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Discussion Starter · #1 ·
I just pulled the motor out (302 V8) and tore it down and realized I don't have quite the compression I was hoping for.
The part # is TRW 2305-255-98 which is a 9:1 flattop piston w/54cc heads. They have also been flycut which doesn't help boost compression either. I'm running '66 289 heads so the combustion chamber should be 54 CC IIRC.

I was hoping for something around 10:1 with my solid cam so I need to find more squeeze somewhere. In my efforts to save $$$ I haven't pulled the pistons and crank out of the block yet as the bottom end only has 15k on it (I’d hate to re-ring a perfectly good bottom end). This is of course a low budget situation.

If I can't mill enough off the heads, which I doubt I can, what are my best options? Might it be possible to mill the block, or would going for a new set of pistons be a better route?

Any tips or suggestions would be greatly appreciated /forums/images/icons/smile.gif
 

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Milling the heads will only yield about half a point..you can go to different pistons..or get a set of aftermarket heads
 

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Like Teebone said you can get about 1/2 a point out of milling the heads. Then you can use the thin copper head gaskets and get a little over a 1/4 of a point out of those. That will get you pretty close without spending a bunch.

You cannot mill the block without a complete dissassembly. If you were going to go that far then I'd sugest just buying the new pistons anyway as you will have that much in machine work and parts to do the job as you would in new pistons.

Remember, if you mill the heads for compression you will also need to mill the intake accordingly. Any capable machine shop has the formula for how much to take off.
 

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If you have a true flattop with eyebrows for valve clearance on a 302, your CR will be more than 9:1...likely closer to 10:1, with the early heads...

There's only one true way to know...you have to CC the piston in the block at TDC, then CC the head and measure gasket thickness and compute the CR mathematically...anything else is pure speculation (which I've been guilty of on more than one occasion)...

If you can point me to a reference guide for this piston or provide a picture, I might be able to speculate further..*G*

I'd look it up myself, but it's been a long day...

In the case of the small chamber heads, milling will have a greater effect, per thousandth removed, than the same operation on the more open, higher CC heads. Still, you'd need to remove .060-080" to make some serious CR gains and would likely run into some intake alignment issues as Hal mentioned..

If you can provide more specific information on the pistons (beyond what the book says), get back to us...
 

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Discussion Starter · #5 ·
Thanks for the info guys.

I just had a nice surprise in the mail today.
I filled a bit late on my taxes and just got my tax return today for a WHOLE LOT more than I expected!
Considering the expense to tear down the current motor I might just spring for a 331 stroker now.
There was a thread earlier today on a 331 stroker using 289 rods, which I already have. I'd just have to buy the crank and pistons. For under $1,000 I "should" be able to piece this thing together and get a good compression to boot.

My 289 heads have been ported and polished and have 1.9/1.6 valves so I think they should flow ok for the extra cubes.
All these decisions...
 
G

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Be very careful with your camshaft selection. Have the flow numbers from the person who did the P&P handy when you call your cam manufacturer of choice.

IME, stroker motors are very dependent on adequate port volume, something you are somewhat lacking with those heads.
 

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Discussion Starter · #7 ·
Here's the best I can do for now for a picture of the pistons.
http://members.cox.net/mbstang/piston.jpg

Part number is 255-98 by TRW, as stamped on the underside of the forged piston.

Phaco,

I definitely agree, I will need to have everything balanced for this thing to work properly.
No need to be throwing away money for something that doesn't work well!
 
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