I recently installed a wiseco 440 big bore kit in my 2000 400ex. The kit came with a new piston, sleeve, stage 1 hot cam and gaskets. I installed the kit without any hang ups, and the motor ran great for about two hours before the head gasket blew. The kit didn't come with any special torque specs so I torqued everything to factory specs. Should I have torqued the head tighter due to the increase in compression (my kit has an 11:1 ratio), or is there some other problem? Any help is appreciated.

 

if you cleaned up the gasket surfaces, oiled all the head bolts and followed the correct torque sequence the only thing I could guess is maybe a problem with the sleeve installation.

 

I had the sleeve installed at a local machine shop, so that could be the problem. Just trying to cover all my bases, but is there a need to retorque the head after a certain number of warm up cycles or is the initial torque good to go.

 

The head nuts should be re-torqed, but I doubt that is the problem.

This can get a little involved so be patient, and dont let it get to you etc.

The normal reason most (not all) blow the gasket is from the studs pulling up from hi compression.

Now there is other reasons it happens, and its usually a combo of things that lead to it (very often hi comp, and hi rpm) but before you can fix it you need to tear it down and take some measurements to determine the "actual" compression which is very different than the pistons listed comp.

I have mixed opinions on this but many believe the smaller studs used on the head are just not able to handle hi comp set ups well, and need to be changed. I ran the stockers with a true 12.6:1 for years, but later pulled them out like nothing and swapped to the hd ones from gt thunder.

There is a indepth explanation on some of the problems and simple fixes and even how to set up a good 440 I think on here (do a search and see what you find, and I will post a link if I can find one) and I know there is one under the mods section at the site linked in my signature. I think its a pretty good one, but then I wrote it so I am a little biased, but I think you will answer some of your questions, and create better ones after you read thru it.

Anyhow some of the questions I would ask to help you figure it out are if you do know what the actual comp was, and if you did a mech comp test, and if you know what your deck height was, and if you know what thickness gaskets were used (both head and base), and a host of others after you answer these.

Do a search here or check out the thread in my sig (you have to find too but its a really small site and easy) answer those couple questions above and lets move on from there. This way we shouldnt miss anything.

 

Oh and you can try to return that stage1 as it wont work right with a 440, and the people who put the kit together should have know better as even HC does not recomend it with big bore or hi rpm set ups.