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I supported Toymods
Location:
I renounced punctuation
Registered:
May 2002
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Re: M engine bits swapin?
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Thu, 18 December 2003 02:19
 
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You can use the early round tappet cover heads on the late blocks but you need to change the front timing cover to the early model one - the front head bolt pattern is different from early to late. Then you need to get the head and timing cover decked whilst they are bolted together so that you don't get oil leaks. The main problem is that you need to use a 41013, 41030 or 41032 head with the 5M to keep the same crappy 8.5:1 compression (they have the same head chamber volume as the 5ME head). To increase the compression, I would recommend using 5MGE pistons (they are slightly high topped).
You can use a 7MGE crank - obviously you will need to change the timing belt pulley to a chain pulley. I have seen a 7M crank in a 5M block running an early 4M head - effectively a 7M but SOHC and 2 valves per cylinder. Of course you will need to see if the head can support enough flow for a 3000 cc motor - I can tell you now the exhaust side certainly won't.
Big cams are also an issue due to the rocker arm geometry. Whilst it is possible to put a grind on the cam anything over 25/65 will result in grossly deranged cam timing. The only solution is to have the cam lobes welded and ground. This is a $500 job for an M series cam.
As for carbs, the easiest option is to fit a Weber carb off a Capri V6 (you can buy adaptor plates for the standard manifold) or a small Holley. If you can get your hands on one of the original twin carb manifolds made for the M series engines (both twin SUs [M-B manifold] and twin down draft [M-D manifold] were made), that would be better but of course you would need to set them up for a 3000cc motor.
In January, I will be having my M series clearout sale. Included will be my triple SU manifold complete with carbs, trumpets and socks.
It seems like a godawful lot of work for a result that will be ordinary. I'd just drop a 7MGE in there and be done with.
Some advice: Rally something that isn't rare. Corona Mk2s and MA4x are pretty thin on the ground now.
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