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Bouncing off rocks
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Discussion Starter #1 (Edited)
i have a sbc crate motor with about 30 hours on it total. the number 8 plug was black and overed in carbon and i noticed it started using oil everytime i took the boat out. i did a compression check and all cylinders were 140-150, number 8 being one of the higher numbers. i pulled the heads and all cylinders looked perfect with grayish color, except number 8. it was caked with carbon. the engine never smoked and after inspecting the valves for that cylinder, it didnt look like the guides were worn or had oil getting past them. there was no scarring in that cylinder, still had crosshatching in it.


i want to put a cam and heads on it this winter, this engine has very low hours on it, but dont want to blow it up. it didnt do this until the last 3 times i had it out. it gets run hard and had been spraying 150 nitrous to it with cast pistons (i know), if i chipped a ring land or something of that nature, would it be obvious without removing piston? would the compression be down on that cylinder. any advise? if its not scored could i drop in forged pistons and run it? need to be honed anyway? is there anything else it could be, other things to check?
 

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E-7 Sheepdog (ret)
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You know you're gonna at least have to take that piston out to check the rings. May be an oil scraper ring problem.

Get the wrenches to it.
 

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You know you're gonna at least have to take that piston out to check the rings. May be an oil scraper ring problem.

Get the wrenches to it.
The nitrus could have collapsed the top of the piston and stuck the top ring, did you compression check it hot? I've actually seen compression checks come up good and have pitted valves, and lose a cylinder when the car warms up. cast pistons usually break skirts and knock.............. other than that they work under 6000 rpm's ............. sounds like a ring problem.............
 

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Bouncing off rocks
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Discussion Starter #4 (Edited)
pulled the piston out, everything looks fine and undamaged. could the nitrous have lifted the ring temporarily? what should i be looking for exactly? the only thing i noticed, which may be normal, i dunno is the oil ring has a thin piece of wire thourgh the middle, which i suspect is some kind of keeper? it only goes halfway around the ring. is it supposed to go all the way around? good thing i pulled it apart because when i pulled the pan off, the oil pickup fell off
 

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pulled the piston out, everything looks fine and undamaged. could the nitrous have lifted the ring temporarily? what should i be looking for exactly? the only thing i noticed, which may be normal, i dunno is the oil ring has a thin piece of wire thourgh the middle, which i suspect is some kind of keeper? it only goes halfway around the ring. is it supposed to go all the way around? good thing i pulled it apart because when i pulled the pan off, the oil pickup fell off
I always weld the oil pickup on the pump, even on cars, I just use an old lincoln buzz box welder and 3/16 nickol rod............. pull a good piston out and compare them up, never seen a keeper on the oil rings, I have seen a bottom spacer ring on some pistons then a 3 piece oil ring never any wire retainers................. if everything looks good, re ring the bad cylinder, touch it up with a ball hone yourself, ck the valve springs and valves and guides on the bad cylinder, throw it back together, it has to work !!!!
 

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I always weld the oil pickup on the pump, even on cars, I just use an old lincoln buzz box welder and 3/16 nickol rod............. pull a good piston out and compare them up, never seen a keeper on the oil rings, I have seen a bottom spacer ring on some pistons then a 3 piece oil ring never any wire retainers................. if everything looks good, re ring the bad cylinder, touch it up with a ball hone yourself, ck the valve springs and valves and guides on the bad cylinder, throw it back together, it has to work !!!!
I had a 396 in a camaro one time that lost a cylinder when it got hot, everything looked good/ we figured the rings lost their tension when the eng. warmed up, reringed the 1 cylinder and solved the problem, everything looked great............ definately threw me for a loop..............
 

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Bouncing off rocks
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Discussion Starter #9 (Edited)
i would have welded it on, but this was a brand new crate engine that i just lifted off the pallett and into the boat.

thinking of just buying a stroker kit or at least forged pistons while i have it torn down this far. would i be able to just drop new std pistons in, or just ball hone myself? or take it to machine shop?

do i need to clearance the block to run a eagle 383 kit?
 

