1967 gmc

[dbrown1992]

Hi guys I have a 1967 gmc 3/4 ton long bed with the 305e and a th400, truck has power steering, power brakes and factory ac. I was just courious to see if the truck is rare at all?

[Funky61]

Welcome Dbrown1992;

Sounds like a nicely optioned truck; does it have the small back window?
Also curious if it has the support rods from the oil pan to the transmission?
How about some photos to share?

[BobBray]

I don't have any exact figures, but to give you a rough idea the 305E was probably the most common engine in '67 2500's. The Turbo 400 would be less common than a manual transmission, but many were built. Power steering and brakes make the truck a little more rare, but factory A/C in a '67 isn't too common. Is the truck a Custom? Does it have body side moldings and a large rear window? Chrome bumpers and grille?

[bigblockv6]

Though the 305E may have been the most common in 67, there are not that many around today. As usual many haved been Chivied with that ubiquitous small block V8. In 67 for the first time there was a large mix of Chevrolet engines in GMC Trucks such as the 230,250 & 292 inline sixes and 283,327 & 396 V8's along with GMC's 305E and 351E V6 engines. I would consider 1967-69 V6 powered pickup as rare today, it was the last of the breed of real GMC pickups.:thumbsup:

[bigblockv6]

Welcome Dbrown1992;

Sounds like a nicely optioned truck; does it have the small back window?
Also curious if it has the support rods from the oil pan to the transmission?
How about some photos to share?

A note on those support rods, if those trucks were not equipped with them there was a recall issued to have them installed.

[dbrown1992]

Funky61, it does have the small window, chrome front bumper and chrome side molding, we just recently picked up a good running 1965 305 motor and 4 speed with a Holley carb and Petronix ignition

[Ed Snyder]

Hi guys I have a 1967 gmc 3/4 ton long bed with the 305e and a th400, truck has power steering, power brakes and factory ac. I was just courious to see if the truck is rare at all?

Welcome to the forum! You'll find that Bob Bray and Pete Chronis (bigblockV6) are very knowledgeable about the V6 engine in general, and 1967 to 1969 V6 powered trucks in particular. The 1967 pickup is my favorite due to 3 things: the only year of the '67 to '72 series with the small back window, the only year of this series with no side marker lights, and the low profile hood it shares with the '68 models. I do, however, prefer the '60 to '66 style Suburbans.

That being said, I do agree that your truck with that combination of options is pretty rare and well worth hanging onto.

I see you're only about 180 miles north of me. If you ever get down this way, let me know when you're coming.

[TJ's GMC]

Whatever you do...please leave it stock!

[dbrown1992]

So I had a few questions about this truck, I put a Holley 500 on it and it uses a different air filter housing and there is a breather tube that was attached to the cover can I move it? And also does this truck have a crankcase breather filter in it?

[BobBray]

Usually, if there is a breather pipe to the air cleaner, the engine does not have a breather filter. The breather filter would be in a small can behind the left cylinder head.

[dbrown1992]

So can I block that hose if I run a breather on the valve cover?

[BobBray]

Should be O.K.. The PCV valves are under the valve covers, so you have to allow fresh air into the crankcase. Most V-6's have the can with the small filter in it behind the left head. On California 'closed' systems, the can was replaced with a pipe to the air cleaner. Later on (about '68 and up) the hole where the can or pipe attached was blocked off with a freeze plug and a breather was added to one of the valve covers, usually with a hose to the air cleaner. The filter in the can, pipe to the air cleaner, and breather on the valve cover all do the same thing: they let air into the crankcase.

[GMCNUT]

Should be O.K.. The PCV valves are under the valve covers, so you have to allow fresh air into the crankcase. Most V-6's have the can with the small filter in it behind the left head. On California 'closed' systems, the can was replaced with a pipe to the air cleaner. Later on (about '68 and up) the hole where the can or pipe attached was blocked off with a freeze plug and a breather was added to one of the valve covers, usually with a hose to the air cleaner. The filter in the can, pipe to the air cleaner, and breather on the valve cover all do the same thing: they let air into the crankcase.

Apologies for hijacking the thread but I have to ask Bob a very closely related question right quick while he's on this topic - Bob, since you know a lot about how these engines breathe, I think you can answer this question: the 305A engines have a road draft tube and breather caps in BOTH valve covers - if someone wanted to add the 305E type valve covers to a 305A (Plaid covers for example) then doing this would eliminate one of the two stock breathers because the 305E only used a breather cap on one of the valve covers - not both like the 305A. So my question to you is, would the 305A still "breathe" OK with only one valve cover having a breather cap?

[TJ's GMC]

On mine all I have is a breather on the cover. Works fine.

[BobBray]

Apologies for hijacking the thread but I have to ask Bob a very closely related question right quick while he's on this topic - Bob, since you know a lot about how these engines breathe, I think you can answer this question: the 305A engines have a road draft tube and breather caps in BOTH valve covers - if someone wanted to add the 305E type valve covers to a 305A (Plaid covers for example) then doing this would eliminate one of the two stock breathers because the 305E only used a breather cap on one of the valve covers - not both like the 305A. So my question to you is, would the 305A still "breathe" OK with only one valve cover having a breather cap?

