Wednesday, 3 April 2019

2018-2019 Winter Jobs 2. Sprint Engine - Problems

I had found a Sprint engine that had been used in a TR7 rally car and bought it for a "reasonable" price so the plan was to give it a quick check it over and fit the engine in the FHC over the winter.
TR7 Sprint Rally Engine
It was running on 45DCOE carbs with a fast road cam etc etc so should be good for about 160-170bhp. Naturally there were a few things I wanted to check and it turned out to be a bit more work than expected.
First thing I noticed was the cam sprocket support bracket was missing. This holds the sprocket in place and allows you to work on the cam without taking the chain off,  like when you need to alter the tappet shims. Not a good sign.
There should be a guide pin in the middle of that sprocket!
Next thing I spotted was that one of the 14 bolts holding the rocker gear to the head was metric. Just one, but it should have been UNC thread!  Why would you put one odd bolt in?

Metric bolt, that should not be in this engine!
Another bad sign, so I now knew whoever built it was either in a big hurry or they didn't know what they were doing.
Either way it prompted me to completely strip the engine to see if I could find any more things to worry about and I soon noticed there was way too much end float on the crankshaft.  I found it because there was a loud "clonk" when I turned the engine upside down on the stand as the weight of the crank assembly made it to slide sideways in the main bearings . It should have been between 0.003"-0.011" but it was more like 0.020". This meant incorrect size thrust washers were used.

At this point I decided it would be best to "park" this engine for the time being and go back to the one I had started to build back in 2014. The quick swap job was back to being a big build after all.


No comments:

Post a Comment