Propane as a fuel and performance

[rickpilgrim]

Chapter 1
Whenever I suggest propane as a fuel I hear a lot of negative feedback about it. To share what I have learned from having 2 vehicles with big block engines running propane as their sole fuel and what I learned yrs ago from it.

If you ever were considering propane as a motor fuel there are some things you need to know. They concern the btu content of all, second is some of the available parts and kits to convert to it and why they lead to disappointment, and the third is how I set up my 2 engines and how to set up yours. The fourth part will deal with fuel tanks and supplies.

The first is the BTU content of these fuels.

Gasoline, 1 gallon = 125,000 btu
Natural Gas, 1 gallon= 100,015 btu
Propane, 1gallon= 91,700 btu

So that means 1 gal gasoline=1.25 gal NG =1.36 gal propane
Or natural gas and propane contain 20% and 26% less energy than gasoline

Those btu results were published about a century ago and were obtained using pure fuel. We no longer have pure gasoline, it has ethonal and other octane additives and chemicals have been added into our gasoline for less pollution, anti evaporites and less carbon emissions. A more recent btu test of 87 Ron gas revealed:
87 Ron gasoline, 10% ethonal content = 109,272 btu
93 Ron gasoline = 118,791 btu

In octane rating terms:
pump gasoline (USA). 85-93 RON
Natural Gas. 104-108 RON
Propane. 105-110 RON

This is one of the reasons that propane appears a losing proposition as an alternative fuel. Another is a lack of firsthand knowledge about the mixers,regulators and tanks that are sold and recommended by vendors who have no experience in trying propane for performance or a spirited daily driver. Stay tuned for chapter 2

[snj8198]

getting edgamacated.

dont make me drive out there so you can install a propane system on my truck to prove your point.

[rickpilgrim]

Steve- when I started the 98 crew cab 434 project I was going to remake the system in my totaled 82 CC for it. Then my propane supplier went out of business and the travel center stopped selling it. That changed the direction of that build back to gasoline. Point is propane is so misunderstood and we seem to have lost the knowledge that you need to use it wether it's the retailer selling the kit or the poor guy who just spent $1000 hard earned bucks to put the system on his stock 350 or 454 truck and discovers it works like crap. I went through all this when I put that jet boat 455 in my 73.
Over the yrs I have heard so much negative about it and no one seems to know the facts anymore. And no, even if you wanted I wouldn't propane you truck engine after you spent all the money on cam,pistons and intake carb and EFI only to find out you have to trash it all to do it. Stay tuned

[snj8198]

Good stuff Rick, looking forward to learning something.

[rickpilgrim]

Chapter 2

You've watched your friend with his Toyota running on propane drive those trails for years now. He goes all day on that little tank, uphill and down, almost on its side, drive through water so deep only the snorkel sticks out. He flipped it once, lucky his spotter was there to hit the kill switch. Your big block Chevy truck has pulled him outta the mud hole a few times and can climb and crawl with the best but you gotta watch the angles so your carb doesn't flood. You check online one day and find that propane kit and wow, $795 is it and only need an old forklift tank? You want that Toyotas smooth running at any angle and "klick" there goes the order button.
The specs they give you look good and it's a reputable company so you just don't realize the mistake you've made. You spend a day or 2 getting it all hooked up and turn the key, the 454 rumbles to life smoother than ever. You jump in and go, off the line it seems ok but man, where did all my power go? It revs up but seems so lazy like half the power is gone. WTF, you ask the company on the phone, they tell you to turn your timing up and make sure the hoses aren't pinched so you do all that but even then 25% of your power is gone, you forklift tank doesn't even get you 80 miles, man you wish you hadn't spent that money.
Propane technology is old, most of it in the late 1940's to mid 70's. Worse yet a lot of those companies are gone, there used to be many sizes of mixers, now we're down to maybe 5, not including lawnmower stuff. Of these, for V-8 carb stuff the impco 425 is the most popular, the M-8 for dual fuel and a few other smaller ones.
The impco 425 looks good on paper, 600 Holley base plate, supports 300hp and is easy to fit to just about any engine without jetting or adjusting etc. sounds good,right?
Flow testing reveals is only flows 423-427 cfm. Maybe enough for a tame 283 but better on a 250 6 cylinder.
The M-8 is the dual fuel version which is better at 528 cfm but even that is only enough for a mild 327.
300 hp capable? Well if you take a 300 or so cid V-8 and optimize it for propane maybe but the most you normally hear is 270ish. Advertising in this country is terrible.
You look at your regulator and the 1/2" hose should be ok, right? It would be if they measured it on the inside. The regulator looks good, well, it's bigger than the one on your bbq grill so..... The reality is if it doesn't have a 3/4" I let and a 1" outlet it's not big enough for V8 use.
On eBay you see this dual mixer setup, 2 impco 425's and 2 regulators maybe that will help. Looks good with that oval air filter and look it bolts right to the intake.
Only problem with all that is 850cfm of flow doesn't pass through a Holley 1850 600cfm base plate, which is what it's base is. Do you ever wonder who thinks up these things? I do
The Toyota's work on this stuff because they are small motors and 4 and 6 cylinders just like a lot of forklifts. More on that in chapter 4
If you need more than 425 cfm of flow use 2 mixers and 2 regulators and when mounting you don't need a 2x4bbl manifold just be creative and make an upside down v box on your former carb pad. LPG is a gas, it mixes with air so evenly, it can go around a 90 degree corner and still be perfectly mixed. You can use a log type intake, even a 5.7 Vortec upper and lower works good. Dual plane intakes work but what your looking for is the straighter the better, think port o sonic.
And if you have dual mixers and regulators don't forget the line to your tank. Min 1 1/4" inside ID for that.
The neat thing is no worries about jetting or setting anything the mixers are self metering by air flow just like a MAF the ratio is pre set.
Once you know what components to use this becomes easier. Now that we know some about mixers it's time to make the engine use that 110 octane clean burning gas.
Stay tuned for chapter 3

[ranger danger]

Years ago (35+) I used to install propane kits for a propane company. The rule was you lose 10% horse power and 10% fuel mileage but propane was .69c per gallon and gas was $1.50 per gallon so it was a good thing. Now, my wife drives a CNG (compressed natural gas) Honda. It gets about the same mpg (35) and hp as a regular Honda but we are getting CNG at .98c per gallon equivalent where gas has been as high as $4+ per gallon. The down side to Propane and CNG is availability and on board storage as well as price at a retailer for propane. The little 8 gallon tank is just to small for anything other than an around town or commute vehicle but the tanks are so physically large that you lose precious cargo space for anything much larger. The great advantage that I see is the clean burn of propane and cng. The oil on my wife's car gets changed about every 20k miles whether it needs it or not!! She is a Chemist for a major oil company so she has taken her oil samples and tested them. After 20k the oil is still clean enough to sell as "New Product"!!!!!! This translates to a very long engine life. Like a million miles is not out of the question. I am looking forward to the continuation of this thread. I suspect it will be very interesting.

[Keith Seymore]

I would encourage you all to check in with Jack Roush Performance here in Michigan.

They race three Mustangs in the NMCA Open Comp category, all fueled with propane and all in the 8 second range in the quarter.

One of them is driven by Jack's daughter Susan McClegaghan.

K

[truckdude239]

I love propane i run my generator on it at home i can get around 24 hours on one tank

[ERASER5]

Propane for a generator is probably the best way to go. No stale gas because you haven't used it since "that big storm" 2 years ago. The oil stays clean, spark plug stays clean. Keeping an extra tank is as close as you gas grill.

Rick, I'm in for this thread. LP is a great way to go, but as yo said, it has to be sized for your needs. No one would put an old Datsun 2 barrel carb on their 454, so why would they think a fork truck fuel system would flow enough for their 454? A little logic goes a long way.

I don't really want to be a Debbie Downer, but the lack of road tax on LP is the main reason there is not much support out there. Importing LP systems for automotive conversions is almost impossible.

