1973 Chevrolet Impala station wagon

Let's hear all the gory details about your car and how it became alternative fuelled.
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webbew
Posts: 38
Joined: Thu Sep 22, 2005 7:30 pm
Location: New Zealand (Wellington)

1973 Chevrolet Impala station wagon

Post by webbew » Thu Sep 22, 2005 8:23 pm

I'm in Wellington, New Zealand, and bought a '73 Chevy Impala s/w with a stock 400ci and TH375 - it was all original, used to be a hearse, only 63,000 miles.

It ran a dual-fuel setup with a small LPG tank in the space above the wheel well, but the system was a bad compromise between petrol and LPG.

The aim is to convert it to dedicated LPG and get as much performance out of the 400 as is reasonable while keeping it streetable and retaining acceptable fuel economy, reliability, and stock look (on the outside ;-)

Over the last few months, had the block reconditioned, new cam, Edelbrock Performer Vortec heads and matching intake manifold, new cam, and a 700-R4 transmission. At the moment, we're a bit stuck trying to figure out the best LPG setup...

webbew
Posts: 38
Joined: Thu Sep 22, 2005 7:30 pm
Location: New Zealand (Wellington)

Post by webbew » Wed Jul 26, 2006 6:03 pm

Update: Eventually went with a Technocarb mixer imported from TorqueGas in Queensland, Australia. After having some trouble finding 2 tanks that would fit into the space above the wheel wells, I got 2 50 liter tanks from them as well, which have now been fitted into the spaces (one used to hold the petrol tank, the other used to hold the spare wheel).

I did not want to compromise the boot space as the 3rd bench folds into it and there isn't sufficient space on the underside of the car (wagon has a clam shell gate where the lower part retracts down under the boot) - this proved to be the most difficult aspect of the whole LPG setup!

Unfortunately, with no LPG experience, I didn't fancy myself being much of a DIYer, so it's been a long road to get people who know this stuff and then get them to actually have time to do it (we seem to have a chronic labour shortage in many trades in NZ ;-) Anyway, it's just about finished now, probably going to be fired up and certified in the next week or two...

webbew
Posts: 38
Joined: Thu Sep 22, 2005 7:30 pm
Location: New Zealand (Wellington)

All finished

Post by webbew » Thu Dec 28, 2006 2:16 am

Have been driving it for 6 weeks now - so far it has only been tuned roughly and it runs pretty ok; since the engine and everything is new (or in the case of the block reconditioned), I'm going to run it in a bit more (1000 miles?) and then it's going to go on the dyno to be tuned properly.
Fuel consumption seems to be a bit higher than I hoped for and power could be better in the upper range, but I won't draw any conclusions yet until the dyno.

One of the cylinders still needs to be turned (and the valve/float/etc. adjusted) so the vapor box clears the inner plastic cover (I've got 2 50l tanks above each wheel where the petrol tank and upright spare wheel used to be), but otherwise it's all finished - I'll post an under-hood picture soon if I get around to it...

stroker
Posts: 10
Joined: Sun Feb 18, 2007 11:55 am

Be carefull you do not run to lean

Post by stroker » Mon Feb 19, 2007 1:09 pm

Greetings Please read the following for some incite so you do not hurt your engine by running to lean
Hi, I had to talk with someone that might have gone though the same type of high performance teething pains that I am now going through. First I built a 4x4 1 ton camper van and then converted to propane, this was 5 years ago. The motor was a 350 30 over 250 cam 1.5 rockers 9.5 compression heads mildly ported and of course balanced. I was running the largest Vaille vaporizer made, along with a 650 cfm Tecnocarb mixer. This system gave me 50,000 miles of trouble free service and I do mean trouble free, -20 +35 C easy to start, plugs were changed at 35.000 miles and was not necessary, went through air care without ever having any problems, however being a bit of a gear head wanted more. So I did my research and designed what I think is the correct motor for my application. 383 Stroker with 11.2 compression X4254H cam with 1.6 roller rockers, lift corrected to .477 / .492 / RHS Vortec heads ported to flow 260 in 184 ex at .500 lift, Along with the this I went to 0 dec height, used Beehive springs, total seal gapless rings. Now you have an idea I might have a bit of knowledge, I will tell you about the dyno and road test.

The builders suggested that I break the engine in on the dyno on gas, this produced 416 HP at 4900 RPM & 494.9 TQ at 3800 RPM however 477 TQ AT 3000 RPM. Now we hooked up the aforementioned propane system and were building good power until 3600 RPM and then just like too small a fuel pump the engine leaned out and lost power. I had a very good idea this was going to happen, so contacted Tecnocarb, drove out and picked up a new Vaporizer and Mixer. Once installed and back on the dyno the engine produced 386 HP and 452 TQ, I was happy with the results and installed in my van. Another thing I should mention is this engine developed 19.5 inches manifold vacuum at 900 RPM. The van was already running headers and mandrel bent 2.5 stainless exhausts, so just a straight forward install. I have since drove this vehicle 2000 miles and it is hard to start, vaporizer freezes at plus three C, will not idle, as in you can set idle at 900 RPM and turn engine off restart and now the rpm is 1600. I realize this sounds like a vacuum leak but I disconnected trans and brake vacuum hoses and but a plug in manifold, removed mixer installed new gasket and there was no change in the results The only thing this system does well is go fast, under full throttle pulls strong, no hesitation from stop, however if I accelerate hard and slow down to 10 miles an hour engine tries to die and I have to feather gas peddle so engine does not die. I talk with another propane guy that told me to run my old vaporizer on the front of my mixer and run the new tecnocarb vaporizer on the rear and turn the idle screw all the way in. This is not what I want to do; I will go back to my old motor and use the new motor with an injection system on a vintage ride before I do this. I am beginning to wonder whether I have a faulty vaporizer or if it needs to be electronically controlled. Okay, do you have any ideas to help steer another propane guy in a new direction to sort out this problem.

Thank You in advance for any and all thoughts
Sincerely Gerry Vass
thehook@shaw.ca

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