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Old 11-13-2013, 12:49 AM   #11
Dave Noll
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Default Re: 2 bbl. Motorcraft & a dwell cam

OK, lotsa input, thanks. Timing is @ 36 initial & 42 total. I bought a box full of these 2 barrel's off E-bay so I have some spare parts. I took all the jets to work & reamed them to between .064" & .070" but I don't know what that would convert to in a Motorcraft jet #.

G.A. - I'm curious what your 2G measures in the venturi & throttle blades.

Ed - Yes it idles best with the mixture screws closed, with the spare parts I've got I might go close up the transition slot too.

Billy - Without giving away secrets, what #'s roughly should the cam have? (or just tell the grinder 6K ?) Going smaller cam would be more palleteable than all the really stiff springs thick wall large dia. pushrod deal. But I'm almost committed to the higher RPM deal at least convertor-wise. I spent the money & got a nice one that will stall 5200 if I get my tune/gearing where it's supposed to be.

When I got the car to the track this year, the motor ran into a wall @ 5800. With what the cam company told me about the profile & the springs I have on it I figured that wall was valve float. Opinion's on if it was the carb ? It's a 1.21/1.68.
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Old 11-13-2013, 02:09 AM   #12
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Default Re: 2 bbl. Motorcraft & a dwell cam

Be carefull with power valves in a restricted induction combo,It will pull manifold vacuum at wot and may effect power valve.The other issue with restricted combos is during overlap the high manifold vacuum will pull exhaust contamination back into combustion chamber,Valve seat and valve shape need to be designed to halt exhaust reversion contamination,also cam events are critical to control reversion.Bill C.
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Old 11-13-2013, 06:29 AM   #13
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Default Re: 2 bbl. Motorcraft & a dwell cam

If it idles best with the adjustment screws all the way in, I would try drilling the idle air bleeds. Also, you may have in your box of carbs a pair of smaller idle fuel restrictions. Having all those parts you could try either (or both) approach(s).

When you get it leaned down it will likely idle up and allow you to close the throttle blades, and cover the transfer slots.
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Old 11-13-2013, 09:51 AM   #14
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Default Re: 2 bbl. Motorcraft & a dwell cam

Just curious, but what CFM would the 2V carb be? I can't imagine a 2bbl Cleveland not pulling well past 6500.

Sean
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Old 11-13-2013, 10:06 AM   #15
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Default Re: 2 bbl. Motorcraft & a dwell cam

Quote:
Originally Posted by Dave Noll View Post
Forgot to mention that, It's already blocked (with a plug from a holley) & I have .066" jets in it.
Dave,
My Ford 2bbl stuff is away from here, is it possible the plug gasket is leaking some? Have 1/8" holes in blades, 1/4" seems plenty big to just about close the blades all the way. Did I read right it idles with the mixture screws turned all the way in? My current cam seems to require near full ign. timing, plan to change it to wider sep. Great info here
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Old 11-13-2013, 05:47 PM   #16
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Default Re: 2 bbl. Motorcraft & a dwell cam

Bobby, Yes you read it right. Idle mixture screws are shut. There's fuel coming out of the boosters @ idle , but with the 1/4" holes in the plates & the idle turned all the way up, that's a lot of air going thru there. I don't THINK I have a leak but I'll re-check.

Sean, This carb is 350 cfm. I know round track 2bbl. Clevelands regularly go over 7k, with a 4412 Holley. A while back I ran this combo on a simulation program & no matter what I tried, power fell above 6K but I figured we don't race computer's & blew it off.

Bill C., About all I can say on reversion control is the cam has 40 degrees overlap @ .050 & a 3 angle valve job.

JMark, I found an article that has the same illustration & saved the file, thanks. I may just weld the advance in the dist. & set it @ 40. Anybody have starting issue's there ?

Thanks for all the input guys.
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Old 11-13-2013, 06:32 PM   #17
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Default Re: 2 bbl. Motorcraft & a dwell cam

1 3/8v either 1 11/16or 1 3/4 tb(can't remember sure) same size as a 500 Holley
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Old 11-13-2013, 06:53 PM   #18
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Default Re: 2 bbl. Motorcraft & a dwell cam

Thanks G.A. for the input. Thats .165" bigger than my carb in the throat. Didn't think they made Rochester 2bbl's that big.
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Old 11-13-2013, 07:39 PM   #19
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Default Re: 2 bbl. Motorcraft & a dwell cam

[QUOTE=Dave Noll;408572]The lowest the idle will go down to is about 1600 which isn't the issue. To get that idle with that cam I have the idle plate screw down about as far as it will go. which has the transition slots completely uncovered & I have a 1/4" hole drilled in each throttle plate. With so much air going thru there @ idle it's pulling fuel out of the boosters. I closed the needle valves, lowered the float level, & drilled out the fuel inlet (seat) to .125. The idle is cleaner now but the plugs are still dark.QUOTE]

So, you have the idle screw turned in so far your bypassing the idle circuit and keeping it running by the fuel dribbling out of the booster. (poorly atomised fuel) To clean that up you lowered the fuel level and closed off the needles.
What happens if you lower the rpm, it starts stumbling/bucking because it's rich?

I would say open up the air bleeds to lean the idle mixture, right now if you open the mixture screws at all it sounds like unatomised fuel is dumping in causing the issues. Once it will idle down enough to cover the t-slots it will be more responsive to the screws.

Overall I think lack of vacuum is your main problem and opening the air bleeds will be a good band-aid. (also try reducing the idle feed restriction size if that doesn't do enough)

Oh, if you lock the dist at 40*, use a seperate toggle switches for ign/starter. Get it rolling over then flip the ign on, otherwise it will kick and break the starter nose off....don't ask, lol
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Old 11-13-2013, 07:46 PM   #20
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Default Re: 2 bbl. Motorcraft & a dwell cam

Just thought of something else, you have 1/4" holes in the plates, I wonder if this is too big and effecting the t-slots. What I mean is, since so much air is going through the plate instead of having high speed air going by the t-slots, I wonder if this is why the fuel is coming out in blobs instead of atomised, which caused you to turn the idle up, which made it worse, so you turned it up more, etc, etc?

Try plates with 1/8" holes and see what happens, you might get some vacuum back and it might clean up the idle so you can use the screws/lower the blade angle closer to the t-slots.
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