thynes

Hi, new member here. I have been reading this forum for months to help with my project corvette that I recently purchased, it's a '90 C4 with the L98 engine. I could use some help with this car. This car sat for the last 5 years, with an occasional start up and run around the block, so it need some love as you would expect.

It has a coolant leak. There is white smoke coming out of the exhaust, and the #7 (rear most spark plug on the driver side) was very clean compared to the other 7 plugs that I just swapped out.

So my first thought is a leaking head gasket, but it is not overheating. Granted this car is not on the road yet, many other things to fix, but the short 4 mile run around the neighborhood tonight did not show any signs of overheating. The temp gauge stayed steady, unless I stopped and idled and then the temp crept up, and the cooling fan turned on, and the temp lowered, as I would expect.

Some of the threads that I skimmed made mention that there may be a intake gasket leak. This is an easier job to fix than a head gasket replacement.

Can you guys please help me narrow this leak down. I don't have a whole lot of experience with the Chevy 350 engine. I have been working on getting this car back together for nearly 4 months and want to wrap this up, now that the snow is gone and nice weather is here.

Thanks,
Tim in Mass

Digidash

Sorry to hear your troubles. My brother had an LT4 and feared a head gasket leak, but turned out to be the intake gasket. So, there is some hope. I am not at all a mechanic and have no place giving advice, but a compression test is something you can do yourself and it may be useful. I am not sure, maybe someone else can comment if cylinder pressure/leak-down can help identify a problem.

For what it’s worth, the 350 in my truck (1999) also had a bad intake gasket with the attendant internal coolant leak. It kept running low in coolant like I was feeding it kool-aid.

carls1957

My problem was my heater control valve leaking.

VikingTrad3r

what about the white smoke? just condensation?

65Z01

I too think a compression check would be the next step.

VikingTrad3r

leakdown. when i did mine, my coolant reservoir began bubbling.

thats how i knew i had two comprimised cylinders.

thynes

#7 Cylinder Bad Head Gasket

#7 Cylinder Bad Head Gasket

As Removed Head

Cleaned Up Head

thynes

So I dug in to the engine last week. I pulled the drivers side head and found a bad head gasket on the #7 cylinder. I also found the combustion chamber and exhaust port "steam cleaned", as expected.

As long as I was there... I also pulled the passenger head off to replace the gasket. The gasket for the passenger side looked fine, so I probably could have left it alone, but it would still be in the back of my mind wondering if it was a ticking time bomb.

So I dropped the heads off at the machine shop yesterday, to have them give it a once over. I didn't see any cracks, but they will probably skim the heads to help with the sealing when I put it back together. They will also look at the valves; I don't think they looked too bad, and the sealing surfaces lapped up reasonably well for an engine with 120,000 miles.

I ordered up new, rebuilt Bosch injectors today.

I will also replace the water pump, as it is cheap and only 4 more bolts to remove it.

Mission creep!

Does anyone know of a source, or part numbers, for the spark plug wire holders/retainers that clip on the heads, my were missing/damanged?

Cheers,
Tim in Mass

thynes

Vette engine parts starting to clutter the garage

The heads were skimmed to clean them up. No leaks with the pressure test, and the valves didn't need a regrind.

Cleaned up the sealing surfaces.

thynes

Head set in place.

Getting closer. 90% done, 90% to go...

28uniflite

I found the plastic spark plug wire retainers on Rock Auto. Buy two sets because some have to be cut in half where you only need a 2-wire holder. Click on the link below.

Rock Auto Wire Holders

thynes

28uniflite,

Thanks for the link, I have them on order.

-Tim in Mass

thynes

So I am hoping for a break in the weather tomorrow, Saturday, to get back to work on this project.

I am in need of some information regarding the torquing of the head bolts. This is the L98 engine, with the aluminum heads, of course.

I have some new bolts with sealant already pre-applied, and I have a diagram of the torque sequence, but I am unsure if I am supposed to oil the bolts up.

I don't think I need to oil the threads, but some places that I read mention oiling the bolt heads/washers.

What is the correct way to bolt these heads down?

-Tim in Mass