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MG MGB GT V8 Factory Originals Technical - Buying a new fuel pump
it looks as if time has come to install a new fuel pump to my GT. The engine is a SD1 Rover with Holley 390 on a JWR dual plane inlet and with RV8 style headers, LT77, 3.3 rearend.
Up to now i have used a Mikuni vane type pump that deliveres 4 PSI of presure, althoug Holly says @6 PSI would be best.
What types of pumps do you yous on your cars and what seems to be recommeded?
I have a similarish set up to your but with the offy carb. I have a standard new MGB one - no problems at all.
|So it should be - the standard MGB pump should be capable of delivering at least 1 Imperial pint per minute, and in practice it is more like 2 pints. That's 15 gallons per hour!|
|Paul Hunt 2|
My stock SU-pump is doing itīs job perfectly in my SD1 Vitesse powered B. My final gearing 3.9:1 which means that I rev higher than you at Autobahn speeds, but I have had no signs fuel starvation. (Weber 500&JWR)
By the way Ralph, are you satisfied with your 3.3:1 final gear? I happen to have a 3.3 crown wheel & pinion on the shelf and are wondering if the change is worthwile?
compared to the 3.9 axle the 3.3 was a very satisfying cange. The car is not that 'nervous' as it was before and there is no real lack in excellerating for a road car, as the benefits of the adequate torque of this engine helps a lot.
If you want to change ring an pinion, the diff carrier has to be machined to the dimensions of the BTB 841 to fit the ring gear.
BTW. MG Rover used the same old MGC ratio for the RV8 but with a LSD.
@ Liam and Paul,
thank you for the information you gave to me. I have used the Mikuni, first only one, then two of these as fuel starvation seems to be a problem with the Holley when reeving in exess of 4500 rpm or during stop and go on the motorway. The carb is O.K., rejetted for the GT and fitted with the right secondarys spring and the right cam and shooters for the excelleration pump system. Fuel level is set to instructions and filters are clean too. There is nothing wrong with the ignition that is upgraded to a Piranha/Newtronic blackbox system.
When i read about fuel delivery in one of my (two) Holley books, there was allways said that the fuel presure should not be below 3.5 PSI at all, although the Mikuni is only capable to deliver 3.3 PSi at WOT when i mesured it.
A friend of me who is running a Facet red top seems to have the same problem with his V8 although he has a Edelbrock 500 installed on an Offy inlet and is running a Piper 285 cam, LT 77 and a modified SD1 axle.
I hope ther will be some further hints what has worked...
Although Im running a 5.0L Ford Im also using a 500cfm Edelbock Carb and a Holley Red Label electic fuel pump (max press 7 psi)
I have put some 40,000 miles on this set up with no fuel starvation problems ever. Not suire if these are available in Europe ,but are readily available here from any hot rod supplier
|My EFI set up uses two in line pumps.|
A low pressure/high suction pump feeds the High pressure pump.
I know you don't use EFI but this low pressure pump might be what you are looking for since it is easily able to keep up with the HP pump which delivers 130 litres per hour.
It can deliver 0.5 bar when used as a primary pump
It cost me $95 Australian. Probably much cheaper for you.
The low pressure pump is made by Pierburg
and is called a "universal autosuction rollervane pump
As far as I can tell itís Pg 75. Part # KP 7.21440.53.0 or KP 7.21440.51.0 there doesnít seem to be any difference. The guys I got mine off called it part #12001.
|One barr is very close to 15 PSI|
|Ralph, Like Gil, I have a 5.0L Ford in my conversion - with a 600cfm Edelbrock and the regular MGB pump was fine for normal driving but larger throttle openings - for say 5 seconds or more - would cause the motor to stumble. I found an old double-ended SU pump at the wrecker, re-built it with new solenoids, and it has worked fine since. Although the MGB pump sounds as if it has plenty of capacity, the doubled pump was used on a number of larger-engined British cars before fuel injection and must have been developed to fit that need. They are still available new from Moss etc so might be a "period" option! Good luck, Bob.|
This thread was discussed between 24/01/2008 and 25/01/2008
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