Stripped camshaft cap holes

Hi there, I was in the process of installing a used cylinder head on an 81 kz1100 when I realized that someone had over-torqued the camshaft cap bolts previously. Four of the holes on the exhaust cam side are stripped out. I got a tap (6mmx1.00) and tapped the holes thinking this would solve my problem but the bolts didn't grab like I'd hoped. My next bet is to heli-coil them, but I'm not sure if this is recommended or if I will find the right size to fit the bolts. If you have any info or tips I'd appreciate it : )


Chris

I think that is the best next step, unless you have someone weld them over then drill and retap them

I have run into the same problem. I just installed helicoil inserts. You can get a kit to do this at any auto parts store. To prevent having to remove the head to do this, I bought a long drill bit, 8mm I believe, about a foot long, from Home Depot. That way you can drill out the old threads with the head installed. You have to pack rags around the hole to prevent metal filings from getting down into the head. I only torque my cap bolts to 100 in lbs. That way there is no chance to strip the threads out of the hole. I have had no problems doing this either....chris3

Thanks for the quick responses. I guess heli-coil is going to be the route I take, but what are the ways that the sizes go on them? The bolts are 6mmx1.00, does heli-coil have a size that corresponds to it?

Just get a 6mm helicoil kit. I think all 6mm are the same pitch. Not hard to install. The exhausts will always strip for some reason. I don't know if it's the heat or possibly there are less threads on the exhausts, but they will strip even at 8 ft/lb. I only tighten to 5.5ft/lb

Yeah it's weird, all the intake threads are in mint condition. Anyways, I will try this tomorrow. Thank you very much for the help I'll post the results tomorrow night

Chris

I ran into the same problem with a head that I installed. Except what I found was that the PO had already helicoiled several of the holes, and the coils were coming out. So I'm not a big fan of them.

Instead, I bought thread-serts (I think that's what they're called). They are a steel insert, and are a much more durable and permanent fix. Plus, you don't need any special tools to install them like you do with the Helicoil (except for the drill bit and tap--which you also need for Helicoil). They just install with a standard flathead screwdriver. And they are fairly cheap. I think I paid less than a couple bucks each for them at the local Ace Hardware. You can get them even cheaper online if you buy in qty 10.

To install them, you first drill out the hole. I can't remember the required size, but they should be able to tell you when you buy them. Then you tap the threads. While drilling and tapping, I smeared a gob of grease around the hole and covered the head with foil to catch any cuttings. Worked pretty slick.

Next, you screw the insert in with a screwdriver.

If you are repairing a hole where there is a knock pin, the oversize hole you drill for the insert is almost exactly the same diameter as the pin, so you can still reinsert the pin with no problems.

Here's a pic of me tapping the hole:

And here I am threading in the insert:

Ah, yeah those are called time-serts I believe. I might have to look into that instead, seems more solid. Thanks for the input.

in addition to the rags and I have found that duct tape the end of a shop vac next to any drilling helps keep shavings out of places they dont belong

I seconded that motion, helicoils suck. i have alot of problems with them in the past. time-serts are the best way too go. requires a little larger hole then helicoils but it is the best way too go. I also use red lock tight. I don't use the dry stuff on the inserts. my two cents.

scott

Well it turns out helicoils are the only product I could get ahold of... Which is OK because they worked out just fine. The cams are in and the engine turns over like a champ.. Now to bolt on the carbs and see what happens! This project is finally coming to an end..