Hi Guys, The swap to a fresh set of NGKB4L's (gapped at .036) and a new set of leads seems to have fixed alot of the running problems my flathead was experiencing. Alot but no everything. At idle is still pops a little out of the exhaust and its running too rich - there is puffs of black smoke and it stinks like fuel. I've adjusted the idle mixture screws un till they are up against the stoppers at which point the motor will die but the black smoke etc was still present. It revs quite freely with no hesitation and no bog off idle but if you hold it steady at say 2000rpm you can notice a slight slight missfire... just a small drop in revs every now and then. There is no back fire and its only very slight but still there none the less (slight adjustment to timing?) I'm more interested in finding out how to cure the richness at idle. I dont want to stuff a new set of plugs by fouling them up! Specs: 2x 94's running 49 jets and 4.5 power valves. Carbs are running straight linkage and have been sync'd with a flow meter. Ignition is Mopar electronic conversion with Orange control box. Plugs are NGKB4L's gapped at .036 (mopar specs). Help? Danny
Probably your jetting or carb adjustment....I'll ask my buddy tomorrow....he knows Holley 94's/flatheads like no one else I know! He's put 45 jets in mine....
Wow. Could be a # of issues. Have you checked the float levels. Mechanical or electrical fuel pump? What size is the eng? Can you block off one carb and run one carb at a time to check?
sounds like your jets are too big, it will be a bit of trial and error, keep dropping jet sizes until you think its OK, try 47s to start with and go from there. make sure your float level is correct and your getting no more than 2.5psi through your fuel pump.
FWIW, I don't know 94's but I had a small block Ford do the same thing with a more modern Holley on it. It had a blown power valve. As I understand it the 94 has a vacuum power valve as well (I have never worked on a 94 so I'm shootin' in the dark here), if it can't be 'blown' like the modern ones, could it be leaking? Hope this helps.
My 2 cents is that this is a carb/fuel thing. Basically too much fuel. Sounds like the float bowls are flooding and constantly feeding fuel, which will burn a bit better at higher revs but not so well at idle etc. Float adjustment has to be right and a problem with this can be compounded by too much fuel pressure as already mentioned - it has to be pretty well on 2 - 2.5 psi or the needle/seat can' t cope and you'll get flooding. As I say, my .02 withoout seeing it. Good luck, it can be frustrating but also surprisingly simple.
if the carbs have been rebuilt make sure the power valves arent leaking. the new kits have the wrong sized power valves in them and they dont seat properly without modifying them or putting thick washers on them
I too would suspect the jet/powervalve size,. Every engine is different and Sometimes you just have to play with the sizes to get it right. Popping sounds.. Alot of popping can also attribute to a vacuum leak. But it sounds to me like you explained it as an occasional pop. Wouldn't hurt to check for a vac leak in the system. Intake or carbs is a good start. Your getting close... I wouldn't throw in new plugs right away. Try cleaning them while you play with the jet size. Get a small set of jets to start with. Instead of buying a larger size drill them out to the next size and try that.
Two sizes of accelerator pump squirters were used on the Holley 94's. The ID is stamped on the top of the squirter and corresponds to number drill size (the bigger number is a smaller hole). The #69 squirter is 0.029"D and the #71 is 0.026"D, a whopping 25% difference in area! If it looks like you can use a leaner shot, check to see if you have the big squirters and size down to the #71s.
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