blue smoke on acceleration , dramatic increase

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golden boy

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always had one cyl down on compression that i suspected was the issue. went looking for this sudden increase in acceleration induced blue smoke and i found another cyl on the same bank that seems to have lost 40 psi since the last time i checked compression. this rebuild doesn't have 5000 miles on it. but a lot of it is running @ the drag strip. just got a lot worse @ the first drag race of the summer last week. ( summer just starting here in Canada). the first thing that comes to mind is a broken ring, or head gasket failure. My question , is how to methodically diagnose this prior to disassembly. 410 mag block, w/ edelbrock heads, atomic injection, keith black hypereutectic pistons 40 over. rev limiter set @ 6100rpm.
 
Try doing a dry compression check on the cylinders, then a wet compression check with 2 - 3 squirts of oil in the cylinders...

If the compression increases with the wet test, then the problem is in the rings... If no increase or just little increase with wet test, look into the valves...

a leak down test can help pinpoint it better after that...
 
that makes sense! i have a leakdown tester as well. will try to borrow a bore scope ,but i find its pretty hard to see much with those. wondering about head gasket fire ring exposed to crank case causing a suck/blow condition??? seems odd to have happened seemingly so quick. its been awhile , but block was honed using washers under torqued head bolts ( to torque plate available) . 3 thou wear in cyl . new rings. ( it was a freshen up).
 
golden boy said:
always had one cyl down on compression that i suspected was the issue. went looking for this sudden increase in acceleration induced blue smoke and i found another cyl on the same bank that seems to have lost 40 psi since the last time i checked compression. this rebuild doesn't have 5000 miles on it. but a lot of it is running @ the drag strip. just got a lot worse @ the first drag race of the summer last week. ( summer just starting here in Canada). the first thing that comes to mind is a broken ring, or head gasket failure. My question , is how to methodically diagnose this prior to disassembly. 410 mag block, w/ edelbrock heads, atomic injection, keith black hypereutectic pistons 40 over. rev limiter set @ 6100rpm.
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If you're lucky in an unlucky way the piston lost a ring land and it went out the tail pipe...that way saves losing a piston in its entirety followed by a cylinder wall.
The blue smoke is oil and that points to the piston coming apart.
Call KB and see about a couple pistons...pricing them... then tear it down to see how many you really need.. then when it goes back together ... add and extra .015-.020 to the gap... in fact.. just gap the top rings @.034 and second @.024.
I usually leave the 2nd ring stock gap.. but I've been hearing from other that they had issues.. with that said I have not but dont want to give wreckless advice.
 
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dont forget to check intake gasket for sucking oil /
 
teringer said:
dont forget to check intake gasket for sucking oil /
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The OP said that he has 2 cylinders that have lost compression. The intake manifold is still a good idea though. I'm thinking it's rings, and sloppy valve guides will cause oil in the chambers too. I've heard about KB pistons breaking ring lands. Wiseco has a affordable piston / ring package. Speed pro pistons is another option.
 
Dan the man said:
The OP said that he has 2 cylinders that have lost compression. The intake manifold is still a good idea though. I'm thinking it's rings, and sloppy valve guides will cause oil in the chambers too. I've heard about KB pistons breaking ring lands. Wiseco has a affordable piston / ring package. Speed pro pistons is another option.
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My machinist does not like the KB pistons at all because he has seen a lot of problems with them breaking due to intolerance of rings/ring gap.

I went with Sportsman Racing Products
https://www.amazon.com/gp/product/B003OCIOFO/?tag=fabo03-20
 
golden boy said:
that makes sense! i have a leakdown tester as well. will try to borrow a bore scope ,but i find its pretty hard to see much with those. wondering about head gasket fire ring exposed to crank case causing a suck/blow condition??? seems odd to have happened seemingly so quick. its been awhile , but block was honed using washers under torqued head bolts ( to torque plate available) . 3 thou wear in cyl . new rings. ( it was a freshen up).
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I don't think that washers under the head bolts would give you the same benefit of a torque plate. 0.003" cylinder bore wear, what's the piston to cylinder wall clearance with those pistons? If it's 0.005", then you have 0.008".
 