Good question! The deal is that the early 305A's with a road draft tube did not have PCV valves. The air came in through the valve cover beathers and was sucked out through the draft tube. Considering that modern engine oil is a lot less likely to turn to sludge than oil was in the old days, you could probably get by with one breather if you change your oil regularly and don't have a lot of blow-by. I would periodically check under the closed valve cover to make sure you don't have a problem developing. Also, put the cover with the breather on the opposite side of the draft tube.

[bigblockv6]

What I would do is update the system to a 62 305D where one PCV valve was used that ran in back from the carburetor to the rear filter and eliminate the road draft tube.

[BobBray]

What I would do is update the system to a 62 305D where one PCV valve was used that ran in back from the carburetor to the rear filter and eliminate the road draft tube.

This would be the best solution if you can find the parts. Road draft tubes only draw the fumes out of the crankcase when the truck is moving.

Peter, what year did they start putting the PCV valves in the heads?

[bigblockv6]

I would say it was 1963 with the introduction of the 305E, I know the biggest difference between the 305D vs the 305E was the emissions equipment.

[GMCNUT]

Good question! The deal is that the early 305A's with a road draft tube did not have PCV valves. The air came in through the valve cover beathers and was sucked out through the draft tube. Considering that modern engine oil is a lot less likely to turn to sludge than oil was in the old days, you could probably get by with one breather if you change your oil regularly and don't have a lot of blow-by. I would periodically check under the closed valve cover to make sure you don't have a problem developing. Also, put the cover with the breather on the opposite side of the draft tube.

Thank you Bob - I wasn't sure what the negative affect might be if I did that. I have a nice set of plaids I'd like to stick on the 305A maybe, so might consider doing that after I get the truck painted.

[GMCNUT]

What I would do is update the system to a 62 305D where one PCV valve was used that ran in back from the carburetor to the rear filter and eliminate the road draft tube.

Pete, would the same positive improvement be the case if I were to use a 351C? I incidentally have a good one that ran great when pulled, but haven't had a good use for it since. Not sure you could get the GMC dealer to install a 351C as optional equipment in a 1960 1000 series truck or not - came out of a 1962 GMC 1000 series truck, and the dealer did replace the 305D that came in it from the factory with the bigger 351C at the time the truck was being bought, so might have been available in 60 too? Do you know?

[bigblockv6]

I can't see why they wouldn't have. Replacing a 305 in a pickup to a larger 351C upon request from a dealer was not to uncommon during that era. GMC did promote repowering all brands of trucks with their V6 engines including their own older trucks, dealers were set up to do conversions.

[dbrown1992]

Could I plug that hose if I run a breather on the valve cover?

[bigblockv6]

Your 67 has a closed positive ventilation system, plugging the hose is not a good idea you may build up too much pressure in the crancase system and the valve cover breather without a tube that runs to the air cleaner will not be adequate. It's not that difficult to come up with an attachment to the air cleaner. My 68 does not have the tube that runs from the back breather, I use a K&N open air cleaner setup but I have retained the factory ventilation system which uses a breather cap with tube to the air cleaner, modifcations were relatively simple:upyes: I will post a pic of the setup in another post.

[TJ's GMC]

Guess I need to fix mine. lol Been running just an oil breather and that's about it.

[bigblockv6]

What you can do is update it to the 68-74 style valve cover breather with tube, eliminate the rear breather/filter and just cap it off with an expansion plug. I'll post a pic of my 68 setup tomorrow when I get home.:ok:

[dbrown1992]

What type of motor oil do you guys like in the 305?

[TJ's GMC]

What type of motor oil do you guys like in the 305?

I run 15w-40 in mine year round. Seems to be fine. I think Straight 30 is the recommended oil though. Be sure to add some zinc in the oil to keep the cam from being wiped out. I plan to start running ZDDP.

[bigblockv6]

I too am running 15W-40 in my 478M but using Rotella oil which already has zinc in it:thumbsup:

[BobBray]

30w Valvoline Racing. Lots of zinc.

[Ed Snyder]

What type of motor oil do you guys like in the 305?

You'll find lots of previous posts on this topic in the archives. If you ask 10 different guys, you'll probably get 10 different answers. In my opinion modern engine oils are so much better than what was available 50 years ago, that you can't hardly go wrong with almost any oil now. That being said, a high zinc oil is definitely better than a low zinc one. My favorite is http://www.amsoil.com/shop/by-product/motor-oil/gasoline/z-rod-10w-30-synthetic-motor-oil/?code=ZRTQT-EA, also available in a 20W-50.

[bigblockv6]

As to the reply I promised on the breather cap used on 68-74, this is the basic setup GMC used in those years with the exception of the K&N air cleaner.:ok:

[TJ's GMC]

I'm jealous of the chrome valve covers and HEI. No fair. lol! I have the same style breather on mine...just doesn't have the port like that one does.

[bigblockv6]

It's not a 305 either!:poke:

[TJ's GMC]

It's not a 305 either!:poke:

Now that's just mean. lol I'm a get a 702 V12 for my 64 and put everyone to shame. LOL!

[buckholt]

I have a 305 v6 e and 4 speed transmission that came out of a 1967 gmc. Looking to sell it. 1000 for all or best offer. If interested call or text me at 9792045927. I'm located in bryan tx

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