It occurred to me as I was assembling an engine today that some folks probably haven't seen any of the pop-up pistons the vendors carry. We've talked about them here, but I don't recall seeing any pics of them.
The second pic shows how far they come out of the block at the top of their travel. You can see that they take up quite a bit of space in the combustion chamber. I often use these with a Ford head milled 1/8" or so. Be sure to check the clearance using modeling clay before milling, in case the head has been milled a few times before.
I find I can run them with a head milled .150" most of the time. More than that and they sometimes hit, there are a number of variables to consider. I have a number of heads milled different amounts to check with. Put one that fits on and go.
I have used those with a stock low head and they work great. I like that combination better than buying a high compression head, although it obviously involves more work.
Thanks Mike, great pictures.
How much metal is under the crown of those things?
Do you know what they weigh compared to standard ones?
Cheers for the pictures
What is the compression ratio when all is said and done? Pretty high I'll bet.
Bob -- You might try a search for threads from a few years back, since there were some discussions about that very thing. (Good luck using our search function.)
But from a "seat of the pants" point of view, I can't tell any difference between this setup and an engine with a Reeder or Z head and regular aluminum pistons.
Jeff, How do you compensate on the head bolt length after you've milled a head .150? Use low head bolts, or use custom length bolts or studs? I have a head that has been milled only .050. I figured that I could still use it by putting a thick washer, like the vendors sell for the aluminum heads under each head bolt.
I would sure consider using studs and nuts for a modified engine. Significant reduction in risk of "pulling" the block threads if you want to torque a bit more on the head bolts. I would "bottom" the studs in the block and then put the nuts on (and use hardened washers as well)
Terry, I generally use a bottom tap in the block to get an extra couple of threads, once in a while you will have to cut a little off a bolt. I've never had a bolt pull out of the block due to the increased compression. When you torque up a bolt you can feel if it bottoms out or if it torques down, at least I can.
Here are some pics of my high compression pistons at j and m machine in Southborough Ma. They are completely build a engine for me. And balancing it as well
I have tons of pics from start to finish for this engine build, John of j and m sends me an update nearly weekly with excellent pics with great description. These guys also work fast, the longest wait is for parts!