503 engine

[Firefool]

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

[junkmandan3]

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

[studda]

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.

[Firefool]

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

[edpruss]

Originally Posted by Firefool

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

Posted via Mobile Device

[alsriv2]

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!

[Firefool]

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.

[Firefool]

More to come.

[Firefool]

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.

[Firefool]

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

[C10 - C90 Bill]

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

[alsriv2]

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

[Firefool]

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

[oily]

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

[Firefool]

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.

[oily]

Should be about 4.62 x 7.50.

[oily]

OOPS maybe 4.62 x 5.70

[oily]

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

[Firefool]

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

[oily]

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

[Firefool]

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

[C10 - C90 Bill]

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

[Firefool]

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.

[C10 - C90 Bill]

Lookin' Good !!

[oily]

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