I have a 600cfm on my 306 in my 72 Maverick.. She is alittle rich when in gear at a stop ( loads up alittle bit ).. From all I read a 500cfm is really all I need for the 306 c.i.. So I bought one on ebay used that I could rebuild.. I don't know where this carb was stored at but sweet baby jesus it is disgusting.. Looks like a family of rats lived in the inside of the carb.. I'm sure you can but figured I would ask anyway's.. If I take all the internals of the 500cfm and put in my 600cfm.. I should therefore have a 500cfm, correct?? Thanks again for any insight..
Depends on what you mean by "all the internals". In any case, a 600 is not too large for a 306, and if it's idling rich, that's a tuning issue, not a result of being too large.
idling it is fine.. idling in gear is when it loads up alittle.. I guess I could tweak on the carb in attempt to line it out.. What I mean by all internals is the jets, primary and secondary venture's, metering rods, etc etc..
Someone more knowledgeable will certainly chime in, but I'm I'm pretty sure the venturis from a 600cfm will be sized incorrectly for a 500cfm. Jets (metering rods) too. I would try to make sure the 600 has the right size metering rods for your application, as well as float adjustment. A high float can cause flooding. A bad needle/seat assembly will do the same thing. Anyone who's read my posts here knows that I am against carbs that are too big for the application, but a 600cfm is definitely not too big for a 030-over 302.
Why not just buy a rebuild kit for the carb "500" you have? I run a stock Holley 600 on my mostly mild 302 w/o any issues; either 550 or 600 should work if they are setup properly.
I rebuilt the 600cfm I got and set the floats at 5/16.. I could rebuild the 500, but when I took the top off of it there was a 1/2 inch of crud in the bottom of the carb, and I guess I was looking for the easy way out I guess.. Might Take the 600 back apart and tweak on the floats.. In my opinion the 600 should work fine since I'm running 70 model 351w heads that have been ported and polished, cut out with bigger valves. And the cam I'm running is 515 lift 280 duration.. My best bet may be to adjust on the 600... And thanks as alway's guy's for the input. Helpful as alway's..
Chief Your 600 cfm is just fine for your 306 . You need to tune the carb . Go to the Holley sight for tuning info . My son and I did his 600 and what a change in the way the engine runs . He change the power valve , accelerator pump cam, accelerator pump discharge nozzle and main jet size . The way you described your problem it sounds like your power valve is the wrong size .
Sorry guess I was asleep, I noticed that little detail when I brought up the posts this time, going to delete my orig...
