300a on my 84 k10

Propane, Butane, LPG, GPL, C3H8, C4H10
Post Reply
Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

300a on my 84 k10

Post by Hillbilly » Mon Nov 14, 2016 11:09 am

I have done a few dual fuel systems on newer 02-08 Silverados and my 79 K30 rock crawler has a 425 on it's lpg only 454.

I was given some more lpg stuff the other including a 119 gallon tank, 2 Es, 425 and a 300A. Since my new job has me driving 90 miles round trip and in an attempt to slow the rust, wear and deer hits on my "good" truck a 02 K2500 with a 8.1 I would drive my rusty old 1/2 ton.

So I am going to convert my 84 K-10 to dual fuel. Currently the truck has a 383 with 180cc dart iron eagle heads, 9-1 compression, eps intake and 209/218 @050 cam. On gasoline is has a 670 cfm holley truck avenger I have modified with new metering blocks and air bleeds to make it have an main circuit (they don't have one from holley). The tranny is a 700 r4, gears are 4.10s and the tires are 33s.
I know dual fuel leads to a compromise in tuning but for now I want to keep it that way. Propane here has way less distribution centers willing to sell it as a motor fuel.

So I guess these questions are more about what will work more than what it the text book suggestion.

The engine currently has a 195 thermostat. It is an old dirt track refugee and was built loose so with a short piston for 6" rods and loose clearances it rattles like a diesel when cold and the hotter thermostat has lowered the rattle and helped some of the oil usage. I was going to use the return line from the heater so it will be cooler than thermostat temp. I plan on rebuilding it someday but It is at the back of about 30 other projects and this body might not last that long.

I was talking to my local lpg dealer, who I did most of the conversions for, he said that when they dual fueled their trucks in the 70s/80s they never used the mixer lift cam. Of course once they were on lpg those trucks rarely if ever went back to gasoline unless they ran out somewhere away from home or they were sold off at the end of their useful life. I have a new choke cable so I assume It would be good to employ the lift when on gasoline.

He also suggested I add a block heater for the super cold days. I bought one and even if it isn't needed I will welcome instant heat on cold mornings. After it sits all day at work though I worry about warm up time. If I drive slow for a few miles is this enough or am I going to have to wait 10 min in the parking lot on some of those -10F days?


C3H8
Posts: 995
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: 300a on my 84 k10

Post by C3H8 » Mon Nov 14, 2016 7:50 pm

Everything you said in your post is pretty accurate, however you don't indicate where you live. The -10 F is not a real concern. You shouldn't have to warm up the engine for more than a couple of minutes. It would not even have to be warmed up that long provided your not pulling out straight onto a highway and winding it up to 60 MPH. Just drive moderately after a short period until the engine warms up properly. The temperature difference to provide good vapourization is approx. 60F. The only thing that should happen is the fuel mixtures will tend to be on the rich side until the convertor reaches optimal temperatures.

I understand the desire to use the return line for the convertor but I'm not a real supporter of that. I tend to prefer the supply line. My rationale is simply that if a heater core begins to get blocked the convertor looses its coolant as the flow drops causing a freeze up faster then if it is on the supply side. The first indication of a blocked heater core is a cold cab or one that takes much to long to warm up. I would rather make it home in a cold cab then be towed home after freezing on the side of the road. Using the supply line provides a better chance of making it home if the heater core reaches a critical point.

Also, use the cam. A mixer on a carburetor becomes like a choke causing poor running at idle on gas and excess use of gasoline during the cruise and power cycles. You didn't mention if it is a 300 50 series or just a 300/20. The 300/20 is small for that engine, however it will function well unless it is pushed too hard.

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Mon Nov 14, 2016 8:27 pm

I have a 20 and a 50 is on the way in the mail. Putting it in the supply makes perfect sense.
I live in southeast Nebraska.

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Mon Nov 14, 2016 11:28 pm

I was thinking about what you said about the heater line. I wanted to put the vaporizer in the return to try and prevent over heating the propane, not so much a concern about heater output.

storm
Posts: 559
Joined: Wed Jan 10, 2007 10:10 pm
Location: NSW, Australia

Re: 300a on my 84 k10

Post by storm » Tue Nov 15, 2016 2:40 am

C3H8s point is if your heater is blocked coolant wont flow through the regulator.

If you are concerned about how hot the fuel gets use a cooler thermostat.

In Australia you must, legally there is no option, run the coolant lines in parallel. Heater in gets T'd off to enable a hose to be run to the regulator. Likewise heater out gets T'd to enable a hose from the regulator so the coolant runs through the regulator regardless of the condition of the heater core.
Every job is a self-portrait of the person who did it. Autograph your work with excellence.

Fuel flow requirements calculations viewtopic.php?f=5&t=1638

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Tue Nov 15, 2016 8:54 am

I fully understand the concern heater blockage could cause reduced flow though the vaporizer. I will be sure to plumb it on the inlet side and see if I can find a "H" to assure flow.

