Maybe a dumb question to ask but here goes. After making changes to my 390, I put a 4b Edelbrock 600 cfm and an Edelbrock Performer on this motor. It also has a new HEI installed with all new wires. Now, for the dumb question. How long do you warm these motors up in the morning before heading out to your destination? If I let it warm up 90 sec or so and idle down the street, then start to go, I sometimes get a detonation or a back fire. Once it warms up, all that goes away, All the adjustments have been made on the carb, and no vacuum leaks and timing is as far advanced as I dare go. All new parts. So, do you all let these motors warm up a while, or does anyone experience what symptoms I have at all?

 

It's all up to you. A minute or two isn't really enough. Five-10 would get it. But driving it warms it up faster. I just crank up and go easy the first mile or two. Then it's warm.

 

Many yrs ago like in the 80's, I was running a 4B Holley that, I got for 25 bucks.

It would spit & cough back and nose dive if trying to give it any gas to get it moving before it was some what warmed up.

But always had troubles with that holley carb no matter what, I did to it.

It found out that it came off a boat 455 Olds motor that the guys said they always had troubles with it.
I thought, hell, I could rebuild it and mostly rejet to correct it.

I even contacted Holly about what was happening to it.
What they said to try did not do any good, sold it on C/List.

Then bought a 600 cfm Holley rebuilt off the net from a rebuilder out of Tx. for $125.
free shipping

It's been about 10 yrs now and, I changed it over to manual choke and it's still runs great. with this carb, I can start up and go within a minute or less without any sputters or spitting back, it take the gas with no problems.

But, I still have the choke on a little to about 900 rpm..
Once a Holley man always Holley Man!
My 2cents.
Orich




It was manual choke but the carb was jetted almost lean

 

As 351 said, I'm 10 minutes down the road before I'm fully warmed up. Full choke to start and about half choke to drive till it's warmed up.

 

Sounds to me it's running lean when cold. Not quite enough choke. You need to adjust the choke unloader so the choke flap doesn't open quite as much after initial start-up. Next morning you get a chance take the air cleaner off. Have your drill bit set with you. Disconnect the choke wire. Start the engine and use the drill bits to measure how far open the choke flap opens to right now. To do this,one at a time stick the drill bits a little down the throat of the carb in between the edge of the choke flap and the wall of the throat until you get one that fits just right. DO THIS WITH WARM FINGERS SO YOU DON'T DROP THE DRILL BIT in to the carb. If fingers get cold...STOP. Once you figure out which drill bit fits that's your baseline. Shut off the engine and hook the choke wire back on. Now adjust the choke unloader so it opens the flap up the same as the next size smaller drill bit.

 

And if ya get lost then look in your manual that has all what Jeff said you'll find more details and a few picture figures showing how to do it.

Also check carb pump stroke linkage arm is in the right hole setting and depends what carb# per the settings. All this plays into ez morning startup & driving.

Orich

 

It only took my truck three - maybe four - minutes to get to operating temperature. I lived close to my school so I didn't want to always shut it off before it even got a chance to warm up. I'd always keep a constant 2,000rpm on my way. I do this in every vehicle with great success, carbureted or EFI. I did however find out post-teardown that I had a 195 degree thermostat in my truck which would have helped it warm up quickly.

 

195 is what I run as well.

 

I'd try cranking a little more richness into your choke.