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Discussion Starter · #1 ·
I put new head gaskets on my 460. I have not finished putting the engine back together. I still have to do the exhaust, intake, carb, distributor, steering pump. I did a compression test and still have numbers of 90 lbs. Is this accurate and I have other problems or do I need to put the engine all the way together and run it before I get accurate numbers?
 

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I put new head gaskets on my 460. I have not finished putting the engine back together. I still have to do the exhaust, intake, carb, distributor, steering pump. I did a compression test and still have numbers of 90 lbs. Is this accurate and I have other problems or do I need to put the engine all the way together and run it before I get accurate numbers?
How many miles are on motor? 82' motors are pretty low compression, you could cut heads down maybe 30 thousands to raise compression!
 

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you could cut heads down maybe 30 thousands to raise compression!
That won't fix bad rings... That well just raise the Compression ratio NOT the compression and could cause other problems like having to run higher test fuel Like race fuel depending on how much you mill the heads. Ether way low compression test that raises with a shot of oil is 90% bad rings.

good luck take care be safe
tim
 

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Discussion Starter · #12 ·
I got the engine out and removed the pistons. The rings are completely shot. Luckily the bores all measure straight and there is no ridge.

The engine is a 72. It's was bored .020 over when rebuilt. There is less than 2000 miles since the rebuild. After talking with some people about the engine builder I used, it's possible that the rings were not gapped properly. I won't be returning to that guy.
 

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Discussion Starter · #14 ·
Yes, I'll be doing the work. There is a ton of carbon buildup in the grooves. I cleaned the rings from two pistons. Put them in the cylinder to check the gaps. Had between .033 .037 on all four. Think I found the problem.
 

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Agreed. Big ring gaps are not an issue. Stuck or butted rings are. Your problem is not the ring gap but sealing in the bore, and it's likely from an oil source (and possibly carbon from rich fuel) that stuck the rings, or improperly installed rings. Find your original oil source (if not the rings), hone the bores and throw some fresh rings in. Drive.

BTW - that assumes the rest of the engine doesn't have issues. I'd check everything over before buttoning it up. You can make a leak-down tester for about $10-15. Really useful for finding where the issues are.
 

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Do not slather engine oil on the cylinders nor the rings / pistons during assembly... it'll gum up the lands, glaze the walls, and bake to a crispy dark brown. The rings will not seat nor rotate and eventually wipe the bore smooth prematurely while consuming copious amounts of oil during it's short, poor-performaning life.

If it were me... I'd deglaze with a ball hone and initially clean the bores with warm soapy water... Dawn is my preference. You know you doing it right when you get flash rust immediately after rinsing.
Then, clean the crosshatch with 50/50 ATF / Marvels... rub it in and wipe it out with white paper towels. Repeat, repeat, and repeat... until the paper towel comes out pink (no gray). Rub the walls again and let it sit overnight before wiping it out again. Repeat this cleaning process until theres absolutely no more gray. Use bright lights and a magnifying glass.
Leave the walls LIGHTLY wet with ATF / Marvels before sliding the dry piston / ring assembly in.
Just me and my ocd with clean bores.😉
 

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Would this be the same procedure for chrome moly rings? I mean as far as the grit of stones used if using a 3 stone hone what would be the preferred grit? 220? 320? Or higher?
 

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TL;DR - the finishes for the different rings are also very different. Keep in-mind that cast and chrome rings were obsolete (except for weed trimmers) decades ago. Ductile iron or steel (both moly) have been the go-to even for low-perf applications, but specific finishes and break-in procedures are required for best results. With modern methods, we can see how the mantra of "load the engine for ring break-in within 20 minutes of first warmup" begins to emerge. The AERA is one good source of data, and this EB article may help for initial concepts, but I always consult the ring manufacturer: Cylinder Bore Refinishing with Honing Tools
 
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