water pump clearance issue
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
Standard Chevy short pump
5.625" Length - 5/8 pilot shaft
There is also a Severe duty short pump
5.625" Length - 3/4" pilot shaft
The correct pump for a 77 is:
71-82 Corvette pump
5.795" length - 3/4" pilot shaft
These are all shorter than the Chevy long pump, but not the same and often incorrectly referred to as simply a short pump.
5.625" Length - 5/8 pilot shaft
There is also a Severe duty short pump
5.625" Length - 3/4" pilot shaft
The correct pump for a 77 is:
71-82 Corvette pump
5.795" length - 3/4" pilot shaft
These are all shorter than the Chevy long pump, but not the same and often incorrectly referred to as simply a short pump.
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From: New Or-leens Loo-z-anna
And I always thought that "Long pump" meant that the impeller shaft was longer...... 
It actually means that the distance from the gasket surfaces to the pump cover is longer!
(so....a spacer could be added between the pump shaft hub and the pulley if necessary to align the pulleys)
It actually means that the distance from the gasket surfaces to the pump cover is longer!
(so....a spacer could be added between the pump shaft hub and the pulley if necessary to align the pulleys)
Last edited by doorgunner; Nov 24, 2013 at 08:57 PM.
Pro
Joined: Sep 2011
Posts: 613
Likes: 11
From: EVANSVILLE Wisconsin
I had the exact same issue when I replaced the water pump on my 80. I ordered 2 different pumps and even though each had different claimed dimensions, they fit the same.
I ended up using 2 thick gaskets with gasket maker smeared between layers to them to keep them from leaking, so far so good on that and that allowed it to just barely fit. I did however have issues lining up the other pulleys then and it was a PITA. I actually had to shim the crank pulley (AND the water pump pulley which seems counter intuitive)..... It should not be this hard..
Thick water pump gaskets....
http://www.summitracing.com/parts/sum-g6303/overview/
I ended up using 2 thick gaskets with gasket maker smeared between layers to them to keep them from leaking, so far so good on that and that allowed it to just barely fit. I did however have issues lining up the other pulleys then and it was a PITA. I actually had to shim the crank pulley (AND the water pump pulley which seems counter intuitive)..... It should not be this hard.. Thick water pump gaskets....
http://www.summitracing.com/parts/sum-g6303/overview/
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
All the Chevy pumps should bolt to all the gen1 sb engines, long, short, severe or corvette.
If not, you've got an inferior made pump.
The critical measurement is the distance to the clutch/fan mount face. All your pulleys must be in the correct position.
If not, you've got an inferior made pump.
The critical measurement is the distance to the clutch/fan mount face. All your pulleys must be in the correct position.
Thread Starter
Drifting
Joined: Aug 2013
Posts: 1,453
Likes: 88
From: Easton Pennsylvania
Before I go out and buy another pump or timing cover I think I will try a set of water pump spacers i found on the net that are 1/8 inch thick. I will then bolt up all the accessories and see where I'm at.
Le Mans Master
Joined: Apr 2011
Posts: 6,284
Likes: 1,170
From: Hermosa
I had to make my own gaskets out of .040" gasket material and then stack them so that the water pump would not push on the front of the timing chain cover with a double roller chain.
Also the bolts that hold the back plate on stuck out farther than the plate itself and had to ground down so they didn't push in on the timing cover as well.
I'm using a roller cam so the distance between the timing cover and cam button became important to prevent cam "walk".
Also the bolts that hold the back plate on stuck out farther than the plate itself and had to ground down so they didn't push in on the timing cover as well.
I'm using a roller cam so the distance between the timing cover and cam button became important to prevent cam "walk".
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Le Mans Master
Joined: Dec 2003
Posts: 5,727
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From: Fremont CA
The stamped steel back impeller cover on that water pump is UNLIKE anything GM ever produced! I guess the Chinese FOOKED UP the English to Metric conversion on that part. Shame! seems to be happening more and more, I just bought a part which was off by 1mm (0.040") and it took 2 hours to remachine part in a mill to get it to fit.
Race Director
Joined: Apr 2009
Posts: 19,294
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From: Charlotte NC
For what it is worth.
I measured an original timing chain cover that I have that came off a Corvette engine (pre-1984) with the timing tab still tack welded in place.
I placed 1 flat steel stock across the gasket surface area (side to side)...and one flat steel stock across the painted area (side to side). I measured it in three areas (on both sides, L & R) and the width of the timing cover is .915".
DUB
I measured an original timing chain cover that I have that came off a Corvette engine (pre-1984) with the timing tab still tack welded in place.
I placed 1 flat steel stock across the gasket surface area (side to side)...and one flat steel stock across the painted area (side to side). I measured it in three areas (on both sides, L & R) and the width of the timing cover is .915".
