GMC 305 V6, anyone out there?

[hannamet]

I haven't seen much reference to this uniquely GMC engine on this forum. Do any of you guys drive one of these? Mine is a 65 with the four speed. I just got it and want to start gathering information about these things. I've been to the 6066 site, which is a nice source. Anyone into these? Brad

[kamikazegmc]

i got one in my 63 w/ the 4spd.

[BobS]

I've got 4 trucks with V-6s, they're something just a little different!

Bob

[rwgregory]

I must have rocks in my head, but I'm on my second 3/4 ton GMC w/305 V-6 & 4-spd.
Owned a '65 for eight years and have been kicking myself ever since the day I sold it.
Just bought a '67 in March of this year and I'm starting to tinker with it. In a nutshell,
I think these were some of the coolest TRUCKS ever built. The amount of low-end
snort these engines produce is practically beyond description.
Brad, welcome to the brotherhood.
rwgregory

[speedking]

I heard it said the V-6 wasn't too good for mileage,but I borrowed a friends '64 with a 305 V-6 in it to go about 250 miles away to get an engine,and at 70 mph,it averaged 18 mpg.That ain't bad,especially after me getting about 6.5 pulling my trailer down from Idaho in my '57 GMC with a 347 V-8,at 40 mph. (scarey handling and 3 dead cylinders.) BTW-check your rear end ratio-a lot of V-6 trucks had 3.08 Post rear ends in 'em.

[hannamet]

The part about checking the rear gears is interesting. I was told it had a posi, but how do I know the ratio without pulling the cover off? Do they tag those rear ends outside the case? It's still sitting in the tall grass, awating an open bay in my barn. Is the 307 posi a "sought-after" item? Brad

PS it would be cool to have a unique thread for the 60-66 V6'ers. Probably not that many around. Has anyone ever converted one to 4x4? Brad

[BobS]

Brad,

4x4s were available with the V6 in all years that the engine was offered in light trucks. It was also available in the KV4000 4x4 and in NAPCO conversions to 4x4 or even 6x6 in the larger trucks.

Bob

[rwgregory]

Brad,
Your truck should have a Dana rear-end under it. Dana-60 for 3/4 ton & Dana-44
for 1/2 tons. All Dana rears came with gear tags attached to the bolts holding the
rear-end covers on. Now you just gotta hope that in the last 40 years nobody has
removed the cover and forgot to replace the gear tag upon reinstallation.
rwgregory

[hannamet]

Thanks RW, now I'm gonna go home and crawl under the truck and see if a tag is there. Do you know what "code" would indicate a posi? Thanks for the info. Brad

[rwgregory]

Brad,
If your truck is a limited slip, there would be two tags bolted to the rear-end cover.
One would be the gear tag,normally toward the bottom of the cover, and the other
one would say:"USE LIMITED SLIP GEAR LUBE ONLY". That one is normally at about
3:00 clock in the area of the fill plug. Of course that's hoping nobody has removed
the tags over the past 40 years! Then again you could always jack up one rear wheel
and see if it spins with the trans in neutral and the E-brake off...
Good luck, rwgregory

[hannamet]

Hey guys, I crawled under that thing and a tag existed on the drivers side about 9 o'clock. It's a bit redundant: it says 3.54 at the bottom of the tag and "46-13" at the top. Duh! Can't most folks divide 46 by 13? I thought it was kinda silly. However, no tag at 3 o'clock that I can see. Guess I'll have to wait a bit since it would'nt be fun pulling it apart where it's sitting right now. The driveline is off or I'd try the jack and spin thing. I'm glad it's got the 3.54 gears, it should do a bit better as a daily driver that I don't intend to do any heavy towing with. The driveline needs new U-joints; something I CAN do without moving the truck. Thanks for your comments. I'm really looking forward to getting this truck running so I can really check it out. Brad

[rwgregory]

Brad,
Now this is a longshot, but hear me out. Wouldn't a missing driveline do the same
thing as putting the tranny in neutral??
Just a crazy thought... I amaze myself at times.....
rwgregory

