Propane ???

The steeper the angle the better. You want the top of your bottles as high as you can get them. The last thing you want is to uncover the pickup tube in the tank when you are going uphill. Take a look at the tank cutaway photo and you will understand.

Also what do you have your timing set at? Propane has a different burn rate than gasoline so performance can be greatly improved by getting it right.

We have an electronic timing box that can correctly set the timing if you are using the Dura-Spark distributor since it has no adjustments.
It cost $150.00 and is made by Autotronics, the same company that makes MSD.

Let me know how I can help.
Buddy Gamel
Precision Sales & Service, Inc.
451 64th Place South
Birmingham, Ala. 35212

877-403-7827
205-591-2267, fax

[email protected]
[email protected]

I have not made any adjustments yet. I have had many projects going at once. Timing is set somewhere around 8 or 10 degrees if I remember right. I am running a 400 with flat top pistons back when dyna gear was in business. They made a set to bump compression to around 10:1 I think for propane. At least the pistons were originally designed with that intent from what I was told. When I put them in I just wanted more compression for the engine. The stock 7.9:1 compression really killed the 400. Anyways I run a comp cam 265 deh and my 3 key way timing set is set to the advanced 4 degrees.

Distributor is stock dura spark but I did do some modification. I do not use a vacuum advance any longer. Mine is all mechanical advance. I changed springs and messed with the weights until I got the advance to come in when I wanted it to.

I do have another question. Is there a recommended method for tuning the impco 425. I still have to set it up as well as the timing?

The mixer is pretty simple to set. Do not move the big bolt in the side. That is the power mixture and it is preset to the correct ratio. Leave the washer in the fuel inlet also. You only remove that for running on methane. The only adjustment is on the idle mixture(small screw). After the base timing is properly set, then set the idle mixture for the smoothest idle and last set the idle speed. If everything is correct the engine should start by turning the starter only and not touching the throttle. You should be able to stand outside the rig and start it and it settle into a smooth idle.



Buddy Gamel
Precision Sales & Service, Inc.
451 64th Place South
Birmingham, Ala. 35212

877-403-7827
205-591-2267, fax

[email protected]
[email protected]
www.alternatefuel.com

Awesome thanks!

I will keep the timing module in mind..

I just looked at your photos and noticed you have a "tamper resistant" mixer. You will have to use an Allen wrench to set your idle mixture.

Buddy

Yeah it has a place for 2 allen adjustments? It uses an 1/8th allen if I remember right. Are they supposed to be really hard to turn? Do they normally come set up fat. Should I lean first or go richer to start? I assume clockwise to lean?

79F150 said:

I have not made any adjustments yet. I have had many projects going at once. Timing is set somewhere around 8 or 10 degrees if I remember right. I am running a 400 with flat top pistons back when dyna gear was in business. They made a set to bump compression to around 10:1 I think for propane. At least the pistons were originally designed with that intent from what I was told. When I put them in I just wanted more compression for the engine. The stock 7.9:1 compression really killed the 400. Anyways I run a comp cam 265 deh and my 3 key way timing set is set to the advanced 4 degrees.

Distributor is stock dura spark but I did do some modification. I do not use a vacuum advance any longer. Mine is all mechanical advance. I changed springs and messed with the weights until I got the advance to come in when I wanted it to.

I do have another question. Is there a recommended method for tuning the impco 425. I still have to set it up as well as the timing?

Click to expand...

Comp grinds a 4deg advance in the cam. I was running a custom grind 4x4 extreme cam in my 400. Was told to advance it (dirt track guy said it was good for mid range). Truck run good but did not have the vacuum I thought it needed. Then I set it back to 0 and damn what a difference it made. Low end and mid range come to life with it set back at 0. Just my .02$

I hear ya and I always toyed with should I have or should I have not done it but I did. I have great power and I run about 11" of vacuum. The only vacuum devices I run is a PCV and a brake booster.