Mechanical fuel pump with correct pressure.

**Lynn** · #1 03-02-2019, 01:29 AM

I know this has been hashed over before. I am really getting sick of this. Replaced the fuel pump (old one died... zero pressure) on the 70 LT-1 Corvette. Not particularly easy to replace, as there is less room than on a first gen Camaro or an old Chevelle. Started it up and fuel is pouring out the carb. Car had been running fine on a little temorary electric pump.

WHO, IF ANYONE makes a Chevy mechanical fuel pump with the correct pressure.

Just installed a new Spectra Premium that was advertised as "100% factory tested & approved. Factory specified pressure and flow."

Absolute BS. Put my mechanical pressure tester on it, and it pegged the needle just cranking. Gauge only goes to 10 psi, but the needle swept right by that number.

Does anyone make a pump that only puts out 4 - 6 psi?

**Lynn** · #2 03-02-2019, 01:07 PM

https://www.yenko.net/forum/showthre...uel%2Apressure

Found the old thread. Apparently Carter still makes a pump without excessive pressure.

x33rs · #3 03-02-2019, 01:38 PM

Funny thing about pumps. Can't tell who actually makes them anymore. The AC pumps I was buying no longer have "AC" embossed on the housings. I've had an AC pump, Carter, and Airtex pumps all sitting here side by side and once out of the box, you can't discern one from the other.
For me lately it's been a crap shoot which one will work anymore. Get one with too low pressure and it complains when it's hot outside plus it runs out of fuel with any aggressive driving. Too high and you have your experience.
The last 2 carter pumps I recently bought in the last month weren't any good. The first one only held 3 lbs. of fuel pressure. The car ran 20 miles and died. I warrantied that pump for another carter, this one held 3.5 lbs. of fuel pressure and I didn't even get out of the neighborhood with it, and it died. I bench tested both afterwards and they were completely dead. I'm assuming something inside just let go...diaphragm or??? But I wasn't impressed and didn't want to try another after towing the car back to the house 3 times in a week. They gave me my money back.
On my Formula that Bruce did a members ride on, I'm still running a "real" AC pump on it that has been on the car for 25 years. I'm waiting for the day it dies, but it's still kicking and holding good pressure. On my wifes Z I'm running a more recent AC pump on that one that doesn't have the AC embossed logo, so really don't know what brand it actually is, but it's been working perfectly for the last 3 years. I have a Carter on the Nomad that I bought 3 years ago and it only holds 3 lbs fuel pressure sitting there idling. Runs fine putting around the neighborhood but pressure goes to zero as soon as you mat the throttle, so it's going to come back off for something else when I get around to it.
So lately after my most recent experience I'm looking at switching all the mechanical pump cars over to a RobbMC pump. Doesn't look exactly stock but they are excellent pumps, they are rebuildable, and he sells the rebuild kits for $20 They come in a couple of different HP ratings and can be had with or without a return line setup, plus they are clockable. They are a 5 or 6 valve high volume style pump similar to what Nascar used to use. You can check them out here..... https://www.robbmcperformance.com/products.html I've used them on customer cars and extremely happy with them.

If you're into the 100 point concour benchmark type of car, well then you're stuck trying to find a correct looking pump that actually works right and performs. On a couple of cars here I skipped the mechanical pump deal all together and just went to a Tanks Inc baffled tank and in tank electric pump setup, and hide the regulator. These setups have been flawless, hold perfect steady fuel pressure under all conditions, and has new car type reliability and quiet operation with the pump submerged in the tank.

seventieshow · #4 03-02-2019, 03:08 PM

On my 71 Z/28 I used a parts store pump when the AC pump failed. Don't remember where it came from (probably NAPA) but it has always worked OK, never checked the pressure.

BCreekDave · #5 03-02-2019, 03:19 PM

I've been buying up NOS AC pumps. If you look for awhile, you can find them for reasonable prices. Got my last one for 50. My only concern is what the ethanol will do to them. Is this overrated for a limited use car? I've seen additives that can be added to the gas that claim to prevent the rubber from deteriorating. Snake Oil?
https://shop.bellperformance.com/pro...thanol-defense

L78racer · #6 03-02-2019, 04:24 PM

Carter musclecar pumps thru Summit work good. Correct pressure.

**L16pilot** · #7 03-02-2019, 04:38 PM

"My only concern is what the ethanol will do to them."

Dave, isn't ethanol free gas available in OH? It is in MD, but horribly expensive. Avgas is great, doesn't break down and has plenty of octane for an 11:1 engine....and is comparable in cost to ethanol free gas..at least in my area.

BCreekDave · #8 03-02-2019, 06:27 PM

Steve,
Yes, currently at one station within driving distance (~10 miles):

https://www.pure-gas.org/

I was planning on mixing 50-50 with high octane race gas which is actually pretty close by.

There is also a local small airport close by. Never bought gas there. Do they usually give a person grief when buying for cars?
Sorry for hijacking this thread.

x33rs · #9 03-03-2019, 01:58 AM

Quote:

Originally Posted by BCreekDave

I've been buying up NOS AC pumps. If you look for awhile, you can find them for reasonable prices. Got my last one for 50. My only concern is what the ethanol will do to them. Is this overrated for a limited use car? I've seen additives that can be added to the gas that claim to prevent the rubber from deteriorating. Snake Oil?
https://shop.bellperformance.com/pro...thanol-defense

I'm not sure if ethanol will attack the old diaphragms or not. If it does, it would be over a long period of time. The 2 Carter pumps I just recently bought both died within 20 miles. I don't think ethanol works that quickly. I believe that to be more of a quality control issue.

The AC pump on my Firebird is going on 25 years old and sees nothing but ethanol pump gas. But I do run a little snake oil in my fuel.

Speaking of additives, whether it helps with ethanol and corrosion I can't be certain but I lean towards yes. What I use is 2 cycle engine oil. I mix 1 ounce per 5 gallons of gas. I started doing this a couple decades ago, mainly to give the fuel some lubrication since fuel lost it's lubricity when lead was removed. All the reading I've done I feel it helps lube the upper end of the engine, valves, guides, seats, during the combustion process, and if you use a 2 cycle with TCW3 it will also have cleaning properties as well. Some of my engines I've torn down over the years have been exceptionally clean up top, never had valve recession issues, overall pretty happy.
If it fights ethanol corrosion thats just an added bonus for me because that's not really what I started using it for.

Mr.Nickey Nova · #10 03-03-2019, 02:29 PM

Have had good luck so far with AC replacement pumps with no issues yet. Been on a couple of my cars for a number years,( knock on wood ). The last AC embossed pump I bought was 27 yrs. ago for my 72 Nova and is still on the car today. Just don't make things like the good old days.