This item is for a complete (single) adjustable pushrod assembly to fit the 1938-47 design of OHV Engines. This design employed the earlier 1930's long steel pushrod tube design - but unlike the earlier design, the top piece had a screw on adjustable top cup and locknut. We keep the most common 500cc length in stock, but can also supply these to order - to your length. All parts are CNC manufactured to the original dimensions, including tolerances for press fitting the pushrod ends to the tube.
Price is per pushrod assembly - 2 pushrods are required per engine.
When fitting, adjust tappet clearance as you would normally - but then re-check tappet clearances after approx 50 miles - as pushrod ends may 'settle' a few thou. The pushrod ends are pressed on with same interference fit as original items - but just like those engines would have been run-in in period - this type of pushrod design means they may 'settle' slightly in use.
UPDATE OCT 2022: These are now available in what we believe are the most common '500cc' length, 'off the shelf'. The length of this pushrod has been copied exactlly from an original 1939 500cc pushrod - as shown in the accompanying photos - it has the following dimensions:
500cc Standard Length Pushrod Assembly: (to the best of our knowledge - please contact us if you have a 500cc engine of a different length):
- Overall length of pushrod, with top threaded 'cup' adjuster removed: 12.540" - 12.550"
- Overall Length Range of pushrod with top threaded 'cup' adjuster fitted: 12.950" - 13.230" (+/- 30 thou tolerance)
350cc, 600cc or Non-Std Length Pushrod Assemblies:
However, we can also provide this pushrod assembly to your custom length - i.e. 350cc (Model 50) or 600cc (Model 19). To make them to your length, we require the overall length of the pushrod - but without the top 'cup' adjuster fitted (see picture of the pushrods between a large caliper to see what we mean). We would normally expect to be able to supply a pushrod to your required length within 2 - 3 weeks of you placing an online order.
PLEASE NOTE: Unfortunately we cannot accept Returns on a pushrod made to your custom length - so please ensure you are absolutely sure you have specified the correct length when you order the pushrod - and expect us to email you before we commence assembly of the pushrod, to make sure the dimension you have providied us with is correct.
What Do I Do If I Dont Already Have a Pushrod To Measure Against???:
If you are building an engine afresh, and dont have any pushrods for that engine - then follow these instructions to measure the length of pushrod required:
- First, loosely assemble the main engine components - including the crankcases with cams and cam followers fitted, barrel, head, rocker box.
- Ensure head has valves fitted and that the rocker box is tightened down with alloy rocker box spacers in place and that the rockers are touching the top of the valves
- Ensure the cam followers are sitting on top of the cams, with the cam base profile touching the follower (i.e. the follower must not be in the cam lobe 'lifted' position)
now use welding wire or rod (or some other similar tool to measure) to measure the distance between the lowest part of the 'cup' in the cam follower, and lowest point of the spherical ball of rocker arm. We will use this distance to calculate a pushrod which has 'mid adjustment' at this length.
Background For This Design:
These pushrods were particular to the 1938-47 OHV engine - this being the first type to employ the adjuster as part of the pushrod. Prior to the 1938 design, a similar long/slim pushrod was also fitted - but the tappet adjustment for the earlier design of engine was done with rocker adjusters screwed into the rockers, therefore the pushrod was a fixed length. We can also supply that (non-adjustable) type of pushrod - Item 1124.
This type of pushrod was only fitted until 1947. In 1948 the OHV engine received a complete re-design and long cam pushers were fitted into the timing case, with much shorter/thicker alloy pushrods fitted, which were less inclined to flex.
Therefore this type of 1938-47 pushrods were only fitted for a relatively short period and are now extremely difficult to find at autojumbles. Added to that, it is not unusual for the threaded adjuster at the top to strip its thread (or the locknut to strip its thread). We can supply locknuts seperately (Item 1126), but if you have a pushrod with a stripped thread on the top adjuster - we can only recommend replacing that pushrod - it is very difficult to remove the threaded top piece from an original pushrod without damaging the tube - as they were originally pressed on with an interference fit and are very difficult to remove.
We manufacture the bottom 'Male' ball end and the top female 'cup' threaded end from Case Hardened EN32B. The tubing is cold drawn seamless steel of the same dimensions and wall thickness as the original tubing. The top tube threaded adjuster and locknut are both CNC machined from stainless steel. The two pushrods ends are pressed on with the same interference fit as original Norton items.
This type of pushrod are now extremely difficult to find - and it is not unusual to find the thread on originals has stripped, and therefore not possible to adjust and lock them. The other common fault - particularly if the engine has been left unused for a period of time, is top ball cup or bottom ball corrode and lose their case hardening. These pushrods have been manufactured to the original design, using original Norton pushrod assemblies for the patterns.
Email us on sales@racingvincent.co.uk. if you require more information before placing order - or state length required when you do place an online order. If no additional details are supplied - we will assume you require a 'std 500cc' length item of the dimensions provided at the top of the listing.
Final Note: we supply each pushrod assembled using high temperature grease, and both cup and ball ends smeared with grease, to protect against corrosion in storage.
Price is per pushrod assembly (i.e. 2 required per engine)
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