Alfa Romeo Forums banner

1 - 20 of 22 Posts

·
Registered
Joined
·
5,394 Posts
Discussion Starter #1
image.jpg
image.jpg
image.jpg
These are the two worst ones. Clean up / use as is vs replace -
 

·
Registered
Joined
·
1,213 Posts
I doubt the strength of those studs is significantly compromised by the almost "dissolved" lower threads. We need Gordon, Richard, or another experienced engine builder to weigh in...
 

·
Richard Jemison
Joined
·
7,229 Posts
Well, you got them out! Remarkable!
Replace them, as if you torque such down to the real needed Tq values (70-75 lbft) to prevent blown head gaskets (actutally Fire Ring migration), not the factory specs, you will have a major disappointing event...
 

·
Premium Member
Joined
·
811 Posts
In the Porsche 911 world, the head studs are a real issue and have been for many years. Air cooled, design differences, .... They might be ok, but I would change. Why chance it
 

·
Premium Member
Joined
·
13,704 Posts
It may cost more to replace them to find a block with good studs.
 

·
Registered
Joined
·
5,394 Posts
Discussion Starter #9
yes, still in the block. Ugh. Maybe I can see if the local shop can get em out.....
 

·
Registered
Joined
·
7,533 Posts
I'd replace them .. A good machine shop will get it done.. especially one who specializes in Porsche rebuilds. I have one here in Wareham MA... Good machine shops don't wince when they see challenges like this... the ones that do, stay away from. The good ones take one look and tell you the price and when to pick up the finished goods..
 

·
Premium Member
Joined
·
5,496 Posts
yes, still in the block. Ugh. Maybe I can see if the local shop can get em out.....
Lol, I missed that too. I thought we were looking at the bottom of the removed studs. Not sure I'd want to use them and I'd be concerned about getting them out.

Around here it costs about $300 to EDM the studs. A set of new studs is another $300. You can get a pretty good block for $500 or less...
 

·
Registered
Joined
·
5,394 Posts
Discussion Starter #12
I just relooked and only two have the corrosion. All others are great all along their length. And, the corrosion does not extend deeper into the stud than the thread depth. Finally, it seems that all the threads contained in the head acorn nut are good— it’s the 4 ish threads below that are corroded away. I think I’ll buy 2 studs, take to machine shop, and see what they say. I believe that these studs haven’t lost appreciable tension strength although I’d like to replace them IF reasonably possible.
 

·
Registered
Joined
·
7,533 Posts
I think technically, the threads are rolled on the studs rather that milled on with a die that removes material. This makes them as strong on the threaded portion as the bare stud portion. You could test them with the old gasket and proper torque but that might give a false sense of security as the stud stretches and any weakness will just be increased probably exponentially.. I didn't take the course Strength of Materials 101 the ME students took in the 3rd or 4th year of engineering school .. I was gone into Bus Ad by that time.
 

·
Registered
Joined
·
1,658 Posts
Better yet take it to a machine shop and let them take it out first. If the threads rip out of your block you have options, easiest is to purchase a good block, if it’s an original block and you really want it, buy timeserts and have the shop install them, then buy your studs.
 

·
Registered
Joined
·
384 Posts
I will give the other opinion. If this is for the street engine with the 9:1 compression pistons that will be driven mostly in a calm, streetwise manner, go ahead and reuse them as-is. Clean the threads, paint them with never-seize, use the Spruell method of cold-hot-cold torque procedure and torque to factory spec. I have assembled (stock, non-modified for additional hp) engines with studs that look like this with no problems. How did this corrosion occur? My guess, not changing the engine coolant at the proper intervals.
 

·
Registered
Joined
·
83 Posts
No doubt that the corroded studs are weaker than the original. It's not only the cross-section that counts, but also the surface texture. The rough surface will have stress concentration locations, especially in a fatigue sensitive application, like an engine.
It might still be strong enough, but no one can tell. Best to replace.
 

·
Registered
Joined
·
5,394 Posts
Discussion Starter #17
I decided after much consultation to give one stud a go, non destructively, to see if it might be persuaded to come out, without going nuts and damaging anything. If it does, with localized heat at the base, then we can replace. If not, and it takes a ton of reefing on it with the breaker bar, will leave as-is and reassemble. I did some quick n dirty calculations and it seems that the loss of the threads below has negligible effect on tensile strength. Digging into the base rod is a different story, but these studs have no appreciable loss of base rod. It is more likely that a torsion moment will cause a shear (when tightening the head bolts) vs a tension break. Again, loss of thread has minimal effect on shear strength of this rod based on what I can figure. Will they elongate? probably not appreciably at 70-75 ft/lbs torque over that cross-section and length.

Will advise how this ends up. The current studs have been in the motor for 45 years. If they last another 30 or even 20 it will be fine, someones else's problem at that time. I will dry-fit an old head gasket and torque down to make sure they withstand the storm before putting everything back together. Kind of hoping they come easily out but I honestly doubt it.
 

·
Registered
Joined
·
5,394 Posts
Discussion Starter #19
👍Andy not a drop! In my “real” job I’ve learned (I think) how to deal with ambiguity. In this case, at 60 years old, I’ve got another 20 years wrenching -God willing. With respect to this decision— very ambiguous to me— the longer I ponder pros/cons the closer the two options are equivalent. So I’m essentially buying a call option, by this approach, in my mind. My guess is that I will end up with 1. Studs won’t come out “easily” and 2. I’ll keep em as-is and give it a go ! Will be in touch soon and thanks for your help and thoughtful advice!
 

·
Registered
Joined
·
3,817 Posts
I've reused worse looking head studs without issue but kept a 'back up' engine in stock as an insurance policy. You may be more likely to have an issue when trying to remove the studs. In the past I used to 'fix things until they broke' -now I concentrate on trying to fix what really needs it. If you were trying to win Lemans or going for a lunar launch, it would be different...I concur with andylarry and suggest coolant changes every other year.
Mark

I will give the other opinion. If this is for the street engine with the 9:1 compression pistons that will be driven mostly in a calm, streetwise manner, go ahead and reuse them as-is. Clean the threads, paint them with never-seize, use the Spruell method of cold-hot-cold torque procedure and torque to factory spec. I have assembled (stock, non-modified for additional hp) engines with studs that look like this with no problems. How did this corrosion occur? My guess, not changing the engine coolant at the proper intervals.
 
1 - 20 of 22 Posts
Top