LPG on 1940 Chev

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wilgoo50
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Joined: Tue Feb 16, 2010 9:12 am

LPG on 1940 Chev

Post by wilgoo50 » Tue Feb 16, 2010 10:12 am

Hello. Just stumbled across this site a week ago and decided to join. I am currently working on a 1940 Chevy 1/2 ton pick up. (Mostly waiting for the body shop to finish up now) I am running a 383 stroker engine, dual 425 Impco mixers, dual regualtors, single vacuum lock off. ( 700r4, NP217 transfer case, '86 S-10 4x4 front diff and clip, '96 rear diff, 4 whl disc, etc etc) Propane cam, est. 425 HP. I have installed the LPG to hopefully keep the running cost down a bit with fuel prices on the Island ( I hail from Courtenay, BC) and as a daily driver I really wanted somthing different. I love the simplicity of the propane set up, no COMPUTERS. I'm looking forward to some new insites about LPG, its not so common on the coast or at least the parts suppliers seem to be few and far between. It would be great to find some West Coast suppliers (local Island spots).


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Steptoe
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Re: LPG on 1940 Chev

Post by Steptoe » Tue Feb 16, 2010 2:19 pm

"Daily driver keep running costs down"
And hammer off at the line and will still light up easy.
Thats exactly what I am doing with my camaro
The secret is keeping the rpms down...ie final ratios ..so at 30 mph Im 1000 rpms
Then comes the issue of torque converter continually slipping...Im running a turbo 350 with a 1200 TC
The next issue it building the engine to run within the rpm range, so a very low duration/overlap cam a increased lift from stock, small carb for bottom end response, efficiency....so im running a single 425

The advantage of "computers" /injection is the engine is efficient right thru the rpm range, carbs are not..they are most efficient at WOT when the cfm requirement = engine displacemt/rpms.
Hence why I start leaning out around 4300 rpms.

You should be looking for good bottom end torque rather bragging rights HP...this gets you off the mark real quick...hp 'kicks in' for when one gets up to hi speed overcoming drag.

Oh I also get better results with a dual plane alley cover and cast truck rams horns than headers
Headers are like carbs, they work best at high rpms, down low they scavange.

So the obvious question is "why did they not build factory engines like this?"
Well they did..small carbs cast heads....but had bigger stock cams
Petrol was cheap
And the marketting issue...right or wrong the marketting guys must have thought a car that tended to be loose on take off...and even potentually damgerous in the hands of inexperianced drivers...real loose on damp roads....and would run out of legs at 5000 rpms....the red line power was all the rage back then.
Also the basic accepted concept back then was rpms= 2x mph ie 3000 rpms =60mph

Have tou worked out what rpms you will be running @ 60 mph?
Your 700r has nice low 1st and 2nd with the higher ratio for cruise in top.
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wilgoo50
Posts: 9
Joined: Tue Feb 16, 2010 9:12 am

Re: LPG on 1940 Chev

Post by wilgoo50 » Tue Feb 16, 2010 11:02 pm

Sounds like you have your car tuned real well. this truck has been a lot of years in the making and like my earlier post said (Still waiting on the body shop....) I have a stock GM Gen I block , cast RMS heads (2.02 in, 1.6 ex) roller rockers (1.6) Edelbrock dual intake .....beefed up 700r4....with this all in and the tire combo (3:73-1 diffs) 60 mph puts me in at approx. 1875 rpm on OD. Trans wired up for lock up in 4th gear only...............One of my concerns with the LPG at this point is the operating temp. I started out with a 160' thermostat and froze up the convertors at idle....bumped up to a 180' 'stat and all seems well now. Working on setting up the fan and I'm curious if anyone wants to throw in any opinions on a good guideline for fan on/off operation (on 190'/off175') (ON 210'/OFF 185')??? any suggestions?

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Steptoe
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Re: LPG on 1940 Chev

Post by Steptoe » Tue Feb 16, 2010 11:29 pm

started out with a 160' thermostat and froze up the convertors at idle....
Thats not the 160 ..
If the converter is above the valley cover/thermostat housing/radator, when filling up you can air lock it
1/either drop it lower
2/ loosen off the top hose (outlet) jubblee clip, fire up the engine then slowlt wiggle the hose nearly off till w2aster comes our, replace ....

LPG loves running cold..If I have a 145 in it runs about 160 and with the 160 in about 165...even towing ..See my avatar.

Mine is still the orginal 69 matching #s block..orginal crank, rods etc...rebuilt with AC?L flattops that ACL make for LPG.
Earlier cast 202 heads with small chambers to up the Compression...and old performer (70s) dual plane spredbore manifold and adapter plate with a divider in and milled anout 5 mm off it (so the air cleaner clears the hood...just..it does runb the paint off ..just.

Fan...forget electrivc fans and BS...go to the std chev fan and thermo clutch with shroud...so long as the raditor is in good nic and clean, you will NEVER have any issues... oh and one of those stock brass raditors in 1st gen type cars...they are SO way over built...
If you go to camaros.net, run a forum search on the subject, u will see me and damn near all the other guys who know what the hell they are talking about say the same...it is the young guys full of marketting BS want the modern 'best' who have troubles.
Sounds like you have your car tuned real well. this truck has been a lot of years in the making and like my earlier post said
viewtopic.php?f=5&t=1068
I converted to CNG back in about '82 then to LPG in about 84 and dedicated in 86
I have played with a few cams and stuff in that time....did rebuild new cam a while back and tuning in in the above thread
I was basically doing the same thing before the internet...decided to make a a reference log to give others who dont have dynos )2 sensors and stuff.
Get Franz s manual..there is a post about how to buy it here somewhere....not just how to but gives in goog old fashised lay persons language a understanding of what you are doing.
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Frank
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Re: LPG on 1940 Chev

Post by Frank » Wed Feb 17, 2010 8:41 am

Welcome to the forum!

I would have to agree with Steps that your converter frosting issue has to do more with water flow rather than with temperature. Keeping the converter low reduces the chance that it can become airbound.

As for your thermostat, I found that I got better fuel economy with the Model 425 (open loop) on my 350 Chevy when I kept the converter as hot as possible. I would try to keep the induction system cool rather the entire engine and the extra heat is nice in the winter. I also used the EFE-TVS (heat riser actuator vacuum switch) to control the vacuum motor in the snorkle as well. The warm air to the carb at start-up minimizes carburetor icing. Your dual 425 setup makes ram-air a bit of a challenge but you could probably fabricate a ducted air cleaner without too much trouble.

Regarding the fan, engine-driven fans consume power, which reduce fuel economy and power. Clutch-fans minimize this parasitic load on the engine. If you have enough capacity in your rad, an electric fan should only cut-in in city traffic. Otherwise, the motion of your truck should produce enough airflow by itself to keep your engine cool but you would have to determine your truck's natural operating temperature once you get it on the road. For reduced power consumption using a 180°F thermostat, I would try 195-ON / 185-OFF to start.

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