Hello again all;
I'm back with more info, and more questions. I understand most of what I need to get for this project, I want to run it by you guys for additional input, which you are famous for
(all prices in Australian Dollars)

right then; down to basics.
Project;
straight LPG supercharged 351 4V cleveland in 1984 Ford Bronco XLT

fed by twin 480 CFM LPG carbies (http://www.gasresearch.com.au/productgoldseries.html)

blower from CAPA, a twin screw m112 eaton at 1.84 litres of air per rev:
M112 Supercharger with snout
$ 3,115.00
(http://www.capa.com.au/prices_eaton.htm)

now I need piping from air intake to S/C unit, and I've worked out pulley ratios and boost levels in the following:

---------------- M112 -------------------- BRONCO 351 4V
M112 chart for my engine:
(((351[cid]x4500[max rpm]/3464)=456)) can inhale 456 Cubic feet per minute (CFM)
(5.75" crank pulley / 2.75 blower pulley) = 2.1:1 ratio
9450 blower RPM at 4500 engine RPM
9450 blower rpm x blower LPM 1.84 = 17388
17388 x 0.03531=614 CFM

CFM excess to boost
blower CFM - engine CFM = excess CFM
614 - 456 = 158
boost = (excess CFM/engineCFM) / 14.7
(158/456)x14.7 = 5.1 pounds of boost.

ok so with that pulley S/C setup i should be pulling 5.1 PSI boost at sea level... now is there anything I've missed before I go ahead with this? I mean I cant see how I'd work an intercooler into this setup, and aside from small ignition retard, the compressed -> expanding LPG should cool things down a bit right? I'm only worried about detonation ruining everything.
so, any thoughts please and anything I've missed.
(already have strengthened conrods, forged flat-top pistons, total engine recondition 3 months ago, stock 2 1/2 inch exhaust)

- Sean

 

? no replies to this post in 4 days ?
does this mean I have it all right... or that my original post was too long to hold people's attention?

 

I've now bought the EATON m112 ($485 US) and its being UPS'd from the US to Sydney as I write this. all I need to do now is find an intake manifold for it to sit on. anyone know where I might find anything to suit this? EATON m112 to a 351 4V ?

 

You've taken the advice I left last time but in my opinion you are way too conservative. You're only running 4500 RPM (on my 361C 4V) I was running up to 6500; those heads like to breathe! Likewise, with LPG's ability to resist detonation I'd be running up to 1ATM (~15psi). If you are going to do it, build the monster. It will be well behaved, I promise.

 

Hey, I'd love to go up to 9 psi, but the blower's max rpm's are 12,000. plus if I wanted to pull past 4500 engine rpm i'd need a new crank.
I also believe 5.1 is very conservative, but that's why I'm looking for a 2.5 inch blower snout pully, which will put me at 8.25 psi at 10350 blower rpm.

is there any problem with welding a sheet of steel onto my old intake manifold and then cutting the blower pattern onto it? would that work as a sc intake manifold?

- Sean

 

You'll want some rigidity there, I wish you had said 'plate' instead of 'sheet'. I'm not sure where you feel you need a new crank. My 351 (but not all) came with a nodular iron crank. Like I said, I spun it much higher than 4500. The only weak link in that motor is the journal size, which limits you on oiling. You can add an orifice to force more oil flow to the crank journals. My opinion (and its only an opinion) is that crank is good to 7500 stock.

Still its such a shame to have LPG and only 8psi.

 

The M112 supercharger arrives on monday. I wont be able to go past 9 psi as the unit has a 12000 spin limit... unless I bolt on *two* m112's... I've seen a couple of pictures of that. right now I'm looking forward to seeing how the lpg supercharging system works out, then depending on the results I'll work my way up. I'm having a fair bit of trouble finding an intake manifold with a wide opening that I can weld *plate* steel onto. any suggestions?

 

UPS delivered my Eaton ex-lightning M112 supercharger today!
all the way from Arkansas to Sydney, took 5 days. I'm thrilled. now I have to fabricate and intake manifold to fit between the M112 and my 351C. any suggestions from anyone? this is the LAST step before I get it installed.
I currecntly have an edlebrock street torker sitting on the 351c.