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+--- Thread: Chummy engine swap (/showthread.php?tid=9715)
Chummy engine swap - PeterN - 20-11-2024
I have a 1930 AE fitted with a 1934 engine with a high compression head and a 4 speed gearbox. The existing engine block is number M233185. This block is ok but it had a crack in the usual place , which I managed to repair, and it's very worn in the valve guides.
I have another block (M236165) which has been leak tested and is fine, but it needs some work.
Before I go ahead with this can I check anywhere if the M236165 block will fit as a direct replacement.
As a bit of a purist I'd rather replace the existing engine and gearbox with period correct ones but that unfortunately is financially beyond me currently (even if I could find said engine and gearbox)
I hope that all makes sense. I'm grateful to listen to all comments
RE: Chummy engine swap - Chris KC - 21-11-2024
As far as I know Peter, all blocks are interchangeable.
Depending on the condition of the faces, you may yet find that your "new" block is also cracked once it's cleaned up.
Personally I would never skim a block if I can get away with gently lapping it on a surface plate. They are slowly getting smaller and smaller and this has knock-on effects for pistons etc.
Is your '34 crankcase a "high frame" or "low frame" type? Off the cuff (I could be wrong) I think both were made in that year.
There's about 5/16" difference to the height at which it sits in the frame, which can result in fouls (if anything this might work in your favour).
Finally, I let it be known at Beaulieu one year that I was looking for a circa-May '34 crankcase (to build up a "correct" engine for my RP) and within 10 minutes I'd found one within a month of my car's build, for a modest 40 quid. So don't give up too easily.
RE: Chummy engine swap - PeterN - 23-11-2024
Thank you Chris, not sure about the high frame/low frame question. Where is there a reference to a dimension which relates to one or the other do you know?
RE: Chummy engine swap - "Slack Alice" Simon - 23-11-2024
Jon Edgar and I did some work on this a while ago.
On reading my notes, I cannot immediately see what conclusions we came to.
This never got finished, because I didn't/don't have a low frame crankcase to play with.
I think the conclusions were: the high frame rubber mounted feet were higher up the side of the 'case, (compared to the solid mounted 'case) to allow for the insertion of the rubber mounts.
They were also further back, to move the engine forward to accommodate the 4 speed box. (Were there solid mounted 4 speed versions, or did the change happen together?)
I must have had a later 'case at some point, because I think I decided that the rear mounts of the later (low frame) engines were raised by a bit (5/16? 3/8?)
to drop the rear of the engine.
I turned up a couple of ally spacers, replicating the recess under the foot, in case I ever had to use a later case in an earlier chassis.
If I can find them, I will measure their thickness.
RE: Chummy engine swap - Nick Lettington - 23-11-2024
I believe* the high frame version has no reinforcing rib behind the starter motor.
The Ruby version has a rib as pictured here...
*credit Ruairidhpedia
RE: Chummy engine swap - Chris KC - 23-11-2024
With apologies to whoever took these photos (found on the web) :
RE: Chummy engine swap - David Stepney - 23-11-2024
"They were also further back, to move the engine forward to accommodate the 4 speed box. (Were there solid mounted 4 speed versions, or did the change happen together?) "
I can answer your question, Simon. The earlier iteration of the 4 speed box (the crash box) was introduced in September 1932. The rubber mounted engine together with the 2 synchro box was introduced in August 1933. All the crash box 4 speed cars had solid mounted engines. ( as mine has.)