TR4/4A Putting aTR4 motor and trans in a TR3

[karls59tr]

I know they are basically the same motor/trans but are there any minor mods or clearance issues to look out for?

 

[martx-5]

The front engine plate will have to be swapped over. If it's a TR4A engine, exhaust header and intake might have to be changed. I'm sure there are a few other minor items like the shift lever, but someone will pop in with the rest.

 

[TR3driver]

The 4-synchro gearbox is slightly longer than the 3-synchro, so you need to elongate the holes in the rear crossmember (where the rear mount bolts to it). ISTR it's about 3/8". It's possible to force things together without elongating the holes, but it drastically shortens motor mount life (BTDT).

If it is a pre-TS50K TR3/A, you'll also need to massage the transmission tunnel a bit, to clear the starter bulge. Plus of course use the later starter (assuming it has the TR4 flywheel in it).

The later TR4's crankcase ventilation system was problematic, so I would probably put the TR3 road draft tube on (if the new motor doesn't have one). (Actually, my long-range plan is to re-engineer a proper PCV system, but I haven't gotten there yet.)

 

[vivdownunder]

The TR4 engine's valve cover has the breather at the back whereas TR2-3A engines had it at the front. That doesn't matter a hoot if fitting it to a 3A, in fact people in the know might think the car is a later TCF series TR3B (with original TR4 engine).

The biggest job is securing and fitting a TR3A front engine plate with its narrower spaced mounts.

Regards,

Viv.

 

[karls59tr]

Thanks for the info guys.