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E-7 Sheepdog (ret)
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You could likey just ball hone deglaze it yourself, although a machine shop should not charge much for it either (they didn't mine).

I have seen a wire inside the oil ring center part (the strainer piece or whatever you properly call that 3rd ring part) BUT, that was on a Ford/Intl. (the 6.9L) Diesel I rebuilt a few years back. Never seen it on a regular Chevy, big or small.

Double check the valves, take them out and roll them accross a piece of glass (Ok, roll them in a circle), this will reveal any slight bends. Look REALL GOOD at the seat areas with them out.
Wouldn't hurt to give them a light spin against the seats by a hand drill with a dab of valve grinding compound if all else looks good, just to insure a good seal. Don't go crazy, just clean the seat mating surfaces basically, then, look at them again, on both teh valve and head to insure uniformity of seal area.
 

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Bouncing off rocks
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Discussion Starter #11
its definitely not the heads, i was running stock iron heads when it started doing this, so i pulled the heads a couple weeks ago, but had already bought performer rpm heads. i installed the rpms and ran it the last 2 weekends here before the weather cooled off and tore it down today with the same results more or less. that piston was black, while all the others were chalky gray/tan. i had cleaned the piston off thoroughly the last time before i put the heads on.

i was going to put a cam in it, new tunnelram intake, oil pump & pan etc over the winter
 

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its definitely not the heads, i was running stock iron heads when it started doing this, so i pulled the heads a couple weeks ago, but had already bought performer rpm heads. i installed the rpms and ran it the last 2 weekends here before the weather cooled off and tore it down today with the same results more or less. that piston was black, while all the others were chalky gray/tan. i had cleaned the piston off thoroughly the last time before i put the heads on.

i was going to put a cam in it, new tunnelram intake, oil pump & pan etc over the winter
W/ a 383 crank you will need all new pistons, a quick ball hone job will work fine, your motor if it was a new crate mtr. should be standard bore and will work just fine, all you are doing w/ a ball hone is roughing them up a bit and knocking the glaze off so the new rings will seat..................A bigger oil pan and even an oil cooler are the 2 first things anybody old school would buy...................
 

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Seriously off center
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i have a sbc crate motor with about 30 hours on it total. the number 8 plug was black and overed in carbon and i noticed it started using oil everytime i took the boat out. i did a compression check and all cylinders were 140-150, number 8 being one of the higher numbers. i pulled the heads and all cylinders looked perfect with grayish color, except number 8. it was caked with carbon. the engine never smoked and after inspecting the valves for that cylinder, it didnt look like the guides were worn or had oil getting past them. there was no scarring in that cylinder, still had crosshatching in it.


i want to put a cam and heads on it this winter, this engine has very low hours on it, but dont want to blow it up. it didnt do this until the last 3 times i had it out. it gets run hard and had been spraying 150 nitrous to it with cast pistons (i know), if i chipped a ring land or something of that nature, would it be obvious without removing piston? would the compression be down on that cylinder. any advise? if its not scored could i drop in forged pistons and run it? need to be honed anyway? is there anything else it could be, other things to check?
Have a PCV hooked up to the #8 intake port?:)sphss
 

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E-7 Sheepdog (ret)
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Seriously off center
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Well. on to plan B. When you look at the the #8 intake port in the head, is it a different color than the others or have a residue? Is there more carbon buildup on the backside (manifold side) of the #8 intake valve than the others?
 

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Bouncing off rocks
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Discussion Starter #19
Well. on to plan B. When you look at the the #8 intake port in the head, is it a different color than the others or have a residue? Is there more carbon buildup on the backside (manifold side) of the #8 intake valve than the others?

no, the valves looked the same,
 

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Sure sounds like a cracked intake manifold or a broken valve guide to me, but the "backside" of the intake valve should be nasty looking IMO......

GT
 
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