[rickpilgrim]

Chapter 3- building a propane motor.

In chapter 2 we learned that the majority of propane kits for carb engines are to small and one size fits all approach that does not work for performance or efficiency. In this chapter I will cover the other third of the problem.

For the last century or so the vast majority of engines were built to run of gasoline. Weather from the 1910's, 20's,40's ,70's or today's engines they were all built to burn gasoline in the most efficient cost effective manner. Today we have very powerful computers just to burn what we call gasoline today. To run propane as a fuel you have to forget most of your gasoline knowledge and building tech.
What is important to remember is propane is 20,000 some btu lower than gasoline but has 110 octane which is far greater than pump gas. You won't make greater horsepower than a gasoline equivalent but you come very close in power and only have a 5% or less loss of mpg.
The first change to the engine. With 110 octane you can go up 2-4 points in your compression. Here is some suggested recommendations from down under or Holden's where propane has a huge following.

Truck, heavy towing or low speed lugging. 9.8/1
Truck, med work load, moderate towing, no lugging. 10.5/1
Ute or heavy Auto 11.2/1
Light auto or sports. 12.4/1
Racing in sanctioned bodies. As allowed

Now the propane there has butane and other additives where here in the usa we have no additives in ours, so you should be safe at those compression ratios. Also a Holden V8 basically is a Chevy engine. Of course cam and ignition timing plays a part in this also, more on that further on.

Your cylinder heads also play a part in this also. Some people running propane endorse stainless steel valves as the only way to go the reality is if you have the proper flowing mixer and regulator and hoses and don't run your tank dry the standard valves with a slightly larger seat radius has worked for me and most others for over 200000 miles at a minimum. Other than that standard hotrod tricks apply. Larger valves, porting and port matching and smoothing are good enhancements. You need not worry about center and end cylinder distribution or any areas where fuel would puddle or drop out of suspension, propane mixes so well with air it never separate no matter the corner or crevice. What does matter from a point of power and efficency is smooth flow to pack the cylinders full.

Cams are pretty much limited to your tastes, but do remember valve overlap, where both the intake and exhaust valves are open at the same time. You don't want that as that's your fuel out the tailpipe. Try to find cams with 112 LSA , in the stock-215 @ .050 range for small blocks and 208-218 @ .050 in big blocks for your truck, you can go higher in .050 for cars but the higher you go the less efficient you are.

Intake manifolds are a flow over design thing. I ran a Offy Port O Sonic on my Olds 455 with dual mixers and my low end power didn't suffer, on the Cad 472 I had a Edelbrock Performer that worked well also. The difference was the Olds pulled hard in the upper range and the Caddy was not as good. More on that later

Headers and Exhaust are a very good idea also. Run 2 1/4 dual min on small blocks and 2 1/2" dual min on big blocks. Don't worry about emmissions, catalytic converters and such. Propane is a clean fuel and by me you are exempt from all of that because your running propane.
In part 2 I will talk about mixer mounting and ignition timing which are just as important in making this all work. Stay Tuned

[mechanicalman]

[QUOTE=rickpilgrim;7068728]Chapter 1
Whenever I suggest propane as a fuel I hear a lot of negative feedback about it. To share what I have learned from having 2 vehicles with big block engines running propane as their sole fuel and what I learned yrs ago from it.

You won't get any negative feedback from me, I want to hear everything you have to say and I appreciate it. That being said.....

I would LOVE to be able to run natural gas, and fill up at home.

[rickpilgrim]

I would LOVE to be able to run natural gas, and fill up at home.[/QUOTE]

So would I IF you could buy the high pressure pump for it you need to fill the tank. Not to mention home NG is not as dense as propane and would require 10/1 or lower air fuel ratio to run it. Someday maybe....

