3-1.4K.

And I thought I found a great deal