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MG MGA - Head bolt torque

Reassembling a rebuilt 1600 engine. Using original studs. MGA manual says 50 ft/lbs., Haynes says 70 ft/lbs. Neither specifies lubricated or not. Archives and Barney not much help(to my surprise). Any wisdom? Thanks ,Bob.
BoPrentice

I believe it's 50, clean and dry
J.H. Hall

Some take more than others ie ones stamped with "22" on the end will take more. But in your case,why don't you just put new ones in, ARP makes them.You didn't use your old rings or gaskets,and fastners go bad also,after 44 years of going thru heat cycles and stretching.Just my 2 cents- Gary
gary starr

Hi Bob. I have torqued my MGA 1500 head to 50 ft/lbs (dry threads) many times, (doing valve jobs) and have never had a compression or coolant leakage problem using this torque value. Interestingly, original MGA tool kits came complete with a "cylinder head spanner", to be used for the sole purpose of tightening and loosening cylinder head nuts. This tool was simply a normal box end wrench, and had no provision for measuring the amount of torque being applied to the head nuts! I am sure that MANY backyard mechanics made use of this crude tool, and presumably managed to remove and install their heads, and have reasonably running engines afterward! I am also sure that use of this wrench must have allowed unbelievable variations in head nut torque values depending on whether the "mechanic" using the tool was a weakling or a muscle bound gorilla! The term "calibrated writst" comes to mind! Consequently I am not convinced that head torque values are actually super critical on B series engines, although I do recommend careful use of a torque wrench, and not the Morris Motors cylinder head ring spanner! I am using the original studs that came with my engine. I believe the factory studs in good condition are more than adequately strong, and can probably be re used as long as they are not visibly damaged or cracked, and the head nuts can be run down the full length of the threads (using light pressure only ) without noticeable binding. If you thread the nuts down the threads, and get obvious binding, this indicated that the studs have been severely overstretched, probably due to excessive torque. In this case I would discard all the studs and get new ones. If you are building a high performance engine, then replacement stock type studs are unsuitable, and high strength studs should be installed. (expensive!) I am guessing that numerous folks on this forum will disagree with my re using old head studs, however, I have had good success doing so on NUMEROUS B series engines that I have rebuilt over the years. Cheers, Glenn PS. before installing the head, remove all the studs and de burr the threaded stud holes in the block. Raised metal around the stud holes will prevent the head gasket from seating properly and WILL cause leaks!
Glenn

Sorry if my web site does not mention head bolt torque. Perhaps I thought it was not particularly important to go beyond the instructions in the factory workshop manual.

I'm with Glenn on this one. I do not build race engines, but I have reassembled street engines dozens of times. I have replaced a few head studs which were obviously stripped or stretched (not by me), but otherwise always re-use the original head studs. Head bolts and studs in the Austin B-series engines are over-engineered and under-stressed, so as long as you don't overtorque the things they can be reused indefinitely.

The original head studs with "22" stamped on the top end are excellent specimens. These can comfortably be torqued to 60 lb-ft (or slightly higher) with no ill affects if you were so inclined. This is why the shadetree mechanic's calibrated arm works so well with the "head bolt spanner" in the original tool kit.

I have seen some head gasket leaks and blow-outs using the laminated copper gaskets, regardless of torque applied. I have never seen a head gasket leak using the black fiber Payen head gasket, regardless of torque applied (as long as it's not left loose).

I have seen some replacement head studs which were garbage when new and could break at 40 lb-ft torque. This is not cause to pay a premium price for high strength racing parts, but does give cause to let the buyer beware when looking for good quality standard parts.

50 lb-ft head bolt torque is right for the MGA street engine, with threads clean and dry. The nuts should spin full length of the threads with finger tips only before assembly, otherwise clean or replace the studs or nuts. No problem using a drop of oil on the threads for initial assembly, but figure the oil will squeeze out and will be gone before you get around to re-torquing the head.

Use original type heavy (thick) steel flat washers (equal to grade 5) and tall nuts. Thin "hardened" steel flat washers bend easily and are not good for the cylinder head. Thin or soft washers are especially BAD (dramatically harmful) for the aluminum rocker pedestals originally used in the MGA.
Barney Gaylord

Barney, what do you think of the stock connecting rod bolts? I'm debating replacing the originals while I have the engine apart again, but I'm not sure what to replace them with. ARP doesn't list rod bolts for the A, and I'm somewhat leery of what I would be sent by the usual sources. But I'm also worried about the years of stress on the originals. I'm only trying to build a stock engine, but I don't want to take any chances of a rod letting go.
Del Rawlins

Same as for the head bolts, over-engeineered and under-stressed, and good for indefinite use as long as they are not abused. I have never felt the need to replace a connecting rod bolt, and have never seen one damaged, not even during other catastrophic failure of the engine.
Barney Gaylord

Thanks, that helps to put my mind at ease.
Del Rawlins

Thank you all, especially Glenn and Barney.I should never have doubted you, Barney. Wonder where Haynes got 70ft/lbs. Bob P
Bob Prentice

70ft.lbs. Canadian = 50ft.lbs. US

Derek Nicholson

Derek,

Can you explain that, please? I was unaware that the component measures were different between Canada and US.

Thanks,

Joe
Joe Cook

Good question, Joe; Derek, would that be feets or pounds or quarts or gallons or liters or litres or meters or metres or yards, or what. Bob
Bob Prentice

Reading the threads, its maybe because Canadians seem to measure torque in ft-lbs whereas the rest of the non metric world uses lb-ft or even lbf-ft!
Malcolm Asquith

Strange. have I got a different Haynes manual? Mine says 50lb/ft for the 1500/1600 cylinder head nuts. The only mention of 70lb/ft is for the Twin Cam cylinder head nuts.

Steve
Steve Gyles

50 lbs is correct for pushrod engines. Try 70 lbs and you'll likely twist them off.

The 70 figure is indeed for Twincams, which used a larger diameter stud.

My experience with racing pushrods has been that all of the factory head studs are inadequate, and we always fit a better quality stud - having snapped them on more than one ocassion when retoquing at the track, it is relatively cheap insurance. Stock should be no problem for the street, however.

The stock 3 main con rod bolts are also quite durable. Have used grade 8 equivalents in a pinch to make a race, but have never seen a test on the original bolts - it would be interesting to see how they measured up.

I have a con rod from a race motor with the piston gone, wrist pin still gamely clamped, the rod bent in a sinuous S shape, and the big end still bolted up (the crank disintegrated on the one....)
Bill Spohn

This thread was discussed between 23/09/2006 and 26/09/2006

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