[TJ's Chevy]

Its a common thing around my area for my customers to request propane kits on their generators. Have a friend of mine who converted his bus to propane...gutless wonder. lol

[rickpilgrim]

Originally Posted by ERASER5

Propane for a generator is probably the best way to go. No stale gas because you haven't used it since "that big storm" 2 years ago. The oil stays clean, spark plug stays clean. Keeping an extra tank is as close as you gas grill.

Rick, I'm in for this thread. LP is a great way to go, but as yo said, it has to be sized for your needs. No one would put an old Datsun 2 barrel carb on their 454, so why would they think a fork truck fuel system would flow enough for their 454? A little logic goes a long way.

I don't really want to be a Debbie Downer, but the lack of road tax on LP is the main reason there is not much support out there. Importing LP systems for automotive conversions is almost impossible.

My point here is that if you google propane conversion kits most of the links take you to eBay, where you find a kit for the Chevy 454 that contains the impco mixer with Holley 600 base capable of 300 hp and it includes everything but the tank, and they recommend a forklift tank. I can think of several people who would fall for this system and have met a few that did at our shop.

[ranger danger]

Originally Posted by rickpilgrim

I would LOVE to be able to run natural gas, and fill up at home.

So would I IF you could buy the high pressure pump for it you need to fill the tank. Not to mention home NG is not as dense as propane and would require 10/1 or lower air fuel ratio to run it. Someday maybe....[/QUOTE]

The CNG high pressure pumps are available although they are expensive. I have one at my home and use it nearly every day. It cost's around $5000 but when I got mine, there were some special incentives that reduced it by about half. They are made in Spain I think and imported by a company in Los Angeles CA

[truckdude239]

I went propane on my generator cause my carb was messed up it was 150 buxs for a carb or 120 for a proane kit. I will eventually get a carb so i can run propane or gas

[SS317]

I've wanted to do propane or CNG for years but have been waiting for better kits, better technology.
Thanks for the information and keep it coming. I love learning about this stuff!!!

[Eddie H.]

The technology for natural gas and propane power is improving. I work on natural gas powered industrial engines with displacements ranging from 330 cubic inches all the way up to more than 16,000 cubic inches. Most still use the old Impco mixers, but one company has developed a full authority electronic control system that is similar to an automotive OBD2 EFI system which provides precise control of the air/fuel mixture under all operating conditions. This system could easily be engineered for automotive use if the demand were there.

[BR3W CITY]

There is an Asian-release GM engine called a .92 or a .97 (obviously just named the displacement). It was orignally a A/J-spec MicroCar engine, but has since been brought over here for use on tractors/city carts and similar. It runs very nicely when setup to rune LP, and for an industrial use is extremely efficient.

[rickpilgrim]

Chapter 3 part 2- ignition and mixer layouts

14-14-14 by 2800rpm

That's the ign timing from a 1974 impco installation manual for a Chevy 350 engine. If nothing else this should tell you how detonation resistant propane is.
Propane's high octane(110) has a lot to do with its burning slower than gasoline. You have to set the spark to fire earlier in the engines cycle to get effective power. The advance curve is different than a gasoline one. You must bring in the advance curve earlier, as impco recommends 28 degrees(14+14) in by 2800 rpm plus 14 degrees of vacumn advance for a stock 8.5/1 compression engine. Now if you have compression of 10/1 or better I'd start at 8 degrees more than your current or factory setting and have 26-28 degrees in by 25-2800 rpm. Also stay with 14 degrees on the vacumn at first but fine tune untill you get satisfactory performance is achived.
Even though one small spark will start combustion I always use a CD ignition box as with the slower burn time a little extra multiple spark wouldn't hurt. Of course a stock will produce all the spark you need for this. Set the spark plug gap at .040 to start with and if your like me with a higher output ignition system you may be able to go to .045 on the gap.

