440 blowout

[alf44]

I have a o2 400 ex with a 440 big bore kit I beleive it has stage two hot cams and all the goodies, fmf pipe white bros rev box k&n. I KEEP BLOWING HEAD GASKETS!! Does anyone else have this problem? Can it be fixed. Help!

[GPracer2500]

It's fairly common for high-comp EXs (especially the bigger bores) to blow head gaskets. The common solution is heavy duty head studs such as those available from GT Thunder.

[Andrewcordle]

I haven't seen it personally, but I have heard of people pushing their headgasket into the cylinder during pressure washing. It sounds like a load of crap to me, but if you are finding that your gasket is moving inwards i guess it could be that. I think the pressure washer thing is just a wives tail personally. Be careful if you are going to try different head studs. Stronger studs don't always mean you can get more torque on your head nuts, You could end up puling them out of cylinder if you go to far.

[K_Fulk]

Your head probly needs decked.

[Andrewcordle]

Would make sense. If the head was warped that could cause your gaskets to go out. I am doubting that compression alone is causing this problem....

[GPracer2500]

The common problem for high-comp 440s is that the stock head studs start to pull out of the cylinder. On the EX the head is secured by studs that thread into the cylinder--they don't go all the way throught the cylinder and into the case like many (most?) other designs. The threads in the cylinder start to give out when there's high cylinder pressures. It was never designed to accomidate such high pressures.

HD head studs solve this by having larger, stronger threads. The HD studs themselves don't provide a whole lot of benefit by being stronger--it's the new, larger, stronger threads in the cylinder that make the difference.

Only use a roll form tap when tapping the new threads for HD studs, not a cutting tap. A roll form tap actually pushes material around to form the new threads rather then just cutting it away. This makes for a much stronger thread.

Certainly have the head and cylinder surfaces checked for trueness by the machine shop when the studs are installed. Make sure to tell them to use a roll form tap!

[alf44]

Thanks for all the info> Apparently the person who built this quad thinks theres not enough surface area between the cylinder and the left rear head bolt.

[GPracer2500]

For reasons I don't really understand, the left rear head stud is the location where I've seen the most blown gaskets. That one stud seems to pull out more than the others. I seem to remember hearing that some builders (or at least one) will only bother to replace that one stud with a HD version.

[2muchquad]

I haven't seen it personally, but I have heard of people pushing their headgasket into the cylinder during pressure washing

WTF?:ermm: :D

[headache]

a friend of mine just put a 440ex together with a 12.5/1 piston, and it blew the headgasket in no time. He changed it out, and so far it is doing good, but i will mention the head studs to him.