Inliners International Forums General Discussion Engines Chevy 261 inline six - chasing coolant leak

I have a 1953 Chevy pickup with a 1959 - 261 inline six engine. I had a massive oil leak months ago due to a cracked front main cap on the crank. After having the engine rebuilt, I now have re-installed the engine, rebuilt the Stromberg two-barrel carb and have the engine timed and running nicely. However, I have a coolant leak that is bugging the hell out of me. When I first saw the leak, I pulled the radiator and used a black light flashlight and could only find coolant sitting in the bottom edge of the timing cover (front engine mount). I checked all the bolt tightness around the water pump and the timing cover and found one slightly loose bolt for the water pump, but the flashlight showed no traces of coolant coming from that area.

Hoping I had found it, I put the radiator back in and let it sit with coolant in it for several days and there was no leak. I just fired the engine back up, ran it for 15 minutes, got it up to temp and found a leak at the exact same spot at the base of the front timing cover.

My question is this, is there really a water jacket area near the front timing cover that could possibly be leaking? When I initially had the engine out a year ago and tore it down to a massive oil leak, it was coming from a cracked front main cap on the crank. With the timing cover off back then, I don't recall any water jacket access. Where could this coolant leak be coming from?

Is it leaking from the head gasket? Or therm housing?

Yesterday, my son came over and as I was explaining the leak issue to him, I noticed that the underside of the thermostat housing, lit up brightly with my blacklight. I have a bracket to hold a McCulloch supercharger (from a 1957 Studebaker Golden Hawk), it is designed to mount directly to the head and then the thermostat housing mounts to it (using longer bolts to go through both the thermostat housing and the supercharger bracket into the head)

Since it clearly showed symptoms of leaking I decided to take it apart too. Boy am I glad I did. While there is evidence of the engine builder using a paper gasket and sealant between the supercharger bracket and the head, all he used was a very thin layer of sealant between the bracket and the thermostat. When I took the thermostat off of the bracket/head, it was 75% metal to metal with the sealant having been squished out.

Fortunately, in my bag of "stuff" I found the correct size gasket and reinstalled the thermostat and the water pump this morning. There is now a gasket and a liberal amount of sealant between the thermostat and the supercharger bracket, as well as between the water pump and the mounting bracket and the mounting bracket and the engine block.

I'm letting it set overnight, will put the radiator back in tomorrow along with coolant and do a pressure test. Fingers crossed.


As for my patience with this truck, it is running thin..... I have been working on this truck for three years now and have signed up to take it to three car shows starting in mid-May. I did the same last year, but with the engine being rebuilt, that didn't happen. I'm hoping for better luck this year.

I'm glad you found it and I hope it is fixed. I also hope the engine builder didn't cut any other corners. I also hope you make it to those shows and have some well deserved fun with the truck. I have a '53 with a 270 GMC. I would like to see pictures of the supercharger mount. I have a few McCullochs around and would like to see that mount.

This link should get you a couple of photos of the supercharger bracket and a couple of the engine partially assembled with the McCulloch.


Engine and Supercharger photos

BobK
Thanks for the pics. In the center one I noticed a red distributor cap. Is that possibly a Mallory Electronic unit? I?m running one also. Do you know of any sources for replacement cap and rotor? I?ve been told they are discontinued. Been looking for a while, with no luck. Hope you can brighten my day.
Thanks in advance for any help.

41 Coupe

That was a temporary setup that I had with a distributor from Summit. I actually use a Vertex magneto, but it was getting re-built when that photo was taken. Very unique truck has a Saginaw four speed from a Camaro and a Halibrand quick change diff.

Thanks for the pictures, That is a neat setup. I have Studebaker V8 brackets and a Kaiser one.

Larry still looking for Mallory stuff.

? me ?

No, the 41 coupe one. He asked me about some Mallory parts a while back.