Is this the cause of my blowby

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AC sports
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Is this the cause of my blowby

Post by AC sports »

Further to my previous post on blowby, I wanted to start another thread since I'm posting pics here. This is after 1000 miles on the street. Scuffing is on both the thrust sides of all 4 cylinders. Piston pins are central, not offset.
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Re: Is this the cause of my blowby

Post by jed »

Yes
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Re: Is this the cause of my blowby

Post by Newold1 »

Way to much oil on piston tops for 1000 miles. Obviously an oil in chamber issue but where the oil is entering still might be a question? Ring pack oil control might be the primary location and the serious skirt scuffing could be from burned oil carbon or from other clearance or fitment issues. Sort of strange some normal cylinder finish wear does not seem to be present at all in the picture as it views here? Can you show a shot of a piston skirt and the ring faces. What ring type are you using and is there any scuffing on the non-thrust side? Is the piston forged as it appears and what clearance is being run for the piston. What RA are you using on the bore finish, it looks a little rough? Was it plateau honed?

Because you are talking blowbye it appears to be a problem with ring seal.

Sorry for all the questions but it helps for a good diagnosis from guys here.
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Re: Is this the cause of my blowby

Post by geraldtson »

That don't look like no 320 grit as mentioned in earlier post?
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Re: Is this the cause of my blowby

Post by ProPower engines »

Take a close look at the 2nd ring as well as the top rings.
The finish on the bore looks waaaaaaaaaaaaaaay too rough for a performance engine unless you are using a hard chrome top ring but I bet you are not. lol :D My guess is you used a moly top ring and the rough finish destroyed the rings moly face and never seated with that many miles on the build the bores should look smooth with a hint of cross hatch left not a freshly honed bore.
It looks like the scuffed part is possibly smaller in size then the rest of the bore is. Or it is thin there and got hot but regardless I would confirm the bores are straight and round with a bore gauge.
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Re: Is this the cause of my blowby

Post by Warp Speed »

I think that early overheat may have taken it's toll. Unless it was just too tight to begin with.
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Re: Is this the cause of my blowby

Post by Walter R. Malik »

Warp Speed wrote: Tue Aug 07, 2018 7:14 pm I think that early overheat may have taken it's toll. Unless it was just too tight to begin with.
Find a cure for whatever is causing the detonation, before "fixing" anything else.
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Re: Is this the cause of my blowby

Post by Warp Speed »

Walter R. Malik wrote: Tue Aug 07, 2018 7:26 pm
Warp Speed wrote: Tue Aug 07, 2018 7:14 pm I think that early overheat may have taken it's toll. Unless it was just too tight to begin with.
Find a cure for whatever is causing the detonation, before "fixing" anything else.
Why are you telling me? Lol
Or are you pointing out I am way off base?
Please explain.....
Btw, are you sure any detonation you are seeing, wasn't caused by driving it after it scuffed, and was pumping a bunch of oil into the combustion chamber?
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Re: Is this the cause of my blowby

Post by powerhouse »

Is that a crack in the cylinder ? Horizontally thru the largest area of scuffing ?
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Re: Is this the cause of my blowby

Post by Walter R. Malik »

Warp Speed wrote: Tue Aug 07, 2018 8:25 pm
Walter R. Malik wrote: Tue Aug 07, 2018 7:26 pm
Warp Speed wrote: Tue Aug 07, 2018 7:14 pm I think that early overheat may have taken it's toll. Unless it was just too tight to begin with.
Find a cure for whatever is causing the detonation, before "fixing" anything else.
Why are you telling me? Lol
Or are you pointing out I am way off base?
Please explain.....
Btw, are you sure any detonation you are seeing, wasn't caused by driving it after it scuffed, and was pumping a bunch of oil into the combustion chamber?
The signs of detonation are there ... I don't know the cause.
It could have been overheating, or excessive oiling, or compression to high for the fuel, or a little of each or a lot of other things.
Whatever is the cause ... needs to be addressed.
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Re: Is this the cause of my blowby

Post by JoePorting »

powerhouse wrote: Tue Aug 07, 2018 8:29 pm Is that a crack in the cylinder ? Horizontally thru the largest area of scuffing ?
I was wondering that too. Maybe the expanding piston cracked the cylinder. Or maybe it's just a deep hone mark. But it looks like a crack.
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Re: Is this the cause of my blowby

Post by Warp Speed »

Walter R. Malik wrote: Tue Aug 07, 2018 9:10 pm
Warp Speed wrote: Tue Aug 07, 2018 8:25 pm
Walter R. Malik wrote: Tue Aug 07, 2018 7:26 pm

Find a cure for whatever is causing the detonation, before "fixing" anything else.
Why are you telling me? Lol
Or are you pointing out I am way off base?
Please explain.....
Btw, are you sure any detonation you are seeing, wasn't caused by driving it after it scuffed, and was pumping a bunch of oil into the combustion chamber?
The signs of detonation are there ... I don't know the cause.
It could have been overheating, or excessive oiling, or compression to high for the fuel, or a little of each or a lot of other things.
Whatever is the cause ... needs to be addressed.
Do you think that detonation was the reason it scuffed all pistons on both minor and major thrust?!?
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Re: Is this the cause of my blowby

Post by superpursuit »

That does appear to be a crack 1/3 down the bore gong horizontally. Not the way a bore normally cracks though. Only a live inspection will determine that I think. There also appears to be a water mark at the bottom of the ring travel.

I do agree that the overheating on initial start up is likely the culprit for the scuffing, assuming the pistons and bores were properly lubed on assembly. I think this scuffing would be the root cause of the blowby. You need to be very careful to keep an eye on those gauges on initial start up.
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Re: Is this the cause of my blowby

Post by AC sports »

Guys I'm investigating this further and will report back.
The finish really is 320 grit flexhone, done after boring and stone finish. It really does look coarser in pic than reality.
Rings are je pro seal, JG.....part number, Nitrite it says on the box, so not sure what composition they are. Top ring has chrome look to it.
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Re: Is this the cause of my blowby

Post by jed »

The block is not cracked!! If it were the piston top would be clean no carbon deposits.
In the picture of the cylinder on the very left the color shows to be a light brown or tan.
This used to mean the cylinder has varnished or glazed over. Maybe maybe not.
The top ring side facing the top of the piston looks scratched and scuffed up from maybe spinning to fast
and the cylinder cross hatch looks perty steep-which could cause the ring to spin faster than required.
There is lots going on in the cylinder, piston,ring package. You definatly have a cylinder surface finish problem.
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