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MG MGB GT V8 Factory Originals Technical - Injection or carbs?

I will be fitting a 3.9 Rover V8 to my GT (have the engine / box etc, just modifying the body at the moment)

I was originally going to use the Offenhauser manifold and Weber or Edelbrock 4 barrel carb setup with a nice bin lid sized air filter. But more recently I've been thinking about injection. Can the injection setup provide the same power as the above carb setup?

My engine will be fairly standard to start with, just has a high torque cam and an increased compressssion ratio of 10:1 and will use RV8 manifolds. Will probably upgrade in the future when funds permit. Can the standard injection setup be tuned / remapped, or would I need an aftermarket programmable ECU? Presumably the standard one would be fine with my original setup.

Also one last quick question. If I use an RV8 bonnet can I avoid having to machine the manifold / plenum?

Many thanks, Paul.
Paul Grundy

Paul - the carbs will give you more grunt - the injection (around 190/200BHP) will save you loadsamoney on our congested roads. You can remap the chip (500) and you can use an RV8 bonnet and thereby avoid changes to the plenum etc.

E-mail if you need more.


Remap the chip? for 500 pounds? that is $1000+ in US dollars!!! There are several companies on the internet that will burn a new eprom for a LOT less than that given the parameters that you are working with, i.e. diff ratio,vehicle weight, tire size etc. FWIW Alyn

500 pounds!
Depending on what you want to end up with I believe you could probably do it yourself using Mega Squirt and dyno time for much less.

I have run carb & F/I & with a 4.2, 70-90mph I can do 25mpg ( & I have done nothing to get better mileage. With a carb we did 20-21. I make up a set of motor mts. that sit the motor as low as I can. (The oil pump base we use gets close to the chrome bunper srearing rack) I cut .800 off the bottom of the trumpet stack, remove the hot water heater on the bottom of the plem. & I need no R hood. (I like a stock looking B) & I still have a TON of tork. I have a 4.2 with a rover 5sp. that I put in a factory G.T. & it was not hard at all. I have 7 B V8s that I have built & F/I is the only way I will go now. I have a custermer that bought the RPI chip & his 4.2 ran better than the cab. I am now running an alu. flywheel & it comes out of the hole real good & accels. faster. You can put in a hotter cams that are made for the F/I & thay work well BUT 2 mpg. dropped off. I have found that the rover dizzy holds thre rover motor back, I use a 61-63 Buick dizzy with lumm. elect ing.& I get real good power out of it & good fule mileage. Send me a E-mail & I will send you some pics.
Glenn Towery

Holley has a FI set-up for roughly 1,300us that contains everything you need. They even have a choice of set-up's TBI (throttle body injection) which is the same size as a normal 4 barrel holley carb, and Rail injection, which is a throttle body, and seperate fuel rail injectors. both kits are roughly the same price, only the TBI set-up being slightly cheaper by a 100 or so.
CJD Dark

Roger (RMW), I assume that when you say EFi will save loadsamoney, you mean it is more fuel efficient than a 4-barrel carb. Certainly, Glenn is saying that, and he should know. So, where in the UK should I start looking for a Rover Hot-Wire system? I have ridden in Geoff King's EFi car, and it is most impressive, but he has the RV8 bonnet, and like Glenn, I want mine to look standard.

Roger & Glenn, I currently have 3.5 litre SD1 motor sitting in my garage. Is it worth upgrading this to 3.9, and if so what's the best way to do this? Or is it best left alone? Or should I just look for a 3.9 engine.

By the way, are you the Roger Williams wot wrote THE BOOK?

Mike H
Mike Howlett

Paul, Roger is right about the carbs giving more grunt with what is available for the 3.9. We deal with FI exclusively. Given a choice for any after-market products for fuel injection you would come up short. A solidly engineered fuel injection system would give as much grunt as a carb set up but, alas, there is not. The reviews for the Holley system were more negative than I would have guessed. The last time I ran the gamut for these products I found no satisfactory products. All said and done, in my opinion, anyone who can afford a fuel injection system and chose carbs over it, took a step into the past to 20 years ago. For all the problems carbs have, fuel injection has the cure 10 times over.

Dann BCC kbc
Dann Wade


Lots of ex-Range Rover Efi on E bay.

Both Geoff and I have 3.5's with RV8 bonnets, and swear by them, the view down the bonnet is infinitely superior (in our opinions) than the standard one, particularly if you fit louvres !

