• Protip: Profile posts are public! Use Conversations to message other members privately. Everyone can see the content of a profile post.

Head bolts pulled out!!!! Advice?

G

GEM930

Registered Member
Joined
30 July 2002
Messages
12
Location
Chico, CA USA
The bottom two head bolts (#1 cylinder) pulled out on my 1997 NSX. - I guess I know why I blew a head gasket now.
Anyway, any advice or suggestions on time-serting just the 2 or should I do all 16? I did a search and I could not find anything on head bolts, so this must be an isolated kind of thing. If that is the case, only doing the 2 would probably be okay, but I just wanted to check. Any help would be great!
Thanks

GEM
 
I have never heard of this happening to an NSX, it sounds like someone over tightened the bolts. I would check into whoever did service to the engine. Sorry I can't offer too much advice on how to correct the problem though.
 
I am also guessing that they were overtightened. Assuming that the same torque wrench and settings were used for all of the bolts, if it were me, I would put tapserts or helicoils (not sure what works best in this block) in all of them. The others are an accident waiting to happen.
 
When you say they "pulled out", do you mean that you can just push them in and out of the hole? If that is the case, i'm not sure whether a heli-coil would suffice or re-tap the hole to the next larger size. I would talk to a good machine shop.

If your head gasket is blown, it is best to replace all of the bolts at one time along with the new gasket. There are head bolts out there called "torque to yield" bolts that you can only torque once. I don't think the NSX uses them, and technically you could probably reuse the others, but the most accurate torque readings will come from new bolts. Make sure to chase all of the bolt holes and torque all of the bolts in the proper sequence with an ACCURATE torque wrench. Also, probably a good time to make sure the head and block are straight, you don't want to do that job twice.

Good Luck
 
Only mods to the engine are exhaust and K&N. No head work. The car only has 40K miles. I had it check out by a dealer in FL when I bought it. It had 28K when I bought it. The only thing that makes me think something may not have been stock is I found what looks like a welded up port or hole on the on the side of the intake manifold about 4 inches from the throttle body.
The studs did not pull out completely. I did not even notice there was a problem when I pulled the bolts. It was only when I started to bolt the heads back on that I noticed a problem. One hole would not thread by hand and the other I noticed what looked like a heli coil inside it. I pulled it out and it was the threads. I milled a jig and drilled and tapped the two that were bad, but I still undecided about installing time-certs in all 16. All other bolt holed thread smoothy by hand. Would there be any unequal torque problems that anyone can think of? Any help would be great.

GEM
 
GEM930 said:
... The only thing that makes me think something may not have been stock is I found what looks like a welded up port or hole on the on the side of the intake manifold about 4 inches from the throttle body...
Click to expand...

Sounds like there was a previous Nitrous system installed on the car if there was a plugged hole on the intake side of the throttle body. Do you have a picture?
 
I’ll try to put a picture of the weld on the bottom of this post, but I can’t promise anything.

Well, it is do or die time on the heads. Can anyone offer any last minute advise on time-serting all 16 or just sticking to the 2???? If I don’t get any advise to the contrary I think I will stick to the “if it is not broke, don’t fix it” school of thought. Since all the other holes thread by hand, I’m only going to repair the two bad holes. If they don’t torque correctly or feel a little off, I will pull them and time-sert those holes as well.

While the idea of the pervious owner having NOS installed does not make me happy, It might be better if the NOS was the cause of the two pulled bolts and not some idiot who over tightened all 16 head bolts. That way I would feel better about not time-serting every hole.

Anyone??????


GEM
 
Sounds like you're on the right track now that you've tapped the two holes. Inspect all of the other threads on the head bolts and look for problems. Just having two slightly over-size bolts should not affect torque readings. I wouldn't re-tap any of the others unless the threads look bad or you detect a problem when you chase the threads on each hole.

Honestly, I am not sure what you mean when you say "time-certing."

Best of luck.
 
is there ARP fasteners/head studs/head bolts available? if so might as well switch to those at this time. That way you know it's going to stay in place for good.
 
