Morris Minor Owners Club

are there different length push rod's avail to suit the 948? I have been building a 948 bored out to 998+020, modified 1100 head ect, to get the comp ratio I wanted I had to get the head machined and block decked, after assy I noticed the tappet adj screws were as far out as possible, I've been running it on a test bench and noticed that at high revs the top of the push rods come VERY close to touching the rocker arms, so I would like 1/4" shorter push rods or I may have to put spacers under the rocker pedestals
any suggestions?
Russ

Only at high revs? Shorter push rods would be better as that maintains the geometry of the rockers, but pedestal shims are an alternative - but remember those will alter the tappet geometry, particularly if you are running a higher lift cam.

RAB

There are two lengths of push rod fitted to the 'A' Series - the shorter ones fitted to the 803/948/1098cc engines and the longer ones fitted to the 1275cc engines. The 1275cc push rods are longer because the 1275cc block is taller.
As above - skimming the head will upset the valve train geometry but any reduction in power will be miniscule.
The solution is to obtain a set of the flat washers/plates (Pt No: 2A515) that normally fit on top of the rocker pedestal and fit them under the rocker pedestal (still retaining the top plates). It will return the valve geometry to something like normal.
With my tuned 948cc bored to 998cc, fitted with a 12G295 head skimmed by 60 thou and a race cam - fitting the plates was the solution and it worked very well. You will have to cut the corner off the plate to clear.
You can buy similar plates (with the corner cut off) from Mini Spares:-

http://www.minispares.com/product/Class ... .aspx|Back to

1275cc engine tuners sometimes fit the 803/948/1098cc push rods when the head has been heavily skimmed.

Phil

As above - space up the rocker peds -BUT MAKE SURE you have a hole through the spacer that sits over the oil feed hole in the head!

ty for your suggestions, I have a spare set of rocker plates so I will use them. Another minor problem I came across was that because the block & head had been machined so much that when I fitted the rear engine plate it was hitting the head and not letting it bolt up flush so I had to machine the radius off the top of the plate for clearance, it was just touching and I may have got away with it but if the head had to come off in the future I think it would have caused a problem in tensioning/alignment because it would be trying to move the head forward, so if you machine the head & block check the rear plate has clearance.

Russ

Not only check the rear engine plate but also the water pump top edge as that cam foul the cylinder head if the block has been skimmed.

Indeed -if fitting a 940 head to a small bore block the water pump usually has to be filed down to get clearance.

Pushrods can be shortened and lengthened to give the opening characteristics needed for a particular application. Shimming of the rockers needs to be carried out first then the pushrod length needs to be determined to give the opening curve commensurate with the application needed.

AC

Unless building the ultimate race/performance 'A' Series engine the spacers under the rocker pedestals will suffice.
The tubular push rods in the attached link can be shortened if required but a lathe and accurate measuring equipment is required to do so.
http://www.minispares.com/product/Class ... ssic/valve push rods.aspx|Back to search
However much is skimmed from the head and the block should to retain the correct geometry be removed from the length of the push rod.
Care must also be taken to ensure that the push rods do not foul the push rod hole/passage where the push rod passes through the head.

Phil