Hi guys,

I have just dyno'ed my 84 bronco with is new engine in it, a propane(lpg) Scat-stroked 408 running at 8.5:1 with 4psi boost from an eaton supercharger...
running through a stock C6 trans, it pulled the embarrasingly low figure of 240hp / 540tq at 5400rpm peak.
I will have the cam specs and photo of dyno sheet on tuesday, but I was really expecting at least 300rwhp from this setup. below is the parts for the engine, including ported aluminium race heads!

:/ my manual states the bronco is 217hp / 410nm stock! !!

anyone got any feedback on this?

351 cleveland block (Hard Blok filled)
Scat 4340 4.00" stroke crank
Scat 6.00" H-beam Rods
ARP main Stud Kit
Probe forged Pistons (4.030")
Speed Pro moly plasma rings
Clevite bearings
Felpro Gasket set
Pro Race steel balancer
Rollmaster timing chain
AFD custom camshaft and lifter kit (mechanical solid roller)
AFD SP2V Extreme Complete Competition Ported Alloy Cylinder Heads
AFD SP2V Intake manifold
Platnium Race Shaft Roller Rocker
Crow hardened pushrods (5/16)

 

It takes a rather larger amount of LP to make good power, the torque seems up there, but hp sure isnt. Make sure the LP regulator is keeping it fed it at the higher rpm. Almost sounds like it's not getting enuf.

 

interesting build ie lp and blown.

from what i've learned...not know...compression would be the culprit. I know the theory of limiting static compression due to super charger but lpg needs a lot of pressure.

So I ask if you know the final dynamic or operating compression equivalent. If your running 8.5 and you have an IVC of, lets say 58 then your dynamic compression would be a bit less than 7:1 and, unless the 4psi makes up for 2 full pts your below what most say you should have to make up for dimished btu by utilizing the high octane.

I'm building a propane 400- carbed so did some leg work ...but it's a guess. It's beyond me other than that.

please keep me informed... and how the heck do you get 540 ftlbs and only 240hp if both at 5400? bet torque was down around 3k?

 

and what are the cam specs?

 

what does the distributor advance curve look like? what's your initial, total and what rpm is it all in by? what kind of distributor is it? vacuum unit?

 

had to modify the above...

 

Horsepower = Torque x RPM/5252.

540 ft-lbs of Torque x 5400 RPM /5252 = 555 Horsepower.

The calibration of your Dyno is off.

Is this a Chassis Dyno or engine Dyno?

You can lose 30% of your power through a C6 transmission, but I believe that applies to torque as well as HP in a Chassis Dyno.

How about your axle ratio and tire size? Are they accounted for?

The Bronco Manual gives Horsepower at the flywheel. A stock Bronco wouldn't break 200 HP on a Chassis Dyno.

 

After much ado about nothing - the truck broke the shops dyno - specifically, the chain that links the drums together. his dyno was reading false. I pick up the truck tomorrow. will post everything i have, when i called today he couldnt remember torque from memory, but confirmed it was making torque low, hp high. as i said ill get the dyno sheets and post them,

oh, and Danlee? thanks mate! i was worried the stock specs in the manual were Rwhp!
but you've brightened my day, so thanks buddy.

more tomorrow

- Sean