standard size rings in a .020 motor?

Lyn Smith · 10-26-2012, 09:45 PM

I bought a street 327 short block from a guy who said it was rebuilt and always used oil even after he rerung it.The first thing i noticed on taking it apart is that the bore was .020 over, but the pistons were not marked as such.I measured the pistons,and they are .020 over but the top and second ring gaps are way over .100.Could they have stuck a set of standard rings in a .020 block?They probably looked at the pistons and thought they were standard.

Adger Smith · 10-27-2012, 09:47 AM

Lyn,
I've seen that happen before. I would say your assumption is correct.
The worst case I've seen is when a guy came in with a 350 he rebuilt and complained of a knock. The engine bore & crank was Std., all except one
.009 rod journal that GM had put on the crank. Then there was the guy that had me build a complete (when I say complete, It was complete from flexplate to water pump) 350 to exchange for his knocking 305. When I got around to taking his core/exchange engine apart I hit the first bolt on the flexplate with the air impact and the flexplate fell of the back of the crank. I had picked the only bolt that was holding a cracked flexplate on the crank. Upon complete disassembly the core engine was found to be O.K. It went back in service as a Std./Std.Std rebuild. What can you find that John Q. Public does??...Go figure!!

Mike Walter · 10-29-2012, 10:32 AM

Lyn, you have a PM.

Mike Taylor 3601 · 10-29-2012, 02:03 PM

Std. rings in .020 bore would have about .070 extra end gap,as Adger said I say you solved that mystery. I explain to customers who are going to assemble their own engine check ring gap,bearing clearances on all rings(the whole set) all rod and mains,check cam timing even on stock engine,the more checking you do during assembly,the less trouble you'll have,find the problems during assembly,not when you start it up
Mike Taylor 3601

10-26-2012, 09:45 PM	#1
Lyn Smith VIP Member Join Date: Dec 2001 Location: Pontiac,il. Posts: 1,195 Likes: 275 Liked 951 Times in 190 Posts	standard size rings in a .020 motor? I bought a street 327 short block from a guy who said it was rebuilt and always used oil even after he rerung it.The first thing i noticed on taking it apart is that the bore was .020 over, but the pistons were not marked as such.I measured the pistons,and they are .020 over but the top and second ring gaps are way over .100.Could they have stuck a set of standard rings in a .020 block?They probably looked at the pistons and thought they were standard.

10-27-2012, 09:47 AM	#2
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: standard size rings in a .020 motor? Lyn, I've seen that happen before. I would say your assumption is correct. The worst case I've seen is when a guy came in with a 350 he rebuilt and complained of a knock. The engine bore & crank was Std., all except one .009 rod journal that GM had put on the crank. Then there was the guy that had me build a complete (when I say complete, It was complete from flexplate to water pump) 350 to exchange for his knocking 305. When I got around to taking his core/exchange engine apart I hit the first bolt on the flexplate with the air impact and the flexplate fell of the back of the crank. I had picked the only bolt that was holding a cracked flexplate on the crank. Upon complete disassembly the core engine was found to be O.K. It went back in service as a Std./Std.Std rebuild. What can you find that John Q. Public does??...Go figure!! __________________ Adger Smith (Former SS)

10-29-2012, 10:32 AM	#3
Mike Walter Member Join Date: Jul 2008 Posts: 117 Likes: 12 Liked 46 Times in 4 Posts	Re: standard size rings in a .020 motor? Lyn, you have a PM.

10-29-2012, 02:03 PM	#4
Mike Taylor 3601 VIP Member Join Date: Oct 2008 Location: Somerset,Ky Posts: 1,364 Likes: 342 Liked 282 Times in 98 Posts	Re: standard size rings in a .020 motor? Std. rings in .020 bore would have about .070 extra end gap,as Adger said I say you solved that mystery. I explain to customers who are going to assemble their own engine check ring gap,bearing clearances on all rings(the whole set) all rod and mains,check cam timing even on stock engine,the more checking you do during assembly,the less trouble you'll have,find the problems during assembly,not when you start it up Mike Taylor 3601