DUB
Race Director
Joined: Apr 2009
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From: Charlotte NC
But one thing that you also have to consider...because it is a fact. That when a water pump is being installed on a Corvette 77-82 (with the R-4 A/C compressor)...and if the smog pump aluminum bracket is still going to be used. The top left bolt location on the water pump needs to be machined down so the steel bracket for the A/C compressor will fit correctly. If it is not machined down the bracket is at a sever angle...and IF you go to install the cast aluminum bracket for the smog pump...you WILL break it. I have searched "high and low" and no one offers the pump with the mount area the correct thickness...and I have to machine it down every time. I have a true original that I keep to make sure that I machine it down to the correct thickness. It is off by about 1/8". Which might as well be a mile.
DUB
Thread Starter
Drifting
Joined: Aug 2013
Posts: 1,453
Likes: 88
From: Easton Pennsylvania
But one thing that you also have to consider...because it is a fact. That when a water pump is being installed on a Corvette 77-82 (with the R-4 A/C compressor)...and if the smog pump aluminum bracket is still going to be used. The top left bolt location on the water pump needs to be machined down so the steel bracket for the A/C compressor will fit correctly. If it is not machined down the bracket is at a sever angle...and IF you go to install the cast aluminum bracket for the smog pump...you WILL break it. I have searched "high and low" and no one offers the pump with the mount area the correct thickness...and I have to machine it down every time. I have a true original that I keep to make sure that I machine it down to the correct thickness. It is off by about 1/8". Which might as well be a mile.
DUB
Race Director
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From: Charlotte NC
My previous post was for those who read this post who this may effect. I know it was not directed at your issue directly...because your engine is orange and not Chevrolet blue. But NOT all small block pumps for a Corvette are the same.
I have not yet installed a short water pump that was not touching the timing chain cover just a very little bit. It does not effect installation of the pump...and even the original timing chain cover I have shows where the water pump back plate was resting against it.
Depending on the interference issues...roll with it. I was under an entirely different impression that the pump was not able to be mated to the block with ease.
DUB
Race Director
Joined: Mar 2006
Posts: 14,112
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From: Florida
Here is a correct replacement Corvette pump for 71 and later and oem timing cover that slightly touches as Dub said. There were no shims anywhere and no special gaskets. All the pulleys line up perfectly as from the factory.
A/C bracket, now correctly mounted, shows in the smooth part below the right most bolt, where I had brazed the broken cast bracket together. Result of a PO not checking the mounting clearances. I didn't re-install the smog pump.
Thread Starter
Drifting
Joined: Aug 2013
Posts: 1,453
Likes: 88
From: Easton Pennsylvania
Ok mike. I was just trying to avoid buying another pump. So I will go out and try a different one. You guys have all been very helpful.
And Btw. I painted my engine Chevy orange because that works with my overall plan for the engine bay. Anyways, I thought early 77's had their engines painted orange not blue. Mine is a Dec 76 production and 14,553rd off the line.
And Btw. I painted my engine Chevy orange because that works with my overall plan for the engine bay. Anyways, I thought early 77's had their engines painted orange not blue. Mine is a Dec 76 production and 14,553rd off the line.
Race Director
Joined: Mar 2006
Posts: 14,112
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From: Florida
Well I finally got a chance to work on my engine and I took my new timing cover that I ordered from ecklers and before I paint it and put it on I checked for clearance with the new water pump and this is what I have,
Clearance issues.
Now if I assume the ecklers timing cover is correct, Then could it be the pump. I ordered it from napa and according to them it is the right one. So what gives? I have a chome water pump which I took off (because its pitted} that is taller than the napa pump but clears the cover by a hair. Stacking two gaskets together won't work cause there is to much gap between the new pump and the block with the new cover. Can someone here give me an idea as to what to do.?
Clearance issues.
Now if I assume the ecklers timing cover is correct, Then could it be the pump. I ordered it from napa and according to them it is the right one. So what gives? I have a chome water pump which I took off (because its pitted} that is taller than the napa pump but clears the cover by a hair. Stacking two gaskets together won't work cause there is to much gap between the new pump and the block with the new cover. Can someone here give me an idea as to what to do.?
Why don't you just measure the old and new pumps from the block to the hub and also measure from the block mount to the impeller cover and post the results. Measurement usually tell all.
BTW my 77 was factory orange. Oct build serial 8xxx
Race Director
Joined: Apr 2009
Posts: 19,294
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From: Charlotte NC
Noonie,
Thanks for posting a photo to show people that the difference if using the aluminum smog bracket does require milling the pump down.
Not by no means do I think i know it all...but I have never had a 77 in my shop that the engine block was orange. Learn something new everyday....another piece of trivia to add to all the others.
DUB
Thanks for posting a photo to show people that the difference if using the aluminum smog bracket does require milling the pump down.
Not by no means do I think i know it all...but I have never had a 77 in my shop that the engine block was orange. Learn something new everyday....another piece of trivia to add to all the others.
DUB