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MG MGB GT V8 Factory Originals Technical - Rover Engine Heko

Greetings guys and gals
have a couple of ??'s regarding rover v8's

3.5l are cheap and plentiful here compared to 3.9l.
Ive been told that the 3.9 is the better engine not because of capacity but because of overall design.

Is it worthwhile buying an reconditioned 3.5l and then adding a stroker kit to it
Or is the money better spent finding a good 3.9l and reconditioning that instead?

Any comments much appreciated


They are almost identical engines in UK spec, just different bores , the bigger bore is generally accepted to give slightly better breathing for the valves, not much difference in HP but rather better low end torque......I compensated on my 3.5 by an offset timing of the cam...all Rover V8 engines have fabulous torque figures anyway and in a car as light as an MG even the 3.5 is quite adequate.

Induction and camshft make more difference than capacity, an efi 3.5 will be more powerful than a twin SU 3.9.

Why not go ahead with the 3.5, you can always convert to 3.9, or 4.2, or even 4.6 later ( if the axle, propshaft and gearbox will stand it....I've already twisted Rover Sd1 halfshafts and done in one diff with my 3.5, and had to buy hot rod shafts )

Michael barnfather

I have fitted Rover 3.5 SD1, "slightly" tuned, in my conversion. It's a good engine. The gearbox also SD1,LT77 exactly, with close ratio gears and Quaife ATB differential in the rear axle.It's a good car.

I see your coolant expansion tank up in the right back corner of the engine bay. But what is the rectangular aluminum box below it, with the two hoses to the valve cover/ intake area? Best, Joe
Joe Ullman

I thought the 3.9 also had a better internal cooling system
ie the water passages are bigger and that the head has stronger bolt mains?
True ?

The box is an oil catch tank for collect oil fumes. If you inject oil fumes by the carburetor way, you contaminate the fuel/air mixture and reduce the explosive capacity of mixture.
I don't know if the internal cooling is different, with the ally rad the engine is never heat.
I have fitted ARP studs kit for hold together the cylinder heads.Nice and strong kit.


Nice looking engine bay !

Is there anything inside your oil-fumes-collection-box? And is there an outlet pipe going somewhere ?

Also, is that a home made air filter on top of your carb ? Did you have a specific reason for not using a low rider air filter ?

And what carb do you have there, I can't quite work it out.

...I love having a nose around other peoples engine bays !

j w mcglynn

The oil catch tank is horizontally baffled with some holes, a supple hose go down under the car. I don't like the big round air filter hiding the carburettor. I like the Holley. I have hand crafted a bulge in the ally bonnet for clearance between them.


So we have the same basic setup (SD1 engine and Holley carb), but they could look more different (bottom picture on this page: ). I like the effect of the big shiney low rider filter under the bonnet.

However, I do like the idea of your oil-fumes box. Did you make it yourself? Pretty simple I suppose ?

j w mcglynn

JW, So why do people block out their plate # when they photograph their cars, I never understood the reason for doing this.
Michael S. Domanowski

In theory, someone can copy my car and put my registration number on it and then I end up potentially picking up the fines and offences they commit (speeding etc) whilst they drive the clone of my car.

However, you'll notice on my site the first car is not blocked out ! doh !

j w mcglynn

This thread was discussed between 06/04/2004 and 07/04/2004

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