Factory propane (LPG)

[drivethechevy]

Dang it has been a long time since I posted or even been on the site, so hello all
I'm hoping this inst a wild goose chase and someone has more info for me.
I know that there was an option in 72 to purchase a truck that came with a propane kit to convert to propane, being that I work in the alternative fuel industry and mainly with propane conversions I would like to know anything anyone can tell me about the factory option kits, could you get them 67-72 as an option, the RPO code if there was one, brand or brands of components found, pictures, gm information about the kits, I'm hoping to replicate the system or better yet rebuild original components but I need to know more.
Anything will help
If you have any questions about any components or how it works just ask I'll do my best to inform and help as best as I can
Thanks
Nate
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[givengold]

I posted a "factory" Blazer from Craig's List a couple of weeks ago. It was up in Oregon.

[SS Tim]

The '70 350 RPO is L56. Good luck on duplicating it though. The option was limited to internal engine mods. like valves and comp. ratio. It was delivered as a complete gas powered vehicle that was intended for the final conversion to be completed locally. So there is no specific turn key GM package to my knowledge. There might be some hints on hard parts in the parts catalog and there are LPG conversion suppliers in the Silverbooks. If you have an assembly manual try that to. The image is from the '72 pickup truck brochure (pg.11).

[drivethechevy]

Originally Posted by SS Tim

The '70 350 RPO is L56. Good luck on duplicating it though. The option was limited to internal engine mods. like valves and comp. ratio. It was delivered as a complete gas powered vehicle that was intended for the final conversion to be completed locally. So there is no specific turn key GM package to my knowledge. There might be some hints on hard parts in the parts catalog and there are LPG conversion suppliers in the Silverbooks. If you have an assembly manual try that to. The image is from the '72 pickup truck brochure (pg.11).

Thanks for the rpo code! I have the same 72 buyers brochure, I know that the dealership could provide the customer with the parts for the conversion if the customer decided they would convert the vehicle on their own. I know the company I work for used to do the conversions for people, if anyone has or can upload any pages of those books that would be a great help!
Thanks
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[drivethechevy]

Well I did some searching and I found some century parts book from 68 and 70 that listed part numbers for the kits they were selling for these trucks, I also found some information about what gm did to prep a conversion, SS Tim you were on the right track, the typical valve guides designed for leaded gasoline fuels would only hold up for about 20 thousand miles so gm installed harder guides, I couldn't find anything about any different compression ratios, but I did find mention of a different set of heads on the engine which may have bumped compression but I haven't found head numbers yet, also trucks with the propane option came with a slightly different distributor one that allowed for more timing advance that the standard equipment would. I'm still hoping to find some photos of component placement and any other info anyone can share
Thanks
Nate
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[ka_jd7and1]

I know that this is a slightly old thread but there is a '72 C20 in the junkyard that is set up for propane. Glovebox showed factory propane conversion. I can try to take some pictures if they would still be of use to you.
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[hcaz095]

that would be great... PM me if you'd like to email rather than post them here. Obv theres not much of a time concern, but I'd like to see it as I'm considering converting over to LPG with my engine rebuild (otherwise I'd swap for more modern equip).

~Zach