Taz_Rx Posted July 30, 2010 Report Share Posted July 30, 2010 Point....... .....Missed. :) Quote Link to comment Share on other sites More sharing options...
ke70dave Posted July 30, 2010 Report Share Posted July 30, 2010 "work" is a bit of a loose term. if your going to the effort of installing some fancy carbys, i would want to have the fuel pressure set to exactly what the carby specifies. though to be honest i thought that fuel pressure wasnt an issue (so long as it was small) with carbys, as you just fill the carby fuel bowl and the fuel is sucked into the engine via the jets....i would have thought that the actual amount of fuel being pump would have more of an issue on carbys than the specific pressure it is supplied at? since the fuel bowl is at atmospheric pressure anyway, the fuel pump just has to have enough pressure to allow the float/inlet valve to fill the bowl. and of course enough flow to maintain the fuel bowl at the required level? (stupid question, does a carby fuel bowl have a return on it? if not how does the fuel pump "know" how much fuel to pump so that it doesnt overflow the fuel bowl...been a few yrs since ive worked on carby engine. I'm starting to think that the reason carby fuel pumps are only allowed to be 4-6psi is that the inlet valve attached to the float in the carby (use to keep fuel bowl at a constant level) can only handly 4-6psi.) on a completely unrelated topic, how cool is this!! http://www.britishracecar.com/LesGonda/LesGonda-BB.jpg Quote Link to comment Share on other sites More sharing options...
Taz_Rx Posted July 30, 2010 Report Share Posted July 30, 2010 The needle and seat - which is operated by the float shuts off fuel to the float bowl when its full..... just like your toilets systern. If the fuel pressure is too high it can force open the N&S and overfill the float bowl. Quote Link to comment Share on other sites More sharing options...
ke70dave Posted July 30, 2010 Report Share Posted July 30, 2010 ah thought so. so the needle and seat can only hold the formentioned ~4-6psi in that case so long as the fuel pressure is low enough to allow the needle and seat to seal, then it should be all good. maybe mr scoobxd got lucky and his needle and seat is able to hold the pressure of his supercheap auto pump. though fuel pressure regulators are fairly cheap so i would get one anyway, and set it to what you want. Quote Link to comment Share on other sites More sharing options...
parrot Posted July 30, 2010 Report Share Posted July 30, 2010 There are electric fuel pumps, and then there are electric fuel pumps. Some provide more pressure than others. I tried running a particular facet fuel pump on a pair of twin webers once, but the pressure was to high, evidenced when petrol started pouring out the throats (and down the bores). So you need to know what pressure range your electric pump is designed to run at, and/or run a separate fuel pressure regulator. Fuel pressure regs aren't expensive, and have been talked about on here a lot recently. Quote Link to comment Share on other sites More sharing options...
Taz_Rx Posted July 30, 2010 Report Share Posted July 30, 2010 Yeah some carbies will tolerate different pressures. Apparently Dellortos don't like much pressure at all, where as solexs can tolerate a bit more..... this is where Scoobzd is making an assumption. Again with down draft carbs, stocko asians don't like much more than 4psi. On the other hand I've put 12psi into a 32/32 weber befor and the N&S could still hold that!!! Quote Link to comment Share on other sites More sharing options...
styler Posted July 30, 2010 Report Share Posted July 30, 2010 (edited) i ended up using a low pressure high volume quality rotary lift pump without regulator being the fact that some regulators actually were really bad and so would affect the delivery, depending on the design of how they restricted the flow of pressure and volume... i needed a low pressure high volume for the application - twin dcoe45's the rotary part meant consistant fuel delivery on pressure and volume and a stop in direct feed wouldnt lock it up, also no return is needed which can sometimes also cause fuel delivery problems, the lift pump part so its self priming when installed or worked on and in case of air entry wont stop delivery or burn out, and quality so it would last and i wouldnt be stuck in the middle of nowhere when if it broke. remember fuel pressure at source does not equal fuel pressure at carbies, theres a drop through the line, something to think about when checking out pump specs. Edited July 31, 2010 by styler Quote Link to comment Share on other sites More sharing options...
