Water pump for an L31?
 

I am looking to buy a new water pump for the new L31 I have . Any ones to avoid? I just did a "5.7 350 water pump" search and found amazon has this one

https://www.amazon.com/ACDelco-252-7...8654463&sr=8-3

I guess the long style water pump will be what I buy since the plan is to reuse the same setup with the pulleys and brackets I had on the other 350. The few differences I am making on this build is I am adding the vintage air surefit to this setup, using rams horn intake and a new edelbrock intake for the same quadrajet.

Pics of the older setup I had

https://67-72chevytrucks.com/vboard/...1&d=1574727310

https://67-72chevytrucks.com/vboard/...1&d=1574727327


and a pic of the old pump

Re: Water pump for an L31?
 

i just used the pump for the 90 k5 blazer with 5.7 and serp belt for my setup as i used the serp belt stuff also .

if v-belt just get one for say a 1985 350 .

dont forget L31 vortec has no bypass hole port in the block so you need to do a bypass hose like a bbc uses . or you can get bubbling / girggling / coolant smell as it pushes up in to the over flow tank .

Re: Water pump for an L31?
 

Use a normal long style water pump. Standard rotation for v belts and reverse for serp belts.

Re: Water pump for an L31?
 

I looked at the 1985 350 options on Rockauto and there is a Gates and an AC Delco which costs about $9 more. Is Gates decent? There is also an Airtex aluminum that is listed as higher volume that costs a bit more. I dont know if that will make a huge difference or not.

https://www.rockauto.com/en/catalog/...ater+pump,2208

On the bypass hose I see what you were talking about with the bypass and saw this pic. But Im not sure how to do a bypass hose?

https://cimg0.ibsrv.net/gimg/www.cor...64692a1e75.jpg

Re: Water pump for an L31?
 

I took a pic of that portion of my engine and I see this. Maybe Im confusing what you were saying about the bypass.

Re: Water pump for an L31?
 

This?

http://chevellestuff.net/tech/images/69_bypass.jpg

Re: Water pump for an L31?
 

They are all fine, water pumps last forever on these things. No need for hi volume unless you have a massive HP build which it seems you don't.

Re: Water pump for an L31?
 

yes that hose .

and the port might be in the block to the water jacket area but the head surface to head hole is not there . this is why you need a bypass hose . the true vortec L31 installs from gm the water pump has a hose and the intake has the spot for it .

Re: Water pump for an L31?
 

If you have just a heater and no ac the heater can serve as the bypass.

Re: Water pump for an L31?
 

Thanks Tom, I guess the AC Delco then.

The AC Delco I was looking at on Rockautos has a port like what I had before so I think connecting that to the manifold is the bypass I would run.

The Edelbrock intake manifold I bought is this one

https://www.summitracing.com/parts/EDL-2116

The Vintage Air Surefit AC system will be added this time removing the heater from the firewall so it sounds like the water pump smaller port connected with a hose to the intake is what I need to do.

Re: Water pump for an L31?
 

some get away with this some dont . . . mine did NOT like it .

and the intake the O.P. posted from edelbrock has the bypass port in the front just under the t-stat . its a 3/8" pipe thread . i used a 3/8" pipe to 5/8" hose barb fitting from these guys in the intake . https://www.ebay.com/itm/5-8-HOSE-BA...72.m2749.l2649

then a molded 45* hose from the local napa / carquest rack to the water pump port on top almost dead in line with the intake port . hooked them up and ZERO problems ever since then .

here is my thread on this problem and lots of people posted info and pics to back it up . and post #42 on 2nd page has my exact fix and hose part# . http://67-72chevytrucks.com/vboard/s...d.php?t=778518

Re: Water pump for an L31?
 

Sweetk30, looks like the bypass parts were included in the intake kit. There is a straight type barb though not the 45 degree type and a plug which I guess is in case you arent using the bybass hose to the manifold.

Question on the water pump install, do you guys use rtv at all on the metal surface and then stick the gasket on it or gasket only? Ive seen a spec of 30 ft lbs of torque used for the bolts, sound right?

Re: Water pump for an L31?
 

i do a super thin skim or use red & tacky thats it on both faces that get a gasket .

Re: Water pump for an L31?
 

Looks like the 45 degree hose barb fitting is what I need just like you said. The instructions on this intake assume the user knows anything about them. No listing of what the holes are for in the manifold. Compared to my original 350 setup the only ones I recognize are the thermostat housing large port and the water pump I assume is the port I threaded the barb they supplied into. The other 2 I think were for heater hoses? I guess I need plugs then if thats the case since the vintage air system is self contained.

How do you mold the hose to get the angle right?

Re: Water pump for an L31?
 

I could not get the bypass to fit on mine using the fitting on top of the water pump and the manifold fitting you show in the picture. I ended up with a 90 degree fitting for the fitting on top of the manifold water passage and a 90 at the water pump. The top radiator hose just barely clears the bypass hose, but it worked. This was with a short water pump. I think you might get away with a straight fitting on the water pump and a 90 at the intake manifold

Re: Water pump for an L31?
 

As long as your heater core isn't clogged and you have it plumbed right it should work. All you need is a bypass from your intake below the thermostat to an intake on the water pump. It doesn't matter how far the water has to travel as long as it circulates.

Re: Water pump for an L31?
 

i tried this first and had problems .

and i did NOT use a straight barb fitting . i used a 45* i had to order off ebay and a molded hose i got off the rack at the parts store .

Re: Water pump for an L31?
 

Ive got the 45 barb you linked to on ebay ordered. The molded hose Ill need to go look for as well as the pumps fitting too which I think then is a 3/4 fitting to the pump and 5/8 barb like this?
https://www.amazon.com/Straight-Pipe.../dp/B06XSMD83X

Re: Water pump for an L31?
 

Been running mine for over 3 years now, no problem at all. A bypass is a bypass.

Re: Water pump for an L31?
 

It's a crap shoot I guess . Some of us win and some of us have to do the bypass hose trick .

Re: Water pump for an L31?
 

I heard you could just drill a hole in the thermostat but that didn't work for me. I just ran a simple heater hose looped from the intake to the water pump until I got my new heater core installed.

Re: Water pump for an L31?
 

Sweektk, did you run a 45 or a 90 type molded hose section? Im still waiting on the 45 fitting from ebay. Did you end up pointing the 45 fitting to point upward or sideways? I bought a 45 and thought it might work but Id have to see how the 45 fitting is best to angle of the manifold. If the 45 hose seems right I would try cutting the hose at the pump shorter ...about where the letter A and number 8 are on the hose. That might get is close.

Re: Water pump for an L31?
 

45* in intake . straight in water pump . molded 90 hose .

shorten the hose as needed . maybe even take 1 or 2 barbs off the nipple you have in the water pump now .

hope this pic helps .

Re: Water pump for an L31?
 

It does help thanks, I got the 45 in today and ive already ordered this hose to pick up tomorrow

https://shop.advanceautoparts.com/p/...0001/5191343-P

I wondered the same thing if I should cut off a few barbs.

Re: Water pump for an L31?
 

I did find the right hose and ended up cutting down a few barbs.