need help with my 305 v6

[Blakeman350]

So I started working on my 67 305 v6. I've rebuilt the card, new spark plugs, new fuel filter and cleaned the gas tank and put new fuel in it. Here's the issues, when I try to start it it back fires through the carb and then when it does start it will only run up to between 1500 and 2000 rpms. I also made sure to double check the vacuum line was hooked up on the carb. I didn't check to see if there was any vacuum before I shut it off. Aside from parts being hard to find and expensive I don't know a whole lot about these engines so a point in the right direction would be great.

[DreamRyder1963]

Start by checking the points. The points on my brother's new distributor were loose and causing similar issues. Also check out 60-66gmcguy.com. It's a good source of info and mods for these engines. Did you rebuild the factory carb or did you go with a new Holley?

[Blakeman350]

I rebuilt the stock stromberg. I'll check the points tomorrow. Thanks for the info

[DreamRyder1963]

Good luck. Let us know what you find.

[1972RedNeck]

Sounds like a spark problem. As said above, check the points. I'd throw a timing light on it too.

[Blakeman350]

So hears a little update. I replaced the points and condenser went to start it and now I have no spark. I got power to the + on the coil but no spark from the coil. It had spark before I replaced the points and condenser. Any ideas anyone?

[DreamRyder1963]

What did u set the gap on?

[Blakeman350]

.016

[DreamRyder1963]

I assume that you bought parts store points, probably a109p if they are BWD. These points double as v8 points and I found that they will only work with a smaller gap then what the V6s call for. I believe I set my brother's on .009

[Blakeman350]

Would the gap on the points cause the coil to not spark? This truck is the first thing with points I've ever messed with.

[DreamRyder1963]

How did you test the coil? I originally thought the coil was our problem until I changed it and the problem continued. The voltage from the coil is not always constant until the truck is running.

[Blakeman350]

I checked voltage at the positive on the coil with just the key on and then while cranking the engine. The voltage was good but when I pulled the wire off the distributor and held it to a good ground spot no spark. I guess autozone will test them for free so I'll pull in out a deal run down there tomorrow.

[Blakeman350]

And try resetting the points like you suggested.

[old Chevy guy]

If the points don't open or close all the way you wont get any spark from the coil wire. Turn it over with the cap off and see what the points are doing. if there working right you should see a spark every time they open, between the point contact that is. New points and condensers can be bad brand new .If it had spark before Im betting your problem lies there.

[old Chevy guy]

I had 3 of these motors, there's not a lot to them, its all pretty simple stuff, keep us posted.

[Blakeman350]

I'll try that right now and let you know. Thanks for the tip

[Blakeman350]

Looks like the points are opening and closing all the way but no spark

[flyingtim01]

Blakeman, have you cleaned the points? Most times new points out of the box have a machine oil haze on them to keep them from rusting on the shelf. A little brake cleaner will take care of it, or a points file. Or both.

[Blakeman350]

Turns out the points I bought were bad from the start, got new ones and we got spark. The truck starts and runs but still won't throttle up more then 1800-2000 rmps. Would the vacuum advance cause this?

[DreamRyder1963]

They engine red lines at 3200 rpm. It's a low end torgue monster like a diesel. How did it rev before.

[Blakeman350]

It's never throttled up right since I've had it but I changed the plug wires today and changed the coil and it reved up but real rough and lots of blue smoke the when it shuts down it won't start because the plugs are wet. So I adjusted the float but still it's getting to much fuel. Fix one problem and find another. Any ideas?

[old Chevy guy]

You said you adjusted the float did you check the needle and seat to see if there was some dirt or rust stuck in between there? Does you motor have the one barrel or the two barrel?

[Old Truck Man]

The timing chain on those V6 GMC,s is very long. if the chain gets loose it will cause the camshaft to be retarded. it will cough & spit run behind itself and not have much power. Grab the front crankshaft pulley & move it back & forth to determine how much slack there is in the timing chain. run a compression check. that 305 has solid lifters pull the valve covers and adjust the valves. check for a part opening throttle. V6,s are great for pulling loads. not a speed demon and use excessive fuel. they are pricey to work on. I like a 250 six better.

[Blakeman350]

Old chevy guy - I checked to seat and it was clear. It has a stromberg 2 barrel on it.
Old truck guy - I adjusted the valves already but I'll check the timing chain like you suggested. I have a 350 I'm in the process of building I'm just trying to get the v6 running right so I can drive it sooner. Thanks for the suggestions and I'll keep you all posted.

[Blakeman350]

I got a quick up date on my 305. I checked the timing chain and it seems to be tight there's no play in the crank shaft. I also checked to see were the rotor was pointing at top dead center which was right at number one. I'm going to do a compression check this week but I'm thinking it's something in the carb maybe a bad or wrong jet. I'm kinda running out of ideas with this one. If anyone has any more ideas let me know and thanks to everyone's help so far.