Propane Help

BPetty · Jun 17, 2016

I also need some help with propane, I have a mild built sbc 11.5 to 1 compression and custom grind cam for propane. I have a 425 mixer, e model evaporate and it just seem to run out at around 5000 rpm. Wanting to know price of stuff I need to go to duel set up.

altfuel1991 · Jun 18, 2016

BPetty said:
I also need some help with propane, I have a mild built sbc 11.5 to 1 compression and custom grind cam for propane. I have a 425 mixer, e model evaporate and it just seem to run out at around 5000 rpm. Wanting to know price of stuff I need to go to duel set up.

Pm sent.
Let me know how I can help.
Buddy

bbone · Aug 8, 2016

Finally adjusted the timing...realized there was no ported vacuum. Seemed to have more power and burn less fuel. However...once I got on the trail and it was fully warmed up it was busting up at low speed/rpm. Now, I have noticed a occasional spark plug wire disconnected so I have been watching that to make sure it isn't the problem. Fuel burn seems to be more realistic now compared to before.

My question now is, the wideband 02 is reading 7 at idle and 22 under throttle...since the timing has been adjusted and seems to be adequate ( went exactly by the timing guidelines by Buddy) is it now safe to move to the power mixture? Or should I have a professional set it up for me?

altfuel1991 · Aug 8, 2016

If you have a way to monitor the A/F ratio you can set it and get it close. With the ratios being so wide it is going to be difficult to make that 500 inch motor work properly with a single mixer. Doing the math that engine will have peak air/fuel flow at 3800 rpm. At 3000 rpm the mixer is at 82% flow. Anything above the peak will only choke the motor.

cumminsontherocks · Aug 8, 2016

awesome thread. ive been running propane for a while and learned more in the last 5 mins then the last 3 years. thanks Buddy

broflow · Jul 23, 2017

So this thread was very informative. I spent the day changing out my plugs to cooler ones with a .030 gap. I also followed the above timing info and set it at 30 total in at 2500. Had to change springs and stop in MSD distributor. I also installed a wide band O2 sensor to monitor mixture. With all this I still have a terrible detonation problem? Very hard to crank when warmed up(like it's advanced too much)

Here's my motor specs
377 small block
12to 1 compression
ported/polished 64 cc dart heads
domed pistons
MSD 6al ignition box with MSD mechanical advance distributor.
dual 425 impcos on an adaptor mounted to an 850 baseplate.

This was a strong running motor on gas. I thought by switching to propane I would have a great off-road set UP?
Any advice would be great.

muddinmetal · Jul 27, 2017

broflow said:
So this thread was very informative. I spent the day changing out my plugs to cooler ones with a .030 gap. I also followed the above timing info and set it at 30 total in at 2500. Had to change springs and stop in MSD distributor. I also installed a wide band O2 sensor to monitor mixture. With all this I still have a terrible detonation problem? Very hard to crank when warmed up(like it's advanced too much)

Here's my motor specs
377 small block
12to 1 compression
ported/polished 64 cc dart heads
domed pistons
MSD 6al ignition box with MSD mechanical advance distributor.
dual 425 impcos on an adaptor mounted to an 850 baseplate.

This was a strong running motor on gas. I thought by switching to propane I would have a great off-road set UP?
Any advice would be great.

12to1 is about the limit for propane... I wonder if you are getting low quality fuel?

Also, big ol' donkey **** camshafts with a bunch of overlap usually kill propane drivability and useable torque

altfuel1991 · Jul 27, 2017

What is the water temperature this engine runs at? Are you running iron heads or aluminum? What are the specs on the cam you are running? Is it an RV style cam that has a lot of low end by creating higher cylinder pressures? If the timing is set properly there is a heat factor playing into this situation most likely. Give me a call if you need to.
Sincerely,

Buddy Gamel
Precision Sales & Service, Inc.
451 64th Place South
Birmingham, Ala. 35212

877-403-7827, office
205-837-8871, mobile
205-591-2267, fax

[email protected]
[email protected]
www.alternatefuel.com
www.workhorseservice.com

broflow · Jul 27, 2017

altfuel1991 said:
What is the water temperature this engine runs at? Are you running iron heads or aluminum? What are the specs on the cam you are running? Is it an RV style cam that has a lot of low end by creating higher cylinder pressures? If the timing is set properly there is a heat factor playing into this situation most likely. Give me a call if you need to.
Sincerely,

Buddy Gamel
Precision Sales & Service, Inc.
451 64th Place South
Birmingham, Ala. 35212

877-403-7827, office
205-837-8871, mobile
205-591-2267, fax

[email protected]
[email protected]
www.alternatefuel.com
www.workhorseservice.com

I believe I have a 170 t-stat in it currently(I need to verify), that being said The few short periods that I've had it running my gauge is registering 200ish. It use to run around 180s the last time I had the truck running. I have since changed from a flex fan to 2 electrics so I'm not sure how that's factoring in?
It has Iron heads.
As for the cam I believe it was around [email protected] with close to .500 lift. The cam was originally picked out to provide 15" of vacuum at idle to allow it to fit into the class I was mud racing it in. I wish I still had the cam card but it was 15 years and 3 moves ago.

What would be the best time to call you?

broflow · Jul 27, 2017

I forgot to include that I have discovered a couple of problems in the last couple of days that are contributing to some point.

I had a large vacuum leak. The rubber plug I had on the large vacuum port on the base plate had come off.
Also I noticed that one of the Model E vaporizers bleeds propane out the vent screen when the primer button is pushed. Rather than feeding propane to the mixer. From what I've heard the diaphragm might be tore in that one? I haven't taken it apart yet to see. Are there any tricks to taking them apart?
Could the associated mixer of not been getting any propane?

Casey · Jul 27, 2017

News flash. There is NO HOPE for propane. :-*

bbone · Jul 27, 2017

mine runs fine....

altfuel1991 · Jul 28, 2017

Looks like you have found two major problems. A vacuum leak will greatly lean out the fuel mixture and a diaphragm in the vaporizer leaking will not allow the secondary valve to open as wide as it needs to be. Both of those issues will cause a very lean condition and send the cylinder temperatures soaring. It is possible that one of the mixers was not getting any propane to it.