quote:Originally posted by Wasatch Cat:
Doug, yes, it was posted on the 351C forum, sorry for the confusion. I am trying to do this with the motor in the car and keep the pistons that are installed. Not that many miles on them. I agree, I don't want to above 10:1, more like 9.5 or so. I may just have to take the time and pull the heads before I order. When you say "the number was only an approximation to begin with" are you referring to the dish volume? Thanks, Evan
The pin height.
Obviously there is a factory dimension on it but since it isn't listed by them you need to measure it yourself and as such you have to consider it as approximate. I remember going through this myself and the engine builder said, it doesn't matter, just put them in.
I have that piston in my engine with the A3 heads. My heads were shaved by the original builder for use in a circle track race car to get them down to 59cc's.
I'm running what you want to build. Something around 9.7 to one.
My suggestion to you would be to shave a set of aluminum heads down like I did and leave the pistons alone.
I thought that the flat tops would give me too close to an 11 to one and I had just replaced an engine with the TRW popups which were nearly 12 to one.
That engine would detonate so bad on pump gas it would litterally shut itself off at 4500rpm.
Now if you ran 106 Sunoco race gas then Hell had come to supper, it was an animal. That just made no sense on the street since you couldn't drive it anywhere unless you had a tanker truck meet you with high octane racing gas.
If you run the pistons the way they are with an unshaved head you are still around 9.5 to one. I wouldn't worry too much about what exactly the static ratio is if I were you.
This is one of those go, no go situations. The engine will be responsive enough with them and the closed chamber heads.