A few questions about my new '69

[GeneralDisorder]

Hello everyone! This is my first post here - I've recently aquired a '69 GMC Custom Camper and basically this is my first american car, and first vintage GM, etc.

It's got a 350 with a Q-Jet. I went round and round with the engine and carb as the previous owners had really messed stuff up. They replaced the engine with one from a '79 van, screwed up the plug wires (6 and 8 were swapped) and then tried to tune the carb to run on 6 cylinders. It was a total mess - they had the carb apart and bent all the rod hangers, etc. They replaced the fuel pump with one that was putting out something north of 10 psi so when I got it running fuel would gush out of the primary throttle shaft and the accelerator pump and the black smoke from the exhaust burned the eyes.

I finally have all that pretty straight. In the process I had to make a new timing mark on the balancer, changed the timing chain, redid all the plug wires, rebuilt the carb, changed the fuel pump, removed/cleaned/painted/replaced the oil pan, etc, etc.

It's now running decent - timed at 4* BTDC, etc.

However - I have a fluctuation on my vacuum reading of about 3 or 4 inHg at idle. It's fluctuating rapidly between about 18 and 22 or so. I suspect it's only doing this when warm though I haven't had a chance to let it cool overnight and see if it runs right when cold now that I just finished fixing the fuel pump problem. I suspect a sticking valve when warm.....

I'm not that familair with GM small blocks, but I do know that when I had the valve cover's off this thing it looked FILTHY in there (bottom end looked alright when I had the pan off though). What to do? It seems to run good at times then sometimes I will hear what I think must be valve train noises as they do come and go. The fluctuating vacuum reading is accompanied by a roughness to the engine and a popping in the exhaust note through all RPM ranges.

I dumped in a quart of ATF hoping that might clean it up a bit if nothing else.

What would you guys do? Any flush products out there or are the lifters easily removed and cleaned? (I'm assuming it's got hydro lifters - I'm told most do?).

On to the second biggest issue - the main gas tank (and probably the saddle tanks as well) is rusty inside. I pulled out the sending/pickup unit and it's chewed. About half the brass float is gone......

Could the crap from the tank be eating the fuel pumps (causing them to put out high pressure)? I'm guessing it's not good for them anyway. I'm going to put a filter before the pump before I destroy the new one. Obviously I'll replace the sending unit but how about the tank? Will the rust stabilize if gas is kept in the tank all the time? It's near full now and looks clear. There's no rust on the outside and no leaks. I live in Oregon so rust generally isn't a concern here.

And what about the saddle tanks? Can they be cleaned and put back into service? At any rate does anyone know where to buy sending unit's for them? I'm pretty sure they suffered the same fate as the main tank.....

Thanks in advance for any help,
Rick

[usmcchevy]

No idea on the vacuum gauge but this may help you. From one of our site vendors.

http://www.gmcpauls.com/Tech%20Tips1.htm
You may need to scroll down to get to the vacuum gauge part

For the rust, in my experience the rust will be just fine.................. Until you NEED the truck or are showing off. Somehow that rust knows just when to let loose and screw your day all up. I'd bite the bullet, take the tank off and have a radiator shop clean it. Good luck

[GeneralDisorder]

Thanks for the link - looks like a good parts resource as well.

What does it usually run to have a tank boiled out? I know of a place that could likely do it (they dip car bodies and other nasty items), but I've never used a radiator shop in my entire career as a mechanic - radiators, coolers, and heat exchangers I'm used to replacing as opposed to repairing in my line of work as it's not often cost effective to repair them.

Rick

[txriverrat]

It should be cheap to have your tanks boiled out, I'd say no more than $20ish or so? That's what I paid for the last one I had done for a BMW. If they're not rusted too bad, you could try just pulling them and washing them out with diesel fuel. I've also done this on a few old tanks that were only mildly dirty.

[GeneralDisorder]

I got a new sending unit/pickup for the tank ($30), blew out the line from the tank to the pump, and installed a second filter between the tank and the pump. So now I have a fuel gauge (yahoo), and I shouldn't be having anymore fuel pressure problems.

I think I'll treat the tank with the POR-15 fuel tank sealer. It's like $75 for the kit and if it works I can then use it on the saddle tanks I'm thinking. Anyone have experience with this stuff? Seems like a good idea as it will basically turn the inside of the tank into a rubberized surface impervious to fuel and water. Even boiling it out or replaceing it with a new one won't gaurantee it doesn't come back someday but the POR-15 ought to make it better than new right?

It runs rough - down a bit on power, and I'm getting some blue smoke. I'm thinking valve job. Maybe all that fuel from the rich running burned some valves? What do you think?

Rick