Author Topic: Push Rod Alignment  (Read 1945 times)

Offline dpaddock

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Push Rod Alignment
« on: 22.01. 2008 21:23 »
Our good friend Groilly remarked herein 20.01.2008 on the difficulty of using the factory "comb" 67-9114 to properly position/align the push rods prior to assembling the rocker box to the cylinder head. The trick is to hold the comb steady, and I recommend the following procedure.

After placing the gaskets and aligning the comb to the rocker box studs, place a flat 2X4X1/16-inch L-brace across the handle of the comb and across the top fin on the timing side of the head, using two small (one-inch) C-clamps. Assemble the push rods to their followers and to the comb slots. (Contrary to the text in Service Sheet 215, it is NOT possible to level the push rods.)

Using rubber bands to hold the rocker arms clear of the valve tips, lower the rocker box onto the head. Use a flashlight to guide your actions and work slowly, using a long thin screwdriver or similar to nudge things as necessary. The comb is readily removed just before the box is pushed home.

NOTE 1: The first time I had the engine out of the frame, I replaced the rocker box studs with hex head cap screws so that thereafter when I needed to remove the box, head and/or barrel I could do so with the engine in-place.

NOTE 2:  I shun the use of gaskets here in favor of sealant. This makes for an oil tight and more-rigid joint.

I hope this helps solve an otherwise very frustrating task.

David
'57 Spitfire


Offline a10gf

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Re: Push Rod Alignment
« Reply #1 on: 23.01. 2008 00:00 »
Good tips, thanks, I have battled with this so many times. But one advantage of keeping the studs wherever possible is the zero risk of damaging threads, especially when in any aluminium. On my plunger I have to unscrew 1 rocker cover stud (if I remember right) to get the top clear of the frame for removal , never had to take out the engine to do top or cylinder work.

e
(ps, thanks for moving the matter to it's own topic!)

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Online groily

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Re: Push Rod Alignment
« Reply #2 on: 23.01. 2008 09:06 »
That is helpful as ever dpaddock and many thanks. I did something fairly similar in fact, to keep the comb steady, and it did all slot together first time, aided and abetted by slim prodder and torch as you say. Didn't bother trying to 'level' the rds either - just put it all together with pistons at mid-stroke to avoid any valve/piston issues during assembly. But I attributed a lot to Lady Luck! My engine already has cap screws holding down the box (nice ones in this case and minimal risk to threads in an iron head luckily) - hadn't realised it might have had studs originally, other than the short ones at the corners, downward facing.  I note that when BSA developed the unit engines, they did a far better job! An A65/50 is a delight by comparison, even though the basic design ain't so different . . . there's progress for you. Anyway, done till the next time - coming very soon as the head'll need check tightening! Groily
Bill

Offline dpaddock

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Re: Push Rod Alignment
« Reply #3 on: 25.01. 2008 23:35 »
Thanks for the feedback, lads.

Erling, the alloy head has bronze inserts for the studs so there's no problem re stripping threads, especially since I use only 12 ft lb of torque. The iron head is "bullet-proof" in this respect. I'd post some photos of this if I knew how to do it.

Groilly, your use of a couple of studs to align the box is very helpful and I forgot to mention this. One can make up two studs and hand-tighten them in place. After the first seven cap screws are assembled, the studs are removed and replaced with the remaining two screws.

David
David
'57 Spitfire


Offline a10gf

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Re: Push Rod Alignment
« Reply #4 on: 26.01. 2008 01:03 »
Hi, I was thinking of the four rocker box bottom studs, and the 8 cover studs.
Notice 1 cover stud taken out, to get the box clear from frame (plunger). The hex adjusters are very nice.

dp, pm me for any info on picture posting.
e

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Online groily

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Re: Push Rod Alignment
« Reply #5 on: 26.01. 2008 15:16 »
Ah, all becomes clear . . . my inspection cover studs have been replaced with small allen-head screws. No serious risk of stripping unless one acts insanely with the allen key! And one does get that extra bit of clearance . . . Very helpful pic and very helpful comments folks, thanks again. Groily
Bill