Ole

Did somebody make a mistake in the factory? In preparation for final assembly of this 85 4 valve, I was in second phase of torquing the main bearings down (41 ft lbs) so I could measure inside bearing diameters with the dial Bore gauge and number 2 ( from the front) stud failed to tighten. What I feared, pulled threads. To my surprize on dissassembly, the stud had pulled Only half the threads or the top 15 mm out. The stud measures 119mm length. The stud length from the main parting surface to the end appeared normal 96mm. The depth of the threaded stud bore 43mm. This stud was not screwed in far enough and if screwed in further would be too short. As far as I can tell I'm the first one to open this engine. I do not want to remove another stud for comparison and risk damaging more threads. Does anyone know the length on standard main stud(12mm)? Thoughts on repair please, using a bottom tap I have added threads now I count 15 (stud has 22), is this enough? I'll need a longer stud, possibly use a head bolt. Or, go up one size to 13mm and rethread the entire hole, or Time cert?

jpitman2

I have seen this elsewhere, on an alloy engine with 3 different length head bolts...there was a short bolt in the middle length hole, and it pulled threads out. DId as you are thinking - plug tap the hole, get the absolutely longest possible bolt , check that it wont bottom before tightening, and do it up VERY carefully.....
jp 83 Euro S AT 50k

mark kibort

I remember that during the first phase of scots rebuild (1nd block) 2 of the studs are shorter than the others.

I have the block from the 1st phase. I also have the old studs.

Let me know if the stuff i have could be measured to help

MK

Ole

Mark, is it possible to tell how many threads or mm are actually inserted in the block. Also the length of the studs?
Ole

mark kibort

i can take the old studs, and then measure them. Then I would take the existing studs and measure to see how deep they went. im hurting my head trying to remember what holes had the longer studs and the differences of the 85 or S4 blocks to the pre 85 blocks, which I have.

mk

Carl Fausett

You cannot/should not re-use the original fasteners when re-assembling your motor. The nuts will deform before the studs will, and once they have been torqued, they are "stretched" and will likely not hold their torque correctly again.

I am sure you found that, if you used a click-style torque wrench, that on the 2nd and 3rd uses of those main nuts that it was harder to get your torque wrench to click and also that you had to turn it farther to do so. The nuts, by the 3rd tighetning, have gone "soft".

I stock special hardened metric Main Bearing and Secondary bearing nuts at 124,000 lb tensile strength just for this reason.

Ole

I have threaded the full depth of the stud hole now. The stud that pulled out is now about 20mm to short when screwed in. If a standard full length stud comes close to this (total length 140mm) I may be able to use it. If not I will need to adapt from another source for this bolt, perhaps a head stud may work. If not it may be a repair with Time-sert as used in the alloy block cadillac main cap. Ole

Carl Fausett

On reading your psot again, more carefully - I see that you pulled the threads out of the block!
Yes - if you are using 16v heads, all 20 head studs are same length (192mm) . If using 32v heads, you have 18 of these, and 2 shorter ones.

Ole

Carl, The no 2 main bearing pulled threads but only the half the threads as if one has partially inserted the stud and then torqued. It is about the same number of threads on the nut end of the stud which works fine in steel but not enough for alloy. This 32 valve stud is only 120mm in length. Too short.

BC

The problem is that to build the engine correctly you do need to clamp and undo a few times while measuring.

How much for your nuts Carl?

Carl Fausett

Wow Brendan - I barely know you....
Not much with the small talk are you, Big Boy?

If a fella just wants hardened Main and Secondary nuts (all 22 of them) I can provide them for about $14.00

The expense is the ARP-brand connecting rod nuts. Summit Racing sells 10 of them for $71 !! I am a ARP dealer so I get them cheaper than that, but they are still pricey.

The Main and Secondary nuts are both Grade 8 Made from high-strength C1021-C1045 steel, minimum 124,000 psi tensile strength.

Our Main and Secondary nuts are 10mm high - thicker than standard nuts, allows them to catch about 1.5 more threads on each stud.

The Connecting Rod nuts are made for us by ARP, and rated at 180,000 psi tensile strength, and made from a special lightweight alloy.

GlenL

Carl,

How do you feel about replacing the washers on the studs?

BC

I have ARP rod bolts, and they came with nuts. I also have my Ishakawra-Johnson scraper, so I will be usuing some of his hardware I think. Maybe just the washers.

So knowing that, how many pieces of hardware do I need from you Carl? I'm sure it could be easier then going to the Dealer and buying the nuts.

Carl Fausett

You need 10 of the M12 x 1.5 6 pt nuts and 12 of the M10 x 1.5 6 pt nuts for a total of 22 nuts.
I have them in stock, but cannot get anything shipped anymore today. They would go out Tuesday January 3rd.

I have never seen good reason to replace the washers. I suppose I would if the surface was galled such that it would cause the fastener to put up a inaccurate torque reading...

BC

Thanks Carl.