Head gasket keeps failing
Thread Starter
Advanced
Joined: Mar 2003
Posts: 98
Likes: 3
From: Oglesby Illinois
Head gasket keeps failing
I have a 70 Vette with an LS5 454, bored 30 over. We rebuilt the motor 4 years ago and ever since every year the passenger side head gasket blows out between cylinders. I have had the head decked, 1 colder plug, removed the heat riser and used high end head bolts and it just failed again a year later. At this point i am certain there is a valley worn between these cylinders probably from trying to remove gasket material during the rebuild. Is there a head gasket that can resolve this issue without me removing the block and having it decked? Or is there anything else that can be done?
Thanks.
Thanks.
Le Mans Master
Joined: Oct 2012
Posts: 9,366
Likes: 969
From: Out back
It probably is the block. Remove the block and have it decked (might as well do a rebuild with full prep if you're going to pull the engine). If you don't want to do all that then I'd switch to a copper head gasket with some spray gasket on it. If it still leaks with that...your block on the passenger side may be no good.
Drifting
Joined: Dec 2009
Posts: 1,349
Likes: 34
From: Porterville Ca
What you really need to do is remove the head, clean it with permatex gasket remover (a acidic or caustic product, instead of abrasion). Then use a straight edge and feeler gauge to check for low spots. Don't even bother discussing a repair or remedy before you verify the cause of the blown head gasket.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Just a few questions back at Ya.
First, what are the symptoms? Bubbles in the radiator? Loss of "tested" compression with adjacent cylinders? Milkshake on the dipstick?
Second, it would be tough to form a valley by scrub pads in cast iron. Aluminum? Yes, maybe, could happen.
Are you using $19.95 a pair gasket or $50 EACH, gaskets? Not using a shim to bump up the C.Ratio are you?
I assume the proper bolt tightening sequence was followed. In how many steps? I know some prefer 3 steps in torquing. I think 5 steps better. Especially with aluminum.
Such as: Just snug, then 20 lbs - 40lbs- 60lbs then 80.
First, what are the symptoms? Bubbles in the radiator? Loss of "tested" compression with adjacent cylinders? Milkshake on the dipstick?
Second, it would be tough to form a valley by scrub pads in cast iron. Aluminum? Yes, maybe, could happen.
Are you using $19.95 a pair gasket or $50 EACH, gaskets? Not using a shim to bump up the C.Ratio are you?
I assume the proper bolt tightening sequence was followed. In how many steps? I know some prefer 3 steps in torquing. I think 5 steps better. Especially with aluminum.
Such as: Just snug, then 20 lbs - 40lbs- 60lbs then 80.
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
bill69 - I would do a little checking into the MLS gaskets made by Cometic or Fel-Pro.
I believe that the MLS gaskets are a bit more "tolerant" of less than stellar surface prep. But please - don't take my word for it - so some checking on your own.
But - honestly - you need to check BOTH the block and the cylinder head with a straight edge to see if you have a sealing surface in need of some TLC.
I believe that the MLS gaskets are a bit more "tolerant" of less than stellar surface prep. But please - don't take my word for it - so some checking on your own.
But - honestly - you need to check BOTH the block and the cylinder head with a straight edge to see if you have a sealing surface in need of some TLC.
Race Director
Joined: Nov 2006
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From: Sunshine Coast, Queensland, Australia
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After making certain block is flat. head is flat. Use a top quality gasket and I am a big fan of spraying it with permatex copper spray gasket.
I am running shim gaskets. Sprayed with permatex copper and do far. All good.
I am running shim gaskets. Sprayed with permatex copper and do far. All good.
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Thread Starter
Advanced
Joined: Mar 2003
Posts: 98
Likes: 3
From: Oglesby Illinois
Just a few questions back at Ya.
First, what are the symptoms? Bubbles in the radiator? Loss of "tested" compression with adjacent cylinders? Milkshake on the dipstick?
Second, it would be tough to form a valley by scrub pads in cast iron. Aluminum? Yes, maybe, could happen.
Are you using $19.95 a pair gasket or $50 EACH, gaskets? Not using a shim to bump up the C.Ratio are you?
I assume the proper bolt tightening sequence was followed. In how many steps? I know some prefer 3 steps in torquing. I think 5 steps better. Especially with aluminum.
Such as: Just snug, then 20 lbs - 40lbs- 60lbs then 80.
First, what are the symptoms? Bubbles in the radiator? Loss of "tested" compression with adjacent cylinders? Milkshake on the dipstick?
Second, it would be tough to form a valley by scrub pads in cast iron. Aluminum? Yes, maybe, could happen.
Are you using $19.95 a pair gasket or $50 EACH, gaskets? Not using a shim to bump up the C.Ratio are you?
