1963 340 HP head gasket (Use steel or composite)

[Richard G.]

[Jim T.]

Re: 1963 340 HP head gasket (Use steel or composite)

Richard I run the current premium gas in my 1968 327/350 L79 with no driving problems, original engine still together.

[Richard G.]

Re: 1963 340 HP head gasket (Use steel or composite)

Thanks
I will just keep it all stock and quite worrying so much.

[Joe L.]

Re: 1963 340 HP head gasket (Use steel or composite)

I need to pull the heads on my 340HP 327. I had installed composite gaskets years ago, and never ran the motor. Now it’s time to pull the heads again and I have the opportunity to change them to a stock steel gasket if I chose to. Years ago, I liked the idea of lowering the compression ratio even if it was only .1 point. I now know it also expands the area between the flat part of the head and the piston and thus reduces the swirl effect from the quench area. Any recommendations on which way I should go? I do plan on showing the car when it is finished. However, drive-ability is more important than the point deductions for the incorrect gasket. Possibly a better question is, when showing the car, can they even tell if it has a steel gasket or not? If it is a judge-able item what might the deduction be?

To expand this question, if one were to replace the pistons, in this motor, what would you recommend as far as dome height if any? I have even though to reducing the dome height somewhat on the stock pistons. Modern thought is to keep the piston flat to promote flame propagation and reduce head volume to gain compression. As I am stuck with the head volume, I am unwilling to mill the heads on this motor. Mostly a rhetorical question as I am planning on keeping it all stock and running less timing if I have to run on the current available octane.

Another question is what should I have for valve spring pressure and what is a reasonable variance from the specification. I have been unable to find any spring specifications for this motor. Cam is the stock mechanical one. Motor is all stock.

Appreciative of any and all input.

Richard------


Unless you are absolutely certain that the head and block surfaces are absolutely flat and true, I would recommend using composite gaskets. My choice would be Fel-Pro 1003. Yes, any composite gasket can be detected during judging. So be it.

If you were to replace pistons I would recommend going with flat top.

Original valve springs for your application are still available from GM under GM #3735381. They're a little expensive, though.

[Richard G.]

Re: 1963 340 HP head gasket (Use steel or composite)

Joe
Thanks for the part number. I was attempting to figure out if my valve spring on the Corvette are any good after all these years. With your provided part number I was able to find the specifications, see below;
I have a valve spring checking tool to confirm the pressure(s).
Rick

Copied from the web;
These springs are 80# closed and 200# open @ 1.25", and are correct for your car - you DON'T need any of the high-pressure aftermarket springs; all GM production solid-lifter small-block cams used the same grocery-getter springs as hydraulic cams did.
These are used on several GM crate engines and the largest camshaft they use these with has .460" lift. We do not recommend them for any more lift than that. Spring Rate (Lbs/In): 262.2 Lbs./In
I don't recall the stripe color, but the GM #3911068 spring is EXACTLY the same as the Federal-Mogul/Speed-Pro #VS-677 spring (F-M makes them for GM); the F-M spring is about half the price of the GM spring, for the same identical part.

[Joe L.]

Re: 1963 340 HP head gasket (Use steel or composite)

Joe
Thanks for the part number. I was attempting to figure out if my valve spring on the Corvette are any good after all these years. With your provided part number I was able to find the specifications, see below;
I have a valve spring checking tool to confirm the pressure(s).
Rick

Copied from the web;
These springs are 80# closed and 200# open @ 1.25", and are correct for your car - you DON'T need any of the high-pressure aftermarket springs; all GM production solid-lifter small-block cams used the same grocery-getter springs as hydraulic cams did.
These are used on several GM crate engines and the largest camshaft they use these with has .460" lift. We do not recommend them for any more lift than that. Spring Rate (Lbs/In): 262.2 Lbs./In
I don't recall the stripe color, but the GM #3911068 spring is EXACTLY the same as the Federal-Mogul/Speed-Pro #VS-677 spring (F-M makes them for GM); the F-M spring is about half the price of the GM spring, for the same identical part.

Richard-------


Just so there's no confusion, the GM #3735381 is not the same as the GM #3911068.