Inliners International Forums General Discussion Engines Another new(ish) guy with a 302 military

Hi all, I was a member here a few years ago when I was working on a 292 and now I'm back with a 302 military that I found locally. I was perusing the local Kijiji and there was an ad for a 302 military with no pictures. I called the guy and he said it was a crate motor and he needed to get rid of some stuff because he was moving. I went to look at it and it was indeed a new on crate military 302. It has a rebuilders tag from 1984 and a paper military inventory tag with some mil spec numbers on it. It was bolted to a real sturdy angle iron cradle bolted to a heavy duty plywood crate.
I got it home and started tearing into it just to be sure it was good. As I pulled the valve cover off I saw that there wasn't a spec of rust or dirt on anything inside. When I pulled the rockers off I did notice there was a repair between two bolt holes. It looks like it was been welded at one time and ground smooth. The rocker shafts look new or reground.I pulled the oil pan and same thing , all clean. Pulled the head and other than a few fruit flies and some very minor flash rust in a couple cylinders all looks good. No ridge , good cross hatch and clean piston tops with .030 stamped on top.
So I've got a pretty good start to an old school hot rod motor for my model A coupe.

The thing is ,I was hoping to just take the oil pan extension off and make a plate to cover it and make a new pickup to make the oil pan work. Well it just won't work. I need a civilian pan and pickup. I'm hoping I can connect with a 6x6 guy or group that needs the externals from this crate motor. I've got the sealed 24 volt ignition , 28 v sealed generator , air compressor , pan and extension of course and a few other do-dads.

Anyways , this was my sort of re-introduction and story of my new project. I've been lurking and reading as much as I can about the GMC's Good to be back "inline"
Jeff

Good to have you back with us. It sounds like a great find. I've never worked wit a military engine but several here have.
For years I've be advocating for someone to write a new GMC Speed Manual. There is a lot of new information about these engines since California Bill's little book from the '50s.

Awesome !! Wish I could stumble onto a find like that!

There are a couple of forums that may help you with information on using your 302 in a civilian application, or aid in selling any unwanted military accessories:

https://forums.g503.com/viewforum.php?f=26&sid=d24d3e3d5e4d29a19e62b152b2f69fbb

And:

http://cckw.org/forum/index.php

The second website also has a nice page that talks a lot about interchanging 270s and 302s:

http://www.cckw.org/270_to_302.htm

It is aimed more at putting civilian engines into military trucks, but it still contains a lot of good information.

Good Luck !!

This is what it looked like when I got it home

https://www.jalopyjournal.com/forum/attachments/33-jpg.4020800/

When I got my 270 in 1977 I took it to a shop with a steam cleaner. We could not get it that nice. Good start!

A bit of an update, a tale of woe as it were. I took the head into a machine shop to get it pressure checked and decked. I wasn't comfortable with the crack repair I found when I took the rockers off. Well , I got the call...."your head is full of cracks, it's been froze"The repair was seeping and there were cracks in some of the spring pockets....DAMN! My score is starting to worry me. I haven't found any evidence the bottom end is bad but I gotta dig some more. I basically paid core price for this thing but I was hoping this was my lottery win.....I am not that lucky I guess!

Hi Jeff,

Well that's a bummer....

Do you think that maybe that engine is a takeout, that was placed in the shipping crate that the new engine came in? Or maybe some swapped heads on this engine while in the crate at some point in the past?

It seems very unlikely to me that a depot would attempt to use a repaired cylinder head during rebuild.

As you know, you probably want to thoroughly go over the block before you use it. I bolted a piece of wood to the deck with a thin piece of rubber to act as a gasket and sealed of the water pump passage in much the same manner. I then pressurized the cooling passages and covered every surface with soapy water, looking for bubbles - luckily none were found.

Also, prior to machine shop work, I had them magna flux it, just to be double sure.

Would be interested to know what you find....

Well , I'm not sure what to think at this point. I believe this might be a Friday afternoon / Monday morning engine. It is clean as a whistle inside and as far as I can tell it's never been run because the plugs are new clean and there's no soot on the piston tops. I think the shop that rebuilt it had a bad head and just assembled it as is...(" it's for the DND nobody will know")I am going to go over the short block and ensure that there is no more issues. I tracked down a good head core and am still excited about this find so I hope there are no more surprises.Fingers crossed!

It's been a while since I last posted anything. I've been busy trying to get this 1930 Model A coupe done. The 302 runs pretty nice . I cast a 3 carb manifold and have 3 Rochester B carbs , they still need some tweaking but should be good enough to get it to move on it's own. I split the stock exhaust and used some black iron plumbing elbows to point the outlets down.It sounds pretty good if I do say so myself.
Here's a little video of where I am now.

That sounds great and looks very nice. Good work on the manifold too. Pretty old school on the exhaust, cool. That should move an A coupe right along. Thanks for posting!

Beautiful! Amazing work!

Is that a simultaneous linkage on the 302 manifold?
I suspect the excellent response is due in part to the relatively small total CFM of all 3 carburetors compared to the large displacement.
Using a 235 Model B (1-9/16" throttle, 1-11/32" venturi) as an example, each flow about 140 CFM @ 1.5 Hg", or 420 total.
The demand of a 302 @ 90% VE and 5,000 RPM is about 433 CFM.

It's a progressive linkage , the out board carbs come in at about half throttle of the center. I dug through a box of b carbs and mixed and matched pieces until i got something to work. I'm sure I'll have some tuning to do once it's on the road.