Up compression ratio on 360

[dustman_stx]

After tossing around all of my options for doing an FE rebuild, I've decided to just leave it a 360. I am thinking about attempting to up compression ratio to 10.5:1. My plan was to up the compression with piston choice, but I'm not sure how to figure it. I think I'm running around 8.4:1 stock. A couple of people offer +20cc pistons, but only in .040 and .060 over that I can find. I'm not sure how much difference that would make, either. Any thoughts? Not trying to break the bank. Would 10.5:1 run OK on premium?

Thanks.

[averagef250]

There's static compression and dynamic compression. To run higher static compression you should choose a cam that's designed for it. Run high static compression with a grunt cam and you'll blow the ring lands off your pistons on 110 octane.

Compression does not make power. You can make plenty of HP and torque with an 8.5:1 FE. I personally would not go over 9:1 in a truck.

Stock replacement 390 car pistons should get you more than 9:1 if wanted.

[dustman_stx]

Do you know the stock piston compression height on a 360? I'm seeing flat top pistons listed for 390's and 360's (aftermarket) that have the same compression height, but from what I understand, that number should be different, at least OEM parts-wise.

[convincor]

390 truck piston has a height of 1.678".
360 and 390 car have a height of 1.778"
But if your doing a rebuild, buying pistons. Regrinding crank, rebuilding the rods why waste the time/money on the 360 parts? Not to mension the 360 rods are pretty wimpy comparared to the 390 parts. Pick up a used 390 for a couple hundred bucks. You can sell off what you don't need like the extra timing cover, drip rails, valley tray to recoupe some of the cost.

[dustman_stx]

390 truck piston has a height of 1.678".
360 and 390 car have a height of 1.778"

So why do these 390 Speed Pro Pistons have a compression distance of 1.776, but say +10cc, even though they are flat top? And I see pistons on Summit for a 360 with compression distance of 1.759, and 390 of 1.760 & 1.660...... How do you know what to buy?????

[dustman_stx]

After researching, it appears as though on 390's, the piston comes all the way to the top of the bore. If I use a 352 piston with 1.880" compression height, that brings my piston all the way to the top. Using flat pistons and assuming a gasket thickness of .040 and a compression chamber of 72 cc on stock heads, that yields a static compression ratio of 10.18. My only concern was with valve clearance, but if the 390's run zero deck height, I would assume I can too. .565 valve lift for the cam I am planning to use.

After looking at Summit, the compression heights I'm seeing listed for stock applications are all larger than what is listed for any of the pistons. For example, according to my research, 352 comp height was 1.880, but the majority of pistons offered for it are 1.816. 390 research says 1.791 comp height, but pistons offered are 1.776 or less. All else the same, that would lower comp ratio considerably. Any reasons for this?