Make sure your mixer or mixers and regulators are sufficient(flow wise) for your engine. I've seen a single impco 425 with a 2" open spacer on a stock intake manifold 350 perform as a stock gasoline 350 engine. Plenium volume is beneficial on cammed engines or those using a single undersized mixer. If your going for 300 or more hp you likely need dual mixers and regulators, unless your really lucky and find a 750 cfm unit.
I used 2 impco 425's on my big block motors, I mounted them on a inverted V box made from 3/16" steel. One mixer on each slope of the /\ and using a cable to link the throttles. Don't skimp on air cleaners either. I used 3x10 dual and a single mixer should have a 14x3 filter. You can mount a mixer in any position because your working with propane. I never had any bog or delay on power delivery doing this even with the port o sonic intake you can flat foot it and go.
Always heat your regulators with engine coolant, it helps the lines and mixer not ice up, which can happen on very warm days also. Has the additional benefit of helping the propane vaporize more efficiently. Make sure those regulators are a matched size to whatever mixer your running.
In chapter 4 I'll be talking about tanks and lines. Stay tuned

[Redcap]

I've been interested in going propane on my truck for a long time. Great thread.

[rickpilgrim]

Chapter 4- tanks and lines

Forklift and auto truck and tractor tanks are very strong. In January of 2014 2 of my crew took the 82 C2500 crew, loaded 900 lbs of bagged salt in it for salting sidewalks. The roads were iced and while going down the freeway were rear ended by an Expedition going around 70 into the 82 going 45 or so. There was also an 18 wheeler along side, ended up C2500 pinned against guard rail by 18 wheeler with Ford half under it.
I had mounted the 60 gal propane tank sideways in the front of the bed, the truck was compressed 20" side to side and both ends of the tank were badly dented. My guys were shook but ok and NOT A DROP of propane was lost. In the police report the officer states " I believe the bed mounted fuel tank prevented the track from being completely crushed in the cab area"

This is the reason that automotive/truck tractor and forklift tanks are the best choice for your propane powered vehicle, however back in 1986 our home heating guy told me that all these tanks have a spring balanced safety system that is set by the motor size and if you exceed that it thinks leak and closes the valve and when the pressure evens out it opens again. I found that to be true with my tractor tank back then and would explain some of the low power/performance issues that users of forklift tanks are having. The Toyota and jeep guys do well with these forklift tanks because they run about the same size motor.
Now if economics require you to use a tank like that expect to pay $125.00 to get either a different safety valve flow tuned to your motor of get that valve removed.
I had a neat little valve and hose on my trucks so you could hook up and run on your bbq tank. It was there for emergency use mainly but I didn't tell you it's made well enough for full time use.
You should size your tank about 10% larger than the gasoline one so you don't have to get it filled up all the time. Make notes of how may miles your tank gets you and once you have it down never go below 10% full.
On fuel lines as with everything correct size is most important. If you've ever driven a propane converted vehicle with those 3/8" and 1/2" fuel lines the throttle response feels weak and slow to respond that's part of the problem.
Although a hose the size of the one on your grill or generator will be enough to feed your 350 under ideal conditions the speed of the fuel rushing through it will shortly lead to frost and icing in the line restricting flow. At minimum I prefer a 3/4" feed line up to 350 cid in stock to mild tune, 1" for 351-500 in stock or mild tune and 1 1/4" for high performance big blocks. This may seem overly large in size but it can be 30 degrees below zero and I've had no icing or frost problems with the lines. Also when you place sudden high demand on the system it will provide it with ease where on cold days that 1/2" line wouldn't keep up.
Routing of lines is up to you and the room you have. I always try to run the tank line up the transmission tunnel using a intake manifold bolt to bracket or turn it across the valve cover to my fender well mounted regulator. Keep the hose away from the exhaust for obvious reasons.
The feed line from regulator to mixer should be one size larger than the supply hose. Even if you have to use a reducer to "downsize" into the mixer. You want that reserve capacity on demand.
In the next installment I will go over the 2 propane conversions I did plus 2 other vehicles that came to our shop looking for help with their systems.
Stay Tuned

[rickpilgrim]

Economy or Performance Propane Fuel Conversions...
A good resource for propane conversions , a bit dated but full of info

[rickpilgrim]

As usual the Amazon link doesn't work but it's on there. Do a search for it on amazon and it will show up

[rickpilgrim]

Chapter 5 - My introduction to propane power.

