Blow by- bad honing?

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Machtuck
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Blow by- bad honing?

Post by Machtuck »

62’ Nova convertible with an inline 194 six (Total oddball) Ran well but blew blue smoke when accelerating. Wanted to overhaul so yanked the engine and found that parts are very difficult to source. Rear main seals and pistons in particular. The engine is already.040 and pistons looked good. No ridge on cylinder. Did a quick hone job. New rings and bearings. New cam and lifters ( cam took a month to get). Complete valvejob and hardened seats by reputable shop here in Nashville. Start up and cam break in went well. Idles and runs great BUT…
Lots of blowby and blue smoke from exhaust when revving or accelerating. Some smoke coming from breather and valve cover drain mast. Rear main seal is spraying oil badly. Obviously the crankcase is pressurized. Did compression test and all cylinders between 150-160. Did not do leakdown
( kicking myself).
Pulled engine back apart. Lots of oil in the intake under carburetor. Lots of oil in the cylinders and pistons. No cracked pistons. Re-checked ring clearances. All within spec: compression rings around .018/ oil rings around.040. ( spec is .015-.055).
Valve guides and seals all check out. A buddy of mine looked at cylinders and doesn’t believe the rings sealed. I’m curious if my “quick hone job” is the culprit and would an inadequate hone job cause this much oil to get in the combustion chambers?? Maybe glazed cylinders?? If i could find .060 pistons, i would get it bored and do it right. Should i take it and get it honed at the shop? Any input is much appreciated.
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Re: Blow by- bad honing?

Post by fabr »

I would hazard a guess that at least one of the piston manufactures have a casting/forging that they can machine what you need. Have it made to the minimum bore your engine will clean up at whether .045/.050/whatever . Make sure a compatible ring set for those bore sizes will be available first though.
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Re: Blow by- bad honing?

Post by abc »

Have the cylinders properly bore miced. I'm guessing that will tell the tale.
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Re: Blow by- bad honing?

Post by rebelrouser »

Hard to diagnose over the internet. If it has good compression, the hone job cannot be that bad. Did it have a good cross hatch, and did you wipe the cylinders with oil until a rag came out clean? Smoke out the breather indicate though that the rings were leaking. Did you maybe install a ring upside down, or mix up 1st and second rings? A out of round cylinder would cause an issue, but you said it had no ring ridge, most wear is in the top inch of the bore as a general rule. If the ring lands were worn, they can draw oil behind the rings and still seal for compression. It is a little expensive, but you can get custom pistons made. I had Ross make a set of pistons for a Lincoln V-12 one time.
Oil under the carb, would lend itself to poor valve stem seals or guide wear, but you said the guides were good. Being an inline engine, not really a way that a vacuum leak could draw oil like a V-8.
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Re: Blow by- bad honing?

Post by 1972ho »

With oil in the intake plenum and cylinder I would think you have a intake manifold that not fitting right and sucking oil up in it.I had that problem once because the block was not decked properly
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Re: Blow by- bad honing?

Post by FC-Pilot »

I did a 194 rebuild for my 63 wagon about ten years ago. Before installing the rings I inspected them carefully. Usually we are supposed to put the dimple up, well on the second ring after inspection it was supposed to go down. The rings did not come with instructions so I had to rely on experience. It never smoked a bit and didn’t use any oil. I would maybe look to see about the rings. I know, it sucks pulling it down.

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Re: Blow by- bad honing?

Post by rebelyell »

As for second rings, they typically have a tapered OD --- typically, slightly larger OD is at bottom of ring.
I know about convention of "dimple-up" but it pays to verify tapers' direction.
Regardless of dimple direction, me thinks it matters most which way the taper is installed.
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Re: Blow by- bad honing?

Post by 1980RS »

I had a SBC like that, ran good at first and then started smoking blue after about 100 miles on the rebuild. I was thinking it was rings for sure as the heads were re-done by me with guide clearances right and new PC seals. After some thought it turned out to be the new Edelbrock intake that was machined wrong sucking oil in from the bottoms of the ports. Put on a different intake and no more smoke.
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Re: Blow by- bad honing?

Post by FC-Pilot »

The 194 like many of the straight six’s didn’t have an intake that could suck oil. The oil in the intake has to come from the PCV valve. I might disconnect it for a little bit to see what happen.

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Re: Blow by- bad honing?

Post by rgalajda »

Is this an automatic transmission car?
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Re: Blow by- bad honing?

Post by Machtuck »

Thanks for the replies. The ring pack came with instructions and They were similar to many I’ve done. The only markings were on the second compression ring. I will say that the oil spacer could just about drop in. My experience has been that oil spacers were always loose though. There is no provision for a pcv. From GM was a breather on front of valve cover and drain mast tube off the rear that vented down to the street.
Looking at the cylinders, it does appear that there is not consistent cross hatching. I agree, with compression readings that good how could it be poor hone?
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Re: Blow by- bad honing?

Post by Tom68 »

Sounds like more than a bad hone, needs a bit of basic detective work.
Ignorance leads to confidence more often than knowledge does.
Nah, I'm not leaving myself out of the ignorant brigade....at times.
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Re: Blow by- bad honing?

Post by BillK »

What do the cylinders actually measure ?

Egge shows pistons. Dont know if they actually have them in stock.
https://egge.com/product/egge-piston-set-with-pins-165/
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Re: Blow by- bad honing?

Post by chevyfreak »

The 194 inline 6 uses same pistons as the 265 v8 from 50s.
Pistons is hard to get. Next size up is the 215 that was used by pontiac but bore is to big to go from the 194 to 215.
194 had rope type rear main seal, here in south africa our chevy inlines used rope seals up until the 1980s, 230s and the 250 units made locally.

We use the rope eliminator seals for the early small journal v8s. Not always in stock on the shelves.
Some part numbers of the seals.
Engine tech = s0629.
Fel pro = bs13241.

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Re: Blow by- bad honing?

Post by BillK »

Just want to add . . . some have mentioned the second ring being upside down. That will definitely cause oil consumption and smoking but should not cause blowby.
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