409 TRUCK BLOCK TECH ASSIST

[394olds]

I have a 64 409 truck block that cleaned up at 4.390. I am planning to use (but have not yet bought) the ICON IC979.078 pistons. This is a 340 HP engine - correct 817 heads. I need the cc volume of the truck notch to do some pre-mockup calcs on the compression ratio plan. Goal is 9.75:1. I recall from years ago that the truck notch volume was of the order of 10-12-15 cc as a rough number. Hoping some "truck block" veterans can fill in the missing notch cc number. If someone has been down this research path with the ICON .078 pistons please jump in!

 

[63 dream'n]

If you do a thread search you might find the answer that you’re looking for…… but generally speaking you’re going to lose a half to 3/4 of a point of compression as a result of the truck block notch……The smart guys will chime in soon …….. I’m sure

 

[MRHP]

Keith has it right.

 

[MRHP]

Hopefully they did not rebore the counterbore. If they did, that drops the compression another .5-.75 if my memory is correct.

 

[394olds]

3/4 of a point is 8 cc - close to what I remember. I just want to take out as much guesswork as possible.

 

[region rat]

I have a 64 409 truck block that cleaned up at 4.390. I am planning to use (but have not yet bought) the ICON IC979.078 pistons. This is a 340 HP engine - correct 817 heads. I need the cc volume of the truck notch to do some pre-mockup calcs on the compression ratio plan. Goal is 9.75:1. I recall from years ago that the truck notch volume was of the order of 10-12-15 cc as a rough number. Hoping some "truck block" veterans can fill in the missing notch cc number. If someone has been down this research path with the ICON .078 pistons please jump in!

Truck motor had 7.75 compression and I think it was a lot less than 340 hp. The 340 was a passenger car engine.If you want 9.75 compression, order 10 1/2 compression pistons.