l98tpi

This past weekend my L98 bottom end seems to have let go. Not sure what the issue is yet, but 90% positive it is going to be replaced. Would like to get some ideas on what to go with whether 383, 396, or 427?

Going to use my current AFR 195 Comp Port Heads, @ 550/550 112 cam, high flow TPI intake. The goal is quick spool up, reliability and durability up to 6500 rpm. And weight is somewhat a consideration as well.

C409

..... Keeping the TPI intake is going to have the biggest influence on your new build ... stay with a 350 and you'll be closer to your stated goals , particularly the 6500 RPM part ... while any engine will spin up , the tuned port won't make power in that RPM range ........

cv67

383 will tax the best TPI system out there with those heads I wouldnt dream of doing a bigger motor with a LTR setup. 427 with a single plane hell yes. 6500 rpm blasts Id want a forged bottom end

l98tpi

definately forged bottom end. Looks as though I cracked a piston with this failure. And looks like I will be leaning more towards a 383.

LoneStarV

If you go 383 it's gonna need a TPIS mini ram or single plane. I have researched this to death. A TPI set up will choke a 383 or larger engine and defeat the purpose of more cubes more rpm more horsepower. You can make it a bit better with larger runners and base ported etc etc. Call TPIS. They quoted me an complete engine shipped with mini ram on it and tune for your vette that will rip your head off your neck for 9 grand.

GREGGPENN

I don't understand this matchup. Are you thinking of swapping to another intake in the future? Even the best longtube TPI on the board needs to be shifted before 6k rpms.

I don't see why you need the extra durability you're looking for...though I'd still opt for a forged crank (myself) if doing a build again. Mostly that's because I don't "like" Eagle or Scat cast cranks anymore.

Of course, I also opted for AFR spring "upgrades" and wouldn't scoff at the idea of a stud-girdle. Just won't fit on mine though.

I'd do the 396 (or 6" rod 383). Low weight and high torque with your intake.

Pay attention to the windage tray and quench too.

You're running a SR cam, right?

GREGGPENN

l98tpi has done his research and pretty well understands the rpm needs for his application. Take a look at member TA's build before assuming a 383 TPI combo is a "bad" thing. Race a [good] 383 TPI vs a 383 MR on an autocross track too.

If I was doing mine again, I'd look hard at a 396 with a FIRST intake.

LoneStarV

I was referring to the stock TPI with some bigger runners and base. That First is a whole new beast. There's a pretty good write up on the First over on thirdgen. It did well but wasn't a world beater. This article compared several intakes on a 383 and the TPIS came out on top. The stock or stock modified set ups need a lot of massaging. One thing i like about the mini ram is the simplicity of it's design instead of all those parts and gaskets needed for the others. It was the horse power king by a small margin and while it's torque was a bit lower it was a strong flat curve. TPIS is making some monster numbers with the engines they build using their mini ram. Their 396 SB that pours out 555HP and 490TQ aint no slouch.

http://www.tpis.com/pages/396sbc

http://xtremecarzone.com.au/index.php?showtopic=386

cumbercr

Sounds like you are looking for a serious engine combination. I recommend you talk to TPI421VETTE (Jim). He can build whatever you are looking for. See his post on the 421 he is just now finishing.

93 ragtop

Quote:

Originally Posted by l98tpi

Would like to get some ideas on what to go with whether 383, 396, or 427?

.

Here is my advise. Find a good, honest, engine builder. Tell him what you want out of the car and let him pick the parts to be used. That's what I did, and it worked well for me. If you depend on internet opinion, or are swayed by trying to use what you already have, you may regret it in the end, and it may cost more as well. The builder will not have the emotional tie to it that we owners do and will have more actual experience with what works, what don't and why. Just my 2 cents worth.

l98tpi

Sticking with the high flow TPI intake I already have. The only reason I'm looking to the 6500 rpm is because I will run up to it easily. Ther are times where I will enter into a straight and there is not enough straight left to upshift so will stay in current gear and wind the rpms up. I have the rev limited set on 6250 right now and am going to raise it to 6500 with this build. I knew I was on borrowed time with the stock L98 bottom end, just wanted to see how far it could go and it did take some serious abuse. I may still possibly go with a 355, but most likely a 383 to get a little more power.

l98tpi

Jim knows his s**t. If I was closer to him my car would be in his hands. But there are some damn good engine guys around here too with experience building race app engines. Of course they have moved on to the LS stuff, they just have to dig into their archives

cumbercr

Jim has shipped engines all over the country and internationally. You'll never find a more knowledgeable and honest guy.

mcm95403

Just my 2 cents worth - don't overlook the GM Fast Burn heads. There's a lot of technology in them. They're "fast as cast" and good for 500hp as-is. I'm getting stock-type throttle response on my 350 even though the ports are 210cc. The ZZ4 crate with these heads bumps up from 355hp to 385hp. The ZZ383 should go to about 455hp and that's with the mild cam it has.

Just remember that the exhaust ports are LT-1 shape and require headers that fit, and the intake ports of your intake will probably need to be welded to cover the top of the ports, but if you're building a 500 hp engine, you'll be port matching it anyways, so that would be part of that.

l98tpi

Thanks for the input. But, I already have AFR 195 Comp Port 65cc heads, a TPIS ZZ409 cam and TPIS high flow LTR intake. I am going to get the bottom end that will be the most efficient at power production along with being a durable package.

88BlackZ-51

sent u a pm

l98tpi

Ur pm box is full now

5abivt

Dont listen to him he put a 195 head on a 421 !

GREGGPENN

There's definitely nothing simpler to install than a MR. And, on an automatic car -- headed down a straight-line track -- it's the "bees/knees". Problem is there are other types of races, rpms where power is best suited, classes by HP (that mean more torque wins), and stick cars where gear selection might not be as straightforward as you think.

For ANY automatic car, I will always agree that an intake peaking just before your shift point(s) is the way to go. For a stick on the autocross track, it's gets more complicated. That where -- if you've followed l98TPIs posts, you'd understand.

Also, that FIRST isn't a "whole new beast". It's been around for years -- though just recently modified to fit LT cars too.

A link to the comparison would be interesting to see. If you're talking about dyno'd HP number in the TPI Shootout, most of us already know what you mean. In many of those TGO threads, the HSR is consider "the winner". Nothing is black and white.

GREGGPENN

You OUGHT to be able to sell/buy/swap for a FIRST intake without losing any money. You'd gain at least 500 rpms and probably a bit more. For someone running a motor above 6k rpms, it's really the only longtube choice. That precludes the SR...and MR.

Hopefully, you know about "negative" pressure on the rods when you run a TPI beyond it's peak?

Obviously, there are other [HP] considerations for your auto-x class -- that I've no clue about -- but the FIRST is definitely the test longtube TPI for a 383 (or higher). Maybe it wouldn't "hold down" your horsepower enough? Is that a consideration for the 383 too?