Cylinder head stud depth
 

The head studs are supposed to be set at 136 mm. I have an engine with head studs that are set to depths between 136.5 to 140 mm, and they are mounted in case savers.

I bought a core motor years back that I am just getting around to. The PO said that there was a cylinder head gasket leak that had caused all sorts of woes. When I took the engine apart years ago, I noticed that a few head bolts had not been torqued properly, mainly because some head studs were not set to a proper depth (too shallow -- extending too far out of the case) and the hex wrench in the barrel nut bottomed on the stud before proper torque was set. Sure it was leaking!
I'm starting to examine the case, and I find that a number of studs will not go to proper depth because they bottom too soon / bind in the bottom of the case savers. There seems to be room below the bottom of the case savers. A few of the studs will go and go and go, and they never seem to stop screwing into the case.

What to do? Can I run a tap in the 'shallow' case savers to try to get a bit more depth? Add washers between the heads and head bolts to be able to properly torque the heads down?

John.

Use regular nuts instead of the barrel nuts.

Damn! Why didn't I think of that ;-)

Hmmm... will they fit? Nope. Cannot get a socket into the hole to tighten the nut.

John.

I think there's others out there using nuts, maybe I'm wrong

Remove the studs and clean the threads with a forming tap.
These special taps are designed to form the threads without removing material.
A standard tap will remove material as it cuts the thread leaving a loose fitting stud.

Supertec head studs eliminate the need to set stud length allowing the stud to be installed into the case completely.
The use of an aerospace grade 12 point flanged nut that does not require any specific amount of thread exposed.

Thanks, Henry. I take it that I will not damage/weaken the the case saver by running a forming tap through it.

John.

You can get a 14mm, 12 point nut in M10x1.5. This will fit. It's used a lot on twin plug applications so you can get your spark plug socket in the hole.
Ideally you will get you stud depths correct though so you can have proper case engagement and use standard barrel nuts. The case savers definitely need a tap (forming) run down them to allow the stud to go in without a huge fight. If it's not too far out, you might try double nutting the stud and tighten it in a little. But it better practice to pull them and clean the threads of the case saver and the stud and go from there.

Thanks, DSP_Turtle. I've got a forming tap ordered, and I'll use it to clean out the case savers.

John.

I got the forming tap, and of course you know that the bottom 1/8 snapped off in the bottom of the hole.

Back to California goes the case.

Cr@po.

John.

Why don't you see if cgarr here on the forums can help you out with that since he's in central MI too- Grand Rapids. He's a great machinist who does 911 case savers, shuffle pins, cyl head work (flycut, valve guides, twin plug) and might be able to help you out.

Thanks, KTL. PM sent to cgarr.

John.

Pm sent


Sent from me

Wowzers!

Yesterday I drove my case 90 miles to Grand Rapids, MI,
met Craig, and watched his magic... 1) He inspected the
broken tap in the bottom of the case saver, touched it with
a probe, and you know what? the broken tap fractured a
bit more, and fell out of the bottom of the case saver into
the recesses of the initial bore hole. 2) He put a bit of heat
on the case saver, pulled it out with a special tool of his own
make, inspected it, called it good and replaced it.

Yippie!

While I was there I found out that he ports cylinder heads. I
have normal (32 mm) ports, and yes, he can port me out to
'S' standards, so I have another trip to make to GR.

Yippie (It bears reapeating)

John.

(PS: While I was there, he used that nifty snap-on
collet stud remover. Is that tool ever a joy to use.)

Nice guy, isn't he? You should meet his brother Denny too. Craig + Denny = G2 Performance = a great couple of guys.

Indeed! I just got back my ported heads from Craig.

John.