the history on this motor is that it was a bluprint crate. 2 pistons ended up with brroken ring lands. Bluprint sold me new pistons /rings and i cleaned it up with a hone and reassembled . this is when i found out about the ring gap fiasco that exists with KB pistons. as near as i could tell they were 26 thou ring gap. when i reassembled i gapped at 32. there was a small mark at the bottom of the 2 cyl that were affected visible after honing. both were at bottom dead centre. so when i was getting a small puff of smoke and a little blow by after the rebuild i just accepted that as normal. when the rings broke in the blow by became minimal, but it always had a small puff of smoke on acceleration until the last pass at the dragstrip when it became a large puff of smoke, and subsequent testing showed one cyl down 40 psi. i will tear it down to check but curious about what i should look for prior. ie; how do i diagnose/differentiate a manifold leak from a head gasket leak. when i pressurize the cyl i likely will get air leaking in the crankcase and the tail pipe is my guess?
 
golden boy said:
the history on this motor is that it was a bluprint crate. 2 pistons ended up with brroken ring lands. Bluprint sold me new pistons /rings and i cleaned it up with a hone and reassembled . this is when i found out about the ring gap fiasco that exists with KB pistons. as near as i could tell they were 26 thou ring gap. when i reassembled i gapped at 32. there was a small mark at the bottom of the 2 cyl that were affected visible after honing. both were at bottom dead centre. so when i was getting a small puff of smoke and a little blow by after the rebuild i just accepted that as normal. when the rings broke in the blow by became minimal, but it always had a small puff of smoke on acceleration until the last pass at the dragstrip when it became a large puff of smoke, and subsequent testing showed one cyl down 40 psi. i will tear it down to check but curious about what i should look for prior. ie; how do i diagnose/differentiate a manifold leak from a head gasket leak. when i pressurize the cyl i likely will get air leaking in the crankcase and the tail pipe is my guess?
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Large puff after a race run and 40# loss of compression on 1 cylinder. Yep! Probably another broken piston. Did you replace all the pistons or just the 2 broken ones?
 
A leak down test will tell you where it is. Then you get to tear it down and look for it.
 
Put KB hypers together with normal ring gaps (.004/bore inch) and they pull the lands out. Most every issue about them killing lands is improper ring gap and horrible tune ups..
 
MOPAROFFICIAL said:
Blooperint engines again..uh oh..
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I struggle to see what BP could have done that would have caused replacement pistons to break?

Sounds like OP has something else going on causing the pistons to fail in the first place. Detonation? Timing? I'd suspect the EFI might have even unintentionally leaned out at some point.

I've been beating on my BPE shortblock for 5 years now with tons of abuse. The only things that broke happened when I sent a hardened washer down the intake. Replacement piston and ring set from BPE still going strong.
 
golden boy said:
the history on this motor is that it was a bluprint crate. 2 pistons ended up with brroken ring lands. Bluprint sold me new pistons /rings and i cleaned it up with a hone and reassembled . this is when i found out about the ring gap fiasco that exists with KB pistons. as near as i could tell they were 26 thou ring gap. when i reassembled i gapped at 32. there was a small mark at the bottom of the 2 cyl that were affected visible after honing. both were at bottom dead centre. so when i was getting a small puff of smoke and a little blow by after the rebuild i just accepted that as normal. when the rings broke in the blow by became minimal, but it always had a small puff of smoke on acceleration until the last pass at the dragstrip when it became a large puff of smoke, and subsequent testing showed one cyl down 40 psi. i will tear it down to check but curious about what i should look for prior. ie; how do i diagnose/differentiate a manifold leak from a head gasket leak. when i pressurize the cyl i likely will get air leaking in the crankcase and the tail pipe is my guess?
Click to expand...
KB pistons come with instructions on how to gap the rings to be used with their pistons, I wouldn't run kb pistons
 
AJ/FormS said:
I second these numbers, they worked for me.
And PowerTiming not exceeding 34* with alloy heads. Got over 100,000 out of her so far.
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With kb pistons? Must be a stock rebuild. I don't know of anyone getting that many miles with them. From what I've read and the people that I've talked to kb pistons are not known for longevity.
 
