SBC V8 Water Pump Failure, 3 Styles of Pumps Tested BYPASS THERMOSTAT UPDATE Options

[nick mironov]

My Renegade water pump failed yesterday. The pump impeller is stamped steel and the blades all just folded over or sheared off. I understand that the cast impellers are much stronger, but that not all manufacturer's cast models will fit into the Renegade housing. Anybody have experience with cast impeller pumps that will fit into the Renegade housing?

Since there is no bypass in the Renegade system, Renegade instructions are to limit the motor RPM to 3,000, or less, untill the thermostat opens. I have observed this, but the pump still failed after 5,500 miles. Renegade now makes a bypass kit, which I going to try, but I would still like to get a more durable pump.

Nick

[messix]

some else just had this problem less than six months ago, search for it.

[wallys914]

You run a Thermostat? I don't... but then again I dont have Heat in my car.

[Bruce Hinds]

It's a mopar impeller, they make a few different styles. There was a thread on this recently....
A high volume thermostate had some bypass holes around the flange which permits a little flow that really helps dampen the opening and closing process during warm up and driving in different conditions.

[zymurgist]

I drilled a 1/16" hole in the flange of my t-stat in the Vette, but that's more for steam than any significant water flow.

[SLITS]

It is hard to imagine that a pump would see sufficient backpressure in a system to flatten the stamped steel impellers. It would seem that the pump would cavitate before that happened. Just speculation.

If it's the same that was used some time ago, it is more than likely a GMB pump. The person that was making the stamped aftermarket impellers was making them out of some very weak material. There was a notch (indentation) in the blades to form somewhat of a gusset for strength.

The impellers could have been stamped from heavier gauge material, but then they wouldn't have been as inexpensive.

The only question as to whether the stock Big Block Chrysler impeller would fit is the depth of the impeller in the housing (the impeller thickness). A cast iron one could be made to the specifications, but one would have to order at least 300 pieces. There is to limited a market for that.

Alternatively, the stock cast iron one could more than likely be machined to appropriate dimensions.

All this is speculation, as we do not have a back housing to examine the fitment of a stock pump / impeller. Oh, and the original pump it was patterned after is fully cast iron. I posted an image of it in the previous thread about the same problem.

[Mike Bellis]

Buy a Mopar Performance high flow water pump for a 383/440 big block. The High flow has cast impeller and is designed for big block engines with A/C. You can get them at Summit Racing.

[nick mironov]

This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.

I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.

I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.

Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.

Nick

[messix]

This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.

I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.

I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.

Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.

Nick

look for the marine aplication. that would have the brass impeller. jegs and summit are your friend with hot rod parts [yes you have a hot rod].

[Mike Bellis]

This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.

I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.

I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.

Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.

Nick

I've never heard of this problem before. I have thousnds of miles on mine without any problems. I used to own a big block Mopar. I'll see if I can track down an exact model number for you. Mopar pumps are cheap. If you go to your FLAPS and tell them you have a 1970 Charger 440 with A/C they can pull one and you can look at it. I have seen with Mopar engines the stamped pumps can corrode the impeller and lead to premature failure.

[Mike Bellis]

Found one for you.

http://www.summitracing.com/parts/EDL-8814/?rtype=7

[messix]

it's the cavitation that bends the impellers. cavitations generates a great amount of force
look here http://www.summitracing.com/search/Departm.../?Ns=Rank%7cAsc

[Mike Bellis]

Here's a marine version.

http://marineengineparts.com/shopsite_sc/s...html/page5.html

[computers4kids]

This type of failure is a typical problem with the SBC conversion, since there is no bypass water flow circuit for cold (closed thermostat) operation.

I talked to Renegade, and they are now preparing to market a bypass system and they are going to sell me one. This should elieve the stress on the stamped impeller, but I would still like to have a cast impeller.

I found the previous thread on this subject, and it still appears that no one has identified a specific model number for a cast impeller pump that wil fit the renegade housing. Stamped impeller pumps don't seem to be a problem to find or fit.

Although one would expect that the stamped and cast impellers to be manufactured to the same specifications to be interchangeable in the same housings, apparantly they are not. Steve at Renegade says that some of them will fit with a double gasket and some need to be trimmed to fit in depth and even in diameter. Steve runs a 6,000 rpm 302 at the track and is successfully using the bypass with a stamped impeller pump.

Nick

I've never heard of this problem before. I have thousnds of miles on mine without any problems. I used to own a big block Mopar. I'll see if I can track down an exact model number for you. Mopar pumps are cheap. If you go to your FLAPS and tell them you have a 1970 Charger 440 with A/C they can pull one and you can look at it. I have seen with Mopar engines the stamped pumps can corrode the impeller and lead to premature failure.

