Engine Run-on help. (dieseling) I promised I searched first.

[68gmsee]

Glad to hear you figured it out. Fun to own but they sure can be a pain sometimes.

[67_C-30]

Originally Posted by jorgensensc

Okay guys, I went back and checked for a 3rd time, but only because you guys are really knowledgeable. I did find one more problem, and I think I fixed the issue. It was the secondaries. as I watched it and I blipped the throttle alot, it would idle low and shut off fine. But the secondaries weren't opening up because I didn't blip it hard enough. So I blipped it hard enough to open the secondaries, but when i let off, the idle was higher than it was before the secondaries would open. So I got to looking at it after I played with the secondary linkage. The primary linkage wasn't forcing the secondary linkage all the way back and completely closing the butterflies. THe engine vacuum was keeping them cracked open. Their was a 1/32 gap between the two linkages. So I bent the primary linkage out a little bit so when it closed it actually closed the secondary linkage like it should. Now it idled back to low even after opening it up all the way causing the secondaries to open and close. That is why when I looked inside the butterflies appeared closed. With the engine running after the secondaries would open, the vacuum wouldn't allow them to close completely (very small gap). I figured this out by playing with the top butterflies on the secondaries. They are weighted and closed, but if I manually opened them, then the engine speed changed. Tat meant the secondaries weren't closed completely, so I looked inside and sure enough they were barely cracked. I pulled the linkage to close them and the truck idled back down. THat is when I noticed the primary linkage wasn't forcing close the secondary linkage. But after you would turn it off and the engine had no vacuum, the secondaries would completely close, then I would look inside and see them closed, start up the truck and it would idle low again. As long as I didn't open up the secondaries while driving the truck would turn off fine. If I really got on it and opened them up it would run-on, but upon restart, idle low. I know it is a long explanation, and I'm sure the engine build still has something to do with the run-on (I got the advance up to about 4 now), but hopefully all of this exercise in checking and rechecking will help somebody else out.
So the moral of the story is this. Make sure your primaries are completely shutting down your secondaries.
Thanks again for all of your help!
SHawn

I'm glad you got it going. The colder plugs would still be good idea since summer (in TX!) is right around the corner. You can probably expect a little shuttering (if not a little run-on) in the summer heat just because of the CR. Hot, humid air coming in the engine only magnifies the problem, but hopefully the colder plugs and running 93 octane will get her by. I would try to set the idle about as low as you can while still idling good. Being a manual shift will help in this regard since you won't have to worry about the RPM drag down that an auto causes when you put them in gear.

[Cunit69]

Thats funny you found out out it was the carb. All this time I thought was the 305 heads.

[jorgensensc]

Originally Posted by Cunit69

Thats funny you found out out it was the carb. All this time I thought was the 305 heads.

I know that was a jab and tongue in cheek, but if you read closely, it still was the heads. The truck still has to have the timing very retarded, High octane fuel, and the idle as low as I can get it. As stated above, due to the high heat and the CR there will still be some run-on in the hotter months. So I still stand by my response in the other thread that I think 305 heads are not the way to go and Vortec heads would be better. Thank you for the input though.
Shawn

[Cunit69]

Like I said in the other post I have a 350 bored 30 over with 305 heads, and have never had any problems with it dieseling. Due to the higher compression 93 octane is essential, and timing will need to be adjusted. My was also a daily driver for about 3 years and made many of road trips over two hours long in Texas summer heat, and never once dieseled. But you don't have to take my word for it.

[whiskeyman]

[67_C-30]

Originally Posted by whiskeyman

Wow. Informative first post!

[68gmsee]

He is just a man of few words.

Btw: welcome whiskeyman.

jorgensensc, would a good compression check would give you an idea of what's happening? I'm not into racing or stuff like that, but I would interested in knowing what the differences would be.