I was in the process of freshening up my 383 stroker that had been sitting on an engine stand for about 4-5 years now. The motor only has a few hundred miles on it but it accumulated some rust deposits in the cylinders from sitting. Anyway, I cleaned up the cylinders with a hone, installed new rings and was in the process of reassembly and while I was torqueing the head bolts, I stripped one when transitioning from 35 to 70 ft lbs.

Question is; what is the best way to repair this? I've used helecoils before and they have worked good for light applications but for something like a cylinder head, it seems that something stronger should be used like a time-sert or something. I have done a thread search but nothing came up with this specific problem that I'm having.

I would just like to see what others have done as I have found that stripping these out is not uncommon.

Thanks for the help in advance.

Terry

 

scroll down to page nine, seems the heli's will work, hope this helps

https://www.google.com/url?sa=t&rct=...47534661,d.cGE

 

There should be no reason for head bolts to strip out threads, unless:

1. there is corrosion in the threaded areas. ALL threaded holes should be chased with thread taps to clean them up after prolonged storage.

2. The bolts were too long and bottomed out in the threaded hole before the head was seated.

Heli-coils...properly installed...should do the job. I highly recommend that you put a light smear of good epoxy on the OUTER threads of the Heli-coil when it is installed. Be sure to wipe any excess out of the INNER threads, once installed...then let cure completely.

 

I had a main bearing bolt strip out on a big block chevy once....fixed it with a helicoil and ran 9.20 at the strip with it the next weekend. Installed properly, they are a good repair.

 

Google for Cadillac Northstar headbolt failure. These were an alum block and stripped threads were common.
The GM fix was to use "Timesert" thread repairs instead of helicoils.
The GM kits were very expensive, but the Timeserts are available at most big industrial suppliers.

http://www.timesert.com/

 

ive used heli-coils on dozens of bbc/sbc heads/mains for years,just follow the instructions,,we used to heli-coil any/all aluminum block chevy engines and heads,never had 1 fail

 

Helicoils are stronger than the original thread, i've used them in head bolt holes and main caps, never had a problem.

 

I just finished a Rodeck aluminum block, a couple of the head bolts felt a little soft, so I replaced them all with heli-coils. However I double stacked them in each hole to have thread contact for the entire bolt. Takes more helicoils, but not difficult to do. Just snap off the tang in the middle of the treads. If the bolt holes won't take two full heli-coils, trim the upper one.
Time serts are great, the tool is expensive, to expensive for just one job. Some parts places rent them. The timeserts themselves are about $10 each. I use them all the time with the wonderful Triton Ford truck engines when they spit out the plugs. Only four threads in the aluminum head on that truck.

 

Those are fun, especially with the engine in the truck.
BTW, you can get the regular helicoils in different lengths, just not everyone carries them.

 

Seems like it's always the plugs in the rear. Anymore I won't mess with them unless I pull the head and do them all with Timeserts. Expensive, but worth it in the long run. Do the valves and the seals while they are off.

 

Yea 7T1, evidently something was not right creating this situation. The threads could have been corroded after sitting for so long. I'll admit, I did not chase the threads like I probably should have. Lessen learned on that but the head bolt (new ARP bolt kit) screwed right in by hand until it bottomed out at the head so I didn't think twice about grabbing the torque wrench and incrementally making my passes through all 17 bolts. I also used the recommended ARP assembly lube on all of the bolts so again, everything was smooth sailing.

All others, thanks for the responses. I have a local Fastenal shop here in town that I will check with but will also look at some of the machine shops to see if they have the helicoil kits and make my decision from there. Sounds like there is a toss-up with which method to use which is good.

What I was trying to see is if there was a definite "do not use" method.

Thanks again everyone

Terry

 

I hope you were aware that the ARP assembly lube is Moly and when torquing with either one, the specs are a LOT less than when using regular oil on the threads.

 

Yea noonie, I followed all instructions "almost" to the letter. ARP says to tighten the head bolts to 70 ft lbs in 3 incremental passes while using their assembly lube. The only deviation I made was instead of 3 passes, I only made 2 (40 and 70 ft lbs).

After installing a helicoil in the stripped hole, I went through and chased all of the threads with a tap, reassembled everything and I'll be damned if I didn't twist another one on the last pass to 70 ft lbs.

I took it all apart again, installed another helicoil and reassembled it again. Everything went fine that time.

