Hello,
I recently purchased a Ford cam shaft part # M-6250-A312 (duration: 290 intake/300 exhaust
Duration at .050 in. cam lift: 214 intake/224 exhaust
Gross valve lift: .472 in. intake/.496 in. exhaust
Lobe separation: 107 degrees intake/117 degress exhaust
Peak horsepower rpm: 5,000
Peak torque rpm: 3,500
RPM range: 3,000-6,500)
I was told (By Down's Ford in NJ) that this would be compatible with my setup. I have a 1991 Ford F-250 with a 302 EFI engine, with a C6 Trans and 2200 rpm stall torque converter. I also added a Ford Motorsport mass air conversion kit part # M-9000T50. I had this part installed last week and I'm having the following problems: poor idle performance, stalling at idle and a slight hesitation on the bottom end,Top end screams like a champ though.
My question is, will the computer in the mass air conversion kit accept these new cam specs? Or do I need to get a chip made for the computer? Is there any other advice that you can give to me? Any help that you can give is greatly appreciated.

Thank you,
Jerry D

 

Hi Jerry,

A custom programmed chip will always help of course, as you will gain power and the engine will be properly tuned, but that alone may or may not make a significant difference in your case. Yes, of course I would recommend having us tune that engine properly, we always do in a cam change and just for the raw power gain; and, it's a good thing you converted to mass air, as it is much more tolerant of certain changes, camshafts being one of them. However, your problem may be a bit more involved, and need more than just a good proper tune, let's look at this a bit........................

You've got a lot of vehicle weight there, and additional load from the big tires & the lift, etc. You don't mention having installed numerically higher gear those 40" tires, which is an absolute must of course, with 40" tires you'd need at least 5:13 gears, and something around 5.56 (me personally, I'd want 6.17's with that much load & tire) would be more appropriate. With that setup and that cam, having even more stall speed in the torque converter would certainly help get it moving (assuming the required gear ratio change has been made), as you generally want the maximum stall speed, which is affected by how much power you're making, to be within about 500 rpm or so of the lowest end of the power band for whatever camshaft profile is being used, and that's *with* the gear ratio change. Without the gear change, no amount of stall speed will help much, and will just generate more heat.

You also don't mention if the camshaft was properly degreed in, was it installed straight up in the block, advanced, retarded, etc., so that should be among the first things to check, that the cam was degreed in or at least installed as per Ford's recommendation for that profile. From there, the amount of difference from original lobe centerlines, duration and overlap of course has an impact. You've got a dual profile cam there it looks like from the centerlines (and I'm not a factory 5.0 cam profile expert nor have I looked up that particular cam), so hopefully that is a cam whose profile is basically compatible with a heavy vehicle, the duration @ .050 doesn't look too radical, so it should be liveable.

Given that I don't really know the factory recommendation on that cam or how it's installed in the block or whether a gear ratio change was done to comepnsate for those 40" tires, it's really not possible to do anything more than just mentioning the basics as I have done, the things that really stand out as potential problems hurting performance, especially on the low end.

This is obviously have to be gone over in more detail, so if you'd like to give us a call, we can go over these things with you, get the rest of the details on your configuration & then give you an overview of what needs to be done to fix this, and just what can be done via tuning, etc.

Our contact info is below if you'd like to give us a call.

 

Jerry,

You might also want to take a peek in some of the Mustang sites. I know some have experienced idle problems after cam swaps and resolve the problem by drilling a small hole in the throttle body butterfly plate.

Seems logical enough. The added duration requires more air to fill the cylinders even at idle. I don't remember if they have experienced the low end hesitation you have experienced, so be safe and check it out first.

I remember reading that some of the aftermarket single throttle bodies on the Mustangs already have the hole drilled. You could be running into the same problem.

If you can easily remove the plate (s), it might be worth a trip to the junk yard just to find out.

 

Thanks for the input guys.
I think we may have done something wrong during the install.The cam should work for the setup i have,according to Downs Ford.
I'm just gonna have to start all over...i'll tear it down and put it back together.Hopefully i see something that we put together wrong.
I'll keep you guys posted.

 

Look for a vacuum leak. Check the condition of the rubber hoses. A Mass air system will stall at idle with a leak where a speed density will not, it will speed up. When you made the conversion you may have cracked a hose. 1991-2002 = 10years. That is a long time for a hose.

Regards

Jean Marc Chartier