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#850620 06/04/21 12:42 am
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I have 4 pushrods - some maybe original but some are aluminum. Lengths vary.
Could some one kindly measure an original factory pushrod and tell me the total overall length?
(from end of "stub" to top of the cup.

Thanking all.

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I don't have any pushrods to measure, though the 'Taylor-Dow Gold Starlet No.5' instruction said:

"The length of the engine push-rods should be checked every time the Cylinder Hd. is lifted, or if the minimum clearance cannot be obtained. The standard length, excluding the spigot os 9.0625". Replace if more than 0.25" shorter than than the standard length."

Kerry


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Thanks Kerry - good info.

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I made mine from bmw r80 push rods . Using part bmw part bsa works fine . [Linked Image from i.ibb.co]

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Kerry, Did it say 0.25" or 0.025"?


1951 ZB GS
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I'm not sure it has been mentioned so I'm gonna assume you are working on a DBD Goldie.

Something to think about when considering push rod length. BSA offered compression plates to adjust C/R.

Later (CB, DB, DBD) eccentric adjust engines have a limited adjustment range which in that case could mean a slightly longer or shorter push rod becomes necessary to get a good range of tappet adjustment.

Add to that heads that have had their seats cut a few times. Those might require a shorter than standard push rod for proper adjustability.

All this to suggest, that an exact original length push rod may not be what you really need. I would do a trial fit (all gaskets and compression plates of course) with the ones you have and evaluate the range of adjustment. For example, if a valve is held open when adjustment is backed all the way off, a shorter push rod is needed. The opposite is true if you can't adjust down to your valve clearance setting.

Also, mid point of the eccentrics rotation is a nice target but not absolutely necessary. Consider that valve clearances often tighten due to gasket settling and seat wear. This means you could accept eccentrics that just barely get your valve adjustment tight enough knowing that clearances will most likely need loosening at the next valve adjustment or two.

Last edited by Stuart Kirk; 06/10/21 9:37 pm.
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bsalloyd,

Well spotted: 0.025" i.e. 25 thou

A 1/4" would be quite a lot!

Kerry


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Originally Posted by Stuart Kirk
Later (CB, DB, DBD) eccentric adjust engines have a limited adjustment range which in that case could mean a slightly longer or shorter push rod becomes necessary to get a good range of tappet adjustment. ... Also, mid point of the eccentrics rotation is a nice target but not absolutely necessary.
I had to make my own pushrods for my Ariel and the photograph shows the adjustable faux pushrod I made to determine the length I needed

[Linked Image]

The Ariel engine has adjustments at both ends so I set them mid-range, measured the spacing with a ruler, and made the faux pushrod short enough that at least a few threads of the fine-thread bolt (¼-28) would be exposed to allow for adjustment in both directions to compensate for the relatively inaccurate measurement of the ruler. Once installed, I turned the bolt to give the faux pushrod a fit that seemed appropriate and then accurately measured the total length to use for making the actual pushrods.


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