'59 Water Pump / Motor Mounts

[Bwmurph]

Hi All,

Hope you are all doing well with this Covid mess !

I just installed a new water pump on my '59 and have a question or two about the motor mount that is bolted through the water pump:
1) I mounted the water pump correctly passing the bolts through the pump and then the motor mount (gaskets on both sides. Then let the motor down onto the front mount; aligned the holes and then began tightening the m/m bolts. I am using a torque wrench but I seem to be compressing the rubber mounts quite a bit and I'm not even close to the torque spec of 25-35 lb/ft; I haven't even hit 20 lb/ft yet. How much should the rubber mounts compress ??

2) For some reason the bolts for the m/m that go through to rubber mounts at fine thread with castle nuts on the top for cotter pins. According to the Assembly Manual they are not the correct bolts; it doesn't bother me that they are not correct (a lot about the car is not NCRS correct), but will the fine threads affect my torque readings?

Thanks, and any help will be much appreciated,

Bernie O

 

[Tom Bryant]

The correct bolts have a spacer tube that the bolt passes through. The nut is torqued against the spacer. You won’t be able to get the mounts torqued without the spacer. Motor mount bolt kits are about $16.50 at Corvette Central and others.

Tom

 

[Bwmurph]

OK Tom, I finally bought the correct bolt kit form Corvette Central.

1st Problem: I remove the bolts, spacers, etc.... from the package and notice they are fine thread. No big deal, but just out of habit I try to screw one of the nuts onto the bolt - it's really hard and doesn't want to go. I try to force it a little and its just tearing up the bolt. I try the other one - same thing. I check and both the nut and bolt appear to be fine thread, but they are not compatible. I call CC and they are going to send me new ones.

2nd Problem: While I have the CC guy on the phone I mention to him that the spacer is definitely too big to go through the holes in the Engine Mount Bracket that bolts to the water pump. He insists they are correct and that they come up form the bottom and don't go through the bracket. HOWEVER, I'm looking at "53 - 62 Corvette Servicing Guide" (ST-12) and, on Page 6-5, it specifically says "Place new upper half (rubber mount) in place on frame bracket, then install spacer and bolt downward through engine bracket into upper mount half to align mount." And, it clearly shows the spacer sticking through the engine bracket.

I'm confused; what do you think ?

Thanks
Bernie O

 

[Tom Bryant]

Hi Bernie,

I'm trying to get a handle on this without taking my '59 apart. It's been since 1971 when I installed new mount cushions on my car. I do have an NOS 61/62 mount and I compared it to the photo of the reproduction 56/60 mount and other than the cutout for the 61/62 water pump they are the same. My 1960 parts book shows the spacer to be 5/8" diameter by 2 5/16" length. The passenger side hole in the mount is 13/16" so the spacer would go through the hole from the top. The driver side is only a tight 1/2" so the spacer will not pass through it and would have to be installed from the bottom. I can only guess that the left mount is done this way to control engine rock. The spacers are GM part number 3700333 qty. 2 so they are the same for both sides. I can't verify that the driver side hole was always smaller or if this was a later change in design but my later parts books from the 70s show the same part number for the spacers.

The illustration in the parts book clearly shows a fine thread on the bolts. They don't list a part number for the Corvette bolts but they do for some 6 cylinder applications. Most are 7/16". These Corvette rubber mount cushions are the same as some 6 cylinder passenger cars. Upper mount is also for a 53/54 convertible and the lower also fits a 52/54 passenger car. I would guess that the bolts in the kit may be cheap Chinese stuff and the pitch may be off. If you have a tap and die set use the pitch gauge to verify that the thread pitch is the same for both the bolt and the nut. You might be better off sourcing bolts and nuts locally that thread together easily. You could run a tap through the nut and a die down the bolt to clean up the threads if they show the same pitch.. Then they should go together.

Tom

 

[Bwmurph]

Tom,
The plot thickens ! Now I get an email from Corvette Central and they say "the nuts are locking nuts. the nuts only go down two threads and then stop You have to force the nuts the rest of the way" So ....... I guess I'll try them and see what happens.
But I do find it strange that the holes in the mount are different sizes - I hadn't even noticed that until your email and I went and checked - sure enough their different sizes. I would have that pass side would be smaller. But what do I know.
And I'm knee deep into the other project for this car - new carpet and HushMat. And this is spiraling WAY out of control - long story , maybe in another post.
Thanks for all your help !
Bernie O

 

[Tom Bryant]

I thought that they might be lock nuts when I first read your post. It didn't make sense though since you are supposed to torque them to 25-35 ft. lbs. It would take almost that to turn one of those oblong lock nuts. The kit maker must just intend for you to snug them down good and tight and call that good enough. I guess that will work. At least you don't have to worry about them coming loose.

Tom