Re: Ruined engine

["content22207" <brobertson@xxxx>]

Slow down and take a deep breath. One thing I've learned messing with
old cars is that every problem has a solution. The secret is finding it.

First: your problem is limited to one end of one head, not the whole
engine.

Second: If you stopped drilling as soon as you hit the "water jacket"
(remember: PRV's don't have a traditional water jacket -- the
cylinders are individual assemblies sitting in big tubs of coolant), I
doubt if you came anywhere near #3 cylinder).

Third: All you need to do is replace useable threads in that same
area. Not that difficult. They don't even need to be isolated from the
water jacket if you seal them with teflon tape (coincidentally, today
I replaced a water pump on a GM 151, with mounting bolts that extend
into the water jacket by design).

BTW: I'd give up on the helicoil at this point. Not only will it be
harder to seal watertight than a bolt, but since the hole is all the
way through (not blind bottomed), the helicoil will tend to eject
itself into the water jacket.

As you've already discovered, it is very difficult to drill straight
through a snapped off bolt (I've done so exactly once in my lifetime).
Even if you start in the center, chances are you'll be off to one side
by the time you hit the bottom. 

Since you've already drilled a hole, can that hole become your new
manifold mount? Obviously the angle has changed, but it appears to
tilt AWAY from cylinder #6 intake runner. You may be able to simply
re-drill the manifold to match the new angle. What diameter is that
current hole? Can it be drilled and tapped into something useable?

If you can't use the current hole, here's a possible variation on
David Teitelbaum's idea: get a machine shop to drill and tap a hole
STRAIGHT through the center of a large diameter socket head cap screw.
McMaster Carr sells them individually as large as 2" -- surely you can
work your way up to a useable hole by then! The head will be too tall,
so cut & file it down to 3/16" or so. You'll now have what is
basically an internally threaded plug with a low profile head to
prevent it from ejecting itself. Tap the big hole in your cylinder
head to match this screw (bad news: taps above 1/2" are rather
expensive), countersink it so the filed down head sits FLUSH OR BELOW
the manifold mating surface (good news: aluminum is so soft you can
get away with a wood boring forstner bit), and install. You'd probably
still end up modifying the original manifold hole somewhat.

If it makes you feel any better, I partially stripped the threads from
one of my intake mounting holes. Since the remaining 1mm pitch was
almost identical to 24 TPI, I simply tapped to 5/16-24 and converted
to the larger bolt. Did the other three bolts too to keep them
matched. Opted for fractional bolts vs 8x1.25mm because it was cleaner
and easier (tap followed original threads as easily as installing a bolt).

Bill Robertson
#5939

>--- In dmcnews@xxxxxxxxxxxxxxx, "jpalatinus" <jopalatinus@xxxx> wrote:
> Well, I am not having a good new year. I removed my intake manifold 
> to fix a coolant leak and broke off one of the bolts (the rear right 
> one on the passenger side) I drilled a hole in it to put in a screw 
> extractor and the screw extractor broke. I bought a helicoil kit 
> and began to drill out the hole.using a 7/32 bit. The hardened 
> steel bolt was difficult to drill, and I guess the aluminum was 
> easier. I put the intake back on just to line the holes up and I 
> drilled a little too much too much to the left and coolant started 
> spewing out of the hole I was drilling. I also see coolant in the 
> right rear intake hole indicating perhaps that it went to the 
> cylinder? I uploaded a picture of the hole in the archieves under 
> ruined engine. I am guessing this is the case right? Is there a 
> way to fix such a hole other than complete engine replacement?, Or 
> am I just screwed. Is there hope for my car, can it be welded?
> 
> 
> Joe P.
> 6808 17167