V-6 Head serial numbers

[atomman]

Trying to ID the application for this Sn; 23466811 with large valves, Magnum?
Have four of them. Also Sn: 243664--, the last two numbers are no readible.
atomman.

[bigblockv6]

I've got both Magnum intake and exhaust valves, here are the part numbers: Intake valve 2476368. Exhaust valve 2476374. the valves you have are much earlier part numbers, might be for earlier non Magnum 401 and 478 engines. I'll some of my parts books and see if those numbers come up.

[atomman]

Thanks. The Sn: is cast into the head, I don't have them apart yet. Just picked them up 2 weeks ago. Unpacking the crates.
atomman

[bigblockv6]

So those were the part numbers for the cylinder heads? again they are very early numbers, my 66 401 Magnum heads first year production are part number 2421158.

[atomman]

Attached are some pix showing the Sn: and valves in head.
Atomman:lolsmack2:

[bigblockv6]

The pic on the left shows the head with larger valves but the only way to know if they are Magnums is by the intake and exhaust ports. Gets some pics taken of the ports then I can tell you what you've got:ok:

[bobdylan]

4181

4182
Couple of pictures showing difference magnum vs. non magnum. Bob

[bobdylan]

Found an old post by BigblockV6 2/27/13 casting number for magnum head 2421158

[bigblockv6]

Yes I reposted that number nearly 2 hours ago:lolsmack2: Another part number used for Magnum heads in 1973-74 is 696030.

[bigblockv6]

I also like to point out that Magnum intake vales are 2 1/4 inches in diameter.

[bobdylan]

what size are intake valves on standard 351?

[bigblockv6]

The standard 351C used the same size intake and exhaust valves as the early 401 & 478 engines. The intakes most likely measured at 2.15 inches in diameter.

[Chuck78]

http://6066gmcclub.com/attachment.php?attachmentid=4225&d=1456445855

^^^^
Here's an attachment showing what looks to be all casting numbers of heads, blocks, & crank forging #'s. beerman posted that on a thread a few months ago, o e of his first posts on this forum (thank you!)


Here's the info relevant to my quest for a 351E/M or maybe a 401M, or else a Magnum top end (from a 432 or 478M) for my 305D:

All 351E, 351M, 401M, 432, & 478M came with Magnum heads, casting numbers are:
*696032
*2421158

351E & 351M 1966-1973 block #'s
*2476578
*695318

401M 1966-1973 block #'s:
*2457329
*2476579

478M & 432 engines will still have the same Magnum head casting #'s but will be much more industrial/commercial application engines, 8 bolt crank vs 6, not a passenger truck engine

_________________________________________
If it's not a magnum engine, here are the #'s:
351C blocks:
-2378091

401 60-66 blocks:
-2457329
-2476579

351C & 401 heads:
-2436646
-2436647
-2366811 (351C only)

[bigblockv6]

Some of the info is not quite accurate, later 401M engines also came with the 8 bolt flywheel and so did all 379 engines. Both 351C & 401M engines were made up to 1972, the 351E was dropped after 1968 and the 351M after 1970.

[TJ's GMC]

Not to hog the thread, but what size are the intake and exhaust valves for a 305E head?

[Chuck78]

Another thread diversion - if swapping the Magnum top end onto a 305 block, are the larger Magnum head and manifold intake ports going to cause less desirable low end throttle response?
Generally speaking, in the hot rod community, larger intake runners will give you the bonus of better high rpm operation in conjunction with a bigger cam and carb, but for a street engine, the larger ports will cause a bit of loss in the crispness of throttle response down low, as it takes a moment more to fill a larger port with air/fuel charge.
The larger displacement of the 351M would very likely offset this effect, but I was curious about the 305's reaction to a magnum top end, especially since we will not be revving these engines any higher than stock ever.

Can anyone confirm the success and behavior of a Magnum top end added to a 305????

[Chuck78]

http://6066gmcclub.com/attachment.php?attachmentid=4225&d=1456445855

^^^^
Here's an attachment showing what looks to be all casting numbers of heads, blocks, & crank forging #'s. beerman posted that on a thread a few months ago, one of his first posts on this forum (thank you!)





So I picked up this alleged 1964 351C that a member said was in the tilt cab series of GMC big trucks, L series I believe. I wanted to check casting numbers to verify it wasn't a 305. Well... These numbers aren't on that list at all! 2457328 is it.
2457329 is a 401. 2457325 is a 305. This 2457329 is not listed, and the right front pad shows no serial number like my 305D does. I will sand off the paint further to see if any remnants of a stamping remain. Can anyone confirm what this is exactly? Supposedly a 64 351, members here said big front cover and fan off crank pulley means from a tilt cab big truck

[bobdylan]

Are you talking about head cating numbers or block casting numbers.

[bigblockv6]

Chuck, just be aware that L series tilt cabs also were available with the 305C engine that had the taller waterpump just like other large truck engines.

[bobdylan]

Are the exhaust manifolds on 305c the same as 305e? Chuck's engine has beam style manifolds like the 351.

[Charon]

305c has the same manifolds as the 305e.

[bigblockv6]

Generally the 305C will have the I beam style exhaust manifolds.

[Charon]

I have 6 305c motors. Just pulled another from a 66. Everyone has the smooth manifolds. I will post some pics later.

[bigblockv6]

Charon, after checking several parts books dating up to 1974 it does support that "all" 305 engines came with the same part number exhaust manifolds which would be the smooth type. Evidently if you see a 305C with I beam manifolds they were replaced some point.:thumbsup:

[Charon]

Here. Is a pic of a typical 305c engine. This came out of a 66 4000 series truck. I have been breaking these down for parts. I have been finding a few of these that have been rebuilt. And everyone uses the .030 over 3 ring pistons. I have been using these to build a small supply of good used cranks and bearings. And water pump cores. Plus the bonus spin on filter housings. And two groove pullys.