Further to "broken bolts"

[OLD AS I]

I've just discovered a stripped thread on an exhaust manifold, 59 V8 block, front driver side, found as I was installing manifold, just at the point to start engine on an engine stand, believe this bolt diameter is larger than the rest of them, what's the best method/way to repairs this, am somewhat disappointed with the machine shop that prepared this block, I went the whole "9 yards" with him, degreased, examined, maged, bored, balanced, supplied all parts. This bolt was pointed out along with 2 broken head studs, guess I should have checked prior to assy., Again, what's the best way to tackle this and repair, thanks

[51 MERC-CT]

The front two bolts on both sides are 7/16" coarse thread as opposed to 3/8" for the rest of the bolts.
Make sure you are not trying to install a 3/8" bolt in the 7/16" holes as others have done assuming that the threads are stripped.

[chap52]

Ya ever wonder "WHY" Henry decided this was a good idea?

[51 MERC-CT]

Originally Posted by chap52

Ya ever wonder "WHY" Henry decided this was a good idea?

Probably to use up all the 7/16'' bolts that someone ordered by mistake.

[Andy]

Helicoil

[JM 35 Sedan]

Sponsored Links (Register now to hide all advertisements)

QUOTE=51 MERC-CT;1416574]The front two bolts on both sides are 7/16" coarse thread as opposed to 3/8" for the rest of the bolts.
Make sure you are not trying to install a 3/8" bolt in the 7/16" holes as others have done assuming that the threads are stripped.[/QUOTE]

Originally Posted by chap52

Ya ever wonder "WHY" Henry decided this was a good idea?

I feel this was done in the beginning, on the early 21 stud engines, because it was felt that a heavier/stronger than 3/8" bolt/stud was necessary to hold the additional flange and gaskets, for the exhaust and cross over pipes, tightly together at those front exhaust ports. Once this was done, these threaded bolt holes remained 7/16" for standardization, and allowing new generation FH blocks to retrofit into older vehicles.

There is a similar situation on each side of the front of the block. There are separate and different size threaded holes for water inlet flanges and motor mounts that began in '32, 21 stud block, and continued to '53 ('54 in Canada), even though two of those larger threaded holes were not used in production from '37 to '53 ('54).

[richard crow]

first try a meteric bolt if that don,t work helicoil

[Ol' Ron]

The Holes are probably OK just run a clean out 7/16 bolt through it. You can make one with a file, cutting a slot down one side.

[fourtydlx]

Ron : Old timers didn't have the dough to buy expensiv tools, add a little trans oil to it

[OLD AS I]

thanks for the suggestions and info, will try the metric trick, good thought

[supereal]

If you can remove all exhaust manifold bolts without breaking at least one, you are the exception to the rule! The constant heating and cooling anneals the bolts, and makes them weak. Retrieving the headless end is best done by welding a nut to the shank. The heat of the welding usually shakes them loose so they can be turned out.

[cas3]

i agree with supereal, weld a nut on. i like to first drill a hole thru the center. this gives the weld some clean metal to bite on, and also will take some stress off the bolt. find center by using a transfer punch with the manifold bolted in place. best of luck, skip