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MG MGB GT V8 Factory Originals Technical - P76 Intake question

Can anyone tell me:
1/ can the original maniflod for the P76 be modified to take a 4BB carbie
2/if so what is the best aftermarket carbie?
3/ what would be the best aftermarket carbie if I used the stock manifold?
regards
mark
mark mathiesen


Mark, good to hear from you again. How's the A coming along ? I have seen an adaptor plate to mount a 4 barrel carby onto a 2 barrel manifold. A Holley 500cmf 2 barrel would be my choice if your'e stuck with a 2 barrel. After market Rover manifolds can be used with the aid of spacers, but I think this would be costly. I'm using a 2 barrel Holley 350cmf in my GT & it doesn't lack any power.HTHs Barrie E
Barrie Egerton

Mark,
the std. intake can be modyfied by cutting, welding
and ginding.
The best item to start with is a P5B/P6B manifold.
I have mounted a Holley 390 on my engine, an Edelbrock 450 would also be a good choice.
Don't by carbs that have too much flowrate, you'll get
distribution-problems with oversize carbs.
May bee take a look into David Hardcastle's "The Rover
V8 Engine" and follow his comments. You'll be surprised
regards
Ralph
Ralph Siebenhaar

lynx engineering in Sydney made a custom 4 barrel,try the various p76 clubs, Ive seen them advertised occasionally[parts peddler, trading post] Remember that this is an engine that went out of production nearly 30 years ago and for the price of performance gear, and reconditioning , a later stiff block Rover engine can be built to 5 litres, much better option.
Russell

Ralph, the P76 is a wider block due to 1/2" higher deck so don't want to have to use spacers;
Russell, thanks for the suggestion but as the wreckers up here in Brisbane just about give P76 motors away these days (have 3 spares now-each cost $50) want to stick with these. Have been told heaps of after market inner bits will fit but no one can advise on the carby situation!
regards
mark
mark mathiesen

The reason they are so cheap ,is because after 30 years they are best used for boat moorings. Never seen one stripped down that had anything resembling white metal on the shells. Try this, take a p76 crank to a reco shop, get him to turn down the journals to Rover size, [seen this done a couple of times -it does not weaken it] crysler hemi rods , pistons to suit whatever bore you want [friend of mine got his out to 5.2 litre] get hold of a p76 SIX cylinder flywheel -it bolts straight on ,and is [from memory round 5kgs lighter] total cost round $2200. To do a sad old p76 justice you are going to have to put on Rover heads ,front cover and sump- all bolt straight on [only have to shorten the pushrods -hollow much better than rover ones] You will still have 3 problems it will still need a reco, you still need a decent inlet, and your chances of finding an engineer to certify it are about 1 in a 1000.- check them befor you start spending money. Rules are being standardised Australia wide, and I know you could not get it on the road legal in NSW. A rover engine with a 3500 engine number can be bored to whatever, the number tells the registry its a 3500. Make sense?
russell

Mark , p76 manifold is highly inefficient no matter what you do .Rover p6 or SDI bit better but you need spacer plates due to p76 block wider, S.Us better than Holley & more economical. Offy manifold manifold good for mild road car, Edlebrock & best for street performance even some club track work [Harcourt best for high performance]but all need spacer plates to suit P76 BLOCK. Willpower/MAXWEDGE manifold made by Bill Laney here in Sydney is made for Rover blocks & one for P76 WIDER BLOCK TOO.iTS SINGLE plan manifold for high performance but has much more torque low down than standard manifold,check with Ross Calgher racing N.Z who did flow testing on all Manifolds[rjcalgher@xtra.co.nz].There's plate available to put blower on Willpower manifold & EXTRA manifold to bolt on top to fit 2 = 1&3 quarter S.Us or 2'' S.Us. similar to M.G.BGTV8 top manifold but more efficient , also kit to convert these two manifolds to injection using top S.U manifold with butterflies in them. Using RoverP6 or early Range Rover or M.G v8heads is no advantage as same size valves[same part Nos] & ports similar but P76 bigger.P76 can be made bigger like 4.6 for less cost.P76 heads have 4 less bolts like latest 4 & 4.6 LITRE TO STOP LEAKS FROM GASKETS as 4 extra bolts tilt head too much & latest 4,6 has same crank journal sizes so buy p blocks all up & save a fortune, email me if you need any more info. ps,Carter/edlebrock/weber AFB 4 barrel carb best to buy ,better than Holley check out [R.P.I.ENGINEERING SITE]REGARDS STEVE
Stephen Foldhazy

Mark,
Before you spend squillions on Hollies, special manifold welding and machineing, you might want to look at the cost of fitting Hot wire EFI. YOu should be able to have the plenum welded and machined for $200 at the absolute outside. Even if total cost works out a little more expensive (I doubt it) the gain in ecomomy and power would have to be worth it. Initially I was wary of EFI ,intimidated by the electronics, but it turned out to be quite easy.
Peter

Russell, thanks for the comments regarding legality. My case is very unique in that I was given an approval in principle in 1990 BEFORE Qld adopted national guidelines. I have a letter from the Qld Transport dated last year advising that as the approval was given in principle prior to adopting national codes Qld transport authorities will honour the approval for the life of the car and not require it to comply with current legislation! Cool hey!!
mark

You got lucky, I was about to shorten the odds if your car was a BGT, might get lucky. Didnt realise how heavy they were , under the weeird equation they use itgets close. Roadsters miss by miles. I'd still argue that a big Rover is a better deal.
Russell

This thread was discussed between 21/08/2003 and 03/09/2003

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