Hey Crew, With the much appreciated help from FlatOz, Project Duals on the Half****ed Special is getting close to completion. I know the proper way to calcualate what powerr valve size you need is to drive around with a vaccuum gauge in the*****pit and see whats shaking. But my manifold isnt plumbed for such technology and I'm not about to break with tradition and do something properly. So, what are most people running in thier dual 94's? Motor is stock 8BA with offy heads and morar ignition. Carbs currently have the stock power valves but I'm guessing we'll need something closer to 3.5? Danny
I don't think there is 4.0 I have two 4.5 in my 59AB, bored, 3/4 isky cam, works good. BTW your setup looks nice. What manifold is that? And is that the hand drier scoop? How come nobody runs real air filters anymore?
Psycho, make sure your valves seal properly, late Holley and 94 valves are interchangeable, but not exactly the same. 3.5 or 4.5 is right.
hey guys, thanks for the sage advice. i'll prob go with 4.5's as a try. the manifold is a sharp super dual, sourced for a better then reasonable price from FlatOz. the heads are still do go on but they will be just plain bead blasted to match the manifold. FlatOz is lending me the scoops as well, not sure what model hand drier they are off lol. danny
They should work ok, as long as they are from a *vintage* hair drier! The new holley power valves have a bigger tip, so they won't seat into the older holleys. As long as you order them from a vintage carb place and not from a local parts house you'll get the right ones.
mate essendon is on tonight, bring the stuff there, should be right to go latter this week. see told you 3.5-4.5.
I took a die grinder to the inside of my 94's to clear late model style power valves. I've yet seen a power valve in a carb rebuild kit that had a marking on it. Using marked, and sometimes they're hard to read, late model style power valves ya' know what ya' have and can power tune accordingly.
I run 3.5's in my Merc Flatty. '51 Merc, stock bore & stroke. Unknown cam, Fenton 2x2 w/94's (duh). It runs great but runs outta 'go' at about 4,000-4,200 rpm. Really*****s gettin' on the freeway inn3rd or 4th and having it bog down just when she gets going. I think I'll try a 4.5 in the front carb and leave the 3.5 in the rear. I'm sooooo close!
hey guys, is it possible to get the later holly ones to fit properly? either modifying the carb or the power valve? living here in Oz its hard to get things like this reliably and cheeply. where as i can get later holley PVs all day long for $8. Danny
You can use a copper crush washer between the power valve and the bowl. I have the correct number around here somewhere, but I can't seem to find it right now. I thought it was discussed on the flathead techno source, but I can't find it. You can look around yourself in case I just overlooked it. http://www.btc-bci.com/~billben/flathead.htm
I'm running the stock ones that came in the NAPA rebuild kits. They were stamped 7.5, and seem to run fine for my needs. Some of the guys on the Ford Barn and some locals around here also run the stockers with no ill effects. Somewhat smaller probably be a bit more effecient. Some expert told me what the proper number theory would dictate but of course I couldn't find any of those!! Man, that intake looks good too!
Refer to my previous post. Also, I think I used a spark plug gasket (washer) when I installed my PV's. I do remember not using the gasket that came with the PV.
"Somewhat smaller probably be a bit more effecient" This is a common misperception with these things--the number refers to the vacuum level at which the valve opens. The Ford valve is not a metering orifice, it's just an on-off valve, and you will see them with all sorts of openings, from small holes to big rectangular windows. The actual metering is done at two cast in restrictions within the passages leaving the valve area up into the body. As with Holley four barrel 4160 types, changing power enrichment involves either drilling or inseting fine wires of known area to restrict flow. Usually stock is OK here. The underlying issue is that when a flatheads carburetion doubles, usually manifold vac drops off too fast, telling the valve engine is at full snort when it's actually only a bit off idle. The low number valves cause it to postpone opening until vac drops further.
Sorry to jump onto this post: I'm also running dual 94's on my 59 AB powered 39 Merc. I blocked off the power valves (which I though you were supposed to do with multi carbs) but the car runs RICH at idle- black soot on the plugs. Any advice on tuning/ settings? jay
Yep, you gotta run power valves. The ones that come in rebuild kits are usually rated 7.5, even if they arn't marked. If you've got a mightyvac you can see for yourself. The 7.5 is too high for a flathead with multiple carbs. I did try running dual carbs with a 7.5 in front, plugged pv in back. It was driveable and ran better than with a 7.5 in both carbs (it wouldn't run off idle at all like that). But after I put a 4.5 in both carbs it was just as drivable and felt a little more kick than with only one power valve.
Referring back to the original poster, there's an article in the current F.A.S.T. Magazine (for four-banger guys) explaining how power can be lost by having your scoops facing the front, and why. You'll be able to get one here www.hotforhotfours.com
Hey Crew, First hand experience here: On sat, FlatOz installed the duals on my ride. We had some hickups with the setup which we eventually over come. At the moment the ride is using 42 jets and stock powervalves and yes it runs rich, especially at idle. Even though, when you get on it, it runs like a*****d ape and certainly upped the fun factor by a power of 10! After speaking to RatBastard, the only true way to work out the power valve issue is to plumb your intake for a vaccuum gauage and run around seeing what your vac is like at idle etc and what it drops to at full throttle under load. According to rat, you go two sizes under the reading so if your pulling 6.5inches at idle, you fo to 4.5 power valves etc. Sound reasonable? Danny
Are you at sea level? I tried #46 jets in both cars, and it was too lean at speed. The car would buck and surge at 50 mph. I put the stock #51 jets back in and it's good. I could probably stand to go somewhere around 49-50 in both carbs, but I don't have a jet****ortment. On second thought, if your still running the bigger power valves, and it's running rich, it might be overcompensating for the small jets. So after you put the right power valves in, you'll have a lean condition, and have to jet the carbs back up to make up for it. Ask me how I know Hey, it's fun taking these old carbs apart over and over and over and over and over and over and over again, for me anyway I've been lucky enough to not strip any threads. I also bought a jet wrench from speedway so I won't have to keep taking the tops of the carbs off, and it works with the carbs on the motor as long as they arn't too close together. Well worth the $12. Has a big screwdriver head on the other end to take out the plugs too.
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