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How much can a L98 BLock (C4 1985) handle in build up?

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How much can a L98 BLock (C4 1985) handle in build up?

 
Old 12-17-2018, 07:35 PM
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tdereggi
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Default How much can a L98 BLock (C4 1985) handle in build up?

How much can a 1985 Vette L98 Block handle, if its used as a starting point for a high HP/TQ engine build up?

I recognize that when paired with 1985 stock iron Heads and TPI intake, the bottle neck is the heads and intake.
I recognize that in stock configuration paired with Stock pistons, rods, and cranks, that the pistons are likely the weakest link.
Ive heard anything upward of 450HP is pushing the stock pistons, and detonation becomes a prime concern.

But How tough is the L98 Block itself?
And How tough are the stock Crank and stock Rods? My understanding is the rods are forged.

Is the block a good candidate for 383 stroker upgrade paired with SC?

To do a high HP/TQ build (say 600-700 HP), and staying with stock 350 displacement, Is it enough to just upgrade the pistons?
Or does it really need the rods and crank upgraded to?
If I stayed with stock 350, and SuperCharger config, how much Boost can it take?

Thats really a financial question, cause its much cheaper to just upgrade to forged pistons, but if Crank and rods also were to be done, it would make more sense to go 383 stroke and bore the engine to, which adds up to much much more.

Maybe a better question isnt how much HP or TQ can the L98 handle, cause so many things contribute to final HP/TQ results, included top side of engine. Maybe better asked is, how much boost or compression can the block take safely?

I also recognize whether its a 2 bolt or 4 bolt main matters. To be honest, I forget which my 85 is. My understanding is the 2 bolt mains can actually be made stronger than the 4bolt, because the metal is thicker, it just requires upgraded stronger fasteners. (otherwise it handles less).

Im asking because, I know its probably much easier and cheaper to buy a custom crate engine. But I was considering building it myself for the fun and learning challenge, and starting with one of my early C4 stock engines, thats guaranteed to fit without mods.

My actual plan is to install a Supercharger now on my streetable roadrace car, and then overtime rebuild a second engine to install at a later time. (piston, heads, cam, etc )
Since I will already have the Supercharger on the base engine, Im wondering if a better upgrade path from there, would be to just keep adding more Boost to the 350, after pistons are upgraded, or whether to take on additional expense to go 383 stroker to add to the SC setup.

Im asking all this for planning/road map purposes. This winter, I'm focusing more on building up the drivetrain, brakes, and the SC add. And in the Spring I will be focusing more on improving my driving.

Tom DeReggi
















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Old 12-20-2018, 02:01 AM
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Hi,
please be aware that the 85 L98 had forged pistons in stock form.
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Old 12-20-2018, 04:38 PM
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> "85 has Forged Pistons".

You're the second person that had mentioned that. But are they? Where did/can you get that information confirmed?

Because, straight from the factory 85 Shop manual pg 6A1-1, it states....

"Pistons are made of cast aluminum alloy, using two compression rings and one control ring. Pins are chromium steel and have floating fit in the pistons. They are retained in connecting rods by a press fit. Connecting Rods are made of Forged Steel. "

"Cylinder block made of Cast Iron" ""The Cast Iron Cylinder heads", "The Crankshaft made of cast nodular iron"

Are you saying the manual is wrong, and its not cast aluminum?
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Old 12-22-2018, 12:52 PM
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No way that block will reliably handle 6 or 700hp for long
Id go with an aftermarket block..Dart, Blueprint, and others make a nice 400 block with different options. It hurts the buy in but sure is worth the piece of mind knowing all those other expensive parts inside arent at as much risk.
A 4 bolt Chevy block can only take so much also. THe 400 block has the same dimensions and looks the part of a 350. The torque is amazing.
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Old 02-05-2019, 09:50 PM
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Originally Posted by tdereggi View Post
> "85 has Forged Pistons".

You're the second person that had mentioned that. But are they? Where did/can you get that information confirmed?

Because, straight from the factory 85 Shop manual pg 6A1-1, it states....

"Pistons are made of cast aluminum alloy, using two compression rings and one control ring. Pins are chromium steel and have floating fit in the pistons. They are retained in connecting rods by a press fit. Connecting Rods are made of Forged Steel. "

"Cylinder block made of Cast Iron" ""The Cast Iron Cylinder heads", "The Crankshaft made of cast nodular iron"

Are you saying the manual is wrong, and its not cast aluminum?
it's my understanding L98 heads are Cast ALUMINUM if so, the manual's wrong on that and maybe more.
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Old 02-05-2019, 10:29 PM
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Force induction changes things a little. Studs and aftermarket high strength or steel billet main caps would help keep bottom end in place. 85 is 2 piece RMS SBC so 010 4 bolt block. There are many possibilities it you aren't attached to the original engine and TPI.
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Old 02-05-2019, 10:44 PM
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Originally Posted by jackson View Post
it's my understanding L98 heads are Cast ALUMINUM if so, the manual's wrong on that and maybe more.
They came both cast iron and aluminum. The block is to weak for what you want to do.
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Old 02-05-2019, 11:01 PM
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The 85 heads are iron and terrible. Aluminum heads came first on 86 vert. In 87 they were on all l98s.
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Old 02-06-2019, 12:56 AM
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Originally Posted by jackson View Post
it's my understanding L98 heads are Cast ALUMINUM if so, the manual's wrong on that and maybe more.
actually 85 does have cast iron heads stock. shortly after they switched to aluminum.
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Old 02-06-2019, 01:10 AM
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Originally Posted by cuisinartvette View Post
No way that block will reliably handle 6 or 700hp for long
Id go with an aftermarket block..Dart, Blueprint, and others make a nice 400 block with different options. It hurts the buy in but sure is worth the piece of mind knowing all those other expensive parts inside arent at as much risk.
A 4 bolt Chevy block can only take so much also. THe 400 block has the same dimensions and looks the part of a 350. The torque is amazing.
i guess good suggestion on after market block. I was reading some comparisons of 350 blocks and the dart and world something blocks had much much thicker cylinder walls. not hard to understand why that will help, expecially with high boost pressure. Im thinking I'll likely go that route, plus that will allow me to drive my car while im building the new block. One of the reasons I had asked about my L98 because I was reading how the iron LS blocks were so much stronger than aluminum LS blocks. so I was wondering how much stronger the iron L98 blocks might have been over the L98 and LT1 aluminum blocks. but I guess it doesnt matter cause really i should get a stronger block
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Old 02-06-2019, 01:19 AM
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Originally Posted by Kevova View Post
Force induction changes things a little. Studs and aftermarket high strength or steel billet main caps would help keep bottom end in place. 85 is 2 piece RMS SBC so 010 4 bolt block. There are many possibilities it you aren't attached to the original engine and TPI.
im getting rid of the tpi intake. but staying fuel inj. im not attached to block. Just exploring where I can save bucks and where I cant. I was definately gonna do something with the caps. its still unclear to me whether I got 2 or 4 bolt now. I had thought it was 2. I dont think there is gonna be much 85 left in this 85 by the time im done with it, lol.
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