Eightrac

Hello, I'm Jesse.

I just bought a 1988 Corvette (convertible, L98, 700R4, Z52) that was advertised as being in excellent shape (which cosmetically it is) and was assured with documentation that the car had been serviced and was in good running order.

Mind you, I'm in ND. It's literally -15°F right now. I test drove the hell out of this car and it gave no indication of anything being wrong. I purchased the car for well below the asking price, which immediately scared me a bit as the owner was easy to take a $2k loss on his advertised price.

I loaded the car up and trailered it home.

That's where the excitement ended.

Yesterday I decided to do some investigating. I discovered the oil had been just changed, the thermostat was brand new and the coolant reservoir was almost empty. Also, there were white spots on the hood where coolant had contacted it.

I lifted the car on jackstands and went underneath. It's clean, aside from a slight valve cover oil leak. Then I opened the radiator cap...

That was a mistake.

It was dark when I looked over the car, in a lit car wash area. When I cracked the radiator, all appeared fine.

Today, sludge. Lots of it.

I then decided to flush the system with some cleaner, a bit of simple green and a few hours of my time. After about 15 minutes of idling with clean water in it, it began to leak profusely from the water pump, then began to erupt like a volcano from the open radiator. I shut it down, allowed it to cool and topped up the water.

I started it and it immediately blew 1/2 of the water supply out of the radiator. Ugh. I jumped on the Internet and found hundreds of claims to blown L98 head gaskets...

Okay, whatever car. You need head gaskets. I'll just suck it up and do it. So, I've purchased some Fel-Pro MLS gaskets, ARP head studs, an intake reseal kit, a water pump, a fuel pump relay (ugh, yeah..) and some other odds and ends...

Now comes where I ask you all a favor.

I'll be getting deep into this thing. It has 89k miles on it. Should I replace the timing chain, as I'll be in there far enough?

I'd like to put a cam in it while I'm in there as well. I'd like to "future proof" a bit as well to support any intake/exhaust changes I'll be doing down the road.

Any other suggestions for a stock L98? 1.6 roller rockers? Valve seals?

Help me decide.
​

ajp01

Short answers.

Valve guide seals Yes. You'll have the heads off and that job is easy at that point. They're cheap too.

Timing chain Yes. No reason not to, plenty to do it. Everything in front will be off the short block anyway.
​​​​

iceman2003

Yes, to the Valve Seals and the roller rocker arms, go with a mild cam upgrade too, without a doubt a very high quality timing chain would be advantageous, if you can afford it an upgrade to Beehive springs... Strength and a few more horsepower wouldn't hurt.

kenmohr

Have the heads gone over. Make sure no cracks or not warped

'78CorvetteS.A.

What does the engine oil look like!?

Natty C

I wouldn't be so quick to conclude a blown head gasket. You didn't really explain what ''sludge'' meant there.

But whatever. Wouldn't hurt to do the job anyway, if you're gonna do it yourself.

car addict

This ^^^

Eightrac

It's literally blowing all of the coolant out of the radiator when it's running. Constant bubbles until that point.

Also, the "sludge" is oil floating around in the coolant. There's no coolant in the oil.

ChumpVette

Congratulations. And condolences.


Replace both head gaskets
Skip the ARP studs. Just use regular ARP bolts
Have heads cleaned/checked. Replace valve guide seals, check valve guides themselves
Change timing set
Change pan gasket


Get the car running and 100% before you venture off into modify territory.

Eightrac

​​​​​​It's clean.

VikingTrad3r

you could have air in the system.

it overheats without the pressure cap and it erupts.

its more common that a noob doesn’t purge the air out after a waterpump job than it is to blow a headgasket.

might want to just be sure you have exhaust gasses in the coolant first. a simple tester.

the cooling system needs to be sealed in order for the trapped airbto escape out the overflow, and have the overflow filled with coolant yhat the system sucks back after cool down

JasonAndrew

How much was it? Where are the pics?!

Eightrac

​It blows air from the radiator immediately, regardless of if the cap is on or not. If I put the cap on,it just forces the cap to release and it overflows the overflow. The car overheats almost immediately.

I've bled the system via the throttle body hose multiple times. It's not air locked. Also, the water pump blows out pressurized water from the weep hole and there's oil floating around in the coolant.

VikingTrad3r

sounds convincing unfortunately!

kenmohr

Check for hydro carbons in the radiator.

Natty C

I once crossed my coolant recovery and air bleed hoses and the coolant blew out of the overflow and radiator fill. lol. Was the dumbest thing.

At first I thought I might have installed a standard rotation water pump instead of the stock reverse rotation one.

LiveWire1

Congrats on the new car! Even if you have to do all the work you intend to do, it's going to be worth it to have a cleaner engine that you know will run perfectly. I'm sure most of us have been ripped off by an unscrupulous seller in the past, and now, everyone just takes it in stride as the cost of buying the car you want. Take the time to clean things up as nicely as possible, and replace other things like vacuum lines, which rot out, and it wouldn't hurt to have a good look at replacing spark plugs and wires. Good luck!
And there's no stupid questions, but I've seen some crazy-*** answers!

VikingTrad3r

haha. yeah i know the feeling. I fought my first c4’s cooling system for ever. It would get hot, push some fluid out into the overflow, then as it cooled it would t suck it back in. leading to a low coolant light. over and over. finally i learned that system has to be sealed up…in my case the intake manifold bolts at cyl8 were loose and the seal was bad. air was being vacuumed in rather than sucking the coolant back up the straw from the overflow.

Eightrac

Alright, I've confirmed blown gaskets on both heads likely due to a botched intake reseal job. Both inner runner bolts were loose, the bolts at the rear of the lower manifold weren't sealed and the oil from the head transferred into the coolant.

Also....

I found an 1990's snap-on 11mm stubby wrench in the oil pan. I have no idea how that could get in there aside from it being in the pan when it was installed. The entire reason I pulled the pan was because the distributor hold-down bolt was missing it's washer. I found it lying on the windage tray inside the engine. There were also a very old set of intake gaskets installed, so I'm assuming the last time this had been worked on was in the mid-1990's.

The lifters, valves and guides all appear good and the valve stem clearance is good. All of valve stem seals were bad.

Now, questions.

To allow use of a higher lift camshaft, how much should I have machined off of the valve guides? I'm looking to go to a cam with .525" lift. I have springs that will work up to .550".

VikingTrad3r

are you thinking there was vacuum leaks causing lean making cyl hot enough to destroy head gasket? im confused on the link btwn the intake reseal to the head gasket leak. but im not even close to a pro mechanic.