[north]

My 69 1bbl engine that I did a valve job on last year is back out of the car. I pulled the head last year due to a bad oil leak and we decided to send the head out in case it was warped and since it was the machine shop we gave it a valve job, valve seals etc. Like a dummy I didn’t send out the block since the bores looked decent and the rod and main bearings looked good.

It ran ok last summer but could never get a smooth idle and the first tank of gas came in at 11 mpg. Did a compression test and had three of six cylinders weak (110 versus 145 on the other three).

We opened up the engine again and discovered that it was already thirty over but the ring gap was way too high because the bore was too big for the pistons. Long story short it needs to go 40 over but I can only find 60 over pistons. My machinist doesn’t suggest 60 over due to overheating risks.

So my plan is to instead use a virgin 68 block I have and punch it 30 and use the 30 over pistons from the 69 engine (machinist said they are in perfect shape.

So what do you guys think? I disassembled the 68 engine and it’s in great virgin shape (it could get away with 10 thousand but figured might as well go 30 and save buying pistons. Both blocks have excellent cranks that can use standard rod and main bearings again.

Being a 68 block I will have to drill the bypass hole on the front to use the 69 water pump without external bypass provision.

I learned something else about the original engine I didn’t notice before. While the head is original the cam (and likely the cam housing) is from a 67 (based on the cam casting number). Which is why the car probably still had the thermostat housing spacer (with the bypass fitting plugged with a bolt). The cam is in good shape but the cam from the spare (68) engine is super nice so I’m going to use that one since it’s nicer and the correct 68-69 cam.

Second question, how do you install a thermostat without that spacer when there is no inset groove to seat the thermostat on neither the thermostat housing or cam housing?? The inset groove is in the spacer with the bypass fitting. I figured that they must have changed the design of either the cam or thermostat housing to seat the thermostat but to my surprise the part numbers for both housings are unchanged for 66-69. What gives?

Third thing is that the spare engine had a mesh oil screen inserted in the fill tube (protruding down into the sump. I’ve never seen this before and both my OHC don’t have them. Now I know why both my cars always sweat oil from the filler cap! I’ll buy some similar looking mesh and make one for my other (the Sprint) car.