400ex keeps blowing headgaskets?!

[Exrider911]

hey guys whatsup, ever since i bought my 426ex from a member on here i had nothing but problems! my 426 keeps blowing headgaskets so i put a 440 cylinder and piston in because the other cylinder was warped. i sent the 440 cylinder off to the machine shop to have them put in the heavy duty gt thunder head studs. We received the cylinder back from the machine shop, assembled the top end and test rode it. We heat cycled it a couple times and test rode it for about ten minutes before it blew the head gasket again. We checked the head and cylinder with a straight edge and all appears to be good.. what can be causing it to keep blowing heads gaskets? We used the Extreme Seal Technology gaskets. let me know

[Fix29]

I've got a 426 with the GT Thunder HD studs and have had good luck with it. I've had good luck with the Cometic MLS gaskets. What octane fuel are you running?

[CJM]

Betcha your heads warped ever so slightly.

What gaskets are you using?

[Exrider911]

Betcha your heads warped ever so slightly.

What gaskets are you using?

checked the head and cylinder with a straight edge and its fine. cometic Extreme Seal Technology gaskets

[Exrider911]

I've got a 426 with the GT Thunder HD studs and have had good luck with it. I've had good luck with the Cometic MLS gaskets. What octane fuel are you running?

i had the same setup on my other 440 and never had a problem. i think its the guys working on it.. idk i wasn't there but they probably used 93. i always run vp 110 ill see what octane they used tomorrow.

[mikey726]

Torque the head to 40 ft lbs. Once I did that, I stopped blowing head gaskets. I also torqued the cylinder to 40 ft lbs.

[DragonGunner]

[QUOTE=mikey726;4336817]Torque the head to 40 ft lbs. Once I did that, I stopped blowing head gaskets. I also torqued the cylinder to 40 ft lbs.[


And how they are doing it as well.

[Exrider911]

Torque the head to 40 ft lbs. Once I did that, I stopped blowing head gaskets. I also torqued the cylinder to 40 ft lbs.

thanks bro ill try that and what headgasket are you running?

[Exrider911]

[QUOTE=mikey726;4336817]Torque the head to 40 ft lbs. Once I did that, I stopped blowing head gaskets. I also torqued the cylinder to 40 ft lbs.[


And how they are doing it as well.

you did the same and you stopped blowing headgaskets? what headgasket are you running?

[CJM]

I had a 416 and 426 running 11:1 on 93 pump, w/gtt studs and cometic gaskets and never had an issue. I always torqued the studs to spec as well.

Either whomever is assembling it is doing something wrong or liek I said straight edge or not it could very well be warped.

[JOHNDOE83]

I gaurentee that your running to lean and thats causing this issue.

Heat warps cylinder, heat breaks gaskets.

heat is caused by lean jetting, if youve gone from 400 to 426 to 440 and didnt change jets, thats your issue.

I run a 220 main in my 440, there is stock bore 400ex on this site using 200 main jets.

get a temp gun go for a ride get a temp reading, thats your issue.

[Exrider911]

I had a 416 and 426 running 11:1 on 93 pump, w/gtt studs and cometic gaskets and never had an issue. I always torqued the studs to spec as well.

Either whomever is assembling it is doing something wrong or liek I said straight edge or not it could very well be warped.

Certified mechanics that are working on it but they obviously don't know what they're doing.. Lol

[Exrider911]

I gaurentee that your running to lean and thats causing this issue.

Heat warps cylinder, heat breaks gaskets.

heat is caused by lean jetting, if youve gone from 400 to 426 to 440 and didnt change jets, thats your issue.

I run a 220 main in my 440, there is stock bore 400ex on this site using 200 main jets.

get a temp gun go for a ride get a temp reading, thats your issue.

Your right man cause now that I think of it it was running lean before I brought it to the shop! they said maybe the head should be skimmed to be 100% sure that it is flat. I'm gonna go there tm with some jets because I'm pretty sure the lean condition is causing this. Thanks

[CJM]

Certified mechanics that are working on it but they obviously don't know what they're doing.. Lol

Just cause they claim it, doesnt mean they know everything.

Ever go to the dealer to repair a car? You would think they have a clue since thats all the guys work on is that make/model, but usually not.

Id say your main issue is your quite lean. Id have them deck the head ever so slightly to make sure its not warped.

[JOHNDOE83]

Just cause they claim it, doesnt mean they know everything.

Ever go to the dealer to repair a car? You would think they have a clue since thats all the guys work on is that make/model, but usually not.

Id say your main issue is your quite lean. Id have them deck the head ever so slightly to make sure its not warped.

Man I have stories for hours about bad dealership experiences, mainly from honda and ford.

Both are great companies, ase certified mechanics just arent that great, I know highschool redneck kids that can out perform any mechanic at the dealership!