gas vs propane?

I read the impco 425 bolts onto the qjet with an is that right?? How much you asking for the 425 and the adapter if ya have em???
 
I was trying to keep the qjet on it if possible...
 
I am running dual fuel on a 350 in my M715.

Carb is a quadrajet, 90 degree adapter on top of it, with a 425 mixer, and Model E vaporizer.

I am running an MSD ignition (6??, I forget), with an adjustable timing control. On propane, I kick it up about 5 degrees. On gas (gas/LP) toggle switch on the dash), I just cut timing back. (Timing control knob dash-mounted also, ignition box under the dash).
 
I caught this thread late but I went propane and I won't be going back. I love it. I run forklift tanks and I can go all day on 1. Some things to think about after what some people have mentioned is running a thief hose. A thief hose is good for when you run out. You can carry a small camp stove propane bottle and it'll let you idle out of the woods. Another option, is doing like I did and running a Y-hose. You can hook 2 bottle up at once. This also allows someone to put a full bottle next to your empty one and take some. Just open both the valves and the gas will equalize across the tanks giving you some much needed fuel :huggy:

also, to tune it, loosen the distributer so you can turn it. Disconnect the vacuum advance on it if you have one. Hook up a vacuum gauge to the intake and look at your reading. Advance the timing until you get max vacuum on the gauge. Lock it down at this point. When you turn it off and fire it back it should drag a little before it fires. My stock timing is something around 10-12. Now it's around 20. It takes a lot of advance. Also, I run a cooler sparkplug. Off the top of my head I can't remember the number but maybe someone else will chime in.
 
So would i need to switch ignition and get a adj timing control or can i run stock?
 
I've been running 10 degrees advance timing for three years and while wheeling it is fine but when I go to 3rd or 4th gear it lacks power bad so I bumped my timing to 15 degrees and going to see what that does. When you advance your timing to 15-20 or even 25 degrees does it have an adverse affect on the engine or any components of the engine?
 
After all ive heard seems i need to change manifold as well mine is the 140038 something and seen ppl saying its crap!?... What other carb will the impco 425 bolt onto was gonna try and get the setup the 4x4girl has for sale on here... And also is the valve what you set the degree on or is that just for a diff ign? Sorry to sound like a newbie im actually decent bs mechanic just never messed with pane except on yota forklifts lol
 
orangecherokee said:
I run an HEI. I've heard folks of running MSD. I don't think you need to change anything except that carb :lol:
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Guess my ole beat up Qjet dont tickle your fancy huh lol
 
4x4 girl said:
you have 2 choices on adapters. they make a adapter to connect quad to impco 425 if you can find one, which I may have. or put a alum. adapter on intake and convert to a holley pattern since a holley baseplate fits straight to a impco 425. I have 2 used kits if you need one.
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I plan to call you in a couple of weeks to get my set up.
 
Waterdog84 said:
Guess my ole beat up Qjet dont tickle your fancy huh lol
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I love quadra-bombs...



































at the bottom of a lake :lol:

I actually had a q-jet throttle plate I was going to use but it leaked like a sieve so I converted to the square bore and got a new plate from Jegs for $100.
 
Ha yeah im gonna look the carb over before doing this i could have a leak somewhere?
 
upnover said:
yes they do. I have not known anyone personally that has use this type system. It is easy enough to configure thought I would think. Utilizing a electric lock off for the pane, and a electric fuel(gas)pump, with an on and off switch. The draw back here that I see is that you need two different timing set ups to run each. I suppose a person could change it manually as needed. Not sure if there is something out there to tune the timing on this type set up from in cab so to speak.
The dual fuel set ups I have seen on line, basically has an adapter that attachés the propane mixer to the top of the carb, so either can be used.
Maybe not much help there, but, is all I know
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Went to Canada, Deer hunting a few years ago. They all have duel fuel switches in cab. All they do is flip a switch in the cab an never misses a lick. Dont know what all it does but you might get on Pirate an post up to get some answers. Alot of guys there from the Canada
 
Waterdog84 said:
Ha yeah im gonna look the carb over before doing this i could have a leak somewhere?
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air leaks. especially with an old unit you can get small vacuum leaks that can affect how the system runs and is tuned.
 
