Crate 350 is dieseling, idle is as low as I can get it...whafuh???

[mofugly13]

I put a Gm crate 350 in about 4000 miles ago. Sometimes when I shut her off, she shudders and wheezes. Not really the same "dieseling" that I've experienced with other vehicles where they run on after shut-off with a chug-chug-chug...chug. Mine sounds more like the last breath of a dying camel. Now, I've never heard the last breath of a dying camel, but I imagine it sounds like my K5 after I shut it off. It doesn't happen every time, either. Maybe every other time or every third time. It did this with the 327 I had in it before the swap also. The only parts I reused on the new motor are the distributor and the Edelbrock 600cfm performer carb. My idle is around 1100-1300. I have tried to turn it down but the screw is backed almost all the way out and is not even tuching the hoo-yah that it pushes on to open the throttle/adjust the idle. My timing is a 8*btdc and the motor runs good and starts good too. When I replaced the cap and coil on my dist I saw that the mechanical advance weights were pretty rusty. I guess I should replace those. Can I just use the Spectre brand weights that Kragen has on the shelf, or should I get some other brand? I see that they come with different sets of springs, which ones do I use? I also have a rebuild kit for my carb. Will rebuilding it help solve my high idle problem? /forums/images/graemlins/thinking.gif

 

[Confedneck]

try the rebuild, i see that your idle speed is kind of high, what about the idle mixture? the 2 screws towards the front of the carb on oposing sides..raise the idle up about to 1500 and back those screws out until it bogs down, then turn them in until the idle evens out nice and smooth, then adjust the idle speed down to where it belongs...try adding some more timing, maybe to about 12* or so at idle..

 

[NerdBoy]

One little thing that you might want to try:
Check your spring tension on the accellerator.
I have an Edelbrock 750 on my motor that didn't want to close all the way. I had to add some tension to the return spring to get my idle to settle down.
It's a shot in the dark, but it might be worth looking at.

 

[84_Chevy_K10]

Try backing your timing down a few degrees and make sure your choke is open all the way when the engine is warm.

 

[Shaggy]

If your idle won't drop below that then it might just be riunning real rich at idle. I run the same motor (different cam though) with the same carb. Adjust the carb for lean best idle using the instructions for the carb. You can DL the instructions at www.edelbrock.com. Dieseling is usually timing related.

 

[mofugly13]

Thanks for all the replies, fellas. When I put the carb on the new motor, I used the instructions to set lean best idle while using a vacuum guage. I did as best I could but I noticed that screwing the mixture screws all the way in and out produced very little change in the way the motor ran, or the vacuum. While messing with the screws I could only get the vacuum guage to vary by 1 or 2 mm Hg. That got me to thinking that it might need a rebuild. When I first bought it the idle was so high that if I let my foot off the gas while I was in drive the K5 would take off. There was n such thing as coasting to a stop, she just kept going. I bought two new throttle return springs and put them both on, that at least got my idle below my TC stall speed. /forums/images/graemlins/thumb.gif I guess I'll try backing the timing down a bit until I have time to rebuild the carb.

BTW Shaggy, what cam are you running? My 327 had a decent Crane cam in it, it had more balls than the crate 350 I have now. I want to put a cam in it but don't want to void the warranty. Running 33's on 3.08's, I could use good cam upgrade...

 

[y5mgisi]

Sounds like its time for a carb rebuild. Also check for vacume leeks. Dieseling (where the engine turns over a time or to after the ignition is shut off) is caused by to high of an idle or motor thats loose as goose