Nordicflame

iTrader: (4)

Have a situation that I’ve never run across.
The Bulldog mains are studded along the inner row and bolted along the outer row.
The studs are necked down have a smaller thread for the windage tray and no they are not the common bolts generally used in this situation
The studs have fine threads and nuts. The bolts are course of course but the Merc manual just says 110 lbs.
I’ve always torqued 90 on studs and 110 on bolts. I’m a bit confused on this one. Has anyone come across this before?
What did you do?
Thanks,
Dave

Nordicflame

iTrader: (4)

No one has run across this before????

Big Block Billy

HI ! I install the studs finger tight and then give them a slight tweak with a vise grip like a quarter turn or less just to seat it. Never put a stud in too tight. I use arp moly on the nuts and stud when installing the main caps. I would recommend 110 ft lbs for all BBC mains unless the arp info that comes with the studs says otherwise. Using oil instead of moly will affect the torque. You may be right about the 90lbs with moly. I may have some paperwork in the draw in my toolbox where the moly is. Or check with Arp or Sps. BBB

BillK

Dave,
I cannot directly answer your question but ... it is very important to find the "correct" specification so you can reassemble it the same way it was done when the engine was originally built. If you torque it differently, you run the risk of distorting the main bearing bores compared to how they were before.
The studs should be installed finger tight in the block and then actually loosened about 1/2 turn. This allows them to pull staight up and evenly spread the stretching force on all of the threads. You really should not tighten them into the block as it can cock them a little sideways when they bottom out.
The torque on the nuts does vary significantly depending on the lubricant used. Moly lube, such as ARP lube, reduces the torque required significantly.
So .... basically you need to know what the torque was on the original assembly, and what type of lubricant was used. Not sure where you will find this info, but if you dont have an answer by Wednesday, I can try to find out for you.

Nordicflame

iTrader: (4)

The Mercury Racing spec on the Bulldog is 110 across the board. I'm assuming this is correct.

Strip Poker 388

iTrader: (6)

I would think the stud vs the bolt would be a diff spec. not sure?

Let us know what ya find out

stevesxm

a bolt or stud is " tight" when it has stretched the amount necessary for the design pre load. that number is a function of length , diameter and material. the factory spec is defined by the factory materials installed as they define with the thread lube they specify. if the bolts or studs aren't original, you need to find out whose they are or simply buy some new ones that have the spec attached. the " torque" is the the force nec to achieve that stretch .

i know of absolutely no condition where a stud should be installed loose under any circumstances. if the stud is bottoming it is too long and should be cut.

also know that using locktite or any thread locker changes the friction w/in the threads and changes the torque value. thats why , if you care, it is important to use the thread lube as defined by the hardware manufacturer.

BillK

Dave,
Dont know how far you have gotten on this, but I called ARP today and they said 90lbs with thier moly lube.
Steve,
From page 36 in the ARP catalog:
" A stud should be installed in a "relaxed" mode - never crank it in tightly using a jammed nut.
If everytning is right, the stud should be installed finger tight. Then, when applying torque to the nut, the stud will stretch only on the vertical axis. "

Hope this helps,

stevesxm

arp the authority... and will not second guess that authority. they are as good as there is... but contradicts what their engineers told me in person a long long time ago.

Strip Poker 388

iTrader: (6)

So the short bolt has the same TQ spec as the long stud and nut in the same size? Doesent seem right to me.


Kinda like some head bolts long and short spec's