How to spot a broken head stud

1972_911T · 08-08-2005, 10:10 AM

I have my eyes set on three engines for my engine upgrade and im planning to go take a look at them this weekend. Two are 3.0's one a 79 and the other a 1980. The third is a 3.2 from an 84.

What I want to know is how hard it is to spot a broke head stud particularly with respect to the 3.0's Will I have to strip off the exhurst and intakes/fan shroud to spot these are any ones more prone to breaking for example the ones on the bottom more prone to breaking than the ones on the top?

Steve

dtw · 08-08-2005, 10:15 AM

Just pull the valve covers and stick a wrench on each head stud nut. Sometimes they're really obvious because the nut is sitting at the bottom of the valve cover.

You should - SHOULD only have issues with exhaust studs on a 3.0, b/c the intakes were steel. However, Tim Walsh and I just opened a 3.0 last weekend with 3 broken intake studs...all the intake studs had been replaced with Dilavar. So I would advise, that if you want to do a good due diligence, that you check all 24.

1972_911T · 08-08-2005, 10:18 AM

Thanks for that, anything else I should look out fro on the 3.0's?

Steve

klaucke · 08-08-2005, 10:39 AM

The 78-79 3.0 had larger ports and intake runners than the 80-83, so the 79 may be more desirable than the later motor from a performance stand point.

1972_911T · 08-08-2005, 10:46 AM

Strange that! I noticed this in waynes book the 1980 ROW engine only has 34mm ports as opposed to the 39mm of the 78-79 but is 8bhp more than the 79, they did increase the CR by 0.1 but carnt see that making much difference. Would profer the 81-83 as this has a bhp of 204 but not managed to find one yet. Think the 3.2 will be too much of a project.

Forgot to post earlier one of the engines has been stud for 5yrs could this cause any issues?

Steve

1972_911T · 08-08-2005, 11:19 AM

Ok bad spelling! was stood as in has not been run for five years.

1972_911T · 08-09-2005, 03:49 AM

Ok my 2.4 is now sold so 3.0 here I come. Other than the head studs what else do I need to do to make sure I dont end up with a pile of junk aluminium and iron? What sort of compression and leak down values should I expect from an 8.5:1 cr SC

Steve

Driver Ed · Driver Ed's Garage

While you have the valve covers off, check for worn valve guides, too. As for compression and leak down, I'm not an expert, but the advice I've been given is not to worry too much about the absolute numbers as much as variation among the cylinders.

Also, don't be tempted to use the leakdown or compression tests as a substitute for visually inspecting the head studs. I made that mistake and found out that a 3.0 SC engine can pass those tests even with two broken head studs.

1972_911T · 08-09-2005, 04:12 AM

Ok thanks! so how would I spot a worn valve guide?

Driver Ed · Driver Ed's Garage

If you can wiggle the valve at all, it's worn, but that's easier said than tested, I think. Also, it's just a gross test -- if they're only slightly worn, you probably won't be able to tell without major head disassembly.

The easier test is to look at maintenance records to see if that work has ever been done!

ben parrish · 08-09-2005, 06:31 AM

Visual inspections are always the first thing to do. Try to look for things but if you don't know what you are looking at......??? I think that it would be nearly impossible to move a valve by hand; the springs have tremendous tension on the valves. If it moves, you have other things to worry about besides worn guides.
Take your time and do the best you can and/or get a pro that you trust to take a look.
Good luck,
Ben

Driver Ed · Driver Ed's Garage

Just to clarify, moving the valve would be side-to-side and not in the normal direction of travel against the spring.