While assembling the other side, I stripped another one. Now I am so upset, I am ready to helicoil the pistons in the cylinders.

The only trend I am seeing is that all of the bolts that are stripping are the lower shorter bolts. none of the main body head bolts are twisting.

Terry

 

noonie,
I just went and verified both specs. ARP with assembly lube says 70 ft lbs. basic stock engine fasteners are supposed to be torqued to 65 ft lbs. Is ARP wrong with their guidance? If what you're saying is fact, then I am way over-torqueing these things. Should I be going less that what ARP is saying. not meant to be a loaded question but I'm getting pretty good at helicoiling which is not something I'm proud of at this point.

Terry

 

ARP is not "wrong" with the torque spec for THEIR BOLTS. But, if you have a stock engine block, those specs. are DEAD WRONG for the torque the block threads will tolerate.

GM's spec. of 65 ft-lbs is based on stock bolts that are dry (not lubed). Normally, GM would reduce bolt torque by about 35% if those bolts were lubed. So, you should have only put about 40-45 ft-lbs on the lubed block threads, if you don't want them to strip. Obviously, that level of torque is not really enough to get the ARP bolts into any state of stretch {as they should be when a metal 'sandwich' is put together}, but more than that will offer the possibility of ripping out block threads---which you, unfortunately, did.

This is a significant problem with aftermarket "speed" parts. Folks want to buy the 'best' for their reworked engine. So, they buy aluminum heads...and ARP [high strength] bolts. But, the head manufacture has bolt torque specs (that are best for their heads), and the bolt mfg has bolt torque specs (that are best for their bolts), and GM sets a spec for cylinder head bolts (that are best for stock build). What is a person to do???

Well, the reality is that, if you are building up a stock engine block, unless you install steel threaded inserts of some kind, you are probably better off installing new stock bolts or bolts that are recommended by the cylinder head manufacturer. Bolt makers tend to set torques at the stress where their bolts have optimum holding power at an acceptable amount of stretch. And, if the mating parts are compatible with their strength and stress level, those torque settings are usually way too high for stock parts. In general, the bolt torque for the part that has the lowest spec, of those parts being placed together, should be used.

Just a little detail that they don't tell you about. If they did, you likely wouldn't spend the extra money for their bolts!!! American marketing at its best. {Sell product. To he!! with what the customer NEEDS.}

Sorry... I'm getting old and cranky--and really, really tired of the culture of GREED we have developed in this country.

 

P.S.

To be blatantly honest with you, I am now concerned about the long-term viability of the remaining threaded holes in your block that attach the cylinder heads. Since all of them have been torqued to 70 ft-lbs lubed, that means they have been torqued with stress equivalent to about 105 ft-lbs dry. That's more than a 50% overtorque on 40 year-old threads in a stock GM engine block.

Only you know how those other threaded holes "felt" as you brought them up to that level of torque. I can only say that, if they felt "spongy" as you reached final torque, those threads were likely reaching their limit of stretch. And, with an item such as a cylinder head...which takes a pounding every time a cylinder fires...those remaining threads might be "iffy".

If it were me, I might be tempted to put heli-coils in all those remaininng holes....just to be CERTAIN that there would not be a thread failure in the future. But, you have to make that call. Maybe other folks can give you their "take" on this situation. But, I thought I should at least give you a 'Head's up' before you get it all buttoned up.

 

Wow, what you're telling me makes perfect sense. Well this really sucks because as you mentioned, I have the same concern with all of the rest of the bolts (at least the lower short bolts).

I've got a call into ARP so now I'm curious as to what they are going to tell me when they call me back tomorrow.

Thank you sir for your time to explain this issue to me. I really appreciate it.

Terry

 

I thought that was pretty well common knowledge, but the last box of bolts I got from them, it was clearly on the box itself.
I'll see if I can run across the spec reference.

BTW, years ago I used the Ford factory service manual for head bolt specs. Ended up stretching every one beyond elasticity. Ford's factory manual was wrong.

 

One more thing, you should have been using their sealer and not the lube anyway since only the end holes are blind.

 

I would add that when I use heli-coils on block to head threads, I don't use bolts but switch to studs. Haven't done it to a Chevy but have on many other motors. I am sure you can get a head stud kit for chevy's, if not, fastenal can get you some, just measure and get the right grade. If there is a next time, you will strip the nut, not the stud or block...