Thread: need some advice for my hotrod project

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can anyone please offer some advice for my hotrod project, i am building a 1934 open motor hotrod, i would like to run a twin turbo 350 running straight liquid petroleum gas (lpg). i have heard the boost would be around 6 psi, a regular street driven car with a turbo 350 and i am thinking 3.55:1 rear end. nothing to flash, just very relaible. i dont think heat would be a issue as the motor wont have side covers, just a bonnet top.
does anyone have suggestions on heads allow or cast and what size chambers etc
after reading many other threads and learning some more, would higher rpm be a better solution as in shorter rods and longer pistons, as such i think i read.
could anyone offer advice on some motor spec etc...any advice for what i might have to consider etc

I don't know anything about running propane, but build it like you would a gas motor I'd guess ( people convert 305's and 350's to LPG all the time, not special built ), forged pistions, 8.5:1 compression, turbo cam ( short exhaust dururation, long intake dururation, very little overlap, 114* LSA ). keeping the boost at 6-8 PSI would work great

Originally Posted by Matt167

I don't know anything about running propane, but build it like you would a gas motor I'd guess ( people convert 305's and 350's to LPG all the time, not special built ), forged pistions, 8.5:1 compression, turbo cam ( short exhaust dururation, long intake dururation, very little overlap, 114* LSA ). keeping the boost at 6-8 PSI would work great

after reading a thread earlier about people building chevy's using 400 blocks with a 350 crank to get better rev's with a bigger bearing, would anyone suggest this as a good idea

this is kind of one of those builds that will kill a wallet real quick. one turbo cost a lot let alone 2, then its kinda like running multiple stages of nitrous. there are a lot of do's and dont's in a build like this, and they are sometimes better left alone if you have no knowledge in this field. and your fabrication skills better be good to get them both to fit CORRECTLY and function CORRECTLY in the engine bay. sorry i cant help with build advice, i can only help with you with the future possible subscription to tylenol 3 to control your headaches.

Don't worry about the propane setup. I just recommend thinking about tank mounting. This is critical for DOT specs. Bulkheads have to be placed and vapor barriors installed. Not a bad deal to do, just time consuming. Intake duration doesn't have to be long, but a bit longer exhaust helps evacuate the extra consumption of Turboed charge in the cylinders. If boost will be down to the 6-8 range, there will some areas of fudging (doesn't have to be "dead-on") if boost is going to be higher, consideration of cam selection needs to be reviewed and is more critical. Propane is higher in BTU's which represents higher octane. Remember it is a dry fuel (vapor) so your consideration of where to introduce the LPG into the system should be thoughoughly thought out.

Originally Posted by nitrowarrior

Don't worry about the propane setup. I just recommend thinking about tank mounting. This is critical for DOT specs. Bulkheads have to be placed and vapor barriors installed. Not a bad deal to do, just time consuming. Intake duration doesn't have to be long, but a bit longer exhaust helps evacuate the extra consumption of Turboed charge in the cylinders. If boost will be down to the 6-8 range, there will some areas of fudging (doesn't have to be "dead-on") if boost is going to be higher, consideration of cam selection needs to be reviewed and is more critical. Propane is higher in BTU's which represents higher octane. Remember it is a dry fuel (vapor) so your consideration of where to introduce the LPG into the system should be thoughoughly thought out.

thank you for a speedy reply with worthy context
it has been suggested here in oz that i might have to consider using twin mixers and gas carbs to feed the fuel, i am tryin to think of a way of using a twin throttle body and and some other form of entering fuel to the motor. what sort of heads would you suggest aluminum or cast with stainless valves.
what size chambers would you recomend

Originally Posted by DennyW

You have advantages if you do run LPG. The cylinders stay clean. You can up the compression, and advance timing some. I believe it is still about 124 Octane. I used to work on Forklift trucks, and it is very efficient. The overall performance is similar. But the advantages to running it are a benefit to the engine life. Heres a little something you can check out to give you an idea.

http://www.pirate4x4.com/tech/propane/index.html

thank you DennyW
when i considered this idea i heard it would be a great idea, firstly for the price of gas and how clean your engine runs and the life span of the motor.
do you know of many types of gas carb or alternatives as i have heard mention of a donut type system on fuel infected cars running duel fuel

Not to burst your bubble, but I have several propane setups I'd give you free. Took 'em off and converted back to dinosaur juice. Lousy mileage, poor fuel availability, and no power, plus reduced valve guide life and no heat in the winter, just weren't worth the hassle.The final straw was when the gov't wouldn't renew my insurance unless I got new inspected tanks.

Originally Posted by DennyW

You have advantages if you do run LPG. The cylinders stay clean. You can up the compression, and advance timing some. I believe it is still about 124 Octane. I used to work on Forklift trucks, and it is very efficient. The overall performance is similar. But the advantages to running it are a benefit to the engine life. Heres a little something you can check out to give you an idea.

http://www.pirate4x4.com/tech/propane/index.html

R POPE
could you please advise of some of the troubles you found you had with this sort of set up.

Originally Posted by R Pope

Not to burst your bubble, but I have several propane setups I'd give you free. Took 'em off and converted back to dinosaur juice. Lousy mileage, poor fuel availability, and no power, plus reduced valve guide life and no heat in the winter, just weren't worth the hassle.The final straw was when the gov't wouldn't renew my insurance unless I got new inspected tanks.

I remember my father had a car back in about 1981 that he converted over.
I think three years later he took the system off.
The tank and the rest of the parts sat in is shop until about 1984.
Someone bought the kit and that was my first time I had ever been around it.

Yes,propane can be great fuel,loves high compression,lots of spark advance. Has some downsides,like finding somewhere to put that big tank, having to convert it back to a gas to burn it,and has a tendency to burn out exhaust valves.Now given that the turbos heat the air up considerably as they compress it, you may be able to add the lp directly letting the heat of the air convert it. Could be very interesting! Hank

You might try Gale Banks. He's been doing the twin-turbo thing for a long time now.

http://www.bankspower.com/twin-turbo-products.cfm

thank you to everyone so far for your positive responses and advice, the tank is going to go behind the rear seat, there is enough room there for it, quite an easy mounting job.
as for the mixer issue i have been infornmed here in i might need two, well either way they will be located just inside a sealed compartment in the passenger front upper leg area inside the dash not too much of a loss of space with heater hoses to help do the conversion.
still to work out the carby ideas, real curious on the rumors to use a donut style, similar to what they use on E.F.I cars using duel fuel and a set of throttle bodies, that way i could use maybe duel throttle bodies.
so i guess a little more to decide on the gas set up, but alot to decide on the type of bottom end for the small block before i have to work out the top end.
i have been looking at a late model roller cam block 4 bolt mains and going from there in the terms of rebuild.
so for now has anyone any ideas for gas carbies or donuts style systems
and how does that bottom end idea sound and what are your suggestions
if your interested i will try and work out how to post up some pics of the car so far