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19-05-2018, 05:59 AM
(This post was last modified: 19-05-2018, 06:28 AM by Erich.)
With the wonderful assistance of Chris Garner, the engine is out of my Ulster Rep. We found that the gearbox does not have a blind spline(a good thing) and that there are double valve springs(also good). Unfortunately, in addition to the buggered crank case, number four has some very deep grooves. I am guessing that it is the little end gudgeon keepers(if there are these). How is the little end gudgeon fitted? Is it a press fit, or are there keepers? Austin pistons and Austin rods.
Erich in Seattle
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Location: Sheffield South Yorks
Car type: 1932 RN saloon
19-05-2018, 08:24 AM
(This post was last modified: 19-05-2018, 08:24 AM by Dave Wortley.)
Erich,
Standard,non-sports A7 had gudgeon pins with a half moon slot in them. Through this passed a high tensile 1/4”BSF high tensile hex head screw, there being a clearance hole for the screw at one side of the split little end in the conrod and a tapping in the othe side. Hence the gudgeon pin was clamped in the little end. It is a weak design, because the gudgeon pin clamping is inadequate, allowing fretting between the pin and the screw. Bad cases can actually be complete removal of a half moon shape in the screw by the harder pin material.Even if it doesn’t get as extreme as that, any wear in the little end hole allows the gudgeon pin to float endwise,creating deep grooves in the cylinder bore. Sports A7 had a bushed little end, end float of the gudgeon pin being controlled by internal circlips in the piston.
Cheers,
Dave.
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Thank you, Dave. That's what I have. I guess I have to consider Sports pistons now, as well as sleeving.
Erich
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My 1929 Rover 10 engine was rebuilt in 2010 by the previous owner.
The Rover has floating pins held in place originally with a wire spring clip. Upon reassembly the more common circlips (Seeger) were used.
Unfortunately whoever fitted them didn’t ensure the pins floated or fit fit the circlips correctly as a result the clips all slipped out of their groove and wrecked the bores by putting the tramlines up the bores.
If using circlips make sure they seat correctly in the groove. You should be able to rotate the clip.
Fortunately I was able have the block re-sleeved and rebored to suit the pistons that were still in good condition.
My pistons are being refitted with pads rather than clips.
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Location: Auckland, NZ
The ordinary Seven pinch bolt arrangement does seem somewhat basic but millions of Austins, Morris, others, and later BMC A and B engines have operated perfectly with the same or similar.
From earlier posts and other sources it seemes vital that gudgeons tight fitting in the pistons are avoided. Otherwise a start with a very cold engine will likely work any pin loose.
(A local member with an Austin 6 experienced a conrod split for the full length. It was welded and reused!)
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I was of the understanding that the Austin sports rods gudgeon pin was located by brass buttons.
This was continued right up to the three bearing Speedy / Nippy engine. ( have seen the inside of on original three bearing Nippy engine complete with brass buttons )
If using pinch bolts they must have a plain shouldered section which locates in the half moon of the pin to stop the pin moving. ( pinch bolts must be HT steel with correct lockwashers, if overtightened they can break )
The circlip location method is much more modern and only suitable for non austin or genuine sports rods.
Hope this helps a bit.
