In need of ring end gap specs for 250 inline 6
 

Hi guys I'm in the process of rebuilding a 250 for my 76 c10.
I'm trying to find the ring gap specs. So far I've came up with .016 for compression rings?
Info from a shop manual would be nice.

BTW the block has been bored .060 over not sure if that changes anything.

Re: In need of ring end gap specs for 250 inline 6
 

I guess I can do the math and figure it out. (I'm just being lazy:lol:)

Maybe another question would be does the fact that the blocks been bored over change anything?

Re: In need of ring end gap specs for 250 inline 6
 

The number that comes to mind is .0045 times the bore size.
So yes an overbore could need a slightly bigger gap.
Also considering today’s swill they call gasoline and likely more heat in the motor it’s likely best to go a bit wider.

Re: In need of ring end gap specs for 250 inline 6
 

I use 0.004 per inch of bore size....

0.0045 would be ok....

Make sure you check bore taper top to bottom....no more than 1/2 a thou.....

Cross hatch should be at 45 degrees...

:chevy::chevy::chevy:

Re: In need of ring end gap specs for 250 inline 6
 

So from internet searches I see both 0.004 or 0.0045 being used.
Also seeing recommendations for bigger gap on 2nd ring. (Any thoughts on this?)
I think if I'm calculating correctly I think my gap will be somewhere between .015 and .017

Re: In need of ring end gap specs for 250 inline 6
 

So for those that are interested:
Chevy 250 inline 6 std. Bore size should be 3.8750
If I figure right, being bored .060 over should make it 3.9350

Using a cheap digital caliper on the top of my cylinders I'm getting something like 3.9320
I don't have a proper tool to measure with but I'm guessing where pretty close to good.

Guess I should have said this sooner but for those that don't know I just had the block bored and honed by a machine shop. (If I had been smart I should have asked the guy what the finished bore measurement was!:banghead:)

Re: In need of ring end gap specs for 250 inline 6
 

So if I'm doing this right...
0.004 x 3.9350 = 0.01574

0.0045 x 3.9350 = 0.177075

If I've got this all wrong please let me know!

Re: In need of ring end gap specs for 250 inline 6
 

Almost

Your entry shows

0.004 x 3.9350 = 0.01574

0.0045 x 3.9350 = 0.177075

Should be

0.004 x 3.9350 = 0.01574

0.0045 x 3.9350 = 0.0177075

I would set ring end gap to 0.016 and be done with it....

Make sure you deburr the ends after gapping them...

:chevy::chevy::chevy:

Re: In need of ring end gap specs for 250 inline 6
 

Oops must have been a typo.:lol:

So do you think I should gap all the rings the same? I think I read something about gaping the 2nd ring slightly larger?

(By the way this engine build is going to be pretty much stock, no turbo or any of that):lol:

Re: In need of ring end gap specs for 250 inline 6
 

I set both compression rings at 0.016, with ring square in bore, one inch down....

One way to check bore taper is set gap with ring down one inch, then push ring down to 3 inch, square ring in bore and remeasure the gap....if it has closed up you know the bore is tapered....

A stock build will usually tolerate a little bore taper, but if the gap has dropped to say 0.010....I would be boring the engine oversize....

Ring flutter will kill rings and pistons ....

:chevy::chevy::chevy:

Re: In need of ring end gap specs for 250 inline 6
 

Thanks for the input.
You must have missed that I already stated that the block has just been rebored. But that's ok:lol:
Thanks again.:chevy:

Re: In need of ring end gap specs for 250 inline 6
 

250 L6 at .060 - over = 258 cubic inches.

Re: In need of ring end gap specs for 250 inline 6
 

Thanks for the info.