[Shiny]

I chased a flooding issue and actually measured the "holding power" of the inlet valve on my QJ (69 Buick 7029240) as taught by Cliff. I measured 12 psi to overpower it... quite a bit higher than 7.

My copy of the 1970 Service Manual has this interesting note:



So at least for 1970, 7 psi was "within spec" for a mechanical pump with a return line/vent.

I don't know if the float, needle, and seat were "weaker" in 1968 but I doubt it.

Several members in other posts have warned variations in pressure will raise or lower the fuel level in the bowl, but I don't know how sensitive carb tuning could be to that variation. Those with knowledge can address that risk.

Mike

[Formulajones]

Originally Posted by 68bird400HO

Doing some more research I see the Robb Mc pump delivers a constant 7 psi where the factory pumps were in the 5-6 psi range. Are there any issues with the additional psi on a stock 68 400 build with stock Q-jet?

Typically a good needle and seat assembly shouldn't have any issues holding 7 psi or more. For what it's worth I've had those stock mechanical pumps show as much as 9 psi even though they are rated at 5-6 so they aren't very consistent anyway. I've also had them show as little as 3 psi. Just another reason why I avoid the darn things these days.

[locomotivebreath]

So I picked up a carter m4690 on a whim after reading this thread . Fits 68 gto and compared it against my M6122 deep can . The 4690 as said looks generic , has a light M4690 etching on the body , box says China . 6122 was bought maybe 10 years ago , stamped made in USA right on the body .and Pierce on the other side . Box also has federal mogal logo on it and 4690 does not . I’ll probably try to use the deep can 6122 when the time comes .

[68bird400HO]

Originally Posted by locomotivebreath

So I picked up a carter m4690 on a whim after reading this thread . Fits 68 gto and compared it against my M6122 deep can . The 4690 as said looks generic , has a light M4690 etching on the body , box says China . 6122 was bought maybe 10 years ago , stamped made in USA right on the body .and Pierce on the other side . Box also has federal mogal logo on it and 4690 does not . I’ll probably try to use the deep can 6122 when the time comes .

That Carter M4690 is the same one I just recently bought from Rock Auto, and what sparked this thread. It is identical to the Delphi I bought in May that crapped out. As mentioned above, I think they are all Airtex chinesium now. I plan on sending mine back.

[locomotivebreath]

When I built my 400 in 2012 , I picked up a USA made Delco unit locally - now why the heck didn’t I get 2 or 3 ?! My resto stalled out for awhile do to life , so I just fired the engine up this summer and the Delco seems spot on .

[68bird400HO]

Looks like I'm going with a Robb Mc. Called them and they said there is a backlog and will be at least 4 weeks to get one out. I would like to be able to at least move the car before then and have a few options with questions.

1) I see that Spectra out of Canada has a pump available, MP1151SP. Does anyone know if they make their own stuff or if this is just another reboxed China pump?

2) Found a Korea made Carter on Ebay? It looks like the one that survived on my car for 23 years. Anyone know if these are actually better than the airtex Chinese ones?

3) I think I could rig up that Holley I have. I took it apart and the diaphragm looks good. The seal for the bottom cap looks a little suspect though, see pics. Anyone know what material that is, or I could use to make a new one?

[Formulajones]

Like I mentioned before, I honestly don't believe, and could not see with the naked eye, any difference between brands of stock replacement pumps (airtex, carter, AC etc...) and documented that in an old thread.

If you just want to roll the dice, I think any one of them would be fine for just moving your car around until the RobbMC shows up. That's really all those chain store pumps are good for in my opinion. In fact I used one just for that purpose to keep the Nomad mobile. That particular pump that came in a "carter" box would only show 3 psi fuel pressure cold and when it got warmed up it showed ZERO, even though the engine still ran, it idled which was good enough to move the car around when needed. I wouldn't dare drive it any distance though.

I did later swap that pump out for a Summit brand high flow pump (80 or 120 gph, can't remember now) and it immediately showed 8 psi on the gauge and stays there even after the engine is warmed up. I can at least drive the car around the block now without worry I'll be walking home.

[Shiny]

See previous post re: Spectra

http://forums.maxperformanceinc.com/...9&postcount=32

[68bird400HO]

Thanks for the refresh on Spectra.

Anyone ever hear of Pierce pumps? Found one and says made in USA on it. It even has the 40607 number stamped on it. Looks new not rebuilt as the Pierce logo is cast into the upper housing.