K im thinkin of buying a NEW Q-jet instead of rebuilding old one... lol I like the carbs i have the late 70's 350 with the 750cfm qjet and seems to be a good setup for the pane to run on if its in good working order... well see ill start a thread on this chebby when it warms up and i get started on it so you guys can give me hell about keeping my Q-bomb haha thanks
 
Waterdog84 said:
K im thinkin of buying a NEW Q-jet instead of rebuilding old one... lol I like the carbs i have the late 70's 350 with the 750cfm qjet and seems to be a good setup for the pane to run on if its in good working order... well see ill start a thread on this chebby when it warms up and i get started on it so you guys can give me hell about keeping my Q-bomb haha thanks
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if you have a fairly good carb you might try the throttle plate and see but I had trouble finding a square bore plate that was in decent shape. going with a new one will give you confidence that it won't be an issue. sometimes peace of mind is worth a lot. just to make sure we're on the same page, you know you don't need the whole carb, just the throttle plate, right?
 
actually NO was assuming the mixer bolted to the carb!!! So the pane mixer will send gas and pane ughhh im fighting with the roch for nothing lol
 
Do i have to have square bore carbs spread bore...
 
The Impco 425 Mixer will bolt directly to a holly square bore base plate. I am thinking in the 650 range. Not sure if spread bore plates are the same. I do know you can use the base plate and get an adapter from the Zone or Advance and it will work fine. They do make a adapter that will fit right on a spread bore quadrajet type intake. Those are nice because they have your vapor tube, or pipe coming off the side and not the front or back, no need for elbows.

Sorry don't know the proper names, but only leaks from the base plate might come from the throttle linkage rod that goes through the base plate to open up the butterfly's
 
Ohh ok i really feel like a newbie when it comes to this pane even tho its a extremely simple design... lol Ill look into the Q-jet plate so any auto parts store will have this adapter cause i would like to have the tubes out the side not the front honestly! I apprecaite the info
 
yeah you can get an adapter at Auto Zone or somewhere for around $13 if I remember right. Also Chip's correct. The rod that opens the butterflys can allow unwanted air flow if the plate is old and wore out. That's why I decided to go with a new one.
 
Waterdog84 said:
Ohh ok i really feel like a newbie when it comes to this pane even tho its a extremely simple design... lol Ill look into the Q-jet plate so any auto parts store will have this adapter cause i would like to have the tubes out the side not the front honestly! I apprecaite the info
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OK Let me clarify, The HOLLY base plate will bolt directly to the Impco 425 mixer. The Q-Jet will not. Using a Holly Base plate will put the vapor inlet to the front, or to the back. In a SBC you will have to put it to the front as it is just too close to the Dizzy.
The do make an adapter that will go between a Impco 425 and a Q-Jet base plate, but they are not easy to find.
Now, if what you have is a Q-Jet spread bore type intake, you will need:
A Impco 425 Mixer
A Holly baseplate(square bore)
and an adapter to go from a square bore to a spread bore(this can be had at Advance or AutoZone
As far as the vapor inlet for the mixer, it's no biggie. A simple 1" nipple(1" diameter X 1-1/2 inch long) and then a 90* elbow, and then another longer 1" nipple to get it out to where you want mount your Converter.
You will want to build some kinda bracket to hard mount it so it don't flop, for it's size, it's kinda heavy, plus it will have the liquid propane hose going to it, and also two heater hoses too.
Hope this clears this up
 
Yes thats great info sorry been reading so much into diff setups i believe ive confused myself i might go with the holley baseplate just to keep it simple im sure ill read into it more but from what ive collected from you all that seems the way to go cause im not really wanting to use my old plate simply b/c its old and i hate half assing something especially when it comes to my vehicles i appreciate you all explaining all this to me in detail tho...
 
Waterdog84 said:
actually NO was assuming the mixer bolted to the carb!!! So the pane mixer will send gas and pane ughhh im fighting with the roch for nothing lol
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You are getting mixed information in this thread, that's part of the problem. You are talking here about dual fuel (running both gasoline and LP). The advice of using a baseplate (throttle plate) on the 425 mixer is if you run straight propane, not dual fuel.

To run dual fuel, you need a carb (qjet or whatever), a 425 mixer, and an adapter that sits on top of the carb, that the mixer bolts to. The adapter turns 90*...the carb sits flat on the intake, the adapter comes up and turns 90* to the side, and the 425 (w/o a throttle plate) bolts to the adapter.

To run straight propane, you'll need a throttle plate (baseplate), and whatever adapter to go from it to the 425. I probably have a spare if that is the route you want to go.

I'll get some pics of my (dual fuel) setup and post in the next day or so. If I forget, PM and remind me. I *might* be interested in pulling mine off and doing EFI, if you are interested in making an offer, let me know.
 
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