Ring end gap - 350 - meaning of minimum, maximum or service limit?? [Archive] - Team Camaro Tech

: Ring end gap - 350 - meaning of minimum, maximum or service limit??

caribbean camaro
Mar 18th, 02, 07:41 AM
My haynes manual for my 85 camaro -
refers to 305 bore and gives the top ring end gap as 0.10 to .025 - service limit .030

Does this apply to a 350? - what does the service limit mean? what are the stock specs for a 350??

I have a set of Perfect Circle standard rings - instructions say .016 minimum or .004 for every inch of cylinder bore?

I reclaimed a dead 350 block and honed it myself this weekend - I intend to rebuild it all on my own for the first time with all original parts -

it showed up the top ring end gap as nearly .040 to .045 in at least one cylinder and over .030 in most cases!

Is this a sign of too much wear???

Assuming I do go ahead with new rings, and this is a purely experimental build, should I expect a smoking 'Joe???


85 Camaro Berlinetta - 305ci, stock heads, flattops, 214/224-443/465, Edel. 600 & Performer intake, 700-R4 & transgo kit, TCI competition 10in. conv, 4.10, Auburn posi

Vintage 68
Mar 18th, 02, 10:15 AM
Whoa - first you need to check that "0.10" number, you sure you didn't mean 0.010"? Or are these readings in MM not Inches?
That would sound closer to a 350 End Gap number. The 'factory' spec.s run in the 0.010 - 0.020 range for the top ring and 0.013 - 0.025 for the 2nd. ring.
I use 0.015 (top)& 0.018 (2nd) for most of the street small blocks I build.
If you are reading 0.030 + for the ring gaps, what is the bore taper reading? ( in service readings should be in the .005" range max.) Sounds like it's rebore time if the ring gaps for standard size rings are coming in that far off.
Lastly. "Service Limit" refers to the normal reading a mechanic should see during the repair of an in service engine during a routine repair, such as the replacement of a broken ring or cracked piston, not requiring any machine work (not a rebuild or rebore of the engine). These fiqures are usually given in the factory manuals as a guide for spotting worn or out of spec. parts.
Good luck on your project.

'68 Rag-top SS350/350 (on it's way to a 200-4R)

caribbean camaro
Mar 18th, 02, 02:07 PM
Thanks for the reply - I am really trying to avoid the rebore as the facilities are not readily available here

I did mis print the haynes manual specs - it is 0.010 - 0.020

If indeed the ring end gaps are that far out as they are - how bad a running engine can I expect at its worst?

Are they any tricks to get a block nearing or past service limit specs to run for a bit of bracket race thrashing in a thorougly tired banger??


85 Camaro Berlinetta - 305ci, stock heads, flattops, 214/224-443/465, Edel. 600 & Performer intake, 700-R4 & transgo kit, TCI competition 10in. conv, 4.10, Auburn posi

Mar 18th, 02, 07:11 PM
Push the rings down the bores farther and re measure.
The bores are probably tapered, they tend to wear more at the top.
You could have gotten file to fit rings that you would then have to file to make work, but watch out for the taper or they might get too tight on the bottom of the stroke.
A forged piston would be better in a worn bore like that, as they require more clearance anyway.

Check my web page for First Gen Camaro suspension info:
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67 RS 327 original owner. 69 Camaro Vintage Racer, 65 Lola T-70 Chev SB Can-Am Vintage Racer

Vintage 68
Mar 19th, 02, 03:55 PM
I agree with David's post about the Forged Pistons. Not only do they normally need and tolerate more bore clearance, they are able to stand up to more "wobbling around" in the cylinders of an older engine without damaging themselves. I've used this 'trick' several times on friends engines when things were getting messy and money was tight. Forged pistons can be had for about $40. ~ $50. (U.S.) more than cast for most small block engines.
I would still really recommend you check the Bore Taper as I suggested in my first post. If nothing else record it for future so you know what overbore the block will need someday. Meassure at the top, again about 1/2 ~ 3/4" down and again near the bottom of the piston travel (you should be able to see a mark). Write these three readings down for each cylinder and compare them to the standard spec.s. Then you will know for sure how worn the block is. If it's really bad and you can't locate machine work locally maybe you should be looking for another block?
Definitely Hone the cylinders with a "dingleberry" or wire-ball type hone using a shallow cross-hatch pattern of 45~50% to reduce oil wicking. A normal Stone type hone will not reach all the worn areas with out over honing and removing even more material. This can also really mess-up the bore "roundness" when you overhone.
As to 'will it smoke or burn oil' if it's worn - well yes, more than normal. But I've torn down small blocks with broken and completely missing rings that were running just fine at the time just getting old. I've found that valve guide wear can cause more problems with oil burning and plug fouling than rings in many small blocks. Replace the intake seals and use them with "Hat Type" just in case.
Good luck with your project.

'68 Rag-top SS350/350 (on it's way to a 200-4R)

Mar 19th, 02, 10:33 PM
i have done a couple of $200 rebuilds with blocks that had big ridges, and both times the engines turned out just fine. make good power, burn little oil, and get good fuel economy. maybe i was just lucky? the way i look at it is that i have a 100,000 mile engine with new rings and bearings.

1971 Nova(looks like 69 camaro from underneath!)
355sb, vortec heads, HOT cam,T-10 tranny, 3.70 gears 16X8" IROC wheels. 12" Corvette brakes on the way.
see pics here http://community.webshots.com/user/novaderrik

caribbean camaro
Mar 20th, 02, 07:43 AM
Nova has my idea in mind fully - I expect it will not be a perfect engine with all the wear - but I just want the experience of doing it myself for a first and see how it runs - its going in a perfectly abandoned donor car and this way I get to make my mistakes - if any - for under 200!

and thanks for the help with measuring all around - most of the cylinders are slightly wider up top but the differences are a couple thou.. and it appears as if they are all worn more to one side . i.e the outer side of the cylinders - based on the fingernail test on the slight ridges we observed

Any hints about the engines condition from that ???

(I cheated on my do it alone plan with this observation - the fingernail belonged to my long trusted mechanic)


85 Camaro Berlinetta - 305ci, stock heads, flattops, 214/224-443/465, Edel. 600 & Performer intake, 700-R4 & transgo kit, TCI competition 10in. conv, 4.10, Auburn posi

Vintage 68
Mar 20th, 02, 12:43 PM
More pronounced wear on the "thrust side" is normal, cylinders will tend to wear out of round.
Did you try checking the ring set you have down deeper in the bore? Just for yucks I pushed a new 'standard' GM ring down into a worn 010 4-bolt bolt core setting in the shop and it measured in just over 0.020 at about an inch down. This block has a noticeable ridge at the top (by the tried and true "fingernail test").
Are you sure that the figures you gave in your first message are with 'standard' rings? Maybe you could try the readings again with one new standard size ring set and see if you didn't accidently get a set of overbore rings slipped in on you.
Just a thought as I've been burnt by someones returned parts before. Now if the sets been opened for any reason I refuse it.

'68 Rag-top SS350/350 (on it's way to a 200-4R)