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How do I find out my pistons or compression?

2K views 9 replies 5 participants last post by  pdq67 
#1 ·
Ok so right now I have a fairly stock 350 that I was told is out of a 86 blazer. I have some 62cc trick flow heads, Kenny Duttweiler 23 degree heads, 195cc intake 2.02 intake valves 1.6 exhaust. I am concerned about trying to put these on my motor because I dont know if the compression is going to be to high or what? So what can I do to find out what the pistons are or compression? Without having to pull the motor apart. I really dont want to have to pull it down to find out I should just go ahead and build my new motor instead of trying to bolt on these heads.

Thanks guys

Zack
 
#2 ·
Take the number-letter codes off the pad right above the pass. upper water pump bolt or right in the top middle of the block above the water pump and post them here or over at the "TAG" section and at least you will know what it originally was unless the block has been decked.

Thuis will do for starters b/c if it has been changed you may have to get inside it and look??

pdq67
 
#5 ·
Worst case you shouldn't have too much static compression. But a stock cam with those heads could yield too much dynamic compression.
 
#6 ·
Do you have the casting number off the rear of te block, drivers side right above where the tranny bolts to the engine. With this we can see where the engine came from. Also if you get the head casting numbers (you have to take off the valve cover) we can see what size chambers the current heads have.
 
#9 ·
Ok so I have a 80 vette motor? So can I just bolt on these heads? Or am I going to have too much compression? What are my options?

Thanks again

Zack
 
#10 ·
Zack,

Go over to the ROSS Racing Piston site and input your motor's spec's and it will tell you.

I use .025" down in the hole for the piston depth to the top of the deck then whatever headgasket thickness you want to use from .015" and .022" shims up to .038" and .040" composite headgaskets thicknesses.

Shoot for a quench of about .040" to .045" and you will be right in there.

I don't know your motor so can't help with piston type be it a four valve notch flat-top at about 4cc's or a dish of some kind so you will need to do some homework there to figure this out. I think dishes go up to 12 maybe 16 cc's but really DON'T know???

Also go over to Pat Kelley's great "Dynamic Compression Ratio Caculating site and read up on it. You can input different cams spec's to play with it.

All this is a hoot to me b/c I play around with both programs for the fun of it...

pdq67
 
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