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Discussion Starter · #1 ·
Hello, I am looking for a 350 in excellent shape. Recent rebuild preferred, high compression, propane heads a bonus. Nothing megabuck thanks.
 

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are you interested in a 350 in poor shape?? never been rebuilt
really low compression, and no propane heads:D

p.s. for you= mega bucks only:boring l.o.l
 

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You may want to check out www.buysell.com under the edmonton region. I know its a ways away, but even better than a 350 its a rebuilt 383. I think the guy wanted around 3500 and not sure what mega bucks is, I know what I just spent on a motor and 3500 for a 383 is pretty darn good.:)
 

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what's your budget? the reason i ask is because depending on how much you want to spend, it's sometimes better to buy a core and rebuild it yourself. at least that way you KNOW what you have. if your budget is only a few hundred bucks then by all means find the best one offered within your price range.
 

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Discussion Starter · #6 ·
I'm thinking your right about at least knowing what you have if you do it yourself. More expensive, but getting screwed isn't cheap either. I reused my 350. No ridge on block, very clean from propane I guess. Heads were fried. I could see the groove worn into each and every valve. Seats just as bad. Bought some 305 propane heads out of buy and sell. Bumped compression to ~10.5:1. also did cam/lifters,timing, oilpump, gaskets, frostplugs etc. etc. Thing didn't smoke before, just low compression. Sure runs good now, couldn't be happier.

Bob.
 

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dont 305 heads flow very poorly?? how is it for power now???
 

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heads

just a thought putting a set of new heads on old engine can sometimes weaken the bottom end, but if it runns good now maybee o.k. just a thought;)
 

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Discussion Starter · #9 ·
gerry said:
dont 305 heads flow very poorly?? how is it for power now???
I figured smaller valves 1.84" intake, ???exhaust, were probably better for low rpm towtruck. The cam was milder than old one (now 204, 214 duration) because more cooling time on seat required for propane. It really upped the compression, maybe too much for heavy tow uphill on propane, but okay for these parts.
The heads came with stellite seats, and special exhaust valves for marine/hd application?(what I was told) Should last a lot longer than 1971 heads that were on it. Seems to have more power than ever? But old heads were REALLY shot.
 

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Discussion Starter · #10 ·
Re: heads

crewcab454 said:
just a thought putting a set of new heads on old engine can sometimes weaken the bottom end, but if it runns good now maybee o.k. just a thought;)

I've heard that a lot. But in 25 years or so never had it happen to me? And I've done it quite a few times. I understand the theory behind it though.It's a 1971 motor that had no ridge, and didn't blow blue even with bad heads. I was guessing it had been rebuilt fairly recently, and the propane gave old heads early failure? Maybe tomorrow I'll be posting for a good running 350? :cool:
 

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you can run as much compression as you can get, with propane and no detonation problems...
 

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Discussion Starter · #12 ·
gerry said:
you can run as much compression as you can get, with propane and no detonation problems...

Gerry you propane expert you.:p LOL!


For light-duty passenger-car applications, compression ratios as high as 10.5:1 can be used without incurring detonation (on propane). For light-duty pickups that see only occasional hard work, 10:1 is a good ratio. For heavy-duty or extended high-rpm use, stay down around 9.5:1 or 9:1 compression.
 

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ive had propane powered trucks since before you were born..
 

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where did you find that info?? that must be for dual fuel application. and on propane only application you can run far more than that but distributer must be recurved.

your ex buddy gerry
 

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for propane bob is right ......heavy duty max 9 to 1 compression
detonation with propane puts holes in your pistons
the lighter the duty the more compression you can run
 

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Discussion Starter · #17 ·
bobknob said:



Gerry you propane expert you.:p LOL!


For light-duty passenger-car applications, compression ratios as high as 10.5:1 can be used without incurring detonation (on propane). For light-duty pickups that see only occasional hard work, 10:1 is a good ratio. For heavy-duty or extended high-rpm use, stay down around 9.5:1 or 9:1 compression.

Gerry please re- read above post. Maybe Prince George propane is different than what the rest of the world uses.:laugh :laugh :laugh Not sure where you got your info, but I think it's wrong.

Mine came from this dude.


Franz Hofmann, the author of this paper, is deeply involved with LPG powered vehicles and gaseous fuel engine combustion and technology. I am an ASE certified Master Automotive Technician, with more than 32 years in automotive repair, fleet management, alternative fuel fleet conversion management, engine combustion research, and education. I hold national certification in all areas of alternative fuel repair and service. I also hold certification in vehicle conversions, service, and management from the Railroad Commission of Texas in several categories.
I have traveled internationally conducting research and conversions with alternative fuels, and a significant amount of research on supercharging and turbocharging. I am currently researching and developing new products for the alternative fuel industry. I belong to SAE, ASE, NATEF, iATN and ASAFT. I have recently completed my Doctor of Motors certification from Dana University.
 

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copied from propane site

Stoichiometric for Gasoline is 14.7/14.8 or there abouts - try 15.6 for propane. Lean huh? Gasoline and air - even with EFI is still considered to be a heterogeneous charge, meaning there are rich and lean spots all over the place (less so with EFI than carb, but you get what I mean). One of the benefits of using propane is that given that it's already a vapour when it mixes with air, it is considered to be homogeneous - or completely mixed (no rich or lean spots). This gives you better flame front propagation and a cleaner burn, oh yeah and a bigger bang.

Propane burns slower than gasoline, but not significantly. It is aslo less likely to detonate (try 854F instead of gasoline's 440F) and can handle fairly high compression ratios. Yes it does require a bigger spark to ignite it, but hey dont we all run MSD6ALs?
 

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copied from university of vermont

Table 3. Octane numbers of LPG Components.


Component Research Motor Est. max. ratio comp

propane 111.5 100 11:1

n-butane 95 92 8:1

isobutane 100.4 99 9:1

propylene 100.2 85 7.5:1

n-butane-1 100 80 6.5:1

n-butane-2 101 83 7:1

regular gasoline 92.95 83-86 9:1.



COMPARISION OF PROPANE TO GASOLINE


Performance and drivebility of propane vehicles is essentially the same as for gasoline vehicles. For propane, the gas displacement effect is 4%, it means that the displacement of air by propane causes reduction in power of 4 % (volumetric efficiency decrease) from an equilevent gasoline counterpart. Gasoline on the other hand, provides evaporotive cooling of the intake air which increases the intake air density and increases the power. Test results show 6 % less power with propane than with gasoline[11]. Propane has a research octane rating of 110 to 120, thus, it resists engine knock better than gasoline (gasoline 87-94 ) allowing a higher compression ratio for the engine, see Figure 1. Propane contains about 5 % more energy per unit mass however the density is nearly 32 % less. The net result is that a litre propane contains 28 % less energy than a litre of gasoline, Table 4. Assuming that an engine is operated on propane and gasoline with equal efficiency, more litres of propane will be consumed to provide equilevent performance. Fortunately, engines generally operate on propane with greater efficiency than on gasoline so that the increase in fuel volume is not as great as the energy comparison suggests. Propane fueled vehicles can achieve the same driving range as a gasoline vehicle by installing a slightly larger tank. Propane use consumes approximately 5 % more fuel for equivelent performance but it costs 15 % less than gasoline. Projections for the next decade, anticipate LPG prices increasing far more more slowly than gasoline[11].
 

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Discussion Starter · #20 ·
Hey proffesor gerry, I'll try and make this short. You are forgetting about heat. Load increases heat, heat increases detonation. That is why cars and light trucks can use higher compression than heavy commercial vehicle. It's all proportionate to work/ load.
 
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