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View Full Version : How can you tell a 305 from a 351?

62cdan
September 24th, 2013, 02:27 AM
Hello Everyone!

Simple question for you V6 Pros...

I have a 1970 GMC 5500 Dump Truck/ Grain Truck.

It originally had a 305 in it, but the previous owner let it freeze, and cracked the block.
He told me, that, the engine that is in it now, came from a similar vintage fire truck, (w/ 22,000 miles on it). It runs fantastic, plenty of power, even in a big truck. A friend suggested that it may be a 351 instead.
Are there any identifying characteristics?
Thanks in advance.
-Mike
FetchMeAPepsi
September 24th, 2013, 02:37 PM
You can look at the serial number right behind the alternator/generator on the head. The head is the thing under the valve cover. the valve cover is where the oil goes in :D

Here's a pic. its probably covered in grease and dirt, but its there

http://windypix.com/?dm=2ND4.jpg (http://windypix.com/?pm=2ND4)
Foley
September 25th, 2013, 04:56 AM
It's fairly easy to find with Fetch's picture. You'll find a flat machined rectangular area with numbers and letters stamped into it. The first three numbers should tell you what you're looking for. :goodluck:
Ed Snyder
September 25th, 2013, 06:05 AM
Actually, it's BELOW where Fletch's photo points, on top of the block, in front of the head, not on the head.
FetchMeAPepsi
September 25th, 2013, 06:40 AM
Actually, it's BELOW where Fletch's photo points, on top of the block, in front of the head, not on the head.

Ed is right. It's below the head on the block but it sticks out below the head toward the front of the truck.

Sorry for the crappy advise. :( I barely knew what a gas cap was when I started this but as the old saying goes... ..."And now I are one" :lolsmack:

It's right around there though. It's probably covered in yuck though so scrub a little and it'll pop right out.
Funky61
September 25th, 2013, 06:01 PM
From Jolly's site
Foley
September 25th, 2013, 07:34 PM
Good job Funky61, and that'll sure give him what he needs, but if you have time, would you PM me about what kind of magic did you use to get that picture from Jolly's stuff, which is on this site now I think, over to where you could make it appear on this thread? Huh? Could ya?
62cdan
September 28th, 2013, 07:56 PM
Upon looking at the pad, it was clean enough to read, it is a 401.
Thanks for everyone's help.
I am not new to old trucks, just new to old V6 trucks!
-Mike
FetchMeAPepsi
September 28th, 2013, 11:17 PM
Upon looking at the pad, it was clean enough to read, it is a 401.
Thanks for everyone's help.
I am not new to old trucks, just new to old V6 trucks!
-Mike

And you're starting with one of the best there. nice find!

:goodluck: