GrandeDave

I'm kicking tires on a C4, Ideally 87-91 Convertible, L98, Automatic.
Anyway, quite a few seem to have recent head work done. "Heads rebuilt"
Is there a reason why this is?
Is this and advantage or should I question why?
Thanks in advance.
Newbie here...
GrandeDave

kimmer

Any reason you don't want a LT-1. You start off with 50hp more.

zr1fred

The reason is aluminum heads, and iron block. The two metals expand and contract at different rates causing scrubbing of the head gaskets. To minimize this, they went to reverse cooling in 1992 in the LT-1's. The heads don't need to be rebuilt, they are good for over 200k, the gaskets aren't. Shops like to push the "rebuilt" heads though, more money for them. It starts out as overheating, and gets worse. Unrepaired it will eventually result in antifreeze in the oil, or cracked heads. Both potentially very expensive.

bangbgC6

The early L98's equipped with Aluminum heads were(are) infamous for the head gaskets walking/ moving even when installed correctly and the heads torqued to the correct spec.

The GM engineers struggled with the different expansion properties of cast iron vs. aluminum when they put aluminum heads on the L98 in 1986. Over the 10's of thousands of heat cycles in normal use the gasket shifts far enough out of position to the head and it won't seal correctly anymore as it is essentially a blown gasket and needs to be replaced. If you have the heads off you may as well clean them up and maybe port and polish, though the performance gains are minimal considering the limited breathing capabilities of the stock L98 intake.

GrandeDave

From forums here, it seems like the L98 is simpler. I plan on turning as much wrenches as possible. Not a mechanic but mechanically inclined.


GrandDave

zr1fred

Ah, no......

cv67

Lt1 easier to work on in every aspect except
for that wacky opti/waterpump design that one was someones bad brainfart.

Cliff Harris

The LT1 has the potential for a LOT more horsepower than the L98. Maybe I should say it's EASIER to get a lot more horsepower out of an LT1.

Mike 92LX

???
They both offer the same amount of performance potential. Nothing wrong with an L98

KYC4

The LT1 is a terrific motor...plagued by one of the most ignorant design flaws of any motor made in the last 50 years...the Opti-Spark. Unreliable, tempermental and a PITA to replace, the Opti is a major headache. This coming from someone who has owned a few and has an LT1 sitting in his wife's '85 TA. Fun motor and killer power...plus it's a blast when you suck the doors off an LS1. They don't see you coming. But Lord have mercy the O-S is not worth the hassle IMHO.

L98s have their own issues. Gasket leaks, limited power potential (as they come) are right at the top. But they are a blast to drive and with some smart bolt-ons and such can surprise folks.

Both have drawbacks and both have pluses. I suggest driving both first and see what you like. Then research them both and go from there. The biggest issue you'll face with LT1s are that they are a 'bastard' engine and the aftermarket is slowly drying up. TPI stuff, while pricey, is widely available.

My 2 cents,

Lee

eutu1984

My 90 has over 170k on it and as far as i can tell the heads have never been off. I think the early aluminum heads were called 120's had problems but the later L98 heads the 113's fixed some of the issues with head gaskets, maybe someone will chime in.

SunCr

GM's explanation for 113 failures (and there were many - it's how I found this place over 10 years ago) was mis-positioned intake gaskets that resulted in leaks that resulted in galvanic corrosion that ate up the gasket. Almost always at #7 and a great many near the end of the original 3/36 warranty which some Dealers denied. A few brave souls then sued GM and they redesigned the 113 with counterbores at the front and rear intake gasket mounts. Those bores accepted gaskets fitted with retainers which then maintained perfect alignment of the gasket during assembly. Only the '91 received that modification, but it's on the ZZ4 (which uses 113 heads) and current production 113's from GM Performance Parts. The good news is that it did occur at fairly low miles with complete failure at around 50,000. The bad news is that the acidic mix weeping into the cylinder often wore a groove into the deck of the block meaning a correct repair required a new block which not everyone did or does and you're forever replacing head gaskets. Clues are yucky looking coolant within months of a coolant change, plugged up heater cores, excessive coolant temps and a Block Learn showing a Lean burn. Compression on motors with a weeping gasket is usually normal. Check for a plug that's cleaner than the rest and for rust on the threads or do a leakdown test - particularly if you're purchasing a low mileage example.

ch@0s

My 86 and 91 both had issues the 86 went at 50K. Its not just a Chevy or Corvette problem it happens with time on many Aluminum head engines.

Tom400CFI

The LT1 and the L98 both offer the same amount of performance potential? How do you figure that? By the time they're "even", you've spent $1k on an intake for the L98, and it's not an L98 anymore.

ch@0s

the TPI is a big hurdle.

ghoastrider1

L-98 heads just arnt much better than the old fuelie heads. A set of cheap vortec heads flow much better, make more tourque and hp. but they arnt alum. Seems the vale seals don't last much over 100k miles either on the stock heads..

Mike 92LX

Sure they do. Reread what I wrote. So if I if stick a TPIS miniram or LT1 intake on an L98 its not an L98 anymore??? LMAO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!

Like I said-they both offer the same potential. In fact you have more head choices with the L98. Nothing wrong with either and with stock cubes they offer the same potential. Optispark problem is blown over board. Most poor running L98s are due to people over camming them and over reving them. On east coast I got tons of them to trap 102-104MPH without changing the intake/heads or cam on a full weight Vette. LT1s are not as weak as people say they are "down low" either. Get the car you like and go to town

Tom400CFI

Go ahead and keep LYFAO. DO you know what an "L98" is? By the time you change the heads intake system and exhaust, which is about what is required to equalize the diff between the two, you don't have a L98 anymore. You have a GM 350 short block w/a bunch of aftermarket parts on it. Not and "L98".

I do agree that both are fine motors; nothing wrong w/either.

ch@0s

Actually yes, what makes the L98 the L98 is the TPI. Without it its a typical SBC. So if you change the intake its technically not an L98 anymore. Chevy sells the L98 without the TPI and a different cam and calls it a ZZ4.

bob guzzy

Most of the head gasket problems I saw were due to the head gaskets leaking or blowing out, mainly from the lack of cooling system maintenance.

Antifreeze doesn't last forever if it starts to smell (skunk like) change it, change the green stuff every 2 years and the orange stuff 5 years.