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Old January 9th, 2019, 02:16 AM
bigblockv6 bigblockv6 is offline
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Default Re: 351 Identification M or no?

Quote:
Originally Posted by azcbass View Post
Hey All

I have been moving through upgrades on my 305E that's in the 66 GMC Open Road camper. New GM HEI setup, duel exhaust, Holley 500. Had to go to a 4.11 rear end because i couldn't find any other gear locally in AZ. It had the 4.57 or 4.56? The former was burned up on a long haul trip across death valley in July quite a few years back. I have the SM 420 trans. I still run 16.5 wheels (not splits) and the only tire i can find for those are Firestone 9.5R x 16.5.

The reason for my post today is to ask some questions on how to get some better performance on the highways. The main thing i'm trying to solve for are those slight inclines that go on for 5-15 miles at a time. I'm reduced to running in 3rd gear at 3000 to 3200 rpm which as i'm geared now i'm maxed at about 40 Mph. These hills are barely noticeable just steep enough to keep me from gaining any momentum in 4th at 2100 rpm which i drop into from a 3750-4000 RPM rev out of 3rd. I'm more than fine with running in 3rd or 2nd if need be for shorter steeper climbs. The reality of my situation is im driving a wind sail with a under powered engine and a gap to big to fill with current setup between 3rd and 4th gear.

So what do i do without a endless supply of cash and the strong desire to stay with these v-6's?

1. gear vendor? ($4000)
2. find magnum intake, heads and headers for the 305? (can i make a
305M?)
3. find a 351 or 401M? do a complete engine swap?
4. Brownie AUX trans?

I did find a 351 just down the street and went to take a look at it last night partially in the dark. here is the CL link to pictures and description:

https://tucson.craigslist.org/pts/d/...786164181.html

The intake manifold and headers did look different from mine. Its was in a 72 GMC 4500 40' long school bus. it looks in good condition and was retired with 40k miles on the clock. I would be very surprised if 140K+ were put on a 40' long school bus? Or is that not as unlikely as i think?



Let me know what other information i can provide to help find a solution or a way to identify that 351.

Thanks!

azcbass
Sebastian Lauber

1966 GMC Open Road Camper
The 351M V6 was actually discontinued after the 1970 model year and usually found in 7500 to 8500 series trucks, it's most likely a 351C.
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