G JD

BKY · May 9, 2016

G with 9 in. Stroke 6/38 bore. With a flat head. My question is what is the distance between piston and head.

skip33652 · May 9, 2016

depends on what piston height, how long rod is, how long block is, and how thick head gasket is

BKY · May 10, 2016

I ment to ask what would be a good safe clearance between piston and head. Thanks.

brutus49DC · May 10, 2016

whatever distance gives you the compression ratio that you desire

BKY · May 10, 2016

Friend built this tractor recently and it has 175 lbs. compression on both cyl. Looking threw spark plug hole it looks realy close. I would guess looking in three the hole is not telling me a lot but just trying to find out something. It sounds like it's deiseling if that makes any sense. Thanks.

forty40 · May 10, 2016

(quoted from post at 15:44:57 05/10/16) Friend built this tractor recently and it has 175 lbs. compression on both cyl. Looking threw spark plug hole it looks realy close. I would guess looking in three the hole is not telling me a lot but just trying to find out something. It sounds like it's deiseling if that makes any sense. Thanks.

For 6.38 bore x 9 stroke with a 1" piston to head clearance, that is right at 9:1 compression ratio. If the intake has been bored, the flow velocity at idle is slow and the engine will likely hammer, detonate, sounds like metal-metal hitting inside. I had to go to higher octane gas. Not a good idea to run it hammering, the rod bearings will not last long.

ericsegaline · May 11, 2016

I had a Lot more than that on a A didn't have any problems

ericsegaline · May 11, 2016

We use clay to check valve to piston clearance

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