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Propane engine builds (tech, questions, advice)

If you want to know how to build a big HP motor with a 425 mixer. Find a guy that builds winning round track motors for hobby classes. I know when I was into dirt track we were getting 500 plus HP with a 500 cfm motorcraft 2150 carburetor. Nascar makes 700 plus with 600 cfm on restrictor plate tracks so anything is possible.
There is a someone on here (Little Tim) that has a big block chevy that I have heard is over 500 cubes and I'm sure has well over 650 HP on dual mixers.
All of this is a major reason I have been talked out of propane. If it will only support a stock motor (325 hp) I don't want it. I can do a decent efi for about the same price as a dual mixer and have less headaches and better mileage. I know a guy with dual mixers that will go through 7 gals of propane sitting in the shop faster than I go though 7 gallons of gas on the trail. :****:
 
The reasons a single mixer will only support around 325 hp are the amount of air it will flow and the matching amount of BTU's of energy producing fuel it will flow and keep the air/fuel ratio correct.

The restrictor plate engines in NASCAR are running in the range of 16 to 1 compression and some very strange cam profiles to make the power they produce and are very close to the edge of destruction at all times.
 
machen4x4 said:
this is what we did to my old truck engine which jd owns now, 22r with got propane kit
my son in law built the motor for us.
ricky had his machine shop in hazelgreen al bore the block 30 over, decked the block and head
balanced the crank, rods and pistons. we went with 10.5 to 1 pistons. probably looking at 11.5 to 1 or even 12 to 1
compression after the decking of block and head. ported and polishid the head, put bigger valves and springs
in the head. comp cams built a cam for us that the rpm range was 2,000 to 6,000 on propane.
put a header on it. motor does pretty good from what i could tell.

we took our new motor to ricky a couple weeks ago to build for my sons rig
it will be the same except more compression and screw in studs for the crank and head, bigger valves and more porting.
Click to expand...

that new motor is going to be a BEAST!! cannot wait to here it run!
 
altfuel1991 said:
The reasons a single mixer will only support around 325 hp are the amount of air it will flow and the matching amount of BTU's of energy producing fuel it will flow and keep the air/fuel ratio correct.

The restrictor plate engines in NASCAR are running in the range of 16 to 1 compression and some very strange cam profiles to make the power they produce and are very close to the edge of destruction at all times.
Click to expand...

That makes sense I reckon, since propane has less energy than gasoline. I'd still be intersted in seeing some dyno charts though.

And from what I've been researching today, a proper propane air-fuel ratio is ~15.5:1 rather than 14.7:1 for gas, so on top of having less energy, it also requires more air to completely burn.
Kinda makes propane look pretty unattactive for a slightly built motor (decent heads and moderate cam). :'(

Looks like to make it worthwhile, you have to run dual mixers on anything more than basic stock motor (mild cam, intake, headers).


Jamie, you might ought to look into running a 425 mixer on your son's new motor, since the standard 225 mixer is only rated at 330cfm and 205HP!
:****:
 
altfuel1991 said:
The reasons a single mixer will only support around 325 hp are the amount of air it will flow and the matching amount of BTU's of energy producing fuel it will flow and keep the air/fuel ratio correct.

The restrictor plate engines in NASCAR are running in the range of 16 to 1 compression and some very strange cam profiles to make the power they produce and are very close to the edge of destruction at all times.
Click to expand...

Nascar is also using a racing fuel with a lower air-fuel ratio, so they can make more power with less air.

Just like E85, it likes a ~10:1 air fuel ratio (for good E85), but like propane, has higher octane and less energy than gas. Differnece is, it requies less air to completely burn, so you can make LOTS of power on E85, but you will burn LOTS of fuel in the process.
 
If you can get the cylinder pressure up and use a decent cam I think you will be very happy with it. Look at all the smith buggies running pane and they seem fine. I still like running gas but to each his own. But I do know a properly built 400 horse motor will Run fine on pane,I don't care what the math says.That article I was talking about in hot rod was using an stock LSX 454 with a magnesium blower with twin injectors per cylinder spraying liquid propane and was 900 plus horsepower by the way
 
Elliott said:
If you can get the cylinder pressure up and use a decent cam I think you will be very happy with it. Look at all the smith buggies running pane and they seem fine. I still like running gas but to each his own. But I do know a properly built 400 horse motor will Run fine on pane,I don't care what the math says.That article I was talking about in hot rod was using an stock LSX 454 with a magnesium blower with twin injectors per cylinder spraying liquid propane and was 900 plus horsepower by the way
Click to expand...

Found it and it looks nasty:

http://blogs.hotrod.com/you-rank-it-propane-powered-70-chevelle-31825.html#axzz2CVXCO6Fu
http://www.mothers.com/04_community_02_rides/04_community_02_rides_mo_01.html
 
Re: Re: Re: Propane engine builds (tech, questions, advice)

Bronco Buster said:
Didn't Nascar switch to ethanol instead of race gas?
Click to expand...

I believe they run a Sunoco unleaded ethanol blend (for octane boost/cooling I reckon) from the info I could find.



