Ignition timing

[75gmck25]

You need to first decide if you want to keep that K3500 as a heavy load hauler, or make it more of a daily driver truck.

HD pickup tires are usually listed as load range E, or in the newer specs a load rating of 120, 125, or higher. To keep the full K3500 load capacity of your truck, I assume you will need an HD tire, not a standard Light Truck (LT) tire.

You can go to tirerack.com to find the sizes tires you want, and then check the specs for the max load rating. You have a lot of 17” tires to choose from, but also check the recommended wheel width and match that up to the wheels you use.

 

[fnny6770]

What about 235/80/17 tires?

 

[fnny6770]

If I recall the rims are off of a 2012 Dodge ram 3500, and since the hubs were a little larger I had to buy the special shims to make them fit correctly but so far they're doing just fine.
As far as a heavy hauler, I don't know what I'm going to do at this point it was my dad's truck he bought in 79 ordered it from the factory as a camper special, it has rust everywhere but the looks don't bother me, but to have it capable of hauling heavy loads that would be nice cuz who knows when I might want to haul a trailer to go camping

 

[Craig Nedrow]

Good advice here. I adjusted my 454 advanced until under a big load it would start to ping, pre ignite, on the gas I used, in this instance farm delivered 87. I ended up at 36 degrees advance, where a loaded 10000 lb trailer with my foot in it did not preignite. W/o the trailer it was a tire shredder, so that is my experience. My engine was a 75 8:1. 4:10 gears, rv cam, headers, air gap intake Holly 750 A/F set at approx. 13.8 full throttle. 14.2 running down the road. Notice the smoke in front of the truck, can’t hardly wait to get my new engine in there.

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[74Blaze]

By my tire size calculation spread sheet.
235/80/17 with 4.10:1 rear and 1:1 final drive would result in 2600 RPM @ 60MPH.

Let me know what your proposed tire size is (if other than that) and I'll run those numbers as well.

 

[fnny6770]

With all this information is it recommended to have Porter vacuum on the vacuum advance or manifold vacuum?

 

[Ricko1966]

With all this information is it recommended to have Porter vacuum on the vacuum advance or manifold vacuum?

Manifold vacuum.

Timing & Vacuum Advance 101 -good article by GM engineer

www.460ford.com