Water pump gaskets keep failing

C1 Specific - Technical and Performance

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Water pump gaskets keep failing

Postby thirstyvette » Thu Sep 05, 2013 2:24 pm

Hi All,

My C1 is running a 350. The engine mount set up has the front plate bolting to the front of the motor. This front plate is then bolts to the chassis. (Front plate is similar to a horse shoe shape)
The water pump is bolted on over the engine front plate.
It requires 2 sets of gaskets.
The water pump bolts basically act as engine mount bolts as the sandwich the engine mount plate between the water pump and block.

Order is water pump - gasket - engine mount plate - gasket - block.

Problem is I am up to my third lot of water pump gaskets now.

They keep dissentegrating. Its as if the torque of the motor twisting on acceleration is slowly wearing away the gaskets.

Its a pain to change.

Has anybody else come across this?
Is there special gaskets I need to use?

Kind Regards,

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Postby DOC » Thu Sep 05, 2013 6:51 pm

First I'll State that I have never run into this issue before.
None the less, I've been a Mechanic for about 40 years.
If this was my issue, I'd Scrap the gaskets all together.
I'd seal the plate to the block and the pump to the plate with three bond 1104 sealant, I'd also look at anyway to install any additional bolts through the plate into the block, the bolts low on the block near the fuel pump come to mind for example.
A good , clear photo of your engine mount might help a bit.

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Postby bfit » Thu Sep 05, 2013 7:15 pm

From what I have read this is a common problem
Up have PM on this

Seeing you  have a 350 in there you are not into keeping it stock
I have seen plenty of SB Chevy motors in hotrods that use a cradle type mount 
That picks up the two bolt holes at at each side of the front of the block
Simple to make and very strong 
You need to be good with fabrication to go around the fuel pump
Normally you would use a donut stile mount each side
But there are many ways to rubber mount the bracket
I don't know if you have sufficient room to do it this way

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Postby thirstyvette » Thu Sep 05, 2013 9:31 pm

Thanks for the advice!!!

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Postby 98lux » Fri Sep 06, 2013 10:13 am

Info from different forum, pm sent with link.

I fixed this problem on my engine mount over 30 years ago. It is a simple and bullet proof permanent fix that is invisible and looks completely stock when done. Bonus is, after you do this, you can change your water pump without having to support the motor and without disturbing the inner gaskets and seal.

The method I use is to support block, remove the water pump and motor mount, clean off all old gasket material, bolt motor mount to block, drill 3/16" pilot hole through motor mount and into block about 1/2". Select one location on each side of the mount where the dowel will go into the mounting pad on the engine block and still go through the motor mount without getting too close to the edge. I drill a hole about 3/8" inboard of the water passage and up or down a little as material allows. (I had a picture but can't find it at the moment) Then using a new high speed drill bit, drill holes out to 5/16" dia. Now measure depth of holes and cut 2 pieces of 5/16" dowel material (drill rod). Remove engine mount from block, apply lock tite to dowels and drive them into the block with a bronze drift so you don't deform the ends. They should protrude out of the block about 3/16 of an inch or enough to go through a gasket and the motor mount. If,upon installation of the motor mount and gasket, they are a little long just grind them off till they are flush. Chamfer the ends of the dowels very slightly to help in starting in motor mount holes. Reassemble with new gaskets with Gaskacinch or some other good sealer and you are done. I did this on mine after fighting water pump gasket failures and have not had a single failure in over 30 years of hard driving. Currently running 400+ hp 355 engine.

Here is a rough sketch of where I located the dowels in the motor mount.
The factory design was not well thought out in that it relied on the compressive forces on the gaskets to resist the shear forces of torsional vibration of the engine. Guess who wins over time? Paper doesn't have much shear resistance. I chose using dowels over shoulder bolts because the holes in the mount are oversize and a shoulder bolt might require drilling out the water pump holes. Also it is difficult to get a perfect index between the tapped bolt hole and the drilled shoulder bolt hole since they are not done in one operation. The added benefit of the dowels is that once you mount the motor mount to the block the dowels support the weight of the block and you don't need to support the block from underneath to line things up and you can change out the water pump in the future without supporting the engine from the bottom. Simple, easy, permanent. I have never had a leak or a loose bolt since I did this modification and I don't baby this thing.

1968 L36 4 SPEED hmm Big Block
1969 454 4 SPEED hmm Bigger Block

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