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Discussion Starter #1
I have searched for this nugget of info and came up empty. I am replacing at least one of the bolts that runs through the upper control arm where it passes through the body below the shock mount on my '84 GTV6. While attempting to replace the bushings, I ran into the somewhat common problem of a stuck bolt. No amount of persuading + pb blaster budged it. Am sawing at least the driver's side out. My question is: what are the specs on that bolt? I want to get it right, instead of finding something that "fits" to my eye, and risking not getting it right.

Can anyone enlighten me?

Thanks
 

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It is possible that nobody other than Alfa Romeo knows that bolt spec but there will be folks who will guess and say grade such and such. I would call APE and see if Larry has good used original bolts.
 

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I have searched for this nugget of info and came up empty. I am replacing at least one of the bolts that runs through the upper control arm where it passes through the body below the shock mount on my '84 GTV6. While attempting to replace the bushings, I ran into the somewhat common problem of a stuck bolt. No amount of persuading + pb blaster budged it. Am sawing at least the driver's side out. My question is: what are the specs on that bolt? I want to get it right, instead of finding something that "fits" to my eye, and risking not getting it right.

Can anyone enlighten me?

Thanks
Before you go cutting anything try this.... Fire and Ice: How to free stuck nuts and bolts and fasteners on a marine engine.
 

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Grade 10 refers to tensile strength but these bolts are loaded in shear.
 

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they are class 8.8 as are almost all alfa hex head bolts. there are a few exceptions (like flywheel bolts) but 99% - ish are 8.8. when you get the bolt out, will be stamped on the hex head.
any of the socket head cap screws are 10.9 or 12.9 - 'cause that is the way they are all made.
"grade" refers to inch fasteners.
 

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they are class 8.8 as are almost all alfa hex head bolts. there are a few exceptions (like flywheel bolts) but 99% - ish are 8.8. when you get the bolt out, will be stamped on the hex head.
any of the socket head cap screws are 10.9 or 12.9 - 'cause that is the way they are all made.
"grade" refers to inch fasteners.
I'm sorry, I thought these two large screws were for the upper control arms. My mistake.

The parts manual does not list the specs on the screws.
 

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I have searched for this nugget of info and came up empty. I am replacing at least one of the bolts that runs through the upper control arm where it passes through the body below the shock mount on my '84 GTV6. While attempting to replace the bushings, I ran into the somewhat common problem of a stuck bolt. No amount of persuading + pb blaster budged it. Am sawing at least the driver's side out. My question is: what are the specs on that bolt? I want to get it right, instead of finding something that "fits" to my eye, and risking not getting it right.

Can anyone enlighten me?

Thanks
I have not seen many bolts NOT undone with an air gun.
 

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Discussion Starter #11
Thanks for all of the input! A mechanic at DiFatta told me yesterday that it is either an M10 or 12(the new bush will be snug but not require force to get the bolt through(he said), smooth shank to run through the bushing, and not any specific or out of the ordinary spec on hardness or strength, as stressors on the whole assembly are attenuated by the bushing. I will update my success for the benefit of others, hopefully by Saturday!
 

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they are M10. now, ossodiseppia has me worried! my notes do not show anything specific on them... as i recall, they are class 8.8... but not as confident in the recall these days. in any case, the heads will be marked, just get the same thing.
 

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It is possible that nobody other than Alfa Romeo knows that bolt spec but there will be folks who will guess and say grade such and such. I would call APE and see if Larry has good used original bolts.
Hi :)

Grade 10 refers to tensile strength but these bolts are loaded in shear.
Double shear too, so not a particularly difficult job for the fastener. Class 10.9 of known quality should be fine.
 

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From my notes:

"New M10x100 fine thread bolts and nylocs. Plenty of anti-seize required between the bolt and the bushing."

Note that it's important they are fine thread. 1.25mm pitch

Also from my notes and the manual, the torque
upper arm to chassis - 39 to 44 Nm
 

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they are M10. now, ossodiseppia has me worried! my notes do not show anything specific on them... as i recall, they are class 8.8... but not as confident in the recall these days. in any case, the heads will be marked, just get the same thing.
I don't know $hit. What I do know, is I have a bunch of suspension fasteners that I removed from a couple of Alfettas. Neither parts manual I looked at had the specs of the screw.

We just need to match the original one that is on your car with one of mine. Many that I have are 8.8. The ones I posted a picture of are the ones I assumed are correct.
 

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Usually, the bolt end caps have letter and numbers on them to identify what grade they are, esp with higher grade versions.

Are there any on these?
 

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Use some WD40 and Scotch-Brite to clean off the existing bolt heads to confirm the grade (my educated guess would be grade 10.9, which is the norm with critical suspension fasteners).

It is interesting that the threads would be fine-pitch. This is the norm with a bolt that is used to fasten a highly-stressed component (think CV bolts, flywheel bolts, etc), that requires a higher-clamping force (which loads the bolt in tension as Ed pointed out). Perhaps Alfa engineers determined that properly-torqued fine-thread bolts/nuts would be less likely to come loose when subjected to the constant twisting motion exerted by the movement of the control arms. In any case, fine-thread fasteners will require a higher torque value than a coarse-thread fastener of the same size (check the manual).

I am not sure if I have posted the following in this forum yet (I am known to do it on the Porsche and BMW forums that I participate in), but anyone who touches a wrench, either as a hobbyist or professional, needs to buy this book and read it cover to cover:

https://www.amazon.com/Fasteners-Plumbing-Handbook-Motorbooks-Workshop/dp/0879384069/ref=sr_1_fkmr1_1?ie=UTF8&qid=1530072670&sr=8-1-fkmr1&keywords=Carrol+smith+nuts+bolts

It is deeply informative and will help you to determine what is necessary in a case where there is no manufacturer-provided bolt or torque spec.
 

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"In any case, fine-thread fasteners will require a higher torque value than a coarse-thread fastener of the same size (check the manual)"

Usually, finer thread bolts are made with material of a much higher tensile stress allowable, allowing a higher installation torque in order to develop a higher assy preload, with better torque application control.

Interestingly, I've seen very fine rolled thread 4340M bolts of 275-300 ksi tensile allowable on aircraft, something a car will never see. Trouble is with those materials is that they are like glass, in that if there is any defect, grinding nick, whatever, they crack almost instantly due to an absurdly low fatigue life. Undamaged, however, they have superb high load service life.
 

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Discussion Starter #20
Again, thanks for all of the input, I succeeded in getting the threaded end free via hacksaw, it is an M10 1.25 thread. The head of the bolt is buried for now in the impossible to see recess of the unibody. It will be liberated this evening (thank you hack saw). I am pretty positive that it will read 10.9, all of the other bolts that have come off the front suspension so far have been. In any event, new 100mm bolts are ordered, and Adrenalina should be back on the road pdq! Thanks everyone!
 
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