Drilling head for 86 intake manifold

[Robertosvo]

I have a question about the missing threaded hole on older heads.
when adding the hole to make it work what depth are people going to?
anyone have pictures? etc

Thanks
Rob

[MAPSVO]

I am not positive but I think it goes all the way through. I have a cracked 86 head out in the shop I'll get out there and take a look. Have to go to work now, will be later this afteroon.

I am interested as well. I might have to use a older head on this next engine and was wondering about drilling and tapping the hole myself. It looks to me that the manifold would make a good drill guide, but was wondering how people are doing it.

[Robertosvo]

Thanks ...let me know your results. I guess the intake or the gasket would be good reference

[MikeFleming]

The new drilled hole will go into the valve spring area inside the vertical wall where the cam cover gasket sits. That wall is ~8-9mm wide at the top, and tapers slightly wider down where the new hole needs to be drilled and tapped.

The bottom of the threads will leave marks on the flat oil valley area inside the cam cover area.

Use a gasket to locate where the hole goes and put it dead center of the hole in the gasket. Then use a drill press to keep the hole straight when drilling and getting the tap started.

Put teflon tape on that manifold bolt when installing the intake manifold. It will leak engine oil otherwise and make a general mess, although slowly.

M8x1.25 standard thread..

[SVORob]

I sure have missed Mr Flemming's reply's
mine looks just like what Mike said.
I just drilled and tapped it

[MAPSVO]

What they said. :like2:

[Robertosvo]

Thanks guys, and yes, you too Mike.
I have a head I am going to do this "mod" too.

While on the subject like Rob stated....I appreciate having your technical assistance around Mike

[MikeFleming]

This *can* be done in-place, on the engine in the car. However one needs to make sure they can hold a drill straight while punching an 6+mm hole through 5/16" of cast iron (this will require a new, sharp drill bit and some drill motor power, some cutting oil, etc.). Be sure to take the cam cover off first and plug all the (three on the intake side, one at rear) oil drain-back holes. Mop up all the engine oil and dry the area with brake cleaner then mask it off with masking tape or similar.

And a large magnet on the inside to collect the filings then scrupulously clean the area before refitting the cam cover. It's much easier with the head off, but that does add a few more hours of work.


While on the subject like Rob stated....I appreciate having your technical assistance around Mike No worries mate. Always glad to help.

[Patrick]

So Rob, you're another one of those who gets excited when he speaks "technical"?

(Talk tech to them, Mike. Make them write bad checks)