[Formulajones]

Never heard of it. Probably another product where a company does a simple process to it after it's shipped from over seas so they can put made in USA on it. LOL

Only way to know for sure is investigate the brand/company, the state their in regarding their laws, and see what they actually do, if you really want to spend a bunch of your time.

[locomotivebreath]

Ok , so my carter M6122 big can pump that I bought some years back , came in a carter box , housing says Made in USA on one side and Pierce on the other .

[68bird400HO]

Originally Posted by locomotivebreath

Ok , so my carter M6122 big can pump that I bought some years back , came in a carter box , housing says Made in USA on one side and Pierce on the other .

Yep, that's the logo. How long ago did you buy it?

[locomotivebreath]

Had to be 8-10 years ago , it was advertised back then as 120gph muscle car pump .

[68bird400HO]

Finally pulled the defective pump off. That don't look right. That little piece of metal fell out of it too.

[Ram Air IV Jack]

Originally Posted by 68bird400HO

Finally pulled the defective pump off. That don't look right. That little piece of metal fell out of it too.

Pat,

Take a look at this pump on eBay; https://www.ebay.com/itm/29580789884...Bk9SR-CKt-nCYg

Might be something to consider!!

[68bird400HO]

Originally Posted by Ram Air IV Jack

Pat,

Take a look at this pump on eBay; https://www.ebay.com/itm/29580789884...Bk9SR-CKt-nCYg

Might be something to consider!!

Thanks Jack. Saw it. That thing looks like it has been on a shelf for a long time. I wouldn't trust it.

[68bird400HO]

Originally Posted by 68bird400HO

Finally pulled the defective pump off. That don't look right. That little piece of metal fell out of it too.

So, didn't finish this last post. It looks like the inside end of the lever snapped off. Also, the little spring under the arm is missing so I assume is in my oil pan now. As it is now, the arm just flops around freely.

[68bird400HO]

Not to keep beating a dead pump, but, I found something interesting that I should share with anyone needing one of these. I noticed that just after 100 miles or so, the cam contact point on the top of the arm looked excessively worn. Comparing this Chinesium pump to an original Delco big can I have sitting here, the arms have different shapes as they come out of the pump. The problem with the newer pumps with this arm shape appear to be that the arm goes higher by 1/4" at the cam contact point. This probably maxes out the travel of that arm and causes them to break.

Note that the RobbMc pump looks to have the original Delco style arm, as does this old Holley I have here. Not sure where or when this new arm design came into play.

See pics below.

[Sirrotica]

It's pretty bad when you're making a copy of something, and still can't get it right. Someone else already did the hard engineering part, it's not like you're making it from scratch..............

[GTO-relic]

Originally Posted by 68bird400HO

The stock fuel pump in my 68 bird 400 finally failed after 20+ years earlier this Spring. In shopping for a new one, the main brands available were AC Delco, Airtex, Delphi, and Carter. I chose the Delphi as the reviews seemed a little better. When it arrived, I had some reservations as it was made in China and they didn't even include a gasket. Put it on and ran great until last week when it died and left me stranded. Didn't even last 200 miles. So, this time I ordered the Carter since it was supposedly made in USA. Just received it looks exactly like the same tooling as the Delphi and also says Made in China. I think Airtex is probably the same and I don't see the AC Delco one out there anymore. I am thinking of just sending the Carter back because I can't enjoy my car wondering if/when the pump is going to leave me stranded every time I drive it.

I put a fresh 455 in my GTO back in December 2021, went through same thing, but with electric pump. I always ran an electric at the tank pushing into a mechanical pump on street engine. Combed Ebay found NOS vintage mechanical pumps, and bought a good one replacement for SD455. also a few SD421 stock pumps as spares. all USA made. then tried to buy a made in USA Carter electric pump self regulated 6.5 psi which I always ran on street cars since 1985. no dice. there ain't none. bought the made in China "Carter", it ran but pumped no fuel right from the get go. then it worked, then didn't work. so I removed it. what a POS. I had already known about the poor quality Chinese parts. every thing in my engine is NOS old USA made parts off Ebay or message boards or friends who still had it laying around. Cam, lifters, head gaskets, SD455 oil pump, bearings, everything. there is a difference, reliability, and superior metallurgy. another thing I noticed is all the vintage Pontiac NOS stuff I had in my saved items on Ebay, it eventually all sold....so everything is realizing the same thing. we have a parts chain with schit parts quality from China