400ex head bolts

[Locknload82]

Head gasket on my 400ex started leaking. checked The head bolts and the threads were stripping on one of them. It had the stock head bolts so I will be going the HD stud route. Found the website for GT thunder, they say you need to use a special Roll Form Tap to tap the threads with. Anyone use a regular tap on these.

Had heard about FDO HD studs, anyone have the website for FDO? Do they also require a Roll Form Tap?

anyone use permatex sleeve retainer when installing?

[GPracer2500]

Much of the added strength from using HD studs comes from the use of a roll form tap. You could use a regular cutting tap but you'd be giving away strength by doing so.

[prepracing]

Originally posted by GPracer2500
Much of the added strength from using HD studs comes from the use of a roll form tap. You could use a regular cutting tap but you'd be giving away strength by doing so.


please explain what a roll form tap is and how it gives more strength

[zrpilot]

Roll forming actually deforms the material to "form" the thread. It produces a stronger thread because of the compressed grain structure caused by forming of the thread.

[GPracer2500]

Originally posted by prepracing
please explain what a roll form tap is and how it gives more strength

There are two types of taps for threading holes. Cutting taps and forming taps. Cutting taps are what most people are familiar with. If you've got a set of taps and dies in your garage chances are good they are cutters. Cutting taps actually cut material out of a hole to form the threads. Form taps don't remove any material from the hole. Instead, they use pressure to "push" the metal around in the process of forming threads. This aligns the grain structure of the metal to follow the shape of the thread making it significantly stronger. Also, there are no chips produced in form tapping.

ETA: zrpilot beat me to it

[JOEX]

Does roll form tapping make it possible to use the original size bolt in a threaded hole that was stripped? Not neccessarily head bolts.

[zrpilot]

Originally posted by JOEX
Does roll form tapping make it possible to use the original size bolt in a threaded hole that was stripped? Not neccessarily head bolts.

No, because there is not enough material left for forming and having the same thread height. You could make a larger thread from the damaged hole, but not the original.

Sorry :(

[JOEX]

Originally posted by zrpilot
No, because there is not enough material left for forming and having the same thread height. You could make a larger thread from the damaged hole, but not the original.

Sorry :(
That's what I figured, Thanks:)

[wilkin250r]

Originally posted by JOEX
Does roll form tapping make it possible to use the original size bolt in a threaded hole that was stripped? Not neccessarily head bolts.

To get to that point, you'd need a helicoil kit. I've done it several times (not on head bolts). They come in standard and metric, and a wide range of depths.

[Locknload82]

Thanks for the info on roll form tapping, had never heard of it before. Have ordered HD studs and a roll tap from GT thunder. We have been fighting this on my stock 400 and my sons 426 all summer (long story). Hopefully this will fix it.

[JOEX]

Originally posted by wilkin250r
To get to that point, you'd need a helicoil kit. I've done it several times (not on head bolts). They come in standard and metric, and a wide range of depths.
I've used Helicoils too with success. I was just wondering if this could be a subsitute, Helicoil kits aren't cheap:ermm:

[zrpilot]

Originally posted by JOEX
I've used Helicoils too with success. I was just wondering if this could be a subsitute, Helicoil kits aren't cheap:ermm:

The roll form tap method is the strongest solution. Followed by the Helicoil.

It seems do the roll form method, or if they have failed, do the Helicoil method. Either way you should get a larger diameter, stronger thread.

[DAVE14]

the last time i got a cyl studded with gt thunder studs the shop that put them in put them in at stock depth when the gts go in deeper so i carefully drilled them a little deeper & used a regular tap to go the whole distance & there hasnt been any problems but but the majority of the hole was a roll form tap I would have bought one but couldnt find one anywhere & most tool shops had no idea what I was looking for

[400exrider707]

Originally posted by DAVE14
the last time i got a cyl studded with gt thunder studs the shop that put them in put them in at stock depth when the gts go in deeper so i carefully drilled them a little deeper & used a regular tap to go the whole distance & there hasnt been any problems but but the majority of the hole was a roll form tap I would have bought one but couldnt find one anywhere & most tool shops had no idea what I was looking for

GT Thunder sells them..


Locknload82 are you planning on doing this yourself, its not a simple drill and tap job. Each stud needs to be at a specific height, and perfectly vertical.:ermm:

[Glamis400ex]

^^^ya, no kidding. When I did the FDO on my 426ex I had them do it. The bolts are $60. For an extra $30, they'll do it right the 1st time.

Glamis

[Locknload82]

Going to have a local machine shop do the drilling and tapping (bought a roll form tap from GT thunder). Even though I have a drill press, I know I couldnt get the holes perfectly straight.

[DAVE14]

the holes were perfectly straight & done from the machine shop but I had to go down a bit further it might of been .250 nothing too deep , I used a drill press then tapped it a little further & a roll form tap I was not able to find to save my soul its been beat on for months with no problems I dont expect a stud to pull my last cyl. had gt thunder studs but also had a helicoil that failed