The Spare Parts Catalogue lists 10 bolts for the bell housing to engine on page 26:
FB.105/20D Bolt, securing Bell Housing to Rear Engine Plate
FN.105/L Nuts on Bolts
FG.105/X Washer, Spring, under Nuts
All of my bell housings match the drawing on plate H for
C.700/1 Housing, Bell, for Clutch Unit R.15
My assembly also uses 3 studs at the top of the bell housing, perhaps these are found on page 13
FT.105/23H along with OD.106/8H Dowel (for alignment)?
In the Service Manual page B.45 Plate B.35 the 3 studs show as I have used them in the past along with the alignment dowel.
Here is my quandry. There are 11 bolt holes (not 10) which accept FB.105/20D bolts. Plus, I have not found the call out for washers and nuts on the 3 studs. I am using the same specification washers and studs as for the “10” bolts. What is the reason for 11 bolt holes and shall I use 11 instead of 10?
Is one of the holes for a locating dowel?
Two dowels, three studs.
We should be cautious about assuming the SPC is always right.
e.g. No mention of nuts and lock washers for those studs.
This picture shows the single dowel at top, three studs where bolts are not possible, three holes for starter bolts, and eleven holes for bolts. Use all eleven or which ten of the eleven and why?
From memory I think one of the bolts is slightly larger in diameter, probably #8 in the photo.
Perhaps you have guided understanding. Indeed, hole “8” on my photo is larger diameter than the others with red numbers. On two bell housings I measure it to be about 0.372" diameter. That is right in the middle of 3/8" bolt shank specifications and is much larger than 5/16" bolts would take.
I wonder if the hole “8” is for right-hand drive usage. My experience is with left-hand drive only. There are two parts listed on page 26 of the Spare Parts Catalogue:
C.655 Fulcrum for Clutch Pedal
C.2824 Stop, Pedal, Assembly
Do any of the parts in these two listings use hole “8” ?
I am only familiar with RHD, clutch pedal stop uses a starter motor hole & clutch pedal fulcrum is off the gearbox. I posted a query re clutch pedal in 2017 “Mk1V Clutch Pedal Mechanism” which may be worth searching.
I got down and crawled under my Mark V to take a look.
There is a larger bolt and nut in hole #8.
Without taking it out, I’m going to speculate that it is a shoulder bolt, intended to locate the bell housing, just as a dowel pin would.
I don’t find it listed in the SPC.
Hmmm. It does seem like hole #8 could be for a shoulder bolt. Yet, there are some constraints on bell housing alignment if a second dowel is used.
The dowel at the top will allow horizontal movement of the bell housing for small alignment shifts to left or right pivoting on the top dowel. The dowel at the top constrains vertical movement to essentially zero, so no vertical shift could occur when aligning bell housing to engine.
If a second dowel is used anywhere around the bell housing, then no horizontal movement of bell housing relative to engine could occur. This would seem to make the clutch adjustment step called out on page B.32 of the Service Manual for aligning bell housing to engine impossible:
“When the clutch bell housing bolts have been entered, but when finger tight only, engage top gear and operate the clutch approximately twelve times to effect alignment. Finally tighten bell housing bolts.”
Note: This quote adds the “engage top gear” description not mentioned at pages E.8 and F.9 where this alignment step also is called out.
The engagement of top gear helps to reduce the bit of ‘wobble’, and hence possible side strain, of the input shaft to aid with alignment when inserting through the clutch plate into the pilot bush/bearing.
I don’t understand the 12 clutch pedal actuations. Why 12? Why not 8, 10, 14? I have had to use this technique when I missed slightly on the alignment of clutch plate and pilot. I fitted about four longer bolts and pulled the gearbox up with a bit of preload then ‘stabbed’ the pedal once or twice until the clutch plate re-centred. Installation was a breeze then. My dad used to turn up wooden stepped dowels to match the pilot and clutch plate i.d.'s, worked every time. Manuals always say to use a spare input shaft to set up the alignment. Who has a spare one of those lying around?
Back to bell housing hole #8, below is a photo from Peter (Biskit) on the 2017 thread he mentions. It shows for his right-hand drive car that hole #8 is empty.
Could people check and report what is done with hole #8 on their bell housings and whether RHD or LHD?
Hi Peter, your idea about reducing input pinion shaft wobble by putting it in gear makes sense. I’m lucky to have acquired enough spare parts hopefully to last my lifetime, so I have spare input shafts lying around. The first time I did a transmission rebuild I did not and so I also have one of the plastic pieces recommended by Rob. I like the wooden stepped dowel also but don’t have a lathe these days.