(Message Deleted by Poster)

[Art Ives]

Message Deleted by Poster

[Clem Z.]

Re: 1969 427/390 Replacement Pistons

if you are going to run pump hi test gas i would go with the lower comp ratio.

[Clem Z.]

Re: 1969 427/390 Replacement Pistons

if you are going to run pump hi test gas i would go with the lower comp ratio.

[Joe L.]

Re: 1969 427/390 Replacement Pistons

Art-----

You're going to have a hard time finding an aftermarket replacement piston that will deliver an exact 10.25:1 compression ratio in your engine. Since the GM pistons for your application are long-since discontinued, you don't really have any choice but aftermarket replacement. You can order custom-made aftermarket replacements, but they'll be expensive.

If I were you I'd go with a Keith Black/Silvolite piston of KB 176. This piston will deliver a compression ratio of about 10.2 to 10.5:1 with your cylinder heads when used with .039" compressed thickness head gaskets, assuming that your cylinder heads have not been excessively surface-milled. Also, considering that your original pistons were conventional cast aluminum pistons, the KB 176 are hypereutectic (high silicon) cast pistons which are considerably stronger.

[Joe L.]

Re: 1969 427/390 Replacement Pistons

Art-----

You're going to have a hard time finding an aftermarket replacement piston that will deliver an exact 10.25:1 compression ratio in your engine. Since the GM pistons for your application are long-since discontinued, you don't really have any choice but aftermarket replacement. You can order custom-made aftermarket replacements, but they'll be expensive.

If I were you I'd go with a Keith Black/Silvolite piston of KB 176. This piston will deliver a compression ratio of about 10.2 to 10.5:1 with your cylinder heads when used with .039" compressed thickness head gaskets, assuming that your cylinder heads have not been excessively surface-milled. Also, considering that your original pistons were conventional cast aluminum pistons, the KB 176 are hypereutectic (high silicon) cast pistons which are considerably stronger.

[Joe L.]

Re: 1969 427/390 Replacement Pistons

Art-----

By the way, I would agree with Clem that the lower compression ratio may be the way to go. However, if you have been running the original pistons (and compression ratio) on 92 octane pump gasoline and have been experiencing no significant detonation problems, then I think that you'll be able to run the KB pistons which I metioned with no problems. Two things, though:

1) Use Fel-Pro Permatorque head gaskets with .039" compressed thickness;

2) Remove all sharp edges from the piston domes/valve reliefs with fine emery cloth

[Joe L.]

Re: 1969 427/390 Replacement Pistons

Art-----

By the way, I would agree with Clem that the lower compression ratio may be the way to go. However, if you have been running the original pistons (and compression ratio) on 92 octane pump gasoline and have been experiencing no significant detonation problems, then I think that you'll be able to run the KB pistons which I metioned with no problems. Two things, though:

1) Use Fel-Pro Permatorque head gaskets with .039" compressed thickness;

2) Remove all sharp edges from the piston domes/valve reliefs with fine emery cloth