400ex 11.1 high comp piston

[jmaxw21]

i resently put a 11.1 high comp piston and a stage two hot cam in my 2007 400ex will i have to worry about the head pushing off. without heavy dutey head bolts?

[dxcody]

Its not really the compression that causes the head studs to stretch, its the heat.

Is your 400 a stock bore?

[jmaxw21]

yeah its stock bore i put an extra oil cooler on befor i did my mods

[dxcody]

you will probably be fine.

Heavy duty head studs are just mostly for insurance on stock bore and 416's etc..


The HD studs were made more for the 440 big bore, if i remember right.

Good to have, but not a 100% must do on standard bore engines.

As long as your jetted right, you should be fine.

[kaptainbutler]

I was thinking of doing the exact same mods to mine. Can you tell that the cam and 11:1 were worth it, or do you wish you had gone a little further?

[slightlybent47]

Your fine as long as you didn't over torque the studs.

[dxcody]

Originally posted by kaptainbutler
I was thinking of doing the exact same mods to mine. Can you tell that the cam and 11:1 were worth it, or do you wish you had gone a little further?

Thats the same setup i have, and i love it.

Anything more than the mods i already have, and i would just buy a 450.

Thats when you start having problems, is when you mod the absolute crap out of 400ex's IMO.

[DragonGunner]

About 2001 I put a 416 kit 11:1 in my 99' with stock studs an went about 2 years on it an alot of hours, then a 426 for about 4 yrs on stock studs, then a 440 12:1 with stock studs an started blowing head gaskets, then it was time for GT thunder studs.

[Pipeless416]

Originally posted by dxcody
Its not really the compression that causes the head studs to stretch, its the heat.

Is your 400 a stock bore?

which is a result of higher compression and thinner cylinder walls. FWIW, i would recommend the studs on anything with higher than stock compression just as cheap insurance. 9 times out of 10 it is the stud between the two exhaust ports that ends up pulling since the metal around it gets the hottest there. i pulled that stud and blew a headgasket before my engine was really modified and it really ruined a trip that we drove 15 hours to get to. many never have problems even with larger bores, but if i were to do it all over again i would have put in the HD studs before i did anything else.

[quadmanw]

This is exactly the set up im about to do. I hope its worth it. Minus the HD studs.. my mechanic has built many of these and has never seen them pull so im gonna hope for the best lol

[jkosakowski]

Im also having the same thing done anyone have it done how do you like it? Mine is getting done in febuary to far away lol.

[CJM]

Bore size is really relative, mine makes very little difference in power 416 vs 426 vs a friends 407. Its the cam, jetting, carb, and compression that make the power. Had I do it all over again I think I woulda done a port and polish with a 416 and 450r carb.