Head gasket

[Cajun power]

if you have PROFESSIONALLY FACED the upper cylinder head and main block? (I'm skeptical...not saying you did not do it...but there is a world of difference between DIY truing and professional).

so if you removed to much material, it may be difficult to actually get valve clearance set...no matter what you must reset valve clearance. PER THE SERVICE MANUAL...Lot of bad information out on the interwebs., And check that valve seats have not stepped out...makes sure the exhaust and intake valve are not borked with soot or heat damage like warp ...also look at exhaust ports...something soot gets cooked and that can cause overheat.
the gaskets you bought may be the wrong type. (for instance...on some mower engines the OEM gaskets have been improved and superceded with better materials...usually a composite, metal/fiber type. you will need to research this...there is alot of junk resellers out there who send wrong parts and not the upgraded parts...recheck everything.
your engine might be running way too lean...this overheat cycle over and over is going to eventually blow out head gaskets. Try to look for any air leaks and adjust the carb spot on.
the mayb be serious internal damage to oil pressure pump...if yours has one. most of the cheaper have slingers...some have an actual oil pump. If oil is not getting where it needs to go, overheat...head gaskets blow out. (and hopefully, only that!)
the cylinder head may be cracked. Sometimes it a very small micro crack that only creates problems after hot cycle. If you suspect this, you can either do a penetrant dye and black light inspection...or shadetree: do a hot cycle, shut mower off and as soon as you can set up and perform a leak down check...the latter might be able to
other causes could be head gasket bolts that have stretched or bolt threads in the head are borked. It's one of those things that can happen from improper torque but also getting slammed by overheat cycles over and over.


if you've done all these things and everything checks out..AND THE LEAK DOWN CHECK IS GOOD AND GOOD COMPRESSION then consider buying COPPER GASKETS...They are superior in almost every way...better squish, and far superior heat transfer. Here is an reputable company that I have recently bought copper gaskets to fit a kawasaki mower engine I rebuilt..

KAWASAKI 11004-7026,FS730V,FX651V, FX69V, FX730V,LAWNMOWERS,9C3

Made in USA Thickness .016" solid copper Bore 3.110" Reusable if not damaged SHIPS FOR FREE USA ONLY INTERNATIONAL SHIPPING $13

coppergaskets.us

 

[Oarhead]

He also asked:
Are these engines junk?

Post up the engine ID info for a more precise Yes or No.

33r777 for this one. Definetly headgasket. Gonna have head milled and do a close check on the block. I also have 33r877, changed everything,(springtime maintenence), fuel filters etc. Starts when choked but dies when throttle to fast run. Ugh...

 

[Oarhead]

How long does a head gasket usually last on your engine? (average time, like one hour, one day, or a year???)
The head and or block is either warped or as startech indicates you are not torqueing the head bolts PROPERLY.
With patience you should be able to check the head and block for warpage.
Also if it has a small dip or groove in the aluminum where it is burning through is not a good thing.
That area you describe is a wimpy place for the single cylinder Briggs Intek engines, some last forever, some don't and proceed by the book (service manual) when replacing the head gasket on those type. Make sure all the cooling fins and flywheel plastic fins are in place. Do not test run the engine over few seconds with the cooling shroud removed.

If all else fails try two heads gaskets.

Gonna pay closer attn to the surfaces. Thoughts on copper gaskets?

 

[sgkent]

is the head worth milling cost wise? I use a machinists straight edge and check it I I I then three spots 90 degrees from that then an X. If it is good then milling it will only raise compression and make any overheating and compression worse. Compare the cost vs new. Best guess is that a machine shop will just lay it flat on a good quality band sander and surface it that way. One does a couple light X patterns with it to keep it even. I can't imagine trying to hold a mower head down on a real head and block milling machine. I used to run a Vulcan mill for that and no way would I trust a small mower head not to go flying if I tried to MILL it.

 

[grpascott]

I have a Husquvarna tractor. 18.5hp. Can anyone tell me why I have gone thru 4 head gaskets? This one being the 4th. Blows out right across from the plug. There is no way I screwed up 3 headgaskets. Getting a little tired of this crap. Are these engines junk? I can change a hot cylinder in a 2500hp EMD but can't keep this running. Should sell everything and buy a diesel....

I had trouble with my 18.5hp intek blowing head gasket too. The head bolts were lousy alloy and kept stretching, so I replaced them with grade 8 bolts. This required adding some additional thread length with a die as the bolts weren't threaded deep enough, but the extra work was worth it. It's been several years now...no blown head gaskets. (Torque to 22 ft lbs.)

 

[slomo]

Replace the head bolts is one of the main things. Once a bolt has been torqued it changes the metal and can cause them to lessen the torque when the engine gets hot.

These only have like 10-20ft lbs depending on engine.

 

[slomo]

It's not the space shuttle guys (Taryl). Little 220, 400 and 800 grit paper and a piece of plate glass for the block. Also use the side garage door window to lap the head. Cheap sanding block, what ever........ Get her done.

 

[GrumpyCat]

Remove the head, take a straight edge Across both head and block. Use a feeler gauge and see if you and put it between the straight edge and the head and also between straight efce and block.

That test will tell you if it is bad but will not be an assurance that it is good. Sure, it is straight from corner to corner but are the corners in the same plane square to the stroke?

 

[Honest Abe]

as already stated, use NEW quality head bolts, and torque as specified . . . . .

 

[bertsmobile1]

Replace the head bolts is one of the main things. Once a bolt has been torqued it changes the metal and can cause them to lessen the torque when the engine gets hot.
What I do is first take emery cloth and a flat block and emery the head and block clean of all discoloration, then I put on the new head with new bolts. I torque to specifications twice. This gives it max torque on the bolts. Torque bolts in the specified order. If this does not stop it from blowing head gaskets you will have to have the head and block resurfaced.

This is only true for CAST IRON engine blocks where the head bolts are done up to 100 ftlbs of torque or there abouts .
If you think 20 ftlbs into alloy is going to cause any structural change to a bolt, even a grade 3 bolt then you must have been asleep during your science classes at high school or gone to a school that teaches creationism and languages with no science at all .
When torquing down into alloy you damage the hole not the steel bolt which is why quality alloy engines use inserts , to protect the block.

On bolts
Higher tensile bolts have deeper cut threads so there is more surface area of metal to metal contact to create more friction between the bolt & the hole which is why the bolt stays in there and why using a grade 9 bolt seems to hold better, nothing to do with the tensile strength of the steel.

Please try not to conflate automative technology with mower technology where there is almost none .