Does anyone make pistons if you were to punch out thirty thousandths or do they just make them up to twenty? Was told you can get twenty thousandths but not thirty, is this true? Been doing some searching as to where to even get the twenty thousandths but cant seem to even find that. anyone help point me in the right direction.

Is boring out that much a bad idea on an already modded motor, or just a 35 briggs in general

Im running a pro-drive with mag 45 internals, IM heads, exhaust and mikuni right now.

Briggs makes .020 stock pistons. There's a reason for that you're dealing with a shitty block to begin with. Theres other ways of building compression that's much safer than that.

I'm no expert but other s will agree with me.

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Reason I ask is I have some scoring on one of the cylinder walls, trying to weigh my options of boring it out to clean it up vs a new block.

what kind of speeds are you getting? what boat are you running?

New block if you're .020 already.

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Still at stock bore, running an 1854 pd full floation a sides and what not with basically every add on so she's heavy to say the least, running about 28mph at 4250 to 4300 light load, boat use to run 31 all day bumping 32. Been running 28 now for a few years, I thought it was the valves until we opened it up.

Prop....maybe

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You can get pistons just about whatever size you want.

Would you do..030???

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I would if i had to, i'd try .020 before ordering pistons and see if that cleaned the cylinders up enough. Briggs gives a specific tolerance for theirs and you don't need to physically have the pistons before doing the work. If that don't clean it up, look into some other options. My machine shop guy would not charge me twice though if .020 wasnt going to work.

Heck I ain't scared, I'll go .080

I wouldn't go boring anything until u have the pistons in ur hand and u can go .080


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They give no skirt clearance numbers. You bore to a specific diameter. If you talk to a dealer or rep, they'll actually tell you not to give the machine shop the pistons. I'm not any kind of guru, but i do know the machine shop wants the pistons and wants the skirt clearance numbers. I've not had an issue just giving them a bore diameter though and have had more than one engine bored out.

Can you guys point me to where I could get .030 if the .020 doesn't work? I still can't find anything on the web

J.E. pistons will make custom pistons.

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Wouldn't it be about the same price to get a new block than getting it bored and getting custom pistons made?

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Boring u looking at 50$ a cylinder resleeving about a 150$ a cylinder and that's on the high side


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What about custom pistons?

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Custom pistons are a little on the high side. I would contact performance v twins. He's a little hard to get ahold of, but is probably going to be your best bet, unless you know exactly what you need. Pin height, etc..

Custom pistons aren't as bad as u would think but some of the company's want u to buy 4 not just 2


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Also when ordering custom pistons let them know there for an air cooled engine. Some piston manufactures will require additional clearance (.001).

Appreciate the help fellas, AKA cant thank you enough for your time.

Culprit turned out to being a compression ring failed.

Let the boring begin, hoping .020 cleans it up.