My 66 F250 has a 428 with less than 200 miles on the engine rebuild. Here are the pertinent specs.

Camshaft - Holman Moody version of ford C3AZ-6250-AA solid lifter unit
Rocker arms - Ford adjustable
Intake - Ford aluminum C6AE-9425-H (Police Interceptor unit)
Distributor - Stock FE
Petronix Electronic ignition module with flame thrower II coil
Plug wires - 8.5 MM
Carb - Holley 750 single pump with vacuum advance
Headers - Ford Power Train Tri-Y
Compression is 10:1
Block is .30 over with oil passage modes and standard rebuild
Cruise-O-Matic trandmission with stock torque converter.

I added power steering and disc brakes. This included shortening the steering column to accomodate the longer PS gearbox. As a result of rebending the shift lever at the base of the steering column I'm now able to shift the COM transmission into
what corresponds to the second green dot on the column gear indicator drive with 1st-2nd and 3rd gear. Previously I could on shift to what corresponds to the first green dot on the gear indicator drive with 2nd and 3rd gear.

The truck accelerates quickly from about 30 - 75. However when driving in 1st gear (5-10) MPH and I give it a hard push on the gas pedal it starts to accelerate and then goes in to lull of sorts. I have not yet burned rubber with this truck. It seem like I should easily be able to do so in 1st gear.

I was thinking that the ignition timing might not be right or maybe the carb needs to be adjusted. I don't recall for sure, but I think the total ignition timig was set at 32 degrees BTDC.

I called a local mechanic with planty of FE experirnce and he said it could be that the timing is off or the carb needs adjustment. He also said he had experience with the AA cam in two 4 speed vehicles where he could rev the engine to the power band before taking off in 1st gear and suggested that since my truck has an automatic transmission that it might need a stall converter. I'm hoping that is not the case.

Also, on one recent ocassion I recently observed that when I tried to start the truck with the breather off (it did not start) and it had a fog or fine mist of sorts come from the top of the carburator. Mt guess is that it was the air / fuel mixture. I thought that might indicate an ignition timing problem.

I don't intend to use this as a race truck, but I believe that the current performance should be quite a bit better than what it is now. I'm interested in learing more about this from those of you who have experirnce with this type of issue.

 

It is possible the stall speed is too low, but I would check the distributor advance and kick it up as high as i could go...typically full advance in at about 2500 rpm. in leu of changing the torque converter, go with either lower gears or shorter tires (even if they are wider)

 

Beechkid,

Thank you for the guidance. I'll study up on how to check and adjust distributor advance. I know it is a vacuum advance distributor, but that's about all I know about it. Quite often when I work on this truck it seems I learn something new. That's part of the fun. As long as the learning is not too hard. If the distributor advance does not work then I'll look at other options.

Larry

 

Bump the max timing to 36° to 38°, 32° ain't enough. What gears do you have in the rear end? You might consider a more aggressive accelerator pump cam. There is a kit with a handful of cams available. If that doesn't work, you might try a 50 cc accelerator pump. If you have a tach, and you should have one, at what RM is the stumble happening at?

 

Bear,

Thank you for the recomendations. I'll work on advancing the timing to 36 - 38 degrees (how do you get the degree symbol on your key pad?). I believe the rearend has a 4:10 gear. The truck does not have a tach. Money has been tight. I'm back to work now so I'll go ahead and get one. One more thing, the truck does not have a kick down rod/cable. I've been checking into that too. I understand that Lokar makes a kit. I'll educate myself on the accelerator pump cam and accelarator pump.

Larry

Larry

 

Hold the "ALT" key down and hit 0, 1, 7 and 6 in that order.

With a 4.10 rear gear you must have something really amiss to make the engine stumble. My 1984 F250 heavy 3/4 ton with 460 (stock except for dist recurve an a reworked Holly 1850 carb) with C6 doesn't even stumble with 12,000 pounds behind it.

 

Bear,

Until this 428 I've never owned a vehicle with a performance or high output motor. This week was the first time I was able to shift it to drive where 1st, 2nd and 3rd gears are available. Having accomplished that common since told me that I should be getting better performance out of this setup.

I've not had the truck to the mechanic who built the 428 since I installed it in the truck last fall. It was a long block when I received it from him and I proceeded from there. So it is quite possible that I have a few details out of sync. He has never heard it run. He is about 75 miles away which is a little inconvenient. Maybe after the holiday I'll drive it down to him and let him fine tune it for me.

In the mean time I'll work on adjusting the timing as you suggested. I'll let you know how things progress.

Larry

 

Per Bear's advise I added a tachometer to my truck. I plan on calling Holman Moody to find out what the red line is on the AA cam. I believe it is 6500 RPM.

While I was in the process of checking/adjusting the ignition timing I discovered that the bolt on the distributor hold down was LOOSE. I was the last person to tighten that bolt too. I was glad to fimd this easy to solve problem. This had allowed the distributor to rotate to where the ignition timing was at about 10°.

I set it to 37° and then took the truck for a short drive. I punched it at about 5 MPH and she took off real fast and there was no hesitation from low RPM through all three gears. I did not watch the tach too see how high the engined reved. I was too busy keeping the truck on the road when she hit 80. My guess is that it reved to about 3500 RPM. I'll check this out again and watch the Tach as she shifts gears. I hope to order a kickdown cable/rod kit this week.

While in park the engine idles at about 950 RPM. My understanding is that with the AA cam it should idle at about 750 RPM. However, when I turn the idle adjustment on the carm any further to lower the idle the engine make a high pitch whistle sound. I assume it is vacuum leaking somewhere. I have not tried to trace it down yet.

I also borrowed a vacuum guage from a friend. My understanding is that I can fine tune the performance some more my using the vacuum guage. I'm going to read up on that next.

Last Fall for several weeks after cam break-in the truck produced a lot of blue smoke at the tail pipe. It was embarrasing how much it smoked. I attributed the smoke to the piston rings not being fully run in yet. This Spring and Summer It started smoking less and less. I attributed this to the rings matting to the cylinder walls. Today, when I reset the ignition timing to 37°, it started producing the blue smoke again at the tail pipes. The engine was rebuilt with non-chrome molly rings. My understanding is that it is common for these rings to need 500+ miles before they fully seat. I hope that is the case for this engine.

I replaced the speedometer cable cable last fall. I think it shows the truck speed to be about 5 MPH faster than it really is. I'll hopefully confirm that by comparing to another vehicle sometime soon. The engine was running at about 2600 RPM at when the speedometer showed 60 MPH. I feel much better about the engine performance now. I'll tweak it where I can as I learn how to do so. Thanks to all for your guidance!