Dan the man said:
With kb pistons? Must be a stock rebuild. I don't know of anyone getting that many miles with them. From what I've read and the people that I've talked to kb pistons are not known for longevity.
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When there is no detonation or interference...they last as long as the rings seal. Magnums are hyper...as well as many chevies and others *that are fuel injection. The pistons are high silicon , brittle and conductive and don't grow much at all..hence the rings butting because they are steel or iron and do grow a lot absorbing the higher than average piston temps. I use them in my 340. Many thousands of miles. I've had them shatter in other motors, yes. I wouldn't recommend anyone running them with edgy compression and a carburetor unless they're tune savvy.
 
Phreakish said:
I struggle to see what BP could have done that would have caused replacement pistons to break?

Sounds like OP has something else going on causing the pistons to fail in the first place. Detonation? Timing? I'd suspect the EFI might have even unintentionally leaned out at some point.

I've been beating on my BPE shortblock for 5 years now with tons of abuse. The only things that broke happened when I sent a hardened washer down the intake. Replacement piston and ring set from BPE still going strong.
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I thought I read he bought motor from another dude who lost a ring land on it already...so then he fixed the one...now he has two..same and the one next to it.. so sounds like rings butting...so who built that fkn motor. unless I'm missing something...'and i could be'.. but ...sounds like all the pistons should come out to be inspected and the rings opened at the very least, since original builder did it wrong.
If I missed a turn or twist in the story..let me know.
:thumbsup:
 
MOPAROFFICIAL said:
I thought I read he bought motor from another dude who lost a ring land on it already...so then he fixed the one...now he has two..same and the one next to it.. so sounds like rings butting...so who built that fkn motor. unless I'm missing something...'and i could be'.. but ...sounds like all the pistons should come out to be inspected and the rings opened at the very least, since original builder did it wrong.
If I missed a turn or twist in the story..let me know.
:thumbsup:
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I'd rebuild the motor and have it honed with a torque plate and then I'd buy a quality set of pistons. KB pistons are brittle and way to sensitive to ring gap and tuning.
 
Dan the man said:
I'd rebuild the motor and have it honed with a torque plate and then I'd buy a quality set of pistons. KB pistons are brittle and way to sensitive to ring gap and tuning.
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Here's a little thing that I learned a long time ago and I mentioned it here and then somebody else I think Mopar Joe or somebody made a video where they did like a ford or some **** with a torque play yada yada yada anyways he left out the important part which is what I learned a while back. Which is a torque plate does not simulate two things and those two things are the actual clamping and Distortion forces from the full density of the cylinder head & main torque forces and 2... the temperatures at which the engine is ran ...everything changes shape with heat.. so even using a torque plate, it's not going to be round when it's fully warmed up UNLESS you can get the engine completely warmed up while honing it...even then the temp spikes ...and it's worth about 2 hp at 7000+ and that's a satirical guesstimate based in the reality that's it's not worth the cha$e for about 98% of us.
 
I originally asked my builder to supply and install the KBs per the book because I was gung-ho for the predicted results.
but that engine ran hot no matter what I did, and would lock-up everytime I shut it off, and it got terrible fuel mileage, and required a lot of throttle to keep it idling.
Before long I pulled it out and tore it down to see what the builder had done.
Well, from memory; the skirt clearance was .0025 to .0030 and the ring gaps were tight, as per the KB book. I was very disappointed at the "large " skirt clearance, but there was no indication that the pistons were sticking, so I assumed the rings were the problem. Again, no damage.
So I sent the block to a different machine shop to even out the bores. And it came back at .0035 every one the same now, and pretty straight. Yes on cold mornings I sometimes hear a lil rattle.
I threw the cast rings away, in favor of Plasma-Moly file-fits, and opened up the gaps to the towing/ nitrous specs of .034/.024 IIRC.
Everything else looked good so I bolted it, Edelbrock heads and all, back together.
With no other changes, all my problems were solved. ALL OF THEM.
So I experimented with increased coolant temp, and found that she liked 207* at the stat-house. And she, by seat of the pants, had no preference to timing in the window of 32 to 36, so I set it to 32 for that summer. The next summer I set it to 34, which made no discernible difference in power. And she has run in that 32 to 34 window ever since. I run it on 87E10 exclusively.
I have not had any heating problems since those changes were made. and she goes like a cat on fire. Even 93mph in the Eighth, at 3457 pounds, at 930 ft elevation.
I would use KBs again, but I would try a lil less skirt clearance next time, and a lil more cylinder pressure, but
I will not use either of the previous machine-shops again.
 
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