Thread:

It seems like a bad idea to run these

I'm building my 64 f100 pickup and putting a turbocharged setup into it. I'm doing something WAY different for this and I have a line on some pistons, but here's my issue:

It's a 3.70 bore JE forged piston set Im looking at, that were custom made for this guy that didnt use them. My setup, with these pistons will require me to run about .040 out of the hole, but the top ring lands are .160 down leaving at best .120 left before the rings pop out.

My setup will be Boosted and at times it might see 20-25 lbs boost and 7000-7500rpms. Is there a rule of thumb for ring land depth on boosted stuff?


Andrew

Use a .60 or thicker head gasket.

I ran a custom size BME piston back in 2000 when I first put the Arias motor together.
Everything went fine until I melted a few (most) with my failed pump gas experiment in July 07.
Then the closest thing I could find in the middle of the season was a set of flattop JE pistons that put the top of the piston .065 down in the hole.
Since a turbo makes up for a world of sins it still ran strong and that's what I made the dyno pulls with in 09.
Infomaniac Ron informed me that the quench was way wrong with that setup.
I've changed rods since then and corrected the problem.

Lesson learned, get an off the shelf piston that you can replace easily.
Especially if you're going to beat the hell out of it.

I wouldn't worry about the rings as long as they don't come out of the bore. As far as ring land depth...are you referring to how far down the top ring is from the top of the piston? It would be nice to see a min. of about .300", but that's not written in stone. I would NOT cut the tops of the pistons to correct the deck height issue. I would use a thick head gasket to set my quench and adjust for the piston being out of the hole.
JMO

ETA: There are guys who have done this intentionally to get all the stroke and rod length they could out of a combination. Pushing the piston rings to the top of the bore can gain you a lot.

Originally Posted by ap67et10

I'm building my 64 f100 pickup and putting a turbocharged setup into it. I'm doing something WAY different for this and I have a line on some pistons, but here's my issue:

It's a 3.70 bore JE forged piston set Im looking at, that were custom made for this guy that didnt use them. My setup, with these pistons will require me to run about .040 out of the hole, but the top ring lands are .160 down leaving at best .120 left before the rings pop out.

My setup will be Boosted and at times it might see 20-25 lbs boost and 7000-7500rpms. Is there a rule of thumb for ring land depth on boosted stuff?


Andrew

3.7 bore with a 1.22??? Are you putting a turbo on a Ford Mod motor?

Generally speaking, 0.120" down for the top ring can be allowable depending on application and build design. If I were in your shoes, given the 25 psi of boost, presumably on gasoline, and the 0.120" net ring depth...I would pass on those pistons if you haven't bought them yet and order a different set of pistons that will put the top ring lower and sleep better at night. This isn't an "every last horsepower" racing engine (or is it?).

Call your Diamond Pistons dealer and have them find a piston that suits your build. Diamond used to offer up to two changes to their shelf pistons for very cheap (but I think it's just one change allowed these days). All you have to do is find the piston for your engine combo, and tell them to put the pin at "x.xxx". For example, if the pistons you are currently considering are a shelf item that has a 1.22" compression height, then special order that shelf piston part number and also ask them to put the pin at 1.18" (<---your allowable one change to the shelf piston part number). The net result will be a zero deck piston (with the 1.18" compression height) but with a ring pack well below 0.250" down...possibly more than 0.300" down depending on the piston part number you start with.

LO

Originally Posted by ap67et10

I kinda am trying to run an off the shelf piston, but not off the shelf for the engine I'm building, it actually from something completely not related to the engine I'm running. I'm only hesitant to talk about it because I'd rather be closer to getting it on the road before I hear the naysayers and butt hurt reactions to what I'm doing.

Don't be bashful. If it works and it's from another motor, then it works. I have a set of Manley rods in my '57 Ford Y-block that are for a small-block Chevy. It was the only off-the-shelf rod that would work for the offset-ground stroker crank. Made a 346 out of a 312. Also used Chevy valves for that build. But with a custom Isky cam, four barrel, and headers, it makes 278hp. That's 100 or so up from stock. If it works, it works.

Carry on.