trying to tune my new /6 engine

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firefighter1

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Hi guys,
I recently dropped in a rebuilt '64 slant 6 engine in my '71 dart. It runs, however does not drive due to the fact that I can't figure out exactly how to tune the newly purchased 390 cfm holley carburetor and timing in harmony. it starts up, but runs rough. I can't seem to get the idle down to the right rpm while keeping the timing correct. Any ideas or suggestions? thanks!
 
first set the valve lash, then set the timing with the vacume line disconnected and idle at 550-600 rpms(any faster and you will be advancing the timing by the wieghts in the distrubitor) then you can adjust the carb. in that order.
 
still having trouble tuning the /s any more details you can think of to help make this process easier?
 
i dont have much experience with a 4 bbl holley, but if you can tell what problems your having im sure someone will be able to point you in the right direction
 
you may have to open up the secondary butterflies, the carb will have to be pulled for this you will see the adjuster...it will take out some of the richness and allow the idle circuit to operate properly and as was stated adjust the valves 10 on intake 20 on exhaust after the engine has reached operating temperature......Wagg's
 
Make sure and certain you have a good base plate seal on the carb, check for vacuum leaks buy closing the choke slowly and see if it smooths out.
Spray WD-40 around the base of the carb and see if the engine revs up some.
Try screwing your mixture screws all the way in and see what happens
and get back to us.
 
Here is a great series of Holley tuning videos. A 390 should not be rich enough on even a stock slant to warrant cracking the secondaries. That's a pretty drastic step considering all the other adjustments those carburetors have. It's usually used to raise the vacuum signal on engines with really big camshafts. I'd be surprised if you really need to go there....but anything's possible I guess. Check out those videos. They should help if all is well with that carb. One thing I recommend different than the videos. Watch them first. You'll see that float adjustment is one of the last things they do. IMO, it should be the first. If the float adjustment is wrong, the very foundation for all the other adjustments will not be right. Good luck.

http://video.boxwrench.net/holley-carburetor.htm
 
StrokerScamp said:
One thing I recommend different than the videos. Watch them first. You'll see that float adjustment is one of the last things they do. IMO, it should be the first. If the float adjustment is wrong, the very foundation for all the other adjustments will not be right. Good luck.

http://video.boxwrench.net/holley-carburetor.htm
Click to expand...


Yes, the float adjustment should be made first. If it is too high, you will run rich. If it is too low, you will run lean and it will delay the fuel signal when applying the throttle which causes it to bog off the line.

I would recommend, first adjust your valves. Second, check for vacuum leaks from the carb to the intake and head. Third, make sure that your timing is correct. Fourth, then try adjusting the carb to see if you can get a smooth idle.

ps. Don't forget to adjust your accelerator pump to the proper spec. That will also cause an off line bog if not correct. Many people forget to do that.
 
thanks for the videos. i will try to play around with it some more. it's frustrating not knowing how to fix these little things.
 
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