timning on propane

working on a 520cube big ford, 14-1comp, steel head with 2 propane mixers on tunnel ram. Installing msd setup and looking for timing specs as i am not used to propane performance setups

What is the application? Not sure that 14:1 is safe with propane or not, that seems like a lot of squeeze. I have heard of 12:1 stuff on propane and kind of thought that might be a little over the top. If you are using the IMPCO 425 mixers, I wonder if that will be enough for that many cubes?

its in a weekend warrior 4x4 with 44 inch tires. It worked well with the duraspark but water in the ignition was always a problem so now i go msd

If it was working fine before with the Duraspark, I'd just time it the same way with the MSD.

I dont know where the timing was set before as i never worked on the engine before, my general question would be - does timing change between propane and gas in the same combination?

Read the plugs and time accordingly. Timing can be different with different combo's, and can be the same with two different deals. Most iron heads like to be about 32* total for a performance application, and you can use that as a baseline to start, but defenately check the plugs and adjust accordingly.

You can usually run more timing with the propane then gas but I have never ran it with that high of compression before. The most I have seen was about 12.5:1.

When I ran my 10.5-1 460 with dual 425 Impco's I know we got all the timing in by around 2000ish and I think limited it to around 30-32 ish can't remember. I do remember that to get good power for trailer pulling we had to richen up the mixers which actually lead to 2 melted pistons. Propane seems good up to a certain RPM (4000ish) and then acts different than gas(could be the way the vaporizers work). On the rebuild I backed the comp ratio off to about 9.3-1. I have lately ditched the dual 425's(sold them) and went with a technocarb rated at about 750 cfm.

Heres the link,

http://www.technocarb.com/index.php?option=com_content&task=view&id=26&Itemid=84


FWIW Mark

PS: I might have to stop by your shop in Edmonchuk & visit.

Thanx everyone. Mark, after talking to my machinist today he told me exactly what you said. Set the timing, ran it for 20 minutes and it overheated!!! Now what is the problem! Some days you just cant win. P.S, come by for a visit anytime Mark

x2 on what Mark said regarding timing - all in early.

Run it rich and you will melt things.

If you run it rich and it begins to detonate, pull fuel - not timing.

well found the heating problem, customer plugged the rad with mud on the last outing and never washed it! As far as timing, silver springs installed, timing 13 at idle, 27 at 1700 rpm, 33 at 2100rpm. If he blows it up now hes on his own!!! Thanx everyone