503 engine
 

I have a 1956 Gmc 630 that has a rusted up 503 engine in it. Using scope to look in cyc's it has what I would call heavy rusting, have not opened motor up. Does any one know of any 503's still out there to be bought, or if any rebuild parts are still around, not even sure it could take a rebuild. Any info would be great.

Pm or email firemedfighter@hotmail.com

Thanks guys

Re: 503 engine
 

I'll be sending you a couple name and phone #s via PM.

Re: 503 engine
 

I'd like to hear a bit more about them as I'm new to the medium/heavy truck scene and am interested in the old motors that came in these trucks.

Re: 503 engine
 

Ok heavy haulers,

My 503 has all the machine work complete, all parts are at my shop even new .060 over pistons. Do any of you guys have or know where I can find torque specs for this engine. Any help would be great not sure how picky they are heck the rod studs/nuts are cotter pinned.

Thank you

Re: 503 engine
 

Send us some pictures please.
Haven't seen a 503 before. (Actually I have never heard of them)
Glad to hear you are pushing thru to get it running again!

Re: 503 engine
 

Sure thing ill take plenty on photos starting to put it together in the morning. I have some during tear down ill post them also.

Re: 503 engine
 

More to come.

Re: 503 engine
 

Motor was so locked up due to what we belive was parked with a bad head gasket 25 years ago plus. I had to remove upper block from lower with pistons and rods stuck in upper block. I then heated upper block with large torpedo heater then drove them out with sledge hammer, they would barely move even at that point.

Re: 503 engine
 

Shes going together dont have alot of time to spend on it but got some done today.

Re: 503 engine
 

Great work.

I have sure heard of 503's but did not know that they were the opposite of the newer 6's (Distributor Side vs Exhaust Manifold Side).

Bill

Re: 503 engine
 

I bet that engine is a torque monster.
Great job on the rebuild.

Re: 503 engine
 

I went down to the local market and found six coffee cans that fit my bore perfect here they are.

Re: 503 engine
 

Wow what is the bore and stroke?
Could you show a picture of the combustion chamber and any other head pics?
:metal:

Re: 503 engine
 

Bore is 4.620 not sure on stroke but I can find out. Hold on to your shorts oily, I should have time one night this week to put head on, head is all done just ran out of time. Ill take some head photos for you guys. I will tell ya one thing I should of put crank on a scale boy its heavy. Ill look up stroke.

Re: 503 engine
 

Should be about 4.62 x 7.50. :smoke:

Re: 503 engine
 

OOPS maybe 4.62 x 5.70

Re: 503 engine
 

OK found the manual. Stroke is 5 1/8"

Re: 503 engine
 

Hey Oily,
Do you have any torque specs for a 503:waah:

Re: 503 engine
 

Yup but will PM you as I dont know the copyright issues.

Re: 503 engine
 

I would like to thank Oily he has saved the day with some torque values, lets all give Oily a big thank you.:four:

Re: 503 engine
 

I believe it would be OK to post them, but Ellen would probably know for sure.

That 503 is one special engine with it's own unique sound. I remember that our neighborhood GMC "General" firetruck had one and I could tell when it was starting up and leaving the station just by the sound of it, before they got on the siren.

Bill

Re: 503 engine
 

Well boys thanks to oily our bottom end is done, rod studs are cotter pinned little challange with keeping torque specs in mind. Took oil pump apart cleaned her all out, timing cover is on as well as rear cover that holds main seal. We are moving right along.

Re: 503 engine
 

Lookin' Good !!

Re: 503 engine
 

How about some head pics. I gotta see the water jets for the exhaust seats. :)

Re: 503 engine
 

Oily you are gonna kill me we just got head on, pops was in a hurry tonight jr and him put it on when I was in other shop getting supplies I have no pic of the under side of the head I truely am sorry you helped me a ton, however I took some other pics.
Motor is rolling right along feels like its starting to pay off for all this work, I cant wait to hear this unit fire up ill post all of that, notice pushrod lenght its crazy. Rebuild has gone smooth compared to our tight race motors we usally are working with, only real problem wss finding parts. And guys from pan to valve cover any ideas......... 3 feet high.
Keep tuned in.