stripped head bolt threads
 

Hi folks,


Putting head back on 2005 civic D17A1 and the threads in the aluminum block stripped when torqueing one bolt.:mad: Questions;


why? I lubed the bolt threads and washer with STP


what makes that bad "creaking" sound my service manual warns about.


I've seen the time-cert kits but they are expensive. hate to buy to fix one hole. There should be used kits one can buy, borrow, rent. Anybody?


If I use helicoils can I put more than one in a hole? They seem pretty short


How about tapping for a larger bolt?


Is there such a thing as a reducing stud? Maybe 12mm in the hole, 10 mm through head?


Advice appreciated!!

Re: stripped head bolt threads
 

you can buy a head bolt. They're like 12-20 dollars each.

Did you tap out the thread? Are the threads stripped on the block?

Re: stripped head bolt threads
 

Why? Either your torque wrench calibration is way out or your threads were fatigued/corroded before you performed the torque sequence (hopefully you used the sequence).

If there is a creaking while turning the bolt in the threads, it's likely due to lack of lubrication. I know you stated you used oil on the threads but if there isn't enough, you'll wipe most of it off the threads as they begin clamping the head and get a dry creak from steel-on-aluminum dry sliding.

Also, it is typically beneficial to run a tap down the threads to clean out any corrosion in the tapped holes. Corrosion will close space in the female thread-form and produce a higher likelihood of friction as the bolt is ran through the hole. You basically want as little friction as possible in order to produce the correct clamping load for the fastener. Any friction will reduce clamp load.

Don't drill/tap for a larger head bolt. How much of the depth was stripped? Is there any undamaged length of thread in the hole that you can grab with a stud? If most of the length is shot, you're probably going to have to helicoil it. Weld repair is out of the question due to the deck surface warping from heat generation.

Re: stripped head bolt threads
 

if there is any "creaking" noise you should stop IMMEDIATELY remove the bolt completely and relubricate it,

dip the entire bolt in motor oil, if that still doesn't work i would use a bit of grease

Re: stripped head bolt threads
 

Thanks Y'all,


I did tighten in steps. The block threads look clean, but running a tap in and out sounds like a good idea. I checked the torque wrench (click type) years ago. I'll check it again against my buddy's. Guess I'll give the helicoils a shot. I'll lube the bolt threads and the block threads this time. Anyone think it would be OK to reduce the torque a little...maybe 45 instead of 49 ft lbs?


cheers

Re: stripped head bolt threads
 

in my experience, the click type are not as accurate as the guage type, especially at high or low torque values,

torque wrenches are most accurate in the middle of their entire range,

what is the entire range of the torque wrench you are using?

Re: stripped head bolt threads
 

So far so good. I installed 2 helicoils in the stripped hole, ran a tap in to clean the other holes, worked some grease onto the female threads, oiled the bolts, and torqued them in. They felt much smoother with the greased holes, and no creaks! So far they are all holding the full 49 ft-lbs! :^) Hope they don't pop out.


thanks gang!

Re: stripped head bolt threads
 

Lol hope it works out man. Every good machinist or builder will chase all threads with a tap before assembling to ensure the correct clamp load is achieved during torquing.

Re: stripped head bolt threads
 

What is the tap size you need i'm doing head gsket now and want to do the job only one time with no issues putting it back together.