View Full Version : 4 bbl carb
10-13-2007, 07:34 PM
I just got a holley 750 cfm carb and a low rise aluminum intake for my truck. Its a 390 with a stock 2 bbl carb and I was wondering what kinda extra work Im looking at besides putting the carb on. Ive been told ill probably need a new ignition because of the extra fuel but i really have no idea what else.
10-13-2007, 07:50 PM
An ignition upgrade is probably a good idea you probably have a points type ignition in it now and upgrading to an electronic ignition is just a good idea but is not "necessary" to put the 4bbl on it, it will work with the ignition you have now but what will be necesary to get the carb to work 100% will be to have the carb properly jetted and tuned, as it is out of the box it will be on the rich side which will work but not efficiently and that carb is also a little on the large side (CFM) for your engine since it is probably stock seeing as you are taking off a 2bbl to do this.
10-13-2007, 08:01 PM
My uncle had said something about putting in an msd ignition, new wires and better plugs and that should help with it being to big for my engine. Is it worth the money or should i try it without?
10-13-2007, 08:11 PM
It will work without an MSD box or equivalent, personally I would not by the MSD 6a or 6al I have seen way to many of them fail 3 of them in my old mans hot rod and it only has 2000 kms on it, the multiple spark boxes won't really help if the engine is too overcarbed (nothing will help this situation) and I find them a bit of a waste of money on an engine that is close to stock. My advice would be to see if you can get a stock electronic ignition out of a later similar engine I think the 429s are the same block (not sure on this as I am not a ford guy) and the factory ford dura spark ignition is a good system just make sure you carry an extra ignition box or 2
10-13-2007, 08:19 PM
My advice would be to see if you can get a stock electronic ignition out of a later similar engine I think the 429s are the same block (not sure on this as I am not a ford guy) and the factory ford dura spark ignition is a good system just make sure you carry an extra ignition box or 2
390's are the same block as 332, 352, 360, 361, 391, 406, 410, 427 and 428.
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10-13-2007, 08:21 PM
Yeah that sounds like it would be cheaper as im not looking to spend a fortune on this truck. Is there a way to limit the carb so its not overdoing it or am i gonna be lookin at a smaller one somewhere down the line?
10-13-2007, 08:31 PM
Just down jetting the carb, this should be done by somebody that knows a little about tuning carbs as going to lean is a lot more damaging to an engine than running to fat. A 750 is not WAY to big for a 390 cid engine just a little on the large side the worst you might notice when the carb is tuned would be a bit of bog from low rpm with snap throttle to WOT
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