In August of 1986 I purchased a 1973 C10 ex public service truck. The utility box had been removed but had a crude wooden rack on it. It took untill almost Chrismas to get re painted and a proper flat rack on it. Money was tight so the almost worn out 307 stayed in it. Summer of 1987 the 307 died and I started converting it to the 1968 olds 455 from a jet boat. This olds had been rebuilt and reworked about 40 hrs before to the tune of 465 hp dyno tag. Also had to install a BPOC TH400. I spent a bit over a month trying to get it to run on pump gas, detonation was the order of the day and if not that ign timing so atdc that it ran hot. I tried 87-93 octane pump gas but no luck, and was not going to run that expensive premium boat gas(102ron) 25 miles away.
While tuning one day our home heating guy showed up to fill our 4 tanks. He came over by me to see what I was doing, told him what I was trying to do. He asked if I would be interested in trying propane with 110 octane, I said I'd try it and the next day a old box was by the door, 2 mixers and regulators and a lot of hoses. He had sold both of his IH trucks and new owner didn't want propane.
After some help from our neighbor the machinest to make a dual mixer./_\ adapter and getting rebuild kits for both mixers and regulators came the fun of putting it together. I had found a 60 gal propane tank from a tractor and that was mounted on the frame where the stock fuel tank had been. It stuck out all the way to the edge of my 8'wide rack from cab to 8" from the 7.50-15 rear tire.
Once that was done I filled the 60 gal tank up, bled it out and test fired it. The big olds fired right up( had set the timing back to boat spec) and ran decent but not a lot of power. Made some calls, propane guy wanted a compression check which was 188-191 psi ( still had that 367,251) miles later) and the best timing was 18 initial 14 mechanical 12 ported vacumn. As I couldn't close the hood with the high rise intake, I procured a Offy port o sonic intake manifold which had no change in performance plus I had 2" of hood clearance. Also when doing longer uphill pulls it seemed to hunt or surge. Turned out the safety valve in the fuel tank was getting overloaded and limiting flow. Propane guy(roger) took out the safety for a small fee, that cured that problem.
Performance wise you could beat a small block 70's vette or mustang 5.0 to 85-90 mph but fuel use was 346 mi per 60 gal tank. A cam change to a 268-280 on 112 LSA got me to 492 miles to 10% full but took the edge off performance. It was in 1998 when the frame went from rust,sold the motor still running strong, kept the propane system and junked the rest of the truck.
In 2008 the reman 6.2 diesel in my 82 C2500 crew broke its crank and being sick of constant repairs went looking for a big block. As usual I wasn't willing to pay $600 for a core 454 that needed everything but they had a lot of 472 and 500 caddy engines that ran good and for $250 secured a 68 eldorado 472 with 48K mi. It was freshened up with rod main and cam bearings and Hastings cast iron rings and new valve job and all new gaskets and oil pump. The machinest cracked a corner off the intake manifold and paid half of a edelbrock performer cad intake, the cam was a comp 260/268 profile on a 114/110 LSA.
Never use moly or chrome moly rings unless the motor is broke in on them. Running propane the moly or chrome moly rings will never seat in the bores giving you high oil consumption. Using cast iron rings got me in excess of 200K mi and beyond.
I rebuilt the propane system and took the 100 lb tank and on the electric dyno it went. The caddy ended up being 438 hp with 531 in torque through smoothed exhaust manifolds. Ign timing was 17 base 15 mechanical 12 ported vacumn, ign was pertronics in small cap caddy and summit cdi box with MSD coil.
Seeing I had the 1973' th400 BPOC HD trans in it went, performance was as good as Vortec 454 or any 454 for that matter, pulled 10K lbs no problem and range from 80% full to 10% full was 457 mi. It was still going strong when it was totaled and the insurance deal got us a 2000 Dodge 2500 x cab 4x4 but wouldn't even let me have any part from the 82.
This ends part 1- part 2 is about problems with kits
Stay tuned