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MG MGA - Bolt specifications for gearbox/engine flange

Anyone have the specs for the 7 bolts that join the gearbox to the engine flange? I can't find them anywhere, so I'm looking for a quick replacement.
Rich

Rich - They are just a common grade 5 5/16" bolt. I don't know off hand what the lengths are. There are at least two different lengths used. You should be able to get them from Lowes or Home Depot. Good luck - Dave
David DuBois

My mga twin cam Service Parts List shows that early engines used seven part number HBZ 0510 bolts. Later engines used six of those bolts and one longer one HBZ 0511 (to also take the vent pipe clip).
HBZ 0510 is a UNF, Zinc coated bolt, 5/16" diameter, 1-1/4" long.
The HBZ 0511 is the same but 1-3/8" long.
THe details of all standard BMC fasteners can be found at:

http://www.angelfire.com/amiga/mga/index.html

Mick
Mick Anderson

Use fine thread bolts so you don't mix thread pitch on the same car, every other 5/16 bolt on the car is 24 threads per inch don't use the 5/16 18 thread per inch bolts from most hardware stores. This is one of those pet peeves of mine I hate following a hack that used the wrong stuff just because it was close.
Randy
R J Brown

Rich,
When I did my Coupe I measured every bolt on the car which was origional and untouched. The transmission to engine bolts: 7 bolts 1 7/8" long overall, 5/16" diameter, fine thread with 3/8" of bare shank. I have a complete listing on and excell spreadsheet. Let me know if you need anything else. Have a good day!

John
1954 TF
1960 Coupe
1962 Roadster
John Progess

Something isn't right here, because one of the flange holes is right behind the slave cylinder. There is definitely not enough clearance for a 1 7/8" bolt ... if it's inserted with the bolt head on the engine side. To insert it the other way, the cylinder will have to be removed, the bolt inserted, and then the cylinder re-installed. I don't think I pulled it off that way, but I'm not sure.

Similarly, the firewall is blocking access to one of the top flange holes, and even 1 1/2" bolt won't get in there.

Finally, one of the bottom flange holes is threaded on the gearbox side. What is strange is that the oil pan is blocking entry of the bolt from the engine side ... so this bolt would have to go in the gearbox side, then be threaded into the gearbox flange, then pushed through the engine side where it would be bolted. Make sense?

I can't see how 7 identical bolts can possibly work. I did happen to find 4 of the 1 1/4" bolts in my unlabeled parts though (HBZ 0510). Sounds like I need these four and then three others... (?)
Rich

Rich,

What model is your car? (1500, 1600, or 1600 MKII).
What engine type do you have? (1500, 1600, or 1622)? The casting mark is on the engine block, left side near the front).
What type of gearbox do you have? (1500 low starter 1500 high starter, or 1600 MKII)?
There are photos of the gearbox types on page 68 of the book "Original MGA" by Anders Clausager, or on the website:

http://www.angelfire.com/amiga/mga/index.html

From my Service Parts List:
1500 has six bolts HBZ 0510 (probably should read seven).
1600 has seven bolts HBZ 0510
1600 MKII has one bolt HBZ 0510, two bolts HBZ 0515, and four bolts HBZ 0520.
Twin Cam has seven bolts HBZ 0510 (early engines), or six bolts HBZ 0510 and one bolt HBZ 0511 (later engines).
All HBZ bolts are UNF (Unified Fine) and Zinc plated.
HBZ 0510 are 5/16" diameter and 1-1/4" long.
HBZ 0511 are 5/16" diameter and 1-3/8" long.
HBZ 0515 are 5/16" diameter and 1-7/8" long.
HBZ 0520 are 5/16" diameter and 2-1/2" long.
Use UNF auto bolts, not hardware items.
Length of bolt does not include the head.

Mick
Mick Anderson

1600 Coupe
R Stokes

This thread was discussed between 18/08/2005 and 19/08/2005

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