I have an '85 F250 4X4 with a 351W that is still stock internally. The additions have been an Edelbrock 4 barrel intake and an Edelbrock 1406. I have also converted the ignition to an MSD 6AL ignition module and an MSD Blaster 2 coil. I contacted MSD and ask them which distributor I needed for my application and they suggested an 8584 distributor. I purchased this distributor and installed it. I contacted MSD on how to select the correct advance springs for my application and I understood and followed their instructions and installed the appropriate springs, a small silver and a blue one.


Now for my question. MSD told me how to select the correct advance stop bushing but I really couldn't understand what he was talking about. I understand the purpose of the stop bushing and I know how to change them but I am not sure how to determine which stop bush I need. The idle timing is 10* BTDC and the distributor comes from MSD with a 21* stop bushing installed. MSD sent several choices of stop bushings but I'm not sure which one best suits my application. I would appreciate any and all help/instructions on how to determine the correct stop bushing.


On a side note I use this truck on the highway and off road as well as around town. I do pull a lot with it. About the heaviest thing I pull with it is a 16 foot trailer loaded with either an 8N Ford Tractor and a bush hog or a large 4 wheeler.


Thank you in advance for helping me with this.

 

The stop sets the upper limit correct? So with 10 initial and a 21 stop bushing you get 31 degrees total? You will just have to experiment with it, you are in the ballpark. If you do a search on the internet. some guys are running 34, 35, 36 degrees total. They experiment with it and run what gives them the most power for the combo. You could run more initial also. I used to run my engines at around 12 to 14 degrees initial. That would put you right at 33 to 35 degrees total with the 21 bushing.

 

Thank you Franklin I really appreciate your input. Would it be to my advantage, for determining the best stop bushing, to actually hook up to my trailer loaded and experiment with the stop bushings? I am just thinking by hooking up to my trailer I should really be able to tell the difference in the horse power change. Just a thought, your opinion please.

 

For the purposes of avoiding pinging, the trailer would probably bring that out more easily. If you don't want to use the trailer, then finding a long hill and pulling it in high gear will load the engine down also.

Basically you want as much timing as the engine will allow without pinging in the lower rpm ranges. That will give you the best power for the type of fuel you run. So you will be mainly advancing the timing till you get pinging, and then turning it back till you don't. This whole thing is somewhat of a lost art and can get complicated. They used to have distributor machines that would spin the dist and the guy in the shop could tune the curve of the dist with the machine, fiddling with the stops and springs without having to have it on the engine. That along with ALOT of experience in what the engine should have is what they used to do in the old days.

 

Thank you again Franklin. I have to move some equipment this week with this truck so I may go ahead and just use the trailer. I am moving the stuff from my house to my son's house so that will provide me with a tuning stop on each end of each trip, about 5 miles one way.


I agree it is somewhat of a lost forever art. Most everyone now want computer controlled everything. I suppose it is probably better that way but myself I still enjoy tinkering with the older style stuff. I have 2 8N Ford tractors I really enjoy tinkering with. I repair small engines for a little "mad" money and the latest newest thing to come out is a small computer to control the larger riding mower engines. You can't engage the choke nor will we be able to control the speed. ALL that can be do is starting and shutting off the engine and nothing more. I don't know how all it works but there will be no choke and no throttle cable/throttle control for the equipment operator to adjust. To me that sucks, I think I am smart enough to know how to operate the throttle of the equipment I am using.