2 bbl. Motorcraft & a dwell cam
 

On my 351C 240hp combo, the cam that the grinder sent me dwell's @ max lift for 60 degrees. 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. :confused::confused::confused: Do I just live with that & jet for down track or am I just completely out in left field ?

Re: 2 bbl. Motorcraft & a dwell cam
 

Don, you may also have to plug the power valve and use larger jets. You may be able to use a lower number (maybe a 35?) Holley power valve. If you plugged it right now you may be able to close the throttle blades enough to cover the transition slots. You likely don't have enough manifold vacuum to hold the power valve shut.
They look about the same, but as many years, and as many Holley & Ford carbs I have rebuilt I never tried a Holley valve in a Motorcraft 2bl. I would verify the Holley valve will work. I would probably just plug it myself. May have to tweak it some to clean it up on the return road.

Good luck.

Re: 2 bbl. Motorcraft & a dwell cam
 

Forgot to mention that, It's already blocked (with a plug from a holley) & I have .066" jets in it.

Re: 2 bbl. Motorcraft & a dwell cam
 

What is your duration @ .050? Lobe sep? Cam grinders tend to want you to put WAY too big a cam in 2V motors. No sense in putting a 7500 RPM cam in a 6000 RPM motor.

Re: 2 bbl. Motorcraft & a dwell cam
 

Billy,
250 @ .050", 299@ .006", 105 lobe separation installed @ 103. Lift right now is .375" with the stock rockers but should be .407". They told me the cam wouldn't be the problem, the carb would. I protested a little cause it sounded big to me but they assured me this was a good one. (it's a Cleveland, run it like one).

Re: 2 bbl. Motorcraft & a dwell cam
 

Rochester 2G totally different but I would expose those trans slots play with the float level-need full timing at idle(On mine 39*) my cam is 260@.050 on the intake 107 c/l (installed to 106ic)runs good to about 71-7200 rpm ??? oh and would close these holes to about 5/32"

Re: 2 bbl. Motorcraft & a dwell cam
 

If your spark plugs are dark, I'm guessing it idles best with the idle mixture screws all the way in?

Re: 2 bbl. Motorcraft & a dwell cam
 

First rule of any engine combo, find the restriction, build to the restriction. You've got way too much cylinder head and valve area, lots of valve lift and as I recall way too little compression so you can't be giving up cylinder pressure with a big cam. You've got a 350 CFM carb that's not going to make power at any kind of RPM so why spin it up there? It sounds to me like that big cam isn't making any vacuum.

Re: 2 bbl. Motorcraft & a dwell cam
 

You need to figure out how to generate more idle vacuum so you can close the throttle blades up. The t-slots need to be covered or you will have a tough time getting it to idle without closing the mixture screws all the way, and even then it won't be enough. More initial timing might help, if you run a distributor with a vacuum advance using the vacuum to add timing under no load can help. If you find that you have all the timing it will stand, I would look at advancing the cam.

As a last resort, make the idle feed restriction smaller, drop it to the point where it's tolerable at idle and doesn't cause a stumble coming up on the throttle. Being a race car you should be able to find the happy medium. You can try to solder the restriction after measuring it, it's the small tube in the middle of the larger one in the booster cluster. You might want to get a spare to play with to do this. The other place looking at what I can find is there may be an idle down channel restriction, making this smaller
will help as well. Again these are last resorts, making more idle vacuum to allow the blades to close is your best bet. Here is a picture to give you an idea on what is going on.

Re: 2 bbl. Motorcraft & a dwell cam
 

i see alot of good input on your thread