Thread: 3.9 Cylinder Head Bolts

Originally Posted by aRRon

I'm about to refit cylinder heads to my '89 RRC 3.9 and read that Loctite should be used on the threads (manual says Loctite 972). Am I right in assuming that it should be high strength/hi temp loctite which is hard to get or will high strength do (claims to be ok up to 150 degrees C)? Is this really necessary or good old cleaned and oiled threads will suffice?

Also there is one medium length head bolt with a threaded stud extending out of the bolt head - I vaguely remember this is for mounting something like the lifting eye or earth strap - can anyone advise where it goes on which head and what it's for??

Never heard of thread lock being used on headbolts in my 20+ years in the industry . If your doing a stud kit into the block then OK but not on bolts. Headbolts use antisieze on the thread only and either antisieze or plain clean oil under the bolt head.

As for the double bolt, this goes on the LH head at the front middle row (for 14 bolt 3.9L head). Its for the steel bracketry for the PS/alternator mount.

For the 4 external headbolts, only tighten to about 20Lb/ft and do them last or just leave them out altogether. Later 10 bolt heads are identical minus these bolts.

There has been evidence over the years that these bolts are a cause for warpage and cracking. LR finally removed them with the release of the 4.0L engine.

Cheers

Andrew

Not strictly correct. Where bolts/studs go into through holes into the water jacket, not into blind holes, then the threads need to have a sealant applied. There is a GM product specifically for this. It is mentioned in Holden workshop manuals and is readily avalable from GM-H dealers. If a locking compound or other is not required by the manufacturer's workshop procedures then anti-seize or oil is acceptable. Otherwise do as you are told by the maker.

As an aside, Loctite thread locking products are compounded to have the same torque characteristics as oiled threads.

I have always read that a thread sealant should be used to prevent electrolytic corrosion between the dissimilar metals.
I use GM thread sealant which appears to work well. I will confirm when I next take the heads off.LOL.
Regards Philip A

Thanks so much Andrew, feel I can go ahead confidently now with maybe using some anti-seize. When they came out there was no corrosion after 20 years but the most pungent chemical smell you could imagine, I 'm guessing they were coated wth something. I also believe in oiling well under bolt heads/washers to enable accurate torqueing.

Where bolts/studs go into through holes into the water jacket

When I used my dental pick to clean every head stud hole on my 92 3.9 I found none of mine were wet. However I still used the GM sealant and the second time I swapped the heads they came off easily.

Regards Philip A

Never loctited but have always used the GM stuff as mentioned. Comes (well did) in a tin, lasts forever. Do yourself the biggest favour and get a ARP stud kit. Part no 123-5401 also main stud kit for ref is 124-5401. You get stud for all three rows (as per early heads, washers and nuts. Lube with assembly (moly lube), the rear most studs may need to be fitted after fitting head as (in Disco at least) head won't pass over stud without fouling in the firewall.

Fabre at Lakemba Sydney has them off the shelf, was around $200- plus shipping at christmas, VPW in Vic has them also (avoid Rocket Industries, unless you like long drawn out masochistic sessions). They are listed as buick V6 215cid for some reason, could never work out how a V6 has the same no of bolts has a V8.

Originally Posted by clubagreenie

They are listed as buick V6 215cid for some reason, could never work out how a V6 has the same no of bolts has a V8.

Probably meant for Buick Motorsport High Performance V6 blocks and heads. The Stage 1 head uses a four bolt attachment pattern and the Stage 2 uses a six bolt attachment pattern. Buick Motorsport says if using the Stage 1 head and four bolt pattern, power level is limited to about 600 hp before gasket failure. Stage 2 heads have six extra bolts. Stage 2 uses all different gaskets to Stage 1 but can be used with a four bolt pattern and is then horsepower limited as a Stage 1.

Originally Posted by Brian Hjelm

Buick Motorsport High Performance V6 blocks and heads.

Contradiction in terms?

Many thanks for solving that one for me.