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Old 04-12-2008, 05:45 PM
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Big block water pump on small block!

Hi,

According to measurements I took of the water pump onto my 383 chevy stroker motor it is a chevy big block short water pump! I measured 5 and 13/16 inches height and according to informations found on a web site a short pump for the small block should measure 5 and 5/8 and the one for the big block should be 5 and 3/4...now my measurement of 5 and 13/16 being closer to the 5 and 3/4 for big block I conclude this is a big block pump.
Now ,if this is so, can this explain weird cooling situations? My guage doesn't show overheating readings but there is strange popping noise from the engine when it has reached its normal temp (running 160 thermostat).

I've always questionned the good functionning of that pump ;I find it strange that once it had reached its temp,so opened thermostat,I could not see much of water movement if I took the rad cap off.This pump had its impeller replaced recently,by a pro shop,it now has a brass GM impeller number14096240,that has 5 straight fins...I question myself as how these straight fins can move water the right way:from rad towards engine?

I wish I could upload few pics. I took of it but its too large a file and just can't find a way to resize it!

But basically knowing a big block pump doesn't mix with a small block will put me on the right path right on if that is the case!

thanks.

Ron.

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Old 04-12-2008, 05:57 PM
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pics. added.

Hello again,

I just managed to attach pictures of that pump inyo my gallery ...hopefully somebody could identify it and tell me more about my situation.
thank you for the interest.
Ron.
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Old 04-12-2008, 05:57 PM
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I would hate to think that the pump has been the culprit to your temperature issues all this time.

I had no idea there was that little difference between small and big block pumps, but if it's like you say, I would try a "known" small block pump and see what it says. I always thought the ports were further apart on the big block pump, but I'm always learning something new so.....

Does your current pump have the bypass hole?
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Old 04-12-2008, 06:06 PM
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Yes there is the by-pass hole to it and the water passages seems to match exactly....now the measurements given on that web site could be wrong also...wouldn't be a first time wrong infos. found on the net?
As for getting a new modern small block water pump goes this would imply having kinda lots of work done to match my custom alternator bracket to it...this I wouldn't mind doing if competency for this type of work would exist around where I am but that ain't the case!
thanks,
Ron.
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Old 04-12-2008, 06:06 PM
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I just looked at the pics......nice ride you got there.

A new pump is cheap enough (here anyway), that if I were in doubt, I'd swap it out.

Do you think your headers might be producing excessive heat under the hood? Just a thought as they pretty much wrap around the engine and exit to the front. Of course, I'd hate to wrap them suckers in the car and I'd hate to remove'em as well!

EDIT: I was afraid the swapping deal might be a bigger issue in this case. The pump you have looks just like the one (short pump) on my '72 with a small block if that helps.

Last edited by BstMech; 04-12-2008 at 06:12 PM.
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Old 04-12-2008, 06:21 PM
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The only real diffrence in a SB and BB pump is the bolt pattern (BB is a bit bigger)


Could be a long SB pump.

But I regress.....A BB pump will not bolt to a SB.
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Old 04-13-2008, 12:50 PM
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Can you try to explain the popping noise a little better? You say it only does it after it gets to operating temperature it makes me think it might be running a little to the lean side with the choke fully open.
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Old 04-13-2008, 05:56 PM
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Quote:
Originally Posted by carsavvycook
Can you try to explain the popping noise a little better? You say it only does it after it gets to operating temperature it makes me think it might be running a little to the lean side with the choke fully open.
O.K. my pump might very well be not in cause here.
I talked to a friend mechanic this afternoon and was also thinking about something similar to sudden combustion caused by faulty ignition or as you suggest a wrongly calibrated carb.I have tried over and over to calibrate the edelbrock 1405 wich is a 600 cfm with manual choke but ever achieved anything satisfying....swapped jets ,springs and rods.

Explain me more about te fully open choke as this is surely the position I leave it to drive the car...closing it only for starting...supposing my carb is adjusted too lean closing the choke down a bit would equal to a richier mixture thuss eliminating the popping wich could be what is called detonation?? something to look in i guess.

To even complicate possible diagnosis i have seen sometimes this popping happening just after having shut-off the engine!This is why I've looked into the cooling (pump,thermostat,rad.,etc) as this happening when the engine was stopped I could think about entrapped air and resulting bubbling .Sometimes the engine want to keep running at shut-off.I get around it by stalling it with the clutch but this is symptomatic of something wrong.Thermostat(s) have been tested before installation and checked good.Temp gauge shows no sign of overheating staying around its 160 rating.
This is a new motor with around 1000 miles after built and it does consume a quart at 3-4 hundered miles still...got told by the builder to put miles on it to see this getting corrected..

So this is a resumee of it all ;the car has been sitting for over a year now but I'll give it a try in the coming months once that snow gone!
thanks for the interest.
Ron.
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Old 04-13-2008, 06:27 PM
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Here we go! You have a 383 stroker under a 500cfm carb. You should have at least a 650cfm carb on that engine. It is being starved for A/F mixture. The running on is from having to open the throttle too much for it to idle correctly. This noise you are hearing is most likely being caused by "kick-back" in the engine from running too lean.
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Old 04-13-2008, 06:58 PM
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Quote:
Originally Posted by TVR383
Hello again,

I just managed to attach pictures of that pump inyo my gallery ...hopefully somebody could identify it and tell me more about my situation.
thank you for the interest.
Ron.

That's a short small block pump.



Larry
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Old 04-13-2008, 08:10 PM
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I agree, BBC pumps won't fit on SBC motors. The Pump you have there is a short SBC water pump. These were stock on early chevy V-8's but are sometimes used when radiator to fan clearance is a problem. I forget the year the chevy went to the long pumps but I think it was in the early sixties.
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Old 04-13-2008, 08:46 PM
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Vettes in the 60 had them.
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Old 04-14-2008, 03:26 PM
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Quote:
Originally Posted by BstMech
The pump you have looks just like the one (short pump) on my '72 with a small block if that helps.
My truck is all original and it's a '72 model.........

Maybe trucks were the last ones to have'em?
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Old 04-15-2008, 07:23 AM
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Dunno maybe,

I just always look for a pump on a mid 60's Vette when someone comes in and asks for one.
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Old 04-15-2008, 07:43 AM
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Quote:
Originally Posted by BstMech
My truck is all original and it's a '72 model.........

Maybe trucks were the last ones to have'em?

I think for that truck you would need to measure the distance from the block to the pulley mounting location on your pump. Maybe the original pumps back then looked like the short pumps but were actually long. A good way to visually reference this would be to look at the crank pulley, if the first groove is right against the dampner then it is a short water pump, if there is about 1.5 inches between the dampner and the first groove then it is a long pump.
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