Technical Head gasket recommendation

Hello, I have an overheating issue on another thread, and as a part of that, I want to pull my heads off and inspect/clean the coolant p***ages. By flushing through other accessible openings, I have cleaned out quite a bit of rust particles, so I want to go deeper and make sure I get it all out.

So I want to have gaskets on hand. I started checking online and found that it is not as straightwroward as I had thought, with different brands, materials, sizes and thicknesses.

My engine is a 1965 Chevy 327/365 hp that was rebuilt at 43,000 miles due to a broken ring (cylinders honed, not bored). I remember that the engine builder gave me a FelPro gasket set with my finished short block, but I neglected to make note of the part number for future reference.

So, just to complicate things a little, I wonder if it would be a good idea to go a little thicker with the head gasket in order to reduce the compression ratio (11:1)? At the time of my rebuild, the machine shop asked be if I would like to replace my domed pistons with flat topped ones in order to be able burn pump gas. I declined because I wanted to preserve the originality, but now I'm kinda sorry I didn't do it.

Any advice on this would be greatly appreciated.

 

I' pretty sure Cometic could make you a head gasket any thickness you want.
Be aware that just"stick'in-a-thicker-gasket-on-it" is not always the cure-all. Stuff like squish and quench are affected by just going with a thicker gasket.
The machinist was on the right track(imagine that!) shoulda went with his advice and gone ta flat tops.
Race fuel is an option. So is replacing heads with Alum. heads. A big lumpy cam(with a tight LSA) will bleed off some of the compression at low RPM where it causes damage.
6sally6

 

The small Chevy has been around SOOOO long, that things like head gaskets have been pretty much perfected many moons ago.
Buy most any "name brand" gasket, install it on CLEAN, DRY surfaces... As long as the block deck and head deck are flat and square (end to end), you'll be fine.
Use proper tightening sequence and steps. DO NOT go to the full torque in one step. Use three steps to get to the 65 ft.lbs., starting in the center, working your way out.

As far as thickness. I really don't know of a big variation, manufacturer to manufacturer. Probably between .038" to .042" is what you'll find. And that .004" isn't going to make much difference in compression ratio that matter.
Yea, just don't use the .018" sheet metal gaskets..!

Mike

 

6sally6 has it. Cometic has a lot of different thickness's. You can drop a full point with ease.

 

.040" clearance between the flat area on the piston and the head surface is correct - not counting the pop-up. If you go more than that, the squish band area will be opened up and cause it to ping easier and probably aggravate the overheating problem. Flat tops would have been a better choice.

Choose a gasket that gives you .040" clearance with your current set-up.

 

It is never a good idea to reduce compression by using a thicker head gasket. It destroys quench and you will have worse detonation than before. Quench should be in the .035 to .045" range for best detonation resistance. Your untouched block should have the pistons at .025 in the hole. That leaves .020" left for gasket and to maintain quench. A steel shim gasket is the only alternative. Not the end of the world. They can be made to work.
But that leaves you with too much compression for even 93 pump gas. Current thinking is no more than 9.5:1 on pump gas. Looks to me like your best bet is to go to flat tops. Still use a steel shim head gasket to maintain quench (very important). You end up very close to 9.5:1. When you get it apart you need to check the piston deck height.
Check the compression calculator on Wallace Racing Calculators. Google it.

 

Tom you type faster than I do

 

Thanks to everybody for the information. I can see that adding compression chamber volume with a thicker head gasket is not a simple thing. I think I will just want to stay with a stock thickness gasket. I'll take measurements when I get it apart and see how mine line up with what you have described.

I have experimented with additives and I think I have a workable recipe with a bottle of Lucas Octane Booster per 10 gallons of non-ethanol 92 octane gas (about a double dose). It is hard to be sure because my exhaust noise drowns out the pinging, but I ran long stethoscope tubes into the engine compartment and I "think" I can hear the pings.