In reply to a message from Repairman sent Fri 19 Apr 2013:
There are 26 studs that hold down the EACH head
C.32331(2) 7/16’’ DIAM, 5 3/8’’ LONG
C.32535(5) 7/16’’ DIAM, 7 7/8’’ LONG
C.32332(2) 7/16’’ DIAM, 4 3/4’’ LONG
C.32534(5) 7/16’’ DIAM, 8 1/2’’ LONG
C.32679(6) 3/8’’ DIAM, 5 0/0’’ LONG
C.32680(6) 3/8’’ DIAM, 2 3/4’’ LONG
The 7/16’’ studs have a 1’’ thread cut at 14 TPI
The 3/8’’ studs have a 3/4’’ thread cut at 16 TPI
These ends go into the block
The 7/16’’ studs have a 3/4’’ thread cut at 20 TPI
The 3/8’’ studs have a 3/4’’ thread cut at 24 TPI
These have nuts/washers.
The 7/16’’ studs have Steel Acorn nuts/spacers
The 3/8’’ studs have steel nuts/spacers
The spacers are 1/8’’ thick, also steel
The 7/16’’ stud Acorns are tightened in 3 stages:
Stage 1 = 25 LB/FT
Stage 2 = 40 LB/FT
Stage 3 = 52 LB/FT
The 3/8 stud nuts are tightened in two stages
Stage 2 = 20 LB/FT
Stage 3 = 28 LB/FT
The nuts are tightened wet. Jaguar uses engine oil.
The tightening pattern is start at the middle and work
outwards on the 7/16’’ studs, stage one, then do stage 2
middle outwards on all nuts, stage 3 middle outwards all nuts
ARP has a thread cleaning tap set 911-0006 to clean out the
threads in the block, about 100$
On to the end of the 7/16’’ taps add a 10mm(?) 12 point long
socket with 1/4’’ extensions to get the taps deep into the
thread holes.
Grainger sells cleaning dies to do the threads, 22$ ea. :
HXD36NC, 3/8, 16
HXD38NF, 3/8, 24
HXD716NC, 7/16, 14
HXD716NF, 7/16, 20
Liberal amounts of vegetable/cooking oil to help cleaning,
cleanup with alcohol, acetone and a vacuum
Jaguar no longer appears to be supplying the studs.
Aftermarket Studs on average cost about 11$ each.
600$ for a full set, thereabouts.
Not sure who supplies these aftermarket studs
After dismantling two motors and successfully removing 112
studs, my observations are the 7/16’’ studs can have multiple
pits up to 3 mm deep. Some can be cleaned up and reused,
others discarded. 3/8’’ studs in general are good, but
because the ends are not covered by Acorns like the 7/16’’
studs such that the exposed ends had more damage. Some 3/8’’
studs were bent and discarded. I suspect previous owners had
messed with the 3/8’’ stud nuts as they are easy to reach. If
you plan to remove the heads, plan to replace some of the
big studs, or all, depends on your comfort level, having a
spare motor can save you a fortune in studs, however of the
112 studs removed to get 52 good studs I still purchased 16
new ones. Why you ask ? My ignorance of having never done
this before allowed me to damage the studs with the stud
extractor tool, and a lot of the big ones were pitted
Torque:
7/16’': Jaguar torques to 52 ft/lb wet
Grade 5 wet 44 ft/lb, dry 55 ft/lb.
Grade 8 wet 58 ft/lb, dry 78 ft/lb.
3/8’': Jaguar torques to 28 ft/lb wet
Grade 5 wet 26 ft/lb, dry 35 ft/lb.
Grade 8 wet 37 ft/lb, dry 49 ft/lb.
It appears Jaguar torque specs are less than Grade 8’s so
I’m currently looking for Grade 8 polished stainless
high-hat Acorns for all 52 studs and stainless washers
Hope this all helps–
The original message included these comments:
Perhaps it’d be helpful if someone with V12 studs in hand can
summarize the dimensions: how many of each length, etc.
–
1987 XJ-S, 1988 XJ-S Tremec TK500. AJ6 Torque kit
Toronto, Canada
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