Inliners International Forums General Discussion Engines 270 Engine Questions

Hello All,

I am rebuilding a 270, for use in a 1944 GMC CCKW (2 1/2 ton truck). The rebuild is mostly stock - not planning on spinning it past 2,850 (per the Army regs, you know).

Since this is my first 6 cylinder project, I would like to ask a few questions:

1) What is the best way to modify the front cover bolts, so that the oil pan does not have to come off first? I'm thinking maybe threaded inserts in the cap, and drill out the threaded holes in the boss on the cover? (Hopefully, the cover will not have to come off again - but just in case...) I gotta believe that this was a frequent modification - can't think of why the engine was designed with two bolts on the inside.

2) What cam gear is best - aluminum of fiber? I was leaning toward aluminum, so I purchased a Cloyes aluminum cam gear and steel crank gear from RA - but some people are telling me to just use the OE fiber gear.

Also, is there anything I should check to ensure they are compatible? (i.e. is there a one type steel gear for use with the fiber gear, and one for use with the aluminum gear?

3) The 0.030 pistons that I purchased have, what I can best describe, as a "hump" on the top surface, right in the middle. Looks like an artifact from when they were manufactured.

(None of the pistons that I have seen from other 270s have this. In fact, it looks like this was machined off of them.)

Will this hump interfere with the valves? Should I chuck them up on the mill and knock this off ?

4) Any suggestions on rod nuts? The old ones are castle nuts - and I assume these were supposed to incorporate some type of self locking feature? They look kinda beat up. Should I replace them ? I was thinking about going with ARP. They have a 3/8-24 with a small enough base (0.645", I think) that it does not hang way over the side of the rod.

5) As there is no threaded hole in the crank snout, should/could I drill and tap it? How much hammering does it take to install a new damper? Is here a concern about damaging the thrust bearing? Seems like a threaded hole would make installing the damper easier, and also positively retain it.

Any help or suggestions would be greatly appreciated!!!

Thanks !!!

Sounds like a fun project.
1. Tap the existing holes for 5/16 bolts. You need not drill them.
2. Aluminum is best. I would get both gears in a set on an engine this old. I'm not sure how well gears of different makes work.
3. There are two styles of 270 pistons. The older style in domed and that sounds like what you have. I have as set of Vinolas with the sticky up thing on them. Those should be removed. I have no idea why they are left on. I think some were let out that were not completed as mine ar rough on top too. The newer style piston is for the later 270 head with a D shaped chamber and are flat tops.
4. A 1/2" hole drilled and tapped in the crank snout is handy. The thrust bearing can be damaged if you drive the dampener on. That said I have done it. It's hard to heat it if it has a rubber ring. Otherwise heating the dampener hakes it easier if you don't burn yourself in the process.
Good luck and keep us up on your progress.

Thanks!! Greatly appreciate the advice!!!

One more question. I am getting ready to install the cam bearings. The new ones appear have a port cut into the oiling grove, opposite the feed hole (the one that connects to the passage from the main bearing).

I am assuming this port is to feed hydraulic lifters on engines so equipped? The bearings I took out did not have this feature. My engine has solid lifters.

In any case, it should be OK to use these bearings, correct?

Thx again.....

I have always had the cam bearing installed since it is so easy to make a mess of them without the proper tools I don't have. If your block doesn't have a passage for oil to go into then the extra port should make no difference.

Thanks again.

I made an installer tool out of some spare aluminum and a threaded rod. Seems to work well.

Will link pictures when I can...