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MG MGB GT V8 Factory Originals Technical - 'Soft-mounting' electric fuel pump?
|Can anyone tell me how to "soft mount" a modern electric fuel pump? I have a Holley pump which will is known to be notoriously loud but perhaps some sort of isolation mounting would help. Do you guys just jury-rig something out of exhaust hangers? Would love to hear of any particularly successful installs. (Probably will leave it pretty much where the SU was, but of course the Holley has to be mounted vertically.) Thanks.|
|Yes, I have a Facet pump mounted vertically on the battery box using a couple of little "cotton reel" rubber mounts - the ones with a stud each side of them.|
|I have a Carter Performance Electric Fuel Pump P4594 7psi on my 74 ½ MGB. I removed the horizontal SU and welded a plate over the hole in the trunk. At the same time I drilled/welded 3 bolts through the plate and mounted the fuel pump bracket to bolts. Between the bracket and the bolts I used 3/8" rubber grommets (the ones with a hole in the middle) so the bracket never touch's the car metal. I have only tested it once, and is it loud. I don't remember any vibration. I know they make a quiet pack but figured it would be pretty well the same idea, perhaps the density of the rubber is different?|
The one thing I have found out is that unlike the SU, this pump never stops running. Once it reach's pressure it will stop pushing fuel until it once again required but it never stop running. If I remember correctly the V8 at 5400rpm, and a SU pump, the pressure will be 0psi. With the Carter at 5400rpm it was something in the order of 4.5psi. I have heard of people using dual SU's, which might be a consideration, depending on how loud the exhaust system and stereo turn out to be.
|I was wondering why the heck this is. The SU design is, like, from the Bronze Age, and yet those pumps are smart enough to stop running when they don't need to. None of the modern ones are set up in this fashion! I have a modern Mallory, and it is relatively quiet, but it keeps on chugging ALL the time. More than anything else, I am worried about it overheating (once the V8 is lit up, you don't really hear the pump). At $120 or so a pop, I'm not really too keen on having to buy a second pump for backup.|
|The SU only stops when the engine is not running and the pressure in the system holds the pump contacts open.|
When the engine is using fuel the SU runs all the time, too.
|This brings up a question for me. My Fuel pump solution for my 302 is to use a traditional Block mounted mechanical pump. I have a high output unit ready to install.|
I am wondering what problems I may see by it pulling fuel through the SU?
I would like to keep the SU installed but disconnected so that if I have a problem with the mechanical I can plug it back in to get me home or to a shop...
|The SU has a couple of one way valves so the mech pump should just pull the fuel through them.|
|Will pulling fuel through damage the SU though?? I believe my mechanical is a 113gph pump and I am worried about it damaging the SU..|
|The SU is a reciprocating pump that only pumps when the fuel level in the carb drops. It only pumps at a rate sufficient to keep the flat chambers up to level. Therefore it is pumping far less at idle or steady-speed cruising than full throttle at high revs.|
|Just doing some early morning scanning. Going to be putting a Rotary in my '66 MGB this Spring.|
Regarding replacing the fuel pump, I got rid of the SU Double-Points pump in my '70 Bentley and replaced it with a Holly-Blue Pump. Lot's of fuel flow (8 MPG City or Highway!), but way too much PSI for even the big SU Carbs on this car. Fuel poured out of the top of the Carbs with the Regulator that came with the Holley. Had to get a lower pressure regulator to get it down into the 1.5 PSI that the Bentley SU's wanted to see.
I assume that a big non-stock pump could overwhelm the small SU's on the "G8" too.
|Bob, MD: What the heck is a G8? Fuel flow capability shouldn't affect gas mileage. The carb will draw only what it needs (it is exactly like using a fat electrical cable to carry a current ... the fact that you have a fat cable doesn't affect current used; it just allows for higher max current). If the pump's flow _does_ affect gas mileage, the car is being fuel-starved and running too lean. Running in a fuel-starved, leaned-out state is not the right way to get mileage.|
There is no downside to having lots of fuel flow capacity ... I'm perhaps slightly dubious of those Facet pumps used with a V8 for that reason.
Edelbrock 4bbl takes 4.5-6psi. Of course a big pump would overwhelm SUs, never suggested it wouldn't.
|Sorry, the "G8" was an early morning abreviation for "MGB-V8"= "G8". Has a nice "ring"...|
I just wanted to pass along my experience with a big flow/high PSI pump and my particular SU's in the Bentley. While the fuel flow has to be very high (that's where my Premium Gas/8MPG comments come in), the Carb's, however, can't withstand much PSI/force before I have raw gas flowing out of the overflows that are on the tops of these Carbs. So, yes, I use all the fuel that the Holly-Blue Pump can pump, but for these Carbs, you have to dial the "pressure" way back from 40 PSI (great for Fuel Injection) to 1.5 PSI for my Carbs.
(Sort of like I need a lot of "current" but not much "voltage").
Just wanted to pass this along before someone either starts pumping lot of raw fuel into the engine, or "over" some hot exhaust manifolds...
|I have fitted a facet red top (competition)fuel pump which pumped the fuel straight through the overflows until I added a Filterking regulator, the one with a dial, so now I can vary the pressure to suit SU's or a Holley and be able to see the exact pressure.Both pump and filter are mounted on the bulkhead above the passenger footwell(in the engine compartment of course).Car is R.H.D. rubber bumper. The pump does click on tickover but it is inaudible once revs rise.|
|I did this by purchasing four "cotton reel" type isolating rubber mounts from Pegasus Racing and I just used them to hang a Mallory 70 gph pump on there. Apparently the Mallory has to be put on more or less vertically. Anyway, there is a web of metal just in front of the battery -- right above where the factory put the SU pump -- that you can just drill holes through (helpful to borrow a right-angle drill to get in there), put some zinc on the holes for good measure, bolt on the rubber mounts, and you are all set. There are some big round holes in that web of metal and it's very easy to reach in and hold the nuts to get things tight. Then you just cut the ends off the metal fuel lines where they formerly connected into the SU pump, put a couple of inches of rubber hose on there, and you're done. Looks very squared away.|
(That being said, even mounted in this way the pump seems a little loud. Maybe the noise of the motor will drown it out; haven't had a chance to try it yet as everything's apart.)
There are probably more sophisticated ways to do this, but with a limited number of tools and a very limited amount of skill I was able to do this in no time flat.
|I went the Facet and 'cotton reel' mount route and found no problems with a Holley, but after a wet English winter the pump failed. I would advise anyone in a wet climate using an electronic pump in the standard location to seal it with a silicone sealer as I did on the second pump - no worries in wet weather now.|
This thread was discussed between 05/02/2001 and 21/02/2001
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