Ring gap for boost

[Tippy]

I'm fairly confident I didn't gap my rings enough the 1st time I rebuilt my engine (3.4 based 3.2) and tore up the Nikasil.

Boost is pretty addicting to me and I live in central Texas where temps get over 100 degrees - I'm leaning on a healthy gap this time.....

What gap would you guys do?

Per Wiseco, they are stating (for boosted race motors) around 0.006" times a 4.000" bore resulting in 0.024" total gap. I have 98mm/3.858" cylinders so should be close to this gap.

Another site is stating around 0.007-0.008" per inch of bore for E85 and high boost. That would be 0.027" to 0.031"

What would you do?

I rather go loose and have a tad more blowby than ever butt ends of the rings!!!

TIA

[stownsen914]

I'd assume the piston manufacturer should give you the best info. Make sure they know you're using plated aluminum cylinders.

[Henry Schmidt]

Manufacturer should get you close. The important thing to remember with boosted and high RPM engines is that the 2nd ring should have .004"-.008" additional gap.
The theory is that you want gasses trapped under the second ring to escape without pressuring the top ring.


Edit

[HaroldMHedge]

Henry,

Do you mean 0.004"-0.008" additional gap?

Harold

[Henry Schmidt]

Originally Posted by HaroldMHedge

Henry,

Do you mean 0.004"-0.008" additional gap?

Harold

Sorry, you are correct .004"-.008"

[Tippy]

Thanks y'all, I set them to the high side of heavily boosted motors.

[safe]

Originally Posted by Henry Schmidt

The theory is that you want gasses trapped under the second ring to escape without pressuring the top ring.

Ah, so that is the reason! Thanks!

[dkirk]

What Henry states is also good advice for naturally aspirated engines. A slightly increased end gap on the second compression ring reduces oil consumption.