I found my second model E had a orange spring so that should be good. I soaked the E I am rebuilding over night in a 5 gallon bucket of water with scoop of dish washing detergent in it. All the dirt and grease came off easily with a tooth brush last night, with the exception of a couple heavy deposits that required a shot of carb cleaner to loosen them. Hopefully tonight I can mount my block off and vaporizer.

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Tue Nov 29, 2016 8:06 am

So I it running with a 1 & 20 off a old forklift bottle so I can go fill my in bed tank. I did buy a 50 & 70 off of Ebay and was initially sent a Feed Back 1 & 20 instead. I complained and was sent a 50 & 70 that is also a feed back but I had my local propane dist order the right fuel valve. This one must also be used because I see the small black disk that is on the top is missing. These are riveted on. Should I steal the one out of my current 1 & 20 and use a machine screw or just tape it over with tape to prevent dirt entry. I assume this allows for rapid air movement in the case of a back fire. Now that I have got this far I see that one of my gas tanks straps under the truck is rusted off. Tempted to just swap on a 425 and remove all the gasoline stuff, but I am almost done now so I hate to do more work.

C3H8
Posts: 995
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: 300a on my 84 k10

Post by C3H8 » Sat Dec 03, 2016 11:32 pm

That blows me away! :shock: I've been in the business 35 years now. I've seen that valve thousands of times. I have never once asked what it's purpose is or even checked the parts book until you just mentioned it. I've never seen a mixer where it had come off so I never even thought about it. In the parts book it is listed as a Riveted, vent valve. I doubt very much it is for backfire relief. I would tend to believe it is to relieve pressure due to a faulty regulator the would over pressurize the mixer above the diaphragm. The valve would relieve that pressure keeping the diaphragm from being destroyed. I do stand to be corrected on this though.

C3H8
Posts: 995
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: 300a on my 84 k10

Post by C3H8 » Sat Dec 03, 2016 11:33 pm

I wouldn't suggest tape. Tape will probably leak sooner or later and then the mixer won't function at all.

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Wed Dec 07, 2016 9:59 am

ok, I will just transfer it out of the 1 & 20 I have when I get it swapped on. Other than a electric block off that was doing odd things limiting flow and not opening despite "feeling" it open, the truck is running on lpg and doing fine. It does feel a bit soft up top but goes down the road fine. I need to adjust the tcc vacuum switch "latch" I had built for the 700r4 lock up to prevent the lock up yo-yo when you use a vac switch to stay on at a bit lower vac. I partially used this to prevent preignition at low speed high load on gasoline. I also need to fine tune the timing a bit.

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Thu Dec 08, 2016 11:12 am

So, I have seen the suggestion that when you have a Quadrajet that the secondary door spring adjustment may need to be a bit lighter than it would need to be when the carb is on gasoline. Do you guys see a similar effect with a holley vac secondary? I wonder if I should go to a yellow or similarly light spring.

C3H8
Posts: 995
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: 300a on my 84 k10

Post by C3H8 » Sun Dec 11, 2016 1:43 am

Clarify. Holley square bore or Holley Spread bore?

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Mon Dec 12, 2016 8:57 am

Holley square bore. Started as a 670 cfm truck avenger but has different metering blocks now to allow main circuit air bleeds which the it didn't have from holley.

C3H8
Posts: 995
Joined: Fri Sep 09, 2005 11:23 pm
Location: Winnipeg, Canada

Re: 300a on my 84 k10

Post by C3H8 » Tue Dec 20, 2016 2:48 pm

Little late but here is what I can offer.
Vacuum operated secondary doors can be a little touchy when it comes to modifications. Installing a 300 mixer on top can affect the opening of the doors and may require a stronger or lighter spring. It is mostly trial and error. Symptons can range from hesitation to a slow build in the power that does not match the original gasoline performance. This is the gasoline side that is affected along with the propane.

Hillbilly
Posts: 32
Joined: Wed Jul 28, 2010 2:12 pm

Re: 300a on my 84 k10

Post by Hillbilly » Thu Jan 12, 2017 2:28 pm

This engine is a starter killer and I finally got pissed over Christmas and tore of the inspection cover and transmission support rods and set the clearance on a brand new starter. While under it I notice is had a massive oil leak. I started with the valve covers but after pulling them is was obvious it was the intake rear seal. I pulled the intake and noticed it must have been pulling oil from the lift valley into the intake ports too. While it was apart I cleaned and lubed all the dist advance and put on a new cap and rotor. The holley has a purple secondary spring. I also installed my 300a 50. After finally getting the timing set to the current 34 intial+mech adv and 44 with Vac adv. I feel like I have a good base line of how it runs down the highway so I can slowly tweek it for highest vac at leave road cruising. Only thing that I am not sure of is pulling a hill at 5/8-3/4 throttle the mixture dips into the 14s. cruising in OD at 65 on the level it is in the 16-17 range. I have adjusted the WOT and is around 14.0-14.2. Runs better than it has in a while. Still need to do a few tweeks but it is doing the 90 mile round trip to work just fine.

Post Reply