Fuel delivery???

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mullinax95

mullinax95

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I'm changing motors in my car from a 273 to a 360 and trying assure that I will have good fuel delivery. I guess the question I have first is that the previous owner has a electric fuel pump mounted near the tank and was using a mechanical fuel pump also. Should that even be done? I ran the car both ways at times with the electric fuel pump on and off and couldn't tell any difference. Why the electric fuel pump is there is beyond me.

Should I just ditch the electric fuel pump and run a stock mechanical pump or just leave everything alone. I have got to get a new mechanical fuel pump but maybe you can help figure out what needs to done. The motor I believe will make around 400HP give or take and will be feed with a 750 mechanical secondary carb. I am going to change the fuel line to 3/8 and hoping the sending unit in the tank is already 3/8 but I'm not sure yet. Here is the pic of the low budget electric fuel pump still on the car.

DSC01580.jpg
 
cudaspaz said:
Seems like he wanted a backup in case the mechanical one took a dump.

I guess that's a good idea.
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Well if it isn't my good faithful friend. LOL!

I hadn't thought about it that way.

I don't know... I guess it could be left well enough alone. What do you recommend for a mechanical fuel pump ...stock or something with a bit more flow. I don't want to have to install a regulator if I can get by without it. I have a fuel pressure gauge that will be installed. I've looked at some mechanical fuel pumps and they range from 6.5 psi to 8.5. Whats the max before the fuel needs to regulated..anything over 7.5?
 
That guy must have been a boy scout ( be prepared). he, he.

My buddy swears by Carter mechanical 120 GPH pumps for his small block stroker builds.
 
I am running the Carter 120 gph. mechanical pump and it supplies my 360 (approx. 375 hp) fine. If your running a Holley carb it should handle 7-7.5 psi no problem. Edelbrocks don't seem to do well above 6 from my experience.
 
just use a mechanical. the carter mentioned dounds just right. using both is a bad idea. the electric one can rupture the diaphragm of the mechanical and leak gas into the crankcase.
 
My grandpa's 83 dodge ram has to have an electrical pump & a mechanical as well. It wont run with just the mech. We have replaced it numerous times to try & solve the problem...no dice. The guy at the shop says the eccentric (I think thats what its called) is dished out so the fuel pumps' not getting a good stroke. Runs fine with the electric/mechanical combo tho.
 
One more vote for the mechanical pump only. A 3/8 sending unit and line to and from the fuel pump will insure more than enough fuel for your 360.
 
Some guys install an electric pump as an auxillary to prime the carb if it's been sitting for a long time rather than cranking the motor over.Is there a switch to turn it on-off somewhere?
 
oldkoot said:
Some guys install an electric pump as an auxillary to prime the carb if it's been sitting for a long time rather than cranking the motor over.Is there a switch to turn it on-off somewhere?
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Yes and that's exactly what I use it for. But now I'm afraid that I will damage the mechanical fuel pump like redfastback said. I've never heard of that but I have never seen a fuel system with both mechanical and electric fuel pumps either.
 
i'd run the 6902 since it has fuel psi up to 7.5 max. 8 will start to push the needles off the seats.
 
mullinax95 said:
Which one of the Carters 120 gph you have.

http://store.summitracing.com/partd...&N=700+4294908078+4294840106+115&autoview=sku


http://store.summitracing.com/partd...&N=700+4294908078+4294840106+115&autoview=sku
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Since I bought it used I'm not positive. I thought he said it was the higher pressure one but It don't go over 7 psi on my gauge so it might be the lower one. I think that's all you need anyway. They're both rated at 120 gph just the one is higher pressure and like Redfastback said if you go too much they'll start to push them off the seats and flood out.

Sorry about the handle screw-up redfastback. Got it corrected now.
 
Wow. Shades of the old Carter Electro-Mech setup. I'll have to rifle through the heap of old magazines to find it.

I'd say that a good electric will serve you well. It's easier to push fuel than pull it.
 
I'm running a Carter 6903 on my 383, same flow and press. as the 6902, feeding a 750 DP'r with no problems now. At first the 8 psi was lifting the carbs float needles so added a regulator and set for 6.5 psi and problem went away.

Terry
 
Just a thought, I'm replacing my stock mech. pump & line with a 110gph Holley mech. and 3/8" line. I'm having Don at FBO bore the pump out to true 3/8". It will help get to the true 110gph as rated. He'll do this for $70. Not neccessary, but if your running 3/8" sending unit/line, it's something to consider if you want to get the max out of your pump.
 
Some will run a small electric pump prior to a mechanical pump to alleviate a vapor lock problem.
 
Beatnik said:
Just a thought, I'm replacing my stock mech. pump & line with a 110gph Holley mech. and 3/8" line. I'm having Don at FBO bore the pump out to true 3/8". It will help get to the true 110gph as rated. He'll do this for $70. Not neccessary, but if your running 3/8" sending unit/line, it's something to consider if you want to get the max out of your pump.
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I also noticed the Carter I have doesn't have a true 3/8 opening. And 3/8 fuel line barbs don't have a 3/8 id either. I drilled out the barbs to 11/32 but that was as far as I could go before they got really thin. The pump had a casting flash on the output side that actually had to opening cut down to approx. 1/4" so I ground out the flash. It then had about 11/32" opening throughout. Not quite 3/8 but close enough for my application.
 
demon seed said:
I'm running a Carter 6903 on my 383, same flow and press. as the 6902, feeding a 750 DP'r with no problems now. At first the 8 psi was lifting the carbs float needles so added a regulator and set for 6.5 psi and problem went away.

Terry
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That's what I want to avoid is have to install a regulator. I might go with a factory pump and go from there.

BUT... I guess I need to make sure that whatever I get it's got to feed a .030 over 360 with a 750 DP making roughly 400 HP.. will a factory pump be enough?


I would really like to go the electric pump route but I had a Holley electric pump with regulator on a big block 383...anyways that dang pump made the loudest hum. I bolted the pump with bolts all the way through the frame and used almost 1" thick rubber in between and it still hummed louder than the motor if I was sitting in the car at idle. I would cut it off it was like a relief to hear it go off. If anyone has any ideas of how to make a electric pump quite I would like to hear them. LOL!
 
If you go with the lower pressure pump you shouldn't have to run a regulator. I don't on mine.

I'm not sure the specs on a stock pump but I'd worry it might not supply enough to feed a 400 hp engine and go lean on the top end.

Holley also makes a good mechanical street pump that you don't have to run a regulator on. I think it's rated at 6 psi. which is what a Holley carb should be run at for optimum perf. If your uncertain about the Carter check out the Holley.
 
fishy68 said:
If you go with the lower pressure pump you shouldn't have to run a regulator. I don't on mine.

I'm not sure the specs on a stock pump but I'd worry it might not supply enough to feed a 400 hp engine and go lean on the top end.

Holley also makes a good mechanical street pump that you don't have to run a regulator on. I think it's rated at 6 psi. which is what a Holley carb should be run at for optimum perf. If your uncertain about the Carter check out the Holley.
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Summit makes it confusing by saying the max pressure is 6 to 7.5 but Mancini states 6 psi (street) on the same Carter pump. I feel comfortable about getting the Carter pump now since I saw Mancini listing.
 
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