Taz_Rx Posted July 30, 2010 Report Share Posted July 30, 2010 remember fuel pressure at source does not equal fuel pressure at carbies, theres a drop through the line, something to think about when checking out pump specs. Exactly! The 12psi I mentioned above at the carby was coming from a Carter Black which is rated at 100GPH @ 14-16psi, so I was getting at least a 2psi drop along the line. Quote Link to comment Share on other sites More sharing options...
mighty_4k Posted July 31, 2010 Author Report Share Posted July 31, 2010 (edited) Looks like Ive got a bit of discussion going lol. Did quite a bit of research before I brought it and a lot of people say that dhlas will run sweet off the factory pump with no regulator and others say that you need a regulator. Ive already got my Holley so I'm definitely installing it hopefully it will help a bit when it comes to tuning at worst I'll have a bit of bling for the engine bay I guess lol. I'm still confused at hell about the fittings so I was wondering if someone can help me out there. I found out the the stock fuel line is 8mm which converts to 1/4" so I have that part figured out what I'm really confused about is the fittings on the Holley. I measured it out to be 15mm which is 1/2" but the problem is I can find no fittings what-so ever that are 1/2" to 1/4" looked it up a bit and the general consensus is that the Holley fittings are 3/8" which is 10mm there's tonnes of 3/8" to 1/4" fittings but 3/8" is quite a bit smaller am I missing something here? I got a feeling that I am missing something hopefully cos its a bit funny that there's tonnes of 3/8" to 1/4" fittings and no 1/2" to 1/4" fittings at all hopefully someone can clear all this up for me.. Thanks guys. Edited July 31, 2010 by mighty_4k Quote Link to comment Share on other sites More sharing options...
Taz_Rx Posted August 1, 2010 Report Share Posted August 1, 2010 Take the whole pump down to your local enzed/hydraquip/pertek and tell them what you want to do. They'll just sell you some new fitting that screw into the pump which have an 8mm or slightly larger (as the hose can stretch over it) barbed fitting. Quote Link to comment Share on other sites More sharing options...
philbey Posted August 2, 2010 Report Share Posted August 2, 2010 (edited) You don't need a pressure reg !.........Too many urban myths floating around on the net confusing people... :hmm: Okies, so the LOW pressure USA off the shelf electric pump ($95) from Super Cheap that's been feeding my TWIN side draft 35yo 40mm Mikuni Solexs on my Twin Cam 2T-G for 5 years now wont work? Damn... :lolcry: So your pump works with your mikunis and no FPR. Who cares? But my DHLA Dellortos with a factory mechanical pump pushing over 5 or so PSI and gave me grief running until I got the FPR dialled. Cos it was pushing fuel past the needle and seat. Holy shit Aesop, your fables have come true! Edited August 2, 2010 by philbey Quote Link to comment Share on other sites More sharing options...
TRD ke70 Posted August 2, 2010 Report Share Posted August 2, 2010 (edited) mmm, interesting to see what many people think and what works for them. Our old rally engine in NZ had the mechanical fuel pump from a 3k twin carb engine with no fuel pressure reg. yes it had the dellortos, both of them, and yeah it ran great, fuel pressure was at 3 psi. only ever had one problem when one of the valves shit it's self. These pumps you can rebuild so we were lucky. Edited August 2, 2010 by TRD ke70 Quote Link to comment Share on other sites More sharing options...
philbey Posted August 2, 2010 Report Share Posted August 2, 2010 (edited) Yeh there's obviously a range of differences with the mechanical pumps, mine has a funny looking pump that I've never seen on any other K engine, I think it's an aftermarket one, not the factory one, which could explain the higher delivery pressure. Edited August 2, 2010 by philbey Quote Link to comment Share on other sites More sharing options...
mighty_4k Posted August 2, 2010 Author Report Share Posted August 2, 2010 Thanks Taz_Rx I'm just gonna end up doing that I think I wanted to know the sizes because I wanted to buy them through eBay cheaper and shipped to my door I would be stupid not to really lol but I'll do go in and buy them the old fashioned way. Can someone please school me about trumpets/ram tubes/velocity stacks? What length is best for a worked 4k? I will be getting good filters like k&n or similar is it necessary for me to run trumpets or will I get away with just running filters? Thanks. Quote Link to comment Share on other sites More sharing options...
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