Carbs and CFI (wet plenum) '82's and '84's!!

Very interesting discussion here. But how does this address Cliff Harris' original blown/eroded head gasket question?

Mike, what would the full firing order be for that alternate camshaft? Why would Chevy stick with this less-than-optimum firing order since 1955? Maybe because of the dry plenum that came with the '85 TPI? Wouldn't a different firing order also change the torsional vibration harmonics of the crankshaft?

 

The spark plug on the left end is #7. These are Bosch HR9BPX platinum plugs. I was really surprised to check my log book and find that these guys have been in there 60K miles (the car has been running fine). The end of #7 is shiny and clean -- the others have carbon on the end:

 

It was a rhetorical question -- no answer needed.

That said, I have a vague recollection that the "shim" type head gaskets back in the '60s were stainless steel. I need to research that, just to satisfy my curiosity...

 

I finally got the passenger side head off tonight. Now I'm in the obsessive cleaning stage.

I discovered something VERY interesting tonight. While cleaning the head gasket surface of the block I found that THERE IS NO HOLE IN THE BLOCK where the head gasket rusted out.

That makes me want to plug the corresponding hole in the head to prevent this from happening in the future. That would make the head side-specific, but I don't care about that. I haven't figured out what to use to plug the hole yet. One thought is to tap the hole and put in a stainless steel set screw. J-B Weld?

 

What about just squirting a little Rtv in the hole after gasket is sitting on the block
good luck Joe

 

I didn't think RTV would hold up and stay in place. I filled in the hole with J-B Weld.

I talked with the guys at Superior Automotive Engineering today. One suggestion was to plug the hole with an aluminum plug. I had thought of making an aluminum plug. I've got the aluminum and that is the method used to plug holes in auto trans valve body plates when installing a shift kit (I've done that).

I did notice that the area around that hole in the head is sort of etched/rusted. That might have contributed to the early failure, but could be a symptom. Hopefully with the hole plugged it won't be a problem in the future.

 

The guys at Superior Automotive Engineering told me they called Fel-Pro about my rusted out gasket. Fel-Pro told them that is caused by electrolysis. The coolant gets acidic after a while and starts conducting (like a lead-acid battery). That eats up various metal parts, especially aluminum.

I guess I have been a little lax in changing my coolant...

I have found a product called CoolTrak, which is a bunch of pH strips and a color chart that you can use to monitor the acidity of the coolant. They say that anything over 9.0 is too acidic and you should change your coolant.

 

Look at the good side. Now you have justification for buying some new AFR's.

I've got a pair of alum. heads to put on an engine I'm in the middle of building and I'm hoping to remember to pick up a few gallons of distilled water to use. My well water is the best tasting well water I've ever had, but it does have some iron & other goodies in it that I probably shouldn't be putting in the cooling systems in my vehicles. I ran across an article (that I can't find right now) that said "distilled" water you buy is usually distilled a couple different ways, and one of the methods was better at deionizing the water for use in our alum/iron engines, but I can't remember which method was better. Where I used to work, we used deionized water that ran through cooling jackets in electrical lines.


.

 

Huh? Hold on there.
Cliff, you have an oem head and block, the head has a coolant channel at #7 and the gasket does also but not the block? I can't imagine any engineer designing a cooling system with a stagnation point like that. This sounds like either a miss-matched head and block or a manufacturing defect. Is this the original head/block set?

 

Yes. I've owned this car since December, 1985.

It has to do with the way the coolant flow is set up in the block. The hole I plugged in the back of #7 also DOES do something when the head is put on the passenger side. That hole is next to #2 in that case.

Interestingly, the hole I plugged does not exist on the other end of the head.

I just discovered tonight that the intake manifold gaskets I just bought do not have the flow restrictors for the rear water passage. I ordered the gasket set for a 1985 Corvette to make sure I got the one for the cast iron heads. It's Fel-Pro HS 7733 PT-6.

