A couple of us Minnesota boys (Dan and Tim Mc.)did a little boneyarding Saturday and I was able to answer this head bolt question that I have had for a while. The 2 head bolts holding the alternator mount on a non A/C car are a bolt with a wider flange head to hold the aluminum mount. This bolt is 1/2" longer than the other head bolts to account for the mount thickness. If the car has A/C you find a steel mount for the alt with the compessor mounted on top. This mount is only 1/4' thick to be captured by the front head bolt. The rear mount bolt is the same type as the stud/bolt used with the power steering mount, but the front bolt goes thru and captures the mount as a normal head bolt, but 1/4" LONGER than all other head bolts. This is not a thru bolt into the water jacket on these engines-so two problems can/do happen=one, a normal length headbolt is used and can/will strip when torqued as there is 1/4" less thread engagement or-two, a longer bolt is used, but too long and the bolt bottoms (can breakout the boss into water jcket too) before clamping the head and mount. I've seen both situations on previosly rebuilt/messed with engines. We found an unmolested original car to confirm this-hope this helps sombody to avoid future headaches. Now if Tim and others will just watch me more closely so I don't set down parts 'gems' I've collected and then leave the yard without them, I'll be in good shape!
Stripped out head bolt on the alt bracket, yes, I have seen this. It happened two days before I was to leave for Flint and the Buick 100th. I ended up pulling the head, and drilling and helicoiling that hole. I'm curious how long that bolt should be. It had a stud/bolt 4.5 in long, after the repair I used a normal head bolt 4.5 in long. I couldn't see any reason for there to be a stud there.
John-The rear is a studed (3/8x16 stud) head bolt 4 1/4" long for the rear A/C bracket, but the front is a normal type head bolt, BUT.... 4 1/2"long-the only head bolt of this length on the engine-and at that, only on an A/C equipted car. It does seem strange that Buick 'trapped' the A/C-alt mount under the front head bolt alone-doesn't 'look right' so many end up doing the wrong thing here doing work later. They did the same with the non A/C bracket, but both bolts are different looking and 1/2" longer.
So there are 5 head bolt types 1. The short ones- all the same 2. Regular length 3. regular length w/ stud 3/4" head 4. regular length +1/4" smaller head for A/C front bolt only 5. regular length +1/2" smaller head for alternator 2 front bolts only Are the markings on the head of the bolts different between #4 and #5 above? Thanks!
Ted-not sure what you mean about the 'regular length smaller head' bolts. On the '65-6 stuff that I'm most familiar with they all take a 3/4" socket-I think the nuts on the studded bolts might be 11/16"-The 1/4" longer looks like the normal on the car I looked at. The 1/2" longer bolts are a different design-I call a flange type-like a built-in flat washer-hope that clarifies-
"This is not a thru bolt into the water jacket on these engines-so two problems can/do happen=one, a normal length headbolt is used and can/will strip when torqued as there is 1/4" less thread engagement or-two, a longer bolt is used, but too long and the bolt bottoms (can breakout the boss into water jcket too)" Dan-- which head bolts are thru bolts into the water jackets on a nailhead? Thanks, Dan
The ones that go through to the water jacket are the 3 center head bolts........that is the center row.........the end bolts on that row do not go through. I use thread sealer on those 3 bolts to seal them. :bglasses:
