1954 AJS 500, tightening the pushrod locknut

Information relating to the Matchless G80 or AJS Model 18 500cc Heavyweight.
56G80S
Member
Posts: 3354
Joined: Wed Oct 12, 2005 10:45 pm
Location: N YORKS UK

Re: 1954 AJS 500, tightening the pushrod locknut

Post by 56G80S »

"...runs past an indicated 70 mph..."

So will mine but I don't do it anymore! Keep below an indicated 65 now. The big end has been in a long time..........

Johnny B
Peter Lecompte
Member
Posts: 163
Joined: Sat Aug 15, 2009 12:52 pm
Location: QUEENSLAND AUSTRALIA

Re: 1954 AJS 500, tightening the pushrod locknut

Post by Peter Lecompte »

Hi, jumping onto this push rods topic. I am building a 1957 G80S engine and going through the basket have found 2 sets of push rods.... 1 set alloy and the other set steel. They are the same length and general overall overall condition looks fine. Question is, does it really matter what set I use? Is one set better than the other?

Cheers
Peter
User avatar
Pharisee
Member
Posts: 1126
Joined: Tue Mar 15, 2016 8:51 pm
Location: Lincolnshire UK
Contact:

Re: 1954 AJS 500, tightening the pushrod locknut

Post by Pharisee »

Peter Lecompte wrote:Hi, jumping onto this push rods topic. I am building a 1957 G80S engine and going through the basket have found 2 sets of push rods.... 1 set alloy and the other set steel. They are the same length and general overall overall condition looks fine. Question is, does it really matter what set I use? Is one set better than the other?

Cheers
Peter
I wondered the same thing... I recently bought a '54 G3LS "basket case". Some work had been done by the previous keeper and he'd also sourced a few new parts. There was a pair of well used alloy push rods with rounded off, rusty steel end fittings and a "new", unused pair of steel push rods. Apart from the obvious weight difference, they looked identical. I will use the new steel ones when the time comes. I have no idea why there are two types, what engines they were used on or when... :(
I'm from the Fens.... Gimme six.
SPRIDDLER
Member
Posts: 8542
Joined: Wed Sep 01, 2004 1:00 am
Location: WEST SUSSEX UK

Re: 1954 AJS 500, tightening the pushrod locknut

Post by SPRIDDLER »

Pharisee wrote:I have no idea why there are two types, what engines they were used on or when... :(
Here's my bar room theory.......
Post-war and up to around 1957 there was a critical steel shortage and Britain was economically bankrupt. The Gov't also needed foreign currency. Manufacturers could only obtain steel with a Gov't licence which required that a percentage of the steel products would be exported.
The aluminium alloy (known as 'Birmabright') was relatively plentiful (hence in 1947 Maurice Wilks produced the first Land Rover bodies from Birmabright). It could be that AMC and other manufacturers used the readily available aluminium alloy wherever they could.
My '54 G3LS has steel pushrods, perhaps because it was produced for export as part of a consignment for the S. African police?
If 'raw' steel and ali were of similar cost it does seem strange that AMC would change to steel pushrods in view of the weight benefit of ali, unless the manufacturing cost using steel was lower than for ali.
'There is a tide in the affairs of men
Which taken at the flood............'
zwarts
Posts: 514
Joined: Mon Jan 01, 1990 12:00 am
Location: LANCASHIRE UK

Re: 1954 AJS 500, tightening the pushrod locknut

Post by zwarts »

My understanding is the the steel pushrods are for use with the all-iron engines ie. iron head and cylinder barrel.
The light alloy pushrods are for use with the later (post'51?) alloy heads.
All to do with thermal expansion affecting the tappet clearances, in theory!
User avatar
ajscomboman
Member
Posts: 3963
Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: 1954 AJS 500, tightening the pushrod locknut

Post by ajscomboman »

zwarts wrote:My understanding is the the steel pushrods are for use with the all-iron engines ie. iron head and cylinder barrel.
The light alloy pushrods are for use with the later (post'51?) alloy heads.
All to do with thermal expansion affecting the tappet clearances, in theory!
Snap, I'm in agreement with Bob, I'd always believed iron head steel pushrods, we could be wrong though.
User avatar
Pharisee
Member
Posts: 1126
Joined: Tue Mar 15, 2016 8:51 pm
Location: Lincolnshire UK
Contact:

Re: 1954 AJS 500, tightening the pushrod locknut

Post by Pharisee »

One has to appreciate that the pushrods are running alongside an iron cylinder barrel, irrespective of whether the cylinder head is iron or aluminium. I would imagine that the heat related 'growth' of the long barrel would have a greater effect on the rocker clearances rather than the growth of the much 'shorter' cylinder head, be it iron or aluminium. As the steel pushrods are a similar length to the barrel, the expansion would be in the same 'ball park' and the impact on the valve clearance less than it would be if aluminium pushrods are used. Maybe the aluminium pushrods were intended for the aluminium barrelled 'C' variants.
I'm from the Fens.... Gimme six.
Andy51
Member
Posts: 742
Joined: Thu Mar 31, 2005 1:00 am
Location: BERKS UK

Re: 1954 AJS 500, tightening the pushrod locknut

Post by Andy51 »

I've never seen steel h/wt pushrods. All 3 early 50s 500 singles I have owned had alloy pushrods, and when I go to Kempton autojumbles I have only seen alloy ones on the stand of our illustrious dating officer. Andy
Locked