I'm coming up on my California smog check and there is no way i'm going to pass. I've removed all the smog equipment, air pump, etc and tossed them. I added Performer intake, Holley carb etc. So I was thinking of switching to propane to make it exempt, plus I hear it works better for hills climbs and off camber situations anyhow. So the question is, can I get away with this idea? Will the state exempt it as a low emission vehicle? Ive checked the DMV site and it's pretty vague, has anybody done it? I have a 79 Bronco with a 400.

 

What is entailed in the smog test?

Is it like a 2 minute run with a sniffer at the exhaust or is it more involved with a full inspection of smog related equipment and all?

 

full blown visual at a inspection only center

 

Hello mstum00.
You could pass emission requirements. Certainly evaporative controls would be no longer relevant in a dedicated lpg vehicle. If you are not being checked for hydrocarbon emissions at the tail pipe-yes, lpg vehicles will produce some hydrocarbons-then you could be in with a good chance. Was EGR a requirement on 1979 Broncos in the US? There could be a point of contention with the smog laws?
Lpg is a good fuel to use in a vehicle like a Bronco. However, to get similar power levels you will need to do some modifications. Need to get the distributor recurved to run on lpg, a cam with a longer duration @0.050" for the exhaust (dual pattern cam), headers and free flow exhaust will all be a positive.
Don't forget a good size fuel tank as well. Typically, economy on lpg is less than gasoline-although some would dispute this assertion.
Hope this helps.
Cheers
Craig

 

I'm running a 400 dodge on propane, timing is at 10 degrees (from 8), true duals, 2bbl intake, open element air cleaner and am making just as much power it does on gas. Anything that woud give more power (cam, headers, etc.) are a bonus. Swap to a 4bbl if you don't already have one too. Imco 425 mixer is a good one. At worst you could have to throw cats on.

 

I convert small engines to propane at work. We get our kits from a company called L.E. Klien out of Texas. Give them a call and they can point you in the right direction.

 

I have just been through the California Smog Certification process (again) with my 1979 F250 460ci. 4x4. With the experience of dealing with many smog stations including a trip to the referee station, all smog emmissions equipment is required to be installed except the charchol canister and the hot air pre-heat for the intake.

Also, from the early '90s to the present all conversions need to be CARB approved and certified. A small technicality for california conversions!

 

I almost feel sorry for you guys, thats alot of BS to go through. I grew up in mississippi and I have had trucks that wouldnt even make it to a smog test much less pass them, but i have never had to deal with them. We have a inspection yearly but its purely visual, meaning they just look at it and then slap a sticker on. Good luck guys.

 

Propane is basically the perfect motor fuel and burn cleaner than any other fuel (including Hydrogen) emissions wise. If you get serious and make it a one way trip (never go back to pump gas) you can raise the compression ratio to about 12 or 13 to one on propane because of its octane being around 110. The higher CR ratio will yeild more power and better MPG because propane has about 40% less energy per gallon than gas so you will use more but a high CR ratio would help offset it. Pound for pound though propane has more energy because a gallon of propane weighs 4 lbs and a gallon of gas about 6.4 lbs (depending on tempature) so a pound of propane has about 10 to 15% more energy than a pound of gas.

 

One thing I just learned talking to a high perf engine builder was the propane still can detonate at that CR and you won't hear it like you do with gas so it can destroy the engine and you will never know why till its apart. (personally I am still going to try 13:1 in my Dodge though) I have seen a 428 run fine on 13.5:1 hauling a camper 90% of the time it was used BUT even with a huge 4 core rad you really had to watch it on hills or it would overheat.

 

Even propane can detonate too but it is a LOT harder to do it too. At 12 to 1 you will never have a problem and not very likey at 13 to one either but I would not go beyond that in a RV usage

 

I've done a ton of research and am building a propane specific motor (400)- wondering where some of your info is coming from.

First you NEED to be concerned about DCR regardless of SCR. SCR, being a simple calculation has little to do with how your motor will operate. You can easily go to a massive SCR of 13:1 plus but you still need to keep DCR down at , around or below 9:1 or you will have a short life motor and heat beyond managing. Nascar motors can be 16:1 or better but have cams that run DCR down to 9:1 or so and they are massive cams- build a lot of power and drain off a lot of compression and I bet you don't want that kind of motor, drivability issues, durability etc.

Many have converted stock motors and have done ok. I could not find a publishable propane build for a 400 or any ford v-8 that really delved into what you need but have been able to apply a bit of trig and work some things out. So, while some of the info above seems a bit off...I would sure like to know where the info is at!!!!

i've looked into some acknowledged regional experts and have learned a bunch and think i have a good, long term, build sheet that would not come close to 13:1 SCR but did the desktop dyno at about 360+hp and 440+ftlbs from a rv, mileage build. Achieving over 400hp and 450 tq would be fairly easy but beyond what i want as i expect good to great mileage as well.

I'm happy with that but would sure like to get as much new info as possible!! I know how i would go about building a race motor using propane as well and i would have SCR over 13:1 and a big cam. A strip motor would have even more of both and some air too.

Propane is comparable to any other fuel but, again is not if you want to get into a great build. Anyway..there is much more to deal with than compression and detonation or everyone would be using it. HEAT!!!!

 

[QUOTE=At 12 to 1 you will never have a problem and not very likey at 13 to one either but I would not go beyond that in a RV usage[/QUOTE]

also...this one quote kind of bothers me- if you want 12:1 and, lets say a cam that gives about 212,218 duration (mild rv cam) at 050 your DCR would be about 10:1 and you would have a torch on your hand. So that would place you into a mid range cam to relieve some pressure and heat---> a lot of power and poor economy which may be the goal but cam selection is huge and if you follow the cam guidlines for compression you would have dcr between 7.5 and 8.5 depending on what octane gas it was looking to use and you would not be taking full advantage of the octane that is propane's advantage- cam companies do not recommend CR for propane.

there is a lot to consider and no simple answers. You can run a propane only build in ca but not a build that can be switched- and there are some restrictions on that as well- not sure what they are. Propane is a great fuel to run on a slighly built motor- ie 10:1 SCR and an rv cam- leads to good, solid power- workable heat issues- and a motor that can last forever and get decent mileage.

 

You want to get CR as high as possible because there is about 30% less energy in a gallon of propane than gas and a high CR will gain power and improved MP on propane so that the gallons used is closer to a normal gas motor.

 

If I were going to build a propane engine, I'd do a good quality stock rebuild with good components and mild compression like 8.5:1. Then turbo it and take advantage of the fuel for lots of boost and use programmable wastegates. Use a draw through application with an intake heater (heater water wrapped around the intake tube) to keep the intake from freezing and make all the power you want. This way the wear and tear on the engine wouldn't be as bad. Constant high compression has to be hard on piston heads and top ring and ring lands since there is no lubrication with propane. This is why diesel is oily, it lubricates the top of the bore. Constant high compression on two rings and an oiler isn't very effiecient which is another reason diesels use five rings. I've seen some wicked installations with twin turbos and propane - like they say, sit down, shut-up and HANG ON!