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MG MGB GT V8 Factory Originals Technical - 3.5 and 3.9 OEM cams

I have neen looking at all of the camming options for the 3.5 and saw on the RPI website that using a 3.9 cam in the 3.5 engine increases power and efficiency. Is this a sensible way to go as a replacement? Is there any problem in doing this and would I gain anything?
The cam bearings have been mentioned in a number of archive threads but I cant find a description of what these are made of and when they wear or how to tell? I dont want to put a new cam in to find they are shot. Is the rule about keeping the push rods all in the same order strictly true when you are fitting a new cam and followers?

You ansers would be greatly appreciated.

Frank
frank swinton

Frank,
In one of Roger Williams books he writes that a later cam will give an addittional 10BHP (as far as I can remember, don't hold me to this)I made enquireies at a machine shop and they said "yes it's better but you'll need also to get a new bolt/nut at the front which is no problem". One other thing which might be of help is that the practice here is not to use Rover Tappets (lifters, followers) but to use the General Motors Holden Variety which are just as good and about one third the cost. Other than this I am ignorent on the subject and await with interest more expert opinion.
Peter

Frank,

I donít know what it will do to the performance - my engine is not running yet - but I can confirm that the 3.9 cam is a direct exchange in the 3.5 engine with no mods of any kind required. If your cam needs changing (and it will if the engine has a few miles on it), you might as well use the 3.9/4.2, itís cheap and is supposed to give an extra 10 BHP. I used a double roller chain with mine, it didnít cost much more than the standard chain and should last longer without stretching.

It is always good practice to keep components together that have worn together so even though you are changing the cam and followers the push rods should be kept with the same rockers, same way up too.

Cam bearings seem to last very well, maybe I was lucky but mine were perfect on a 113K miles engine, a good visual check and measure for clearance and if all is well I would leave them alone.

A good tip from Peter about the cam followers but General Motors Holden parts will be as rare as rocking horse droppings in the UK and probably more expensive than Rover parts. I bought my cam followers from RPI but it would be worth checking Rimmer Bros http://www.rimmerbros.co.uk/, they might be cheaper.

Geoff



Geoff King

Peter/Geoff,

Thanks for that, I think the 3.9 sounds like a very good bet to get a little more out of the engine while keeping the cost and efficiency within tolerance. Good to know there are no other mods required, I want to try and keep it simple.

Cheers

Frank
frank swinton

Frank,

I would prefer to deal with Real Steel who have their own Cams rather than RPI.

Paul
Paul

Does anyone have the application or part#s for the GM lifters? When I ask the local parts house for Buick 215 lifters, I get, my listings don't go that far back.


Kelly
Kelly

All pre 1970 Buick V8 lifters are the same, according to Kenne-Bell.
George B.

This is the No. off the quote I got at a machine shop
Part NO. HT969 Description HOLDEN LIFTER cost 4.00

That no. may be local and not apply to USA
Peter

Thanks for the info! You just saved me a lot of money.

Kelly
Kelly

This thread was discussed between 29/05/2002 and 05/06/2002

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