Hell, I may build a damn efi e85 motor and run a 30 gallon fuel tank (which still takes up less real estate than 2 pane tanks)
 
Most duel mixer setup run some kind of aluminum box with two mixers bolted to the top and under it a throttle body Body bolted to the intake . The problem with this idea is when you open your throttle it pull through both mixers at the same time. If your motor makes say 12 in vacuum you get 6 in through each mixer. That pulls propane to slow to be efficient from idle .I made a box that bolts to the intake and V up and bolted TWO mixers with throttles on both mixers. Hooked both mixers up with progressive linkage and pull through one until your motor builds some rpms and then the other opens up. Starts better, better throttle reponse off idle and when puttering around better milage. Plus supplies enough air to make power up high. The problem is you got double money and you still have to mess with those damn bottles
 
halcat said:
Most duel mixer setup run some kind of aluminum box with two mixers bolted to the top and under it a throttle body Body bolted to the intake . The problem with this idea is when you open your throttle it pull through both mixers at the same time. If your motor makes say 12 in vacuum you get 6 in through each mixer. That pulls propane to slow to be efficient from idle .I made a box that bolts to the intake and V up and bolted TWO mixers with throttles on both mixers. Hooked both mixers up with progressive linkage and pull through one until your motor builds some rpms and then the other opens up. Starts better, better throttle reponse off idle and when puttering around better milage. Plus supplies enough air to make power up high. The problem is you got double money and you still have to mess with those damn bottles
Click to expand...

roger (extremetownie) had the same problem on his Dodge stroker in the Power Wagon, it would stumble, cough, and generally not run good on the 2 mixer setup, but ran fine at WOT.

And with the single mixer, it would only turn ~4700 rpm or so.
 
I wheeled with Roger , i'm from sparta too. I ran a single mixer for a while on my 427 big block with a 6500 chip, it would hit the chip, it just took a while to get there. When I went to two mixers on progressive linkage, by the time your foot got to the floor it would hit the chip. Grinding a cam made a big difference, two mixers made a bigger difference, just take an extra bottle or two with you.
 
I am not sure what kind of problems some of you have been having with dual mixers but what I am reading is not normal. I have a lot of dual mixer setups on engines from 5.3 and larger and none of them do what has been described. They have good throttle response from idle on up through the rev limiter. When properly set up there is no hesitation. Generally we install a start valve for priming the system which allows some fuel in below the throttle blades for quicker starting.

If any of you are having problems give me a call. I will be glad to help you figure it out.
Sincerely,

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

877-403-7827
205-591-2266
205-591-2267, fax

[email protected]
[email protected]
www.alternatefuel.com
www.workhorseservice.com
 
Buddy, I went wheeling this weekend and the engine would "load up" on tough sections. It would not build any RPM and would just spit and sputter while trying to climb. The tanks are in the right position, the tanks were full. When there was not a load on it, there was a slight stumble right off idle, then it would clear out. It suddenly started doing this for no apparent reason. Your thoughts?
 
AllGoNoShow said:
Buddy, I went wheeling this weekend and the engine would "load up" on tough sections. It would not build any RPM and would just spit and sputter while trying to climb. The tanks are in the right position, the tanks were full. When there was not a load on it, there was a slight stumble right off idle, then it would clear out. It suddenly started doing this for no apparent reason. Your thoughts?
Click to expand...

It's begging for mercy. Haha. ;D
 
Found this thread on jalopyjournal, lots of propane hotrods running around apparently, especailly in OZ and NZ.

http://www.jalopyjournal.com/forum/showthread.php?t=290927&page=5

Here are some dyno pulls and a quote from a company called Fastco

New LPG Chevy street rod & race engines from MILD TO WILD dyno tested & tuned 100% turn key , full show dressed.

Chevy 355cid / 360+ BHP LPG engines priced @ $5700 USD turn key..........
Our LPG engines are built from the ground up for LPG fuel, the system we use is IMPCO with high flow diaphram..we use high compression pistons in these engines @ 11:1 comp a must for LPG engines to take advantage of LPG octane of 108+ greatly increasing BHP & torque output & MPG of engine , we install a custom ground hyd roller cam for LPG application. plasma moly rings file fit a must for LPG app's, Liberty severe duty SS valves installed in alum heads... because of high exhaust tempetures with LPG engines stock or mild performance type valves cannot be used.
A high output ignition system must be used on LPG engines we use new Revolution HEI dizzy with 60,000 volt coil & ATE 1200 6AL amp box ...wired a must use addition with LPG engines for fast clean starts & much better MPG
SBC 355 cid / 360+ BHP LPG engine / dyno tested & tuned 100% turn key priced @ $ 5700 USD
Who says GREEN cannot be MEAN.......... NOT US ! we make go'n green tons of hot rod'n fun.

E-mail us @ [email protected] for more information & details on our custom built LPG engines.... and a LPG engine to suit your application


I'm not sure what mixer they are using, but I'm sending an email to ask. They are in New York state.

This one they are claiming 380 Hp (single mixer setup) and pulling to 6000rpm
http://s4.beta.photobucket.com/user/fastco/media/PETESMEANGREENMACHINEDYNOTEST.mp4.html#/user/fastco/media/PETESMEANGREENMACHINEDYNOTEST.mp4.html?&_suid=13534695413320683284865130159
 
You no, all this propane swap started out years ago because it was an easy way to get a carborated engine to run in off camber angles off road. With this article now you have to build a special motor for pane. I think building a motor for propane would be fine if you were going to drive say 200 k miles and take advantage of it's cheaper price . All thow I did,most people don't build motors just for off road, we use what we got, dig one out of the junk yard put on our fuel system and go . Looks to me like you would Be better off spending your money on a good after market stand alone injection system and ride! That's what i did. When i take a notion to go wheeling on sunday morning I dont have to wonder if I got full tanks I stop by co-op, swipe my card, fill up and I'm off!
 

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