I assume the proper bolt tightening sequence was followed. In how many steps? I know some prefer 3 steps in torquing. I think 5 steps better. Especially with aluminum.
Such as: Just snug, then 20 lbs - 40lbs- 60lbs then 80.
A scotch brite pad was used on an air tool.
Hmmm...I don't remember, I got them from summit racing. They may have been $50 a pair. I don't think I pent $50 per? But keep in mind the driver side has never had an issue.
I followed the manual which was 3 sequences of torquing. Same thing as the previous one, i followed the same sequence on the drivers side and never had an issue.
Burning Brakes
Joined: Jan 2003
Posts: 961
Likes: 275
From: Frederick MD
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,810
From: Cool Northern Michigan
Bill69,
At this point I think I would take the offending head to a competent machine shop. Hopefully they will allow you to watch as the head surface is checked for flatness.
If it only needs a "clean-up", leave the good head in place on the engine. If the bad head needs a lot of material removed, then the good head should be removed and shaved to match.
Something tells me it's not the block at fault. Blocks get lots & lots of coolant run through them. Heads, on the other hand, have small coolant passages and are more prone to warping from compression heat, exhaust heat and sometimes poor oil circulation top-side. If an engine ever boils over from lack of coolant its usually the heads that suffer.
Ask the machinist what recommended gasket thickness will be needed to make up for the removed material from the head and go from there.
There is no sense in pulling an engine on speculation a block might be warped. A straight edge a feeler gauge is a pretty crude way of determining exact measurements. And that's fine on a lawnmower but yours needs more precision in this case. It can get you a ballpark figure at best.
At this point I think I would take the offending head to a competent machine shop. Hopefully they will allow you to watch as the head surface is checked for flatness.
If it only needs a "clean-up", leave the good head in place on the engine. If the bad head needs a lot of material removed, then the good head should be removed and shaved to match.
Something tells me it's not the block at fault. Blocks get lots & lots of coolant run through them. Heads, on the other hand, have small coolant passages and are more prone to warping from compression heat, exhaust heat and sometimes poor oil circulation top-side. If an engine ever boils over from lack of coolant its usually the heads that suffer.
Ask the machinist what recommended gasket thickness will be needed to make up for the removed material from the head and go from there.
There is no sense in pulling an engine on speculation a block might be warped. A straight edge a feeler gauge is a pretty crude way of determining exact measurements. And that's fine on a lawnmower but yours needs more precision in this case. It can get you a ballpark figure at best.
Burning Brakes
Joined: Jan 2003
Posts: 961
Likes: 275
From: Frederick MD
Bill69,
At this point I think I would take the offending head to a competent machine shop. Hopefully they will allow you to watch as the head surface is checked for flatness.
If it only needs a "clean-up", leave the good head in place on the engine. If the bad head needs a lot of material removed, then the good head should be removed and shaved to match.
Something tells me it's not the block at fault. Blocks get lots & lots of coolant run through them. Heads, on the other hand, have small coolant passages and are more prone to warping from compression heat, exhaust heat and sometimes poor oil circulation top-side. If an engine ever boils over from lack of coolant its usually the heads that suffer.
Ask the machinist what recommended gasket thickness will be needed to make up for the removed material from the head and go from there.
There is no sense in pulling an engine on speculation a block might be warped. A straight edge a feeler gauge is a pretty crude way of determining exact measurements. And that's fine on a lawnmower but yours needs more precision in this case. It can get you a ballpark figure at best.
At this point I think I would take the offending head to a competent machine shop. Hopefully they will allow you to watch as the head surface is checked for flatness.
If it only needs a "clean-up", leave the good head in place on the engine. If the bad head needs a lot of material removed, then the good head should be removed and shaved to match.
Something tells me it's not the block at fault. Blocks get lots & lots of coolant run through them. Heads, on the other hand, have small coolant passages and are more prone to warping from compression heat, exhaust heat and sometimes poor oil circulation top-side. If an engine ever boils over from lack of coolant its usually the heads that suffer.
Ask the machinist what recommended gasket thickness will be needed to make up for the removed material from the head and go from there.
There is no sense in pulling an engine on speculation a block might be warped. A straight edge a feeler gauge is a pretty crude way of determining exact measurements. And that's fine on a lawnmower but yours needs more precision in this case. It can get you a ballpark figure at best.
Safety Car
Joined: Nov 2008
Posts: 3,726
Likes: 558
From: Seattle Washington
I would block sand the Deck surface. What I mean by this is to take something really flat like glass and some 320 sand paper. Take a felt tip marking pen and color the surface first. Then do some block sanding in the area You suspect. You will quickly see if one area is lower than another by the scratch marks in the ink. Obviously do the same to the Head. Diesel guys do this all the time.
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rotary air tool on deck: scotchbrite abrasive pad=NO, but 3M Bristle Disc=YES