Ring gap suggestions

[c1500sbc]

Too many mixed opinions when trying to Google and look up on forums.

Forged pistons in a 383 small block with a Weiand 177. Just had the assembly balanced and crank polished. Probably gunna run 6-8psi of boost.

Pistons measure right at 4.037 where JE suggests measuring the skirt. All the cylinders measure right at 4.04. Clearance should be good?

From what I’ve gathered I’m thinking to gap both the top and second ring to .023?

[steve cowan]

Too many mixed opinions when trying to Google and look up on forums.

Forged pistons in a 383 small block with a Weiand 177. Just had the assembly balanced and crank polished. Probably gunna run 6-8psi of boost.

Pistons measure right at 4.037 where JE suggests measuring the skirt. All the cylinders measure right at 4.04. Clearance should be good?

From what I’ve gathered I’m thinking to gap both the top and second ring to .023?

2 things to consider in my opinion
What are the ring gaps for application from piston/ring manufacturer?
What were the ring gaps in old combination, might be worthwhile checking, see if the rings were butting together on the ends.
Disassemble of an engine usually tells more of a story than putting one together.
Ring gaps on the larger side of the scale are better than to tight.

[c1500sbc]

I did check the old rings. I believe the previous owner just purchased some rings that were the “prefit” type. It was an NA motor but the ring gap on both was .025 maybe closer to .026.

According to JE’s website they recommend for a moderate boost street engine to gap the top ring .0050 x cylinder bore and the second ring at .0055 x cylinder bore.

Which equates to a .020 and .022 ring gap.

From reading online, that’s too tight in most people’s opinions.

[steve cowan]

I did check the old rings. I believe the previous owner just purchased some rings that were the “prefit” type. It was an NA motor but the ring gap on both was .025 maybe closer to .026.

According to JE’s website they recommend for a moderate boost street engine to gap the top ring .0050 x cylinder bore and the second ring at .0055 x cylinder bore.

Which equates to a .020 and .022 ring gap.

From reading online, that’s too tight in most people’s opinions.

My NA 383 I just run has 18" top ring 1.2mm and 20" second ring 1.5mm .
I agree 20-22 is a bit tight for boost but opinions will differ.
I can't give you a definite gap to use -
I have had BBC 300 shot nitrous which had big ring gaps but leaked down at 2%.
Alot depends on bore for round and taper,piston rock,hone finish ,ring deflection in ring groove etc.

[BillK]

What does the ring manufacturer recommend ???? I would think they would know better than any of us

[Walter R. Malik]

What does the ring manufacturer recommend ???? I would think they would know better than any of us

The ring and piston material, along with NA or pressurized, will make a big difference in what should be used

[rebelrouser]

.004 per inch of cylinder bore normally aspirated with cast or forged pistons, hypereutectic piston .0065 per inch of bore normally aspirated, on supercharged and nitrous I always consult the ring manufacturer, I believe it makes a difference how much boost and how much nitrous.
I always gap the second ring about .004 bigger, does everybody still do that? Old Smokey trick. End gap is a minimum clearance not a maximum clearance. The ideal is to have almost no gap at operating temperature, but how does one really know? If it is too tight damage is done, if too loose excessive blowby, How many of you guys have blow by gauges, electronic or otherwise?

[dannobee]

Blown or nitrous, 0.006" per inch of bore as a rule of thumb.

Big ring gap = big catch can. Small ring gap = big trash can.

[Mark O'Neal]

Too much is fine, too little is not.

.022 and .024