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Joined: Tue Aug 23, 2016 10:38 am
Posts: 84
I am converting my winter beater 84 K10 to dual fuel with the use of a "sniffer" to allow me to burn propane. I have a fair bit of lpg experience having converted a few new 2000-2006 Chevy trucks to use newer systems that actually adjust off of the 02 sensor and my 1979 K30 rock crawler is a propane only set up now with a single impco 425 (460 cfmish) on its 454, some day going to 2 425s ( I have the parts and the tunnel ram but lack the ambition). This conversion will be low budget using 70s parts.

So I guess I am more interested in where to run the a/f cruising with propane. Because it is a gas it provides no cooling effects when the fuel vaporizes and most papers I have read from the 70s suggest running the system lean to prevent melting the exhaust off the vehicle because the fuel that doesn't burn during the combustion process tends to ignite in the exhaust.

I guess just wondering if anyone has anything to add. I know this is way less common that it once was but lpg here is at least a dollar less than pump gas so even with the loss of BTU, a 50% reduction in cost should lower operating cost significantly.

Tue Nov 01, 2016 9:42 am

Joined: Thu May 08, 2014 7:47 pm
Posts: 235
maybe this will help you.

AFR_LAMBDA_EN.PNG [ 15.38 KiB | Viewed 196 times ]
Tue Nov 29, 2016 1:13 am

Joined: Tue Aug 23, 2016 10:38 am
Posts: 84
well I have been messing with my truck for a few weeks. I am using a "sniffer" that allows dual fuel but will most likely only use gasoline again if it is an emergency or for some reason decide to drive my truck long distances cross country. Nailing down the timing with the current being all in by 2200 with 34 intial+mech and 44 with the addition of vac. There is limited control over the mixture but it is 17-16.5 at level ground cruising. The carb does seem to go to rich earlier (15.5-14.9) than a gas carb but I am unsure if the characteristics of a gaseous fuel are similar to gasoline under 3/4 throttle. Since there really is no fuel to vaporize I am not sure if the "super heated oxygen" has any bearing. The other fact is this carb is 432 cfm so it maybe going into power enrichment earlier. Still so far it runs nearly the same as it did on gasoline and isn't on the ragged edge of detonation like it was before. The 113 gallon tank makes it nice so I only have to fill once a week and lpg is just a little over a dollar here.

Tue Jan 10, 2017 11:01 am
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