engine is dying.. help!

[70c10guy]

Hi all, so my cam swap was a success. After break in, she ran excellent. Day after I started it and drove it. Drove fine, later in the day I started it and it won't stay running after it fires up. Vacuum is around 13" and I also have a holley dp that I tried adjusting the idle mixture screws. I had to turn the curb idle up so it would stay running but when I reached 15" of vacuum, I couldn't get anymore so I slowly backed out the idle speed. And it just dies. This truck was just running beautifully and it still does! Just won't idle. And I have to drive with 3 feet. (t5 manual). Any help would be appreciated, thanks!

[aruss99]

Timing??

[toolboxchev]

Get her running, check for intake manifold leaks. Guys here know 90 percent of the time its not the carb. Check all functions of the distributor, everything.

This site is the most helpful bunch I have ever run into. They are awesome!

[70c10guy]

I just put the truck back together, timing is set to 10* btdc vac advanced disconnected and once conenected it idled fine. But now with everything untouched it won't stay running, how could this be? I literally was just driving it.

[rsgt]

Is your vacuum advance hooked to ported or full. If it is on full try the ported and see if it will stay running.

[70c10guy]

It's on manifold and it's been on manifold!

[70c10guy]

That would just retard the timing which will bring the rpms down even more if I did have it running, iive tried it before and it ran like crap and ran hot as well.

[Gromit]

Sounds like your vacuum advance is adding too much advance at idle - at 15 Hg it is maxing out - probably at around 26 to 28 crankshaft degrees BTDC (plus a couple since there is likely no bushing on its pin)

Crane sells a limit plate (part 99619-1) but I just make my own and pop rivet them on.

This is all if you want to use manifold instead of ported vacuum.

I just set the stop to limit vac advance to 8 degrees; which is .086 of travel from the vac advance

http://www.nastyz28.com/~copo/distributor.htm

If you get the Crane plate ($6) I'd recommend following the way the z28 guy installs his - note it is on the other side of the pin than the Crane instructions show.

[hamjet]

If it ran and idled fine in the beginning and now it won't idle but runs fine after the RPMs are up, "I" would be looking at the carb for plugged idle circut.(DIRT).. once the RPMs are up it goes into the power valve circut and thats why it runs fine. It does'nt rule out a vacuum leak.. First I would bring the idle back up and spray around the carb base.. If it does'nt run fine with the RPMs up then forget everything I stated, then I don't know what I'm talking about...LOL

[CC69Rat]

What type of fuel pump are you running on it? Is it still the original gas tank? Has the tank been cleaned? How long was it run this way before you started the cam swap, carb, etc? Daily driver or was the truck sitting for a while?

[70c10guy]

I just rebuilt the carb on it but I will try rebuilding it again and see what the culprit is.. fuel filter is a couple weeks old, sock in the tank has been cleaned, it sure does sound like fuel issue because it runs fine when cruising highway. The truck is and was a daily driver and I put top tier fuel in her. Fuel pump is also stock replacement type

[geezer#99]

Originally Posted by 70c10guy

Hi all, so my cam swap was a success. After break in, she ran excellent. Day after I started it and drove it. Drove fine, later in the day I started it and it won't stay running after it fires up. Vacuum is around 13" and I also have a holley dp that I tried adjusting the idle mixture screws. I had to turn the curb idle up so it would stay running but when I reached 15" of vacuum, I couldn't get anymore so I slowly backed out the idle speed. And it just dies. This truck was just running beautifully and it still does! Just won't idle. And I have to drive with 3 feet. (t5 manual). Any help would be appreciated, thanks!

What rpm and how long was the cam broke in for?

Otherwise it's timing related.
What's your initial timing and have you checked it yet?

[Skinny Kid]

I wouldn't immediately suspect the carb. If I have done a major repair and then something goes wrong it almost always directly related. It's very rarely coincidence that something else goes wrong. Go over everything you did carefully and eliminate all of that before you move on with the diagnosis.

[KY_GMC]

I had this same issue with a new engine and carburetor rebuild.

Turned out that the hold down clamp was not keeping the distributor in place. I would set the timing, take if for a few runs, and then I had to limp home to find out the timing moved.

Spent yesterday revising the hold down clamp to make it hold better. So far, it is holding.

[70c10guy]

Sooo... I figured it out! I checked for vac leaks and nothing. So I went straight to the carb. I took the bowl and metering block off and it was full of crud!! I can show pics but idk how to post em.. but you get the idea! Thanks all for leading me into some possible problems. Now I know what else to check in the future! She idles strong and holds timing at 12*btdc with no pinging whatsoever. Adjusted the mixture screws on the carb and holds 15 in hg at idle. Thanks guys!

[aruss99]

Glad you got it fixed!

[Boog]

Glad you figured it out. You need a better filter between the pump and carb.

[leftybass209]

PO of my truck wasted a bunch of money replacing the manifold and carb because it wouldn't stay running, same issues you've described. When I dumped the tank it looked like a rusty muddy sandbox, no wonder

I LOVE forums for getting good info out quickly. Unfortunately not all info is good info! Glad you got this sorted out!

You may want to give your tank a good look-see. The filter can only do so much and carbs are finicky little creatures. Also make sure you have a good metal line running from pump to carb, and that any rubber fuel line you do have is in good condition. I pulled several black specs of rubber from the fuel pump, and out of the idle circuit of the carb. Fuel was slowly chewing up the parts store fuel line the PO used.

[hamjet]

I figured it was the carb the way you were describing it, good fix..

[67ChevyRedneck]

Great you found it, but thought I would also mention, since you're using manifold vacuum, to make sure you're unhooking and plugging the port when setting initial timing.

[70c10guy]

Yes I'm glad also, glad it wasn't major. And yes I am plugging advance to set initial! I need a good filter.. any recommendation?

[Gimme Jimmy]

Check your intake Manifold gaskets. There may be a huge vacuum leak.

[CC69Rat]

I would suggest draining and pulling your gas tank out. I know it's a lot of work but there's obviously a bunch of crud in the tank. It's just a matter of time before this happens again.

If you pull the tank wash the inside out really good. We usually use a long piece of chain to drop down into the tank and let it bang around on the sides and bottom.. (one person on one end, another person on the other end..pick it up and rotate from side to side etc) you'll be suprised at what comes out of the tank.

That's why I asked earlier in the thread how long the truck sat before you got it. Old gas breaks down, the inside of the tank can rust and just over time trash collects inside the tank. Then you start driving it again and the crud finds its way to your new carb, fuel lines, fuel pump, filters, and starves the truck for fuel.

Just my opinion until you clean out the tank, or just go ahead and move it under the bed and get it out of the cab if that's the case.. this will happen to you again. 69 Camaro gas tanks work very well in our trucks you just need a flip down tag bracket.

New tank, new lines, new filter would be my approach. Just my .02

[70c10guy]

The truck didn't sit before this! When I removed the intake I took the intake and carb off together and I dosconnected my fuel line right before the filter. All the crud from the filter was fed into the bowls because I had the filter higher then the carb when I was taking it off the truck!

[CC69Rat]

Rgr that.