Lost bolt attaching alternator to head

EBruce · #1 (**permalink**) 07-07-2014, 10:02 PM

Hi Gents-
While sitting at a red light I heard a horriffic metal on metal sound and limped back home (no overheating, 3 mile drive). Upon opening the hood I noticed the bolt attaching the alternator into the head had broken off, shifting the alternator towards the bracket while the fan blades smacked the bracket (the bad metal on metal sound).

Engine is a Ford Racing 427 with Z heads and a Powermaster alternator. Any thoughts on the type/size of bolt I need to replace? It screws directly into the head.

Thanks!

Texasdoc · #2 (**permalink**) 07-07-2014, 10:43 PM

Is this a bbf or a sbf? I have an extra ARP bolt for a sbf. Don't know if it will fit a big block. Where are you located in Texas? I'm in north ft. Worth.

RICK LAKE · #3 (**permalink**) 07-08-2014, 04:09 AM

Ebruce. Unless this is a arp bolt with fancy end on it, You have a choice.
I have used both. Home depot or Lowes carry long bolts in grade 5 which is good for you. Since we don't know why the old one came lose, here a way to fix it.
You didn't say if there where any spacers behind the alt and between head. You are going to need to check to see if the belt is straight on all pulleys. I have found a piece of string or bunge cord both work well to center belts on pulleys.
With a threaded stud length, you install it to give 3-5 threads with the nut tight and cut off the extra. Loc-tite stud into head with blue or red and reassembly part. Also get a nyloc nut for this. (Air craft nut to keep on and tight)
With long threaded bolt, you want about 7-10 threads into the head and leave 3-4 extra and not bottom out stud in hole for tightening. Also red or blue loc-tite. If bolt is too long, cut off threads until get right length. Habor freight sell a $10.00 caliper for measuring depth of holes in motors and heads. Get one for easier repairing of this problem.
After road test, if bolted into head check for it being tight. If no movement, don't tighten. Problem with loc-tite is one install only and no adjusting after. If you are looking for a torque setting, about 35ft pounds on aluminum heads and 40ft. pounds on iron ones.
Side note, if you have the room, adding a 3rd bracket to the alt would help support the alt and stop any vibrations fron the motor or belt. Small piece of steel strap 1" wide, grind the edges, drill 2 holes, bend the ends in a vice, paint and install will help down the road. Some Alt have a bolt hole in the back of the unit for additional brackets. Use another hole in the head of a front intake manifold mount bolt. There may be a kit for this already on the market. Try Summit or Jegs. Good luck. Ps you will need to get the correct thread pitch and sae or metric. Guessing 3/8" or 8mm for size. Coarse thread. Match up the hole with old bolt.

EBruce · #4 (**permalink**) 07-21-2014, 09:07 PM

Rick-thanks for the response. Your guess was spot on, appears the bolt was 6.5" in length, has 3/8" x 16 thread pitch. I am going to clean out the inside of the head as there are some metal shavings then loc-tite the bolt into place at 40ft pounds. Not sure if third bracket would work but would be nice due to the vibration.