I spent the day degreasing the donar engine for my 60 Valiant.this was a running engine and I did a compression check before pulling it to confirm the lower end condition as I was hoping not to have to do a complete rebuild.The compression was 136 to 141 on all holes,the oil pressure was 50 psi with 30 weight oil and the engine held 19 inchs of vac. at idle.All of these numbers led me to beleive that the lower end was real solid and ready to accept a shaved head ,H-P intake,and Comp Cams 264 cam.
When Ipulled the head I was taken aback as the cylinders seemed to have a nasty ridge at the top of the bores, the rest of the cylinder looked good though ,no grooves or scratchs.
Im sure that some of the ridge is carbon buildup but what is a acceptable ridge before needing bored and how do I measure this?
Thanks in advance,
Slanted Attitude

As long as the rings seal (which they do by the compression #'s you give) I wouldn't be worried about it. A newer engine will get closer to the 150psi mark but since you said yours has some miles on it already.... I would lap the valves a bit to clean them up. Also, take some rough brillo pad, soak it in wd40, and rub the ridge to clean it up if you think there is some carbon there. I believe in 3m brand, dark red is the roughest.

A cylinder ridge is an indication of high miles, but not necessarily of how much oil it will burn. I've had engines with virtually no ridge burn oil like crazy and vice-versa.

That said, if you up the compression and change the cam, be prepared for lots of blow-by. I'd do the engine while you have it apart.

While you're at it you might as well work on anything that could use some maintenence or touch ups. It's cheaper than ripping into it later only to replace seals and gaskets a second time.

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Slant Six... out of the ordinary - just like me!

Well ,I finished tearing down the engine tonight and have decided to take the plunge and rebuild my first engine.I have worked all over and all around engines for most my life but have never actually built one from scratch so here goes. Now I just have to find a good machinast and ask alot more ??????????. Wish me luck.
Slanted Attitude