 

So the heads are interchangable rotated 180 from left to right? That would probably make sense (from a bean counters' perspective anyway), only one casting, less spare part inventory, etc. It does present a problem at #7 though with a column of stagnant coolant under pressure and temperature. Without convection at the channel bottom on the block surface there's a good chance you have some local boiling which might cause the gasket to errode there. Local nucleate boiling by itself isn't that big a heat transfer problem since phase change is a very efficient cooling mechanism, but combined with heat, pressure, and a high Ph level, it could cause the gasket failures you are having. There is also the possiblity of a pocket of vapor forming there in the channel, in which case the heat transfer is virtually nil and a hot spot develops there. Also, any differential thermal expansion effects would be most pronounced at the ends of the head around 1-7 or 2-8.

 

One other aspect to all this is that the exhaust valve for #7 is next to that hole...

I also had some gasket rusting on the middle bottom coolant holes. They are next to the exhaust valves for #3 and #5, so it appears to be related to the heat in that area.

 

Hi Cliff -
Let me toss this out for what it’s worth – might be blowing smoke here but bear with me – LOL.

Letting the engine set for extended periods of time with out running might aggravate your head gasket problem. Engine coolant has finite amounts of anti-corrosion additives and if not circulated, there will be small areas where the additives get “used up” because of local stagnation. This scenario occurs frequently in motor homes, which sit for extended periods of time.

However, since you have an area with an orifice in the head but not in the block, the coolant might be stagnating there even though the engine is running and perhaps the corrosion inhibitors are being used up at that particular spot. This is just a SWAG since I don’t know this for sure. There might be cooling system crud that has settled into the head orifice and up against the block making the local stagnition situation even more severe.

I’ve heard this is also what happens between the coolant hoses and whatever they are clamped onto. Seems like every radiator hose that I’ve removed from an older vehicle has the thermostat housing corroded where the hose slides over it. Again, this might be because of small amounts of stagnated coolant trapped between the hose and the housing in which the corrosion properties have been exhausted.

Personally, I’d be a little hesitant in sealing off that hole in the head. Like you indicate, it might be wiser to just change the coolant a little more often and be sure to use distilled water or perhaps a name brand “pre-mixed” coolant. Electrolytic action is happening all through the cooling system so might as well be prepared as best one can

Anyway, some food for thought.

Jake –

 

I tend to agree with the coolant being the Culprit with c4 head gasket failures. The electrolysis that occurs between the aluminum heads and iron block will slowly eat away at the water journals especially if denatured water is not used in the coolant. I recently had to get aluminum welded onto the heads to repair them. Being that the coolant circulates in one direction the #7 cylinder being subjected to more heat just makes the reaction occur faster I assume. Enjoy the rebuild.

 

This car is my daily driver, so it definitely doesn't sit for long.

I had a REALLY BAD experience with DexCool in this car. Back around the mid '90s I saw that DexCooi claimed 5 year coolant change intervals and "compatible with all cooling systems", so I changed to DexCool. BIG MISTAKE. My coolant turned to rusty sludge. I tried all kinds of chemical flushes and wasn't able to really fix my cooling system until i did a drain-run-drain scheme until the coolant was completely clear. That took about 10 days, but it finally fixed my problems.

I have recently read that you can switch to DexCool from the green stuff, but you have to get EVERY DROP of green coolant out first. It seems that green and orange don't mix.

 

That is true. If you switched to Dex w/o a thorough flush first, then you created your own issues, unfortunately.

 

Cliff just curious how many miles on your car? by the way I just finished replacing my head gaskets on my 95 and it was #7 and it looked like # 8 was not far behind.

 

Right now I'm at 118K miles. For many years this was my weekend car, so I didn't drive it very much. In 2002 I bought a C5 so that became my weekend car and the '86 became my daily driver.

 

Cliff,

How are you coming along with this? Did you seal up the passage in the head?

Carl

 

I plugged the hole in the head with J.B. Weld.