16valve piston-valve clearance

The Penta engine ran 16v head on a B230 block. Unless there is a special penta pump, 16v head on a B230 block is by the book.

RS1 said:

The Penta engine ran 16v head on a B230 block. Unless there is a special penta pump, 16v head on a B230 block is by the book.

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And I'm sure the Penta pistons have valve reliefs.

Why not just run ridiculously low compression pisons? like a nice 7.5 to one? and then... 30 psi from a holset? and... win?

740tankDriver said:

so, the oil pressure to the lifter is so that the pressure from the spring is not sufficient to press the "plunger" back in the lifter itself?

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No...

The oil pressure in the lifters makes them ride against the base circle of the cam with zero clearance. This way you don't have to shim them as they wear, like you would have to do with solid lifters. They are pumped up to zero clearance as long as the cam isn't pushing down on them.
There's a one-way valve in the lifters. Once the cam starts pushing down on the lifter, this valve shuts, trapping the oil in the lifter. Oil cannot be compressed, so the lifter is now "solid".

^^^

aka magic.

Bumping this thread back from the dead! Im the process of building a NA 16v, i dont have money for pistons so i was wondering if anyone had any experience with milling the head and using a thinner head gasket of a 16v and how much is possible without the valves and piston getting to close. I will be running a 16v head, PZ cams, Ford springs, solid lifters (Knox), AQ171 pistons along with ITB's. If anyone has any input that would be great! I would like to get the compression up as high as possible while still being safe. Redline will be 7000+.

Thanks

Josh has a tool to cut reliefs in the pistons.
yoshifab.com

I am using the AQ171 pistons, they already have reliefs in them.

Most engine builders recommend a minimum of .100".

You need to measure the clearance you have now, then mill accordingly. Every engine is slightly different. If you deck the block, or align bore/hone the crank journals, clearances change.

snailpoweredbrick said:

Bumping this thread back from the dead! Im the process of building a NA 16v, i dont have money for pistons so i was wondering if anyone had any experience with milling the head and using a thinner head gasket of a 16v and how much is possible without the valves and piston getting to close. I will be running a 16v head, PZ cams, Ford springs, solid lifters (Knox), AQ171 pistons along with ITB's. If anyone has any input that would be great! I would like to get the compression up as high as possible while still being safe. Redline will be 7000+.

Thanks

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If you're really foing to be doing all that stuff....really just sit down and budget for pistons like




n.a. or turbo we ALWAYS want it to make more torque. In a turbo that's from static comp + boost/charge denisty/ call it whatever, but in n.a. the thing si easier; engine volume and dynamic compression.

The 16v head will flow, don't have to worry or waste time thinking about that.

But if you want the thing to go you need compression and camshaft---since you have the ITB taken care of--or on the list..

With the nice chamber design and alloy head I wouldn't even think of less comp for an n.a. motor than about 11.4-11.5:1 static
IF you get around that, then when you get performance cams--not the limp, wilty, not even warm OEM stuff---then you'll have some fun power cause you might have high 9s to maybe 10:1 dynamic compression..

snailpoweredbrick said:

I am using the AQ171 pistons, they already have reliefs in them.

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Then you need to mock it up and clay it to see what kind of clearance you have available.

Sir, you are so right.

If I buy pistons, I'm going e85. What's a good compression ratio for e85? I'm thinking 13:1 static?