75 vs 76 Water and Oil Pump Interchange

Moderator: Moderators

75 vs 76 Water and Oil Pump Interchange

Postby jjcrum » Fri Jul 15, 2016 9:50 am

Hello H-Bodiers,

I've got a 140 block, crank, and head out of a 75 Monza at the machine shop and I need to get them a water pump, oil pump, and timing set. When I went to find water pumps I find that they are listed as 71-75 and 76-77. What are the differences? My accessories (brackets, pulleys, etc) are coming from my (dead) 76 Pontiac Sunbird engine, so should I go with the 76 pump or will it not mount/interface with the block correctly? What about the oil pump? Do I need a different timing set? Please help, I have been searching about for the last 2 days and can't seem to find the answers and the shop is getting antsy.

Thanks,
John
jjcrum
 
Posts: 2
Joined: Thu Jun 29, 2006 7:58 pm
Location: Denver, CO


Re: 75 vs 76 Water and Oil Pump Interchange

Postby Smiley » Sat Jul 16, 2016 4:59 am

if the block is a 75 then use a 75 oil pump and timing belt.
"The 1976 to 1977 2300 engine received a new cylinder head design incorporating hydraulic lifters to replace the taper-screw valve adjusters, improved coolant pathways,
longer-life valve stem seals, a redesigned water pump and thermostat, and a five-year, 60,000-mile (97,000 km) engine warranty. The engine's name was changed to Dura-Built 140."
The 76 water pump may also fit and be an upgrade.
Are they sleeving the block ?
the early 140 fan is a reverse rotation unit and rather small, good time to upgrade it.
User avatar
Smiley
 
Posts: 639
Joined: Tue Jul 17, 2012 2:50 am

Re: 75 vs 76 Water and Oil Pump Interchange

Postby kgroombr » Sat Jul 16, 2016 8:25 am

Having disassembled every variation of oil pump from a Vega, they all appear to be internally the same. I am 99% certain that all of them have the same volume and pressure. I have an early model (only NOS one I could find) on my 76 and it runs great with no issues. The major difference I found is that the early ones were thin in some of the areas that mount to the block,so I am thinking there were some issues with the oil pump due to those areas cracking and breaking (don't over-torque it). Later ones have thicker metal and strengthening ribs in those areas.

Here is a list of them:
3994265 oil pump (first design) marked 3994229
6263112 oil pump (71-75) marked 6262874
370636 oil pump (76-77) marked 6262874

The last two oil pumps appear to be completely identical, I think it was just a part number change.

Water pumps are interchangeable, but the 76-77 version has improved cooling capacity. The water necks between the two are different. 71-75 stuck straight out where 76-77 angles up. Because of this you will need to have the correct lower radiator hose as they are physically different and have different part numbers. Finding a molded lower radiator hose is difficult and you will probably have to use a universal (bendy) type hose.

Timing belts are interchangeable for all 140 ci aluminum block engines, but some are better than others as far as strength and durability.

Ken
User avatar
kgroombr
 
Posts: 1115
Joined: Thu Nov 20, 2008 8:27 pm
Location: Evans, GA

1972 Chevrolet Vega Kammback GT

Re: 75 vs 76 Water and Oil Pump Interchange

Postby jjcrum » Fri Jul 22, 2016 10:04 pm

Thanks Gentlemen, that was exactly the kind of info I was needing. I was able to find an American made NOS later style water pump for not a lot of dough, but the ONLY oil pump assemblies I was able to find were early style NOS GM pieces. One was $299 and the other $150. One guess as to which one I went for. :) Because it's the earlier design, I'll be sure to not over torque (thanks for the heads-up, Ken!).

Ken, what brand(s) of timing belt have you had success with?

Smiley, the block has been sleeved and I'm using JE forged pop-up pistons that were advertised at 9.5:1. The shop is taking the sharp points and edges off and will CC both the block and head (which was ported and blended) to get an accurate comp ratio. I'm converting to ethanol and I'm going to put a small turbo on it. With me living at a mile high, and with the ethanol, I should be able to handle a little more compression and still make a little boost while being a driver. As for the fan, how is it reverse rotation if the water pumps spin the same way? I have the factory accessories on the 76 140 that came in my 76 Sunbird and was planning to either re-use that fan or switch over to electric fan(s)... what are your thoughts on upgrading?
jjcrum
 
Posts: 2
Joined: Thu Jun 29, 2006 7:58 pm
Location: Denver, CO

Re: 75 vs 76 Water and Oil Pump Interchange

Postby Smiley » Fri Jul 22, 2016 10:20 pm

It is reverse from a V8 with V-belts because the Vega fan is driven off the backside of the timing belt.
years ago I redrilled one and put it on before I realised it was blowing into the radiator. :bang:
It is only an issue if you plan to buy an aftermarket mechanical fan for the stock Vega 4 cylinder.
User avatar
Smiley
 
Posts: 639
Joined: Tue Jul 17, 2012 2:50 am

Re: 75 vs 76 Water and Oil Pump Interchange

Postby kgroombr » Sat Jul 23, 2016 8:28 am

jjcrum wrote:Because it's the earlier design, I'll be sure to not over torque (thanks for the heads-up, Ken!).


One of these days I need to take pics to show the differences.

jjcrum wrote:Ken, what brand(s) of timing belt have you had success with?


I have only used Goodyear as I purchased a few of them several years ago and a dirt cheap price. I also have a couple Sealed Power and they look like good quality. I never have compared them, but I am thinking that all drive belts come in different qualities, and I am certain the same applies to the Vega timing belt. Rockauto.com has some Sealed Power at a good price.

Ken
User avatar
kgroombr
 
Posts: 1115
Joined: Thu Nov 20, 2008 8:27 pm
Location: Evans, GA

1972 Chevrolet Vega Kammback GT


Return to Engine Tech

Who is online

Users browsing this forum: No registered users and 2 guests