M Barnfather

I changed my 215 from a 4 bbl to EFI & love it. I may have lost or 2 HP, but not really noticable. Gas miliage went way up- from 21-22 to 28-29.

I modified all 3 pieces of the Fi intake per Roger's tech & got it under a stock hood. The car looks like a very stock 1966, so it was inportant to me to use a stock hood.

The Rover FI from 1989-'92(?)is a great system with a stand alone wiring harness. I bought mine in peces on E-bay & have the 14 CUX computer & use the O2 sensor which is superior to the earlier system with the 14 CU compurter & no O2 sensors.

Glenn modified my fuel tank & I use a Volvo Turbo pump which mounts outside the tank & pulls fine, so only 1 fuel pump required.
Jim Stuart

I'll put my two cents worth in (just try and stop me!)

I had the vacuums take offs welded and then had machined various bits off the plenum for less than $150 Australian. If I had looked around a bit, probably much less. I took 12mm off the top of the tray and 16 off the bottom. I ended up with 12mm clearance,(ie try 9mm top and 15mm bottom).
Thats got to be much cheaper than setting up hollies SU's etc.
For the fuel supply I used a high volume feeder pump (that peirburg make),pulling through a large filter and then feeding into a High pressure Bosh pump. ie Fuel tank--Big Filter-Feeder/sucker pump-High pressure pump--engine-Fuel tank.
High pressure pumps get very noisy unless fed. ie they suck at sucking. There's a thread in the archives with part numbers etc.
The Big filter acts as a anti-surge tank, the high suction feeder pump prevents cavitation noise from the High pressure pump. This is a cheap easy/quick to set up arrangement and so far flawless.
Feeder pump- $90 Australian
Big Filter-$20 K mart
High pressure pump- $150
Some bit of tubing and clamps $20.


Lambda sensors certainly improve consumption at cruising speeds, I get 32 (UK)mpg on motorways regularly.

You may have problems sourcing a tank with an internal swirl pot in the UK, there is always the RV8 tank, but it is very expensive, and I believe holds less fuel than the standard MGB one.

I'm using a high pressure pump from Rimmers,it's important to get it a close to the outlet, and a low as possible,I have pics of the intallation if you need them.

M Barnfather

Mike B,

I'm getting quite keen on the EFi now. I've had a look on but only found one system and that wasn't complete. Where should I look on ebay? I think I must be in the wrong place.

I'd like some pictures if you can send them to me please. My e-mail should appear here. One day we'll meet up and I can see the real thing!

Mike H

Mike Howlett


This is not cheap route but may be worth asking a few questions about possible set ups.

A RV8 bonnet is required to get a decent large filter on with a carb and adding vents would improve cooling so ma ybe a worthwhile investment whichever route you choose.


Forgot to mention, you need a return line to the tank. You'll probably have a tank with a pick up incorporated into it already (mine's a '75 and it did). Just buy a very very late model MGB sender ($40 or $50) for the tank. This incorporates its own fuel pick up, which means you now have a new fuel pick up and and can use the old pick up as the return line. No other alterations required!. The big half liter filter is more than large enough to act as a swirl pot.
You could try running without a feeder pump but would probably run into problems with cavitation as I did. Try it and if it doen't work splice in a feeder pump. You can locate the pumps in the boot if you're using a feeder.

Mike, You've got mail.

Best Ebay searches are 'rover v8' 'TVR' and '14CUX', there are a couple of guys who are pretty continuously selling parts off stripped Range Rovers, if I see stuff I'll e-mail it direct from E bay to you.

M Barnfather

Thanks chaps, especially Mike. I'll keep looking - there's no rush as my car's bodywork is full of holes at the moment and I have no time..!

Mike H
Mike Howlett

I finished the write-up on MG EFI fuel system conversions. This system work and works very well. It was taken from a Ford Bronco Website and is what the bronco guys do to convert to EFI on the early bronco's so that they can 4x4 and not have problems. It also adds a large Qty of fuel to your system, close to if not a full gallon(US).

Go to the tech section, then V8 conversion, then Air/Fuel... Or just use the link below..

FYI - This extra fuel comes in handy.. My Stock pump is acting up and I was able to run my car for a good 5 minutes off that filter assembly before it started stumbling...
Larry Embrey

This thread was discussed between 09/03/2005 and 14/03/2005

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