Hi Guys,
Thanks for the comments regarding the 300.
It wasn't until I looked back through my posts, I realized I failed to let you guys know about the engine trouble I have encountered this year. Around the time I built the new shed the 300 was misfiring. After a quick inspection I noticed a bent push rod and seized exhaust valve on cylinder 3. After removing the inlet manifold, I discovered every cylinder was contaminated with water.
I assumed a cracked cylinder head, and set to making a test rig, testing each head for leaks. I blanked the water jackets off submerged in hot water then pressurized with air (photo below), all seemed ok. then I spoke with the guy who machined the engine components, after seeing my blanking plates (the hardest part as far as testing heads go) he let me use his test machine pumping hot water through the heads and then pressurizing, again no leaks the heads seemed ok.
I spoke with the mechanic who built the engine, he was suspicious there was a water leak in the block between the water jacket and a cylinder the result of corrosion from sitting for so many years. I spoke with the machinist regarding this theory, he suggested (and I know this sounds primitive..) to bolt 1 head on and seal the water pump, turn the engine on the stand so the block without the head is facing up. Fill the water jacket with petrol and inspect for leaks. The results were interesting however no leaks. The day I did the test was warm and sunny, I filled the water jacket until it was full to the brim, I watched for a while and nothing happened, I walked away and left it. About an hour later I walked past and noticed a tiny drip falling from the crank (sump was off) I though this is it, I?ve found it, on close inspection the petrol had expanded in the sun, ran over the machined surface on the block where the head bolts on down at cylinder #8 ran past the piston and down to the crank. At that point realized how the smallest of leaks is easy to see doing this test and my block is ok.
From here I was still unsure, luckily Chuck had a mate with a spare 300, I bought it as my plan B. I purchased a set of push rods, new valves and gaskets and with a mate of mine who is a mechanic put the engine back together. After we did the first fire up, I took it into the dyno so I could run the cam in and test the engine under operating temperature and load. It all went well.
I have a few theories to what caused the failure, me doing short runs after rebuilding and not getting correct temperature, using coolant from the start (a few old school mechanics have suggested never use coolant before an engine is properly run in), incorrect inlet manifold gasket used from kit, incorrect torque on LHS head, I checked RHS it was correct. To be honest I don?t know however time will tell and I have a spare engine in transit (thanks Chuck).
Has anyone encountered a similar problem after a rebuild? It's frustrating to not find the point of failure.
I dropped into the panel shop yesterday, didn?t get to see my Skylark as it was late and the shed its in was locked. My mate who is doing the body work told me he has painted the underside and inner guards. The body is 80% block sanded and should be painted soon.
Take care
Marcus