[hannamet]

Uh, DUH! I'm probably the kinda guy that should'nt be under there in the first place. At any rate, the second "tag' isn't there, so I'm pretty sure it isn't a posi. I will eventually take the cover off and look, when I get it inside. Any ideas about an aftermarket air filter? The OEM is missing, and I was wondering what others do with the stock V6 carb? I'd like to start by making this a short trip daily driver for my daughter, leaving everything stock and SLOW........ Thanks, Brad

[BobS]

Brad,

I've rebuilt one of the carbs and replaced another one with a Holley 500 cfm 2 barrel because the throttle plate was cracked. The Holley definitely runs better than the Stromberg. You can find more information on the swap on Jolly's site.

http://www.6066gmcguy.org/holley.htm

Bob

[rwgregory]

Brad,
Hope you don't mind me getting a chuckle at your expense, but I just couldn't resist.
As for an air cleaner, practically any aftermarket 1 or 2 bbl. air cleaner with the right
size hole should work. Just check out your local discount auto parts store & see what
they have. I'm in the midst of collecting the parts to do the 500 Holley carb swap on
my '67 so I will have a stock air cleaner available sometime in the not too distant
future. If you still need one somewhere down the road, maybe we could do some
"bidness". Good luck with your project.
rwgregory

[hannamet]

Are you guys going with a "new" carby, or are they readily salvaged off of a common vehicle? Not sure what I should look for. Sounds like the answer to me versus trying to make the single work. I'll read Jolly's stuff again, its been awhile. You can laugh at me anytime, I try to laugh at myself, but I don't always "get it?".

[BobS]

I went with new to eliminate some of the hassle of chasing down problems with a used carb. I bolted it on and it ran great.

Bob

[rwgregory]

Brad,
I'm also going with new parts only because there are many self proclaimed carburator
"experts" out there that can royally screw-up a perfectly good mixer. Personally, I
would only buy a used carb from someone I knew. FYI, I'm figuring a total cost of
about $300/325.00 for the complete changeover,(carb,adapter plate,air cleaner,
plumbing,fuel filter & misc. hardware). I've read good things about this swap, and am
eager to get mine done. Best of luck if you choose to go this route.
rwgregory

[hannamet]

I'm gonna go new as well. On another topic, is there something unique about the V6 starter or is it basically a chevy starter? Mine is AWOL, and I've gotta hunt one up. I haven't tried a Chevy starter yet, but I will if it will bolt on. Shimming or other issues regarding GMC startes I should know about? (My service manual hasn't shown up yet!). Thanks, Brad

[rwgregory]

Brad,
The only time I ever dealt with a V-6 starter was when the starter on my '65
grenaded on me. I had a local auto-electric shop in San Diego rebuild it for me at a
fraction of the cost af a new one. This was back in the late '80's and if memory
serves me well, the V-6 starter was unique. However, they were redally available but
they weren't cheap! As far as shimming, it wasn't necessary. It just bolted right on.
To buy one outright, you may want to try NAPA. They still list lots of parts for 305's.
rwgregory

[hannamet]

I was looking for the starter on Rock Auto and when I compared part numbers for a 1965 GMC V6 starter to a 1973 Chevy 350 V8 starter, they appeared to be one and the same. We'll see. I've got the Chevy starter in hand, so that would be a savings. Once I finish dismantling the 73, I should be ready to start putting the 65 together. Oh I love summer time! Brad

[BobS]

I think the starters are different, not sure though. I'll be back home this weekend and will compare the two, side by side.

Bob

[BobS]

The motors could be the same and I think a lot of the parts for rebuilding one will be the same but the noses where they bolt up are very different. The GMC is a lot beefier.

Bob

[hannamet]

Thanks Bob, guess I'm in the market for a starter, or at least a rebuildable core. Anyone have one? thanks, Brad

[Jakes-66-K10]

BobS, I am just picking up a '67 with a 351E V6. Sounds like you're the guy to ask for V6 questions. Just curious about part interchangability between the 305 vs 351. Is it the same block with a different crank/piston size?