A timesert is a female threaded hole repair tool.
The Timesert is a metal sleeve threaded on both the outside and the inside. With the inside being the same as the original damaged thread. The damaged threads are drilled and then tapped to a larger size, the timesert is screwed in bringing the thread size back to the orignal size. Since it is Steel instead of Alum and it is threaded into a larger dia thead to hold it in, it is stronger then the orignal threads.
A helicoil is similar except that instead of being a solid sleeve it is a stainless steel "thread" that again brings the oversize retapped damaged threads back to the original size.
Helicoil and Timesert are brand names there are a number of similar products using different names.
 
To repair them or not is a tough call, without seeing anything.
Generally you can "feel" if the threads are weak or not when you are torqueing then to spec. You can also see in with a digital torque wrench as it does not tighten to spec solidly or quickly. The only way to test this is a mock retorque. I would definetly replace all the head bolts, no matter what you do.
As there do not seem to be a rash of head bolt problems being reported, I would say for a stock motor the OEM head bolts should be fine. Honda knows the loads and the bolts are engineered to take them, both in dia, strenght, and design, as to how much they stretch.
 
Been there as well...

Are you sure this is not the Pre-SC Porsche 911 Forum? I had a 77 and went through the same problems as the heads/head bolts expanded and contracted at different rates. This caused the heads to pull most of the bolts creating a nice Spyhunter smoke screen effect as the oil poured on to the exhaust.

Anyways, the shop that did my block did not replace every bolt. The head pulled hard on one side and not the other. I asked the asame questions and the machinist felt confident the head would torque fine only repairing the damaged threads.

I have never heard of this problem on the NSX. How was the temp. of the car? Did it ever get really hot? I would love to get to the root cause of the pulled bolts. Any service history?Any local mech from the last owner that knows the car and prior mods?

I am very sorry you had this problem.

BE
 
I have had no luck on getting a hold of the original owner. I doubt he would tell me anything, anyway. Does anyone have any idea if the welded spot on my manifold is supposed to be there? That may be the cause of the head bolts pulling out (NOS???). My valves were leaking as well. I will check on the the new head bolts, but my manual does not say to replace them. It does, however, tell you to replace several other bolts, so I assume if they needed to be replaced (stretch bolts) it would tell me to do so. I'm still up in the air about all the other bolt holes. With the jug I milled installing them seems easy enough, but I increase the risk of screwing things up with each hole. On the other hand if I get this thing back together and have the same problem somewhere else I'll wish I had. What to do???

Thanks for all the support/advise. I guess I need to wait another day to check on the head bolts, so I'll keep checking the posts. Does ARP make bolts for the NSX?

GEM
 
Well, ARP does not show an NSX application. I also checked the manual again and it does not say to replace the bolts. I don't mind spending the money on new bolts, I'm just not sure it is necessary(since they are non-stretch), and I don't know how long it will take to get them. I also tried to post on hotrodders.com, to ask about replacing all 16, but I had to sign up and I'm waiting to get access to post. Again thanks for all the help....



GEM
 
looking at the pic I would guess that it was drill for a nitrous port. I can't think of another good reason to make a hole in the IM.
 
I've heard that pulled head bolt threads are not all that uncommon on these. You might call someone like Factor-X for advice. I think GJ switches to ARP studs but I'm not sure if that's because he had the same problem or just because it seems prudent on a tubo monster.

Anyone familiar with Spiralock? If I didn't feel the need to go with ARP studs I would look for the Spiralock version of thread "wire inserts" and do all holes now then continue with stock bolts.

http://www.spiralock.com/
 
I talked to Factor X today and they suggested I only fix what is broken. So off to the garage to put the heads back on....Wish me luck.

Thanks for all the help!
GEM
 

Similar threads

Veke Nak
C30A engine build routes
Replies
9
Views
514
stuntman
stuntman
M
How much would I regret getting an Auto (and old ABS, NA1) instead of a 6MT
Replies
13
Views
337
m3brendan
M
CPS996
Resurrecting a 91 w/32,000 miles on thats been in storage for 15 years.
Replies
8
Views
636
drew
drew
M
I Take it Out for One Road Trip a Year - And This Happens...
Replies
18
Views
1K
Hass
Hass
e-rod
'91 First CEL at 69k (stock), code #44
Replies
9
Views
641
Old Guy
Old Guy
Back
Top