Actually, this is the third SBC conversion that has had impeller failure in the last year: 1 Tony in WA, 2 drivability and 3 nick in SF.
Here's the best thread on the pumps that I've seen.(IMG:http://www.914world.com/bbs2/uploads_offsite/i239.photobucket.com-4253-1273205192.1.jpg)

[TC 914-8]

Yep I was one of those recient failures.

I went to the local AP store and tried to match up the crysler water pump with one in stock. one had too deep of impeller 6 blades, another had too large of a shaft blocking the rear inlet on the volute. I settled for a stamped 6 blade that seemed to fit and didnt block the inlet. for curiousity I stopped off at Shucks to see what they had. I found an 8 blade stamped steel with shallow blades that fit into the volute, not restricting the inlet. You can feel the outlet hoses " pressurize" when the enging is reved up. I almost question the hose sizing 7/8 supply to the rad, and 1-1/8 return to the pump.
fyi,I don't run a T-stat, I do wonder if I an over pressurizing the outlet, hoses swell when reved, but in all reality it is a circulating pump, as fluid moves out, the same volume returns to the inlet. No head required, the only restrictions are the block and radiator, if they both flow well, the return water to the pump should keep it from cavitating.
Well see if this one lasts or if the cast impeller is the way to go (IMG:style_emoticons/default/confused24.gif)

[nick mironov]

That failure looks exactly like mine...

The thread that was referenced in the previous reply was the thread that I found and it was informative. However, that thread does not have specifics on which manufacturer/model of a cast impeller pump will fit. It appears that Drive-Ability had to alter the housing to get his unidentified cast impeller pump to fit into the housing. There are lots of cast impeller pumps to be found on the web, but which ones actually fit?

Nick

[jimkelly]

maybe i will just keep running my stock water pump then.

[SLITS]

In the other thread, someone asked what Ford did to prevent cavitation on their race engines. Ford redesigned the impeller to be a six curved blade, smaller diameter cast iron unit. They sold it for years in the Motorsports Division as a high performance impeller (to prevent cavitation at high rpms). Ford stopped making them so our GM had them cast and machined.

Like I said before, the minimum number of units is 300. So far that would leave us with 297 in stock if we did the Mopar units. (IMG:style_emoticons/default/sad.gif)

[messix]

Yep I was one of those recient failures.

I went to the local AP store and tried to match up the crysler water pump with one in stock. one had too deep of impeller 6 blades, another had too large of a shaft blocking the rear inlet on the volute. I settled for a stamped 6 blade that seemed to fit and didnt block the inlet. for curiousity I stopped off at Shucks to see what they had. I found an 8 blade stamped steel with shallow blades that fit into the volute, not restricting the inlet. You can feel the outlet hoses " pressurize" when the enging is reved up. I almost question the hose sizing 7/8 supply to the rad, and 1-1/8 return to the pump.
fyi,I don't run a T-stat, I do wonder if I an over pressurizing the outlet, hoses swell when reved, but in all reality it is a circulating pump, as fluid moves out, the same volume returns to the inlet. No head required, the only restrictions are the block and radiator, if they both flow well, the return water to the pump should keep it from cavitating.
Well see if this one lasts or if the cast impeller is the way to go (IMG:style_emoticons/default/confused24.gif)

tony, nuke boomers cavitate thier props at 1500 feet, thats a lot of pressure and it still gets cavatation.

[SLITS]

Here's the deal. I will send a pump (that was imaged) to whomever wants to try it in the housing. It would be the non-A/c pump. We can adjust the impeller depth if it is to deep.

The non-A/C pump has the larger diameter impeller.(4.185" - Pump # 1317). The A/C pump has the smaller diameter impeller (3.500" - Pump #1352). The stamped steel versions should have the same diameter and height as the cast iron impellers.

Gasket mounting surface to tip of impeller is 1.210" on both pumps. Gasket mounting surface to top of fan blade hub is 3.070" on both units.

And for the post that the shaft was to large in diameter, it could have been the big bearing model (don't remember the number now).

Anybody game? If it works, we can sell you the rebuilt proper OEM pump ... cast iron through and through (Shameless plug). Or, if you want the aluminum pump fitted with a cast iron impeller, that can be done too!

Please note that the bearing and seal would be destroyed with removal of the impeller, so the pump would have to be rebuilt as a new seal and bearing would have to be fitted).