[461-69bird]

a couple of my header bolt threads have stripped, can I use a helicoil to repair them on KRE d ports? or is there another solution? if so what size would I need?

[steve25]

Yes they can be Heilcoiled and they are 3/8" course thread.

Course is 12 threads per inch.

If you do not have expensive stainless steel bolts that you use I would take this opportunity to change over to 3/8" fine thread on all of those 6 bolts since that will give more clamping force and be far less likely to pull out again on you.

You can also change over to running studs in some of the holes to gain better longevity and clamping in the process.

Either way you will need the whole Heilcoil kit, not just the incerts, and since you need to drill out the original hole to accept the incerts you may have to pull that head to do so properly, or jack up the motor to get the needed drill bit angle on target.

I have not looked, but since you live in Europe there may be a much easier to get metric Heilcoil set that's close enough to 3/8" to work for .

When you put everything back together be sure to use antiseize on all the threads.

[461-69bird]

thanks Steve.

I`ve got to pull the heads due to a gasket failure.

[chiefbigb]

3/8 16 should be the size you want.

[67Fbird]

if any of the holes are "blind" you will want 2 of the helicoil taps so you can grind the end off 1 (trying to make a bottoming tap) Also note after you drill and tap your holes don't be shy with the chamfer... a little more is better than not enough when you are intalling a helicoil.

[tc]

We use keenserts at work for fasteners that have repeated use in aluminum. You don't need the tool if you are careful pounding the locking pins down. I have never seen a problem using these even using a extension bar on the hex ( allen ) wrench. There may not be enough material as these require a larger thread diameter than a heli-coil. There are thin and thick wall inserts.
http://www.repairengineering.com/keensert.html

[Dragncar]

Anyone ever pull a rocker stud on a set of High Ports ? I believe the HPs are tapped into aluminum while E heads are heli coiled, true ?

[Scarebird]

I think I have a custom tool I made to drill the holes for Helicoil straight for exhaust holes. Essentially you use the aluminum guide dowel to line up with the hole then tighten the nut on the other side and drill.

I will need to check.

I can send it and the tap if desired.

[461-69bird]

Thanks Scarebird but I'm in England.

[mgarblik]

I have a new set of High Ports I will be prepping for Eric in his road race application in the next few months. IMO, every threaded hole in a cylinder head of a race head should have a thread insert in it. The only exception might be accessory holes in the end of the heads that would be in the back and only used for grounds or to hold a bracket. Front accessory holes that will hold accessory brackets should be heli-coiled as well. I can report back on any issues encountered. Coils are inexpensive and pretty easy to install IF you have a mill to set up all the angles. Installing free hand without a drill guide is a recipe for disaster IMO. I like Time certs, keen serts and other solid bushing repairs as well, but a bit of overkill as a first line preventative repair. As mentioned, a larger hole is required vs a coil repair. It would be nice if KRE offered a full heli-coil package as an option on their heads. They already have the cnc program to drill and tap all the holes. All they would need to do is screw in the inserts and break off the tangs. I think allot of people would pay an extra $150.00. for a pair of heads with all the coils installed. In bulk, the coils could be bought for .25 cents each.

[Dave Polichena]

Originally Posted by Dragncar

Anyone ever pull a rocker stud on a set of High Ports ? I believe the HPs are tapped into aluminum while E heads are heli coiled, true ?

Yes, I ended up putting inserts (Timeserts) in all the holes. Eventually went to shafts for piece of mind. Keep in mind, I was running .800+ on lift.