Inliners International Forums General Discussion Engines Place to start for a 270 GMC

HI all I have a 1959 gmc 100 with a Chevy 235 in it and the original to the truck gmc 270 which I would like to rebuild just wondering a good book going over toruqe specs and all that for rebuilding it and if any one could recommend a mild camshaft for it also? Does it share main cap bolts with the chevy l6?

Can't recommend a book.
Before you take anything apart, if possible do a compression test:
1. plugs out
2. throttle and choke blocked open
3. crank it over the same number of turns for each cylinder (10, etc.), or until the gauge stops.
4. write it down
5. should be 10% or less difference between highest and lowest
6. post what you find

Your cam choice will depend on what you will REALLY use the truck for. The rest of your build should reflect the planned use as well. As far as I know there are no books about building these engines newer than the mid '50s. A lot has been learned since then, old parts have disappeared and some new choices have discovered. Search old posts here, the Stovebolt site, and the HAMB.Here is a link to a 270 build going on there now. Some good info buy maybe more mods than you'll need. Pistons for the later 270s can be difficult to find. The torque specs can be searched online.

newer than the mid '50s
and some of those say very clearly "Don't use new tappets on a new cam. Go to the junkyard and get some tappets that have embedded grease instead".

Yes, and hardened from use. There is a lot of folklore to these builds.

The reason it is out of the truck is it spun a rod bearing or so the last owner said, I will try to do a compression test anyway.It currently had a 64 impala 235 and it feels wrong.

64 impala 235?

Perhaps a 62 impala 235 . . .

for what its worth I had problems with cams and lifters, ruined 3 of then useing the milk can lifters. I then got some from a fellow back east that were cast iron I believe and if memory is correct I had to use longer push rods. Patrick did sell them also. anyway I've been good for several thousand miles. I also use a hi zinc oil. just looked and Stovebolt has iron lifters
Jay D.

Might have been or the guy I bought it from was mistaken.
So you guys are saying if I do buy a new cam run old lifters?

Perhaps the guy was mistaken. The last year for a 235 in any Chevy was '62.

As for the folklore about old lifters . . . no. If you are buying a new cam it is best to source new lifters from the same supplier.

I posted here Inliners circa '15 about the material changes that took place between the last stovebolts and last generation of 235/261 sixies. Many have had problems as a result of mixing parts that 'fit' but are not compatible in terms of metallurgy.

regards,
stock49

Well I got it on the engine stand, when turning over I can hear a clunk from the bottom end so this supports what the previous owner told me that it has a bad rod bearing. I canont get my compression tester tight on the plug hole so I think im just going to tear into it ill post what I find. Now I am getting scared about were to find parts for the GMC motor.

Well... Looks like someone had some fun this this engine, at least 2 or 3 spun rod bearings maybe more most metal ive seen in a pan ever... One bolt came completely out off the rod. were do you guys buy GMC paint cant seem to find any.

Check the size of the tab on the rod bearings compared to the slot on the rod and cap. Someone may have used the wrong bearing. There are two sizes of the tabs.

I hope the crank is OK, rods are plentiful.

Going to need some parts here defiantly some scarring on the crank I think it will polish out, need pistons and a couple rod caps. Who sells pistons and rod bolts?

A scar (metal removal) doesn't worry me as long as it doesn't extend to the edge of the shell (either the crank cheek or the other shell half), which will drop the pressure. High spots (metal displaced but not gone) are a different matter: have to be removed.

Ill have the machine shop look at it and make sure it is safe to do.