Head gasket issues

Tatuerik666

Tatuerik666

Member
#1
#1
So I have a built predator 212:
Big valve 32/28mm hi comp “non-hemi” style head
1.2 billet roller rockers
5.200 chromoly pushrods
Dual 32lb valve springs
Ti-retainers automotive style keepers
Stainless steel valves
308 cam
ARC +.20 rod
.570 flattop piston
ARC ultra lite flywheel
ARC billet side cover
Mukuni flatslide 24mm carb

Engine is well vented from valve cover and side cover. Drilled out the oil return hole in the block to 3/8
I am about to install my 3rd head gasket on it. The first gasket was a new stock one,the second was a MLS .27. I have head studs as well. What could cause it to happen? I did notice some oil on my piston. And with further inspection I found a bad valve stem seal which I replaced as well. Bike rips hard and runs good,then pop goes the head gasket. Any ideas or suggestions. I’m a beginner and learning. Any help would be appreciated image.jpg
 
Minimichael

Minimichael

Well-Known Member
#5
#5
Those gaskets look destroyed! Did that destruction happen at blow out? They're metal (tin?) and look singed and literally disintegrated. I'm guessing the deck or head or both are warped, and perhaps your +.20 rod is pushing compression too high? Consider a copper head gasket if they're an option for clones with these mod levels. And consider trying a thicker one to help raise the head further off the deck to relieve a bit of compression? Be sure you're vented to atmosphere too, rather than too much back and forth from cover to cover. Finally I'm a beginner too so don't just listen to me.
 
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Tatuerik666

Tatuerik666

Member
#8
#8
Minimichael said:
Those gaskets look destroyed! Did that destruction happen at blow out? They're metal (tin?) and look singed and literally disintegrated. I'm guessing the deck or head or both are warped, and perhaps your +.20 rod is pushing compression too high? Consider a copper head gasket if they're an option for clones with these mod levels. And consider trying a thicker one to help raise the head further off the deck to relieve a bit of compression? Be sure you're vented to atmosphere too, rather than too much back and forth from cover to cover. Finally I'm a beginner too so don't just listen to me.
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I have 2 vent hose to valve cover to side cover and one to atmosphere. I don’t believe there warped.
 
Minimichael

Minimichael

Well-Known Member
#11
#11
Do you know your compression? Your clearance from piston to deck at TDC? What volume in that hi-comp head? Also, is your atmosphere vent checked one-way from the stock valve cover outlet? If so maybe change that to two way so the case can breathe in as well as out.
 
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Tatuerik666

Tatuerik666

Member
#12
#12
Minimichael said:
Do you know your compression? Your clearance from piston to deck at TDC? What volume in that hi-comp head? Also, is your atmosphere vent checked one-way from the stock valve cover outlet? If so maybe change that to two way so the case can breathe in as well as out.
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I’ll be honest I don’t know all of that. I just watched YouTube videos and made it work for the most part. I know the head is a OldMiniBikes big valve hi comp. 14cc? I don’t have any valve to piston contact so I believe with clearance im good there. And my valve cover is an aftermarket billet one. I have 3 barbs coming out of it. 2 to the side cover and 1 with a 1 way check valve to atmosphere. I also have head studs. So maybe I can do a little more torque on the head?
 
Minimichael

Minimichael

Well-Known Member
#13
#13
Tatuerik666 said:
I’ll be honest I don’t know all of that. I just watched YouTube videos and made it work for the most part. I know the head is a OldMiniBikes big valve hi comp. 14cc? I don’t have any valve to piston contact so I believe with clearance im good there. And my valve cover is an aftermarket billet one. I have 3 barbs coming out of it. 2 to the side cover and 1 with a 1 way check valve to atmosphere. I also have head studs. So maybe I can do a little more torque on the head?
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I believe 14cc means it's the gx160 head. I don't know enough about your piston but between the head and the +.20 rod you are definitely raising compression. I wouldn't torque too much over spec...

Also if you go with a copper head gasket, they sell a copper gasket adhesive spray to seal. And if you aneal it first, be sure to quench - I don't care what others say on that one.

1 way venting theoretically is supposed to be good because it can maintain a negative case pressure and help prevent leaks from the side cover. But the oil at the piston as you mention could be a pressure issue? It may not hurt to try connecting the one way back to the side cover and then run the open two way barb to atmosphere. With a small air filter of course.

And which push rod (or was it valve stem?) was damaged? Exhaust? Maybe the valve isn't getting oiled right? Is there oil in the exhaust port too?
 
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ole4

ole4

#15
#15
When I use the Buriss studs I torque to 19FT lbs and have used the single metal as well as MLS and have not had any issues. If you do not criss cross or use too much torque you can deform the head on some of the castings. On your pictures it looks like the top of the gaskets are where the issue is. Use a straightedge on the head to check for flatness and the deck but its hard to see if the deck is off with a straightedge. Do not go over 20 FT lbs on the stud nuts. If you have a surface plate you could lap with 600 wet or dry and some oil to see if the head is flat.
 
Tatuerik666

Tatuerik666

Member
#16
#16
ole4 said:
When I use the Buriss studs I torque to 19FT lbs and have used the single metal as well as MLS and have not had any issues. If you do not criss cross or use too much torque you can deform the head on some of the castings. On your pictures it looks like the top of the gaskets are where the issue is. Use a straightedge on the head to check for flatness and the deck but its hard to see if the deck is off with a straightedge. Do not go over 20 FT lbs on the stud nuts. If you have a surface plate you could lap with 600 wet or dry and some oil to see if the head is flat.
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If I had a bad valve stem seal and oil was getting in with my piston with the hi compression my engine has would it blow head gaskets? possibly? Bc I noticed the stem seal was completely fucked when I took my motor apart to repair the gasket. Also had a little oil on my piston.
 
Minimichael

Minimichael

Well-Known Member
#18
#18
Tatuerik666 said:
If I had a bad valve stem seal and oil was getting in with my piston with the hi compression my engine has would it blow head gaskets? possibly? Bc I noticed the stem seal was completely fucked when I took my motor apart to repair the gasket. Also had a little oil on my piston.
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I'm wondering that too. Maybe the seal was blown because of pressure from the case, which could be also be out of whack from such high compression pushing a lot of blowby down. Maybe even 2 vents to atmosphere and only between the covers!
 
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Tatuerik666

Tatuerik666

Member
#19
#19
Minimichael said:
I'm wondering that too. Maybe the seal was blown because of pressure from the case, which could be also be out of whack from such high compression pushing a lot of blowby down. Maybe even 2 vents to atmosphere and only between the covers!
Click to expand...
Well I got another MLS head gasket on the way. And I replaced the valve stem seal. I’ll re assemble it and see if it pops again. If it does. I’ll change my vent hoses around and see what’s up. I’m gonna try an .18 MLS gasket. Everything else is out of stock. I also might order a stock length rod too.
 
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