Latest Engine Build

So after a year or so it finally runs, although I can't seem to get good power from the setup.

Specs are:

Ported Aluminium Head with 220cfm@0.550 intake (28"H2O) (over 330hp potential) and 165cfm exhaust, 11.2:1 compression
custom hydraulic cam 285/292 (230/237@0.050) 0.510/0.530 lift, 112LSA
Twin Impco 225 mixers (329cfm@1.5"Hg each) running sidedraught on a custom intake manifold.
250ci crank and 200ci rods with custom ACL pistons,
Balanced and blueprinted
Ford EF Falcon 12 counterweight crankshaft
Main stud girdle and ARP bolts throughout

Megajolt programmable crank fired ignition system

Timing was 28 degrees total

This combination made 240hp@5200rpm at the flywheel with 280 lb/ft flat around 3500rpm. Torque seemed to be healthy and come on quite early, on a good run it was making 260lb/ft right from the start of the dyno pull at 2700rpm.

Needless to say I was expecting to get a bit more out of a setup like this , now the head and bottom end seem to be overkill for the horsepower being generated.

So the question is, is it the cam that is letting things down (ie not being suited to LPG) and if so, are there any suggestions to help fix it?

I like the sound of the engine but could you tell me the exhaust specs and intake specs?
What did the cyl head flow with the intake on and did you flow the exhaust port with an exhaust pipe?

Cam timing doesn't seem to be an issue

The reason I ask for this information is I suspect the Inlet or Exhaust is affecting the power & torque curves

As I would have thought your engine would have produced more

Hi ausxb,

the engine builder didn't flow the head with intake or exhaust on unfortunately.

Intake is hand fabricated from 1 3/4" mandrel bent tube:
Exhaust is 6-2 tuned length extractors into twin 2" outlets, diameter is the same 1 3/4" I think

http://carphotos.cardomain.com/ride_images/1/2465/3329/6161664001_large.jpg

http://carphotos.cardomain.com/ride_images/1/2465/3329/6161664002_large.jpg

Could it be the added intake air mass of LPG needs a longer intake duration to reach the same power levels?

Link to the dyno graph is below:

http://carphotos.cardomain.com/ride_images/1/2465/3329/6161664003_large.jpg

Wicked. :wow:
Maybe you're not getting the power you think you should, but it sure looks awesome.

Hey I've had a look at the pics and a couple of things stand out

1st the 2" secondary pipes on the extractors. 2" pipe flows approx 120hp therefore 2x120hp = 240hp which is what your engine
produces. I would recomend 2 1/4" pipes 2 1/4" pipe flows approx 150hp therefore 2x150hp = 300hp?
I would make them approx 40-50" long you'd need to experiment with lengths on the engine dyno to see what the engine
responds to best.

2nd the inlet manifold. I see the runner length is quite long. Long runners produce torque at low rpm I'd recommend
redesigning the manifold with equal length runners into a plenum much like the inlet manifolds on fuel injected
engines and mounting the throttle bodies on the side. runners length's should be approx 8-12".

I dont think the cam needs to be any bigger on the inlet or exhaust.

What power were you expecting from this engine?

nice build . i have NFI about LPg

BUt are you not leaving something by not having a higher comp ratio (i 'undersatnd' lpg will support'a higher comp ratio than something like 98 petrol(95 gas in usa)?

also i note your head is 220cfm at 550thou lift but your cam only lifts to 510.

what were the flows at 500thou on the head

Hi,
thanks for the comments,

after a quick visit to the engine shop it looks like the extractors only have 1.5" primaries, which probably isn't helping things.. It seems most of the similarly modified crossflows are running 1 5/8" primaries on motors up to around the 300hp mark.

As for the intake manifold, the throttle bodies are probably within the 10" from the valves and the pipework across the rocker cover just for the mixers. Would this pipework be counted as part of the resonant length?

Head flow at 0.510" is 218cfm@28"H2O which, according to the usual calculators is 336hp.

After a bit of a dig around various forums and it seems that LPG can have the effect of stepping your cam size down 10% or so (maybe equivalent to a couple of sizes?) and after finding some actual dyno results with a Crow 14650 camshaft (230@0.050, around the same lift and a bit tighter LSA), the highest around was one car at 190hp at the wheels and another at 245hp at the flywheel.

Since my engine is in that ballpark, I'm thinking the next step to get to the desired power will be to take advantage of the LPG and run a bigger than usual cam and hope it smooths things out in the same way, then play around with cam timing and try and get a custom set of extractors made.

My aim for this engine was to try and get a streetable 300hp on LPG, and to do my bit to add to the collection of data on Mike's new cylinder head along the way.

I've never run anything on gas, but if this were gasoline, your lamda would indicate you are a little rich across the board. Are those the expected numbers for LPG?

I agree on the 1.5 primaries. You might need a little more exhaust pipe after the collector as well.

There's absolutely nothing wrong with the power or torque figures. There is no rational basis for complaint. You need to do waht we call in the trade Index Tests on the dyno run.

First Index, On a six cylinder with a manual transmission, I use a standard 1.265 rear wheel hp to flywheel multiplier to get real net flywheel hp. In this case, its based on Borg Warner 78, T5 manual, XR6 size tires.

240 rear wheel hp is therefore about
304 flywheel hp (227 kw DIN Net )
and 280 lb-ft

is 354 rear wheel lb-ft, or 480 Newton meters DIN Net.

At 2700 rpm, there is 169 hp or 126 kw DIN Net, and at 3500 rpm, there is 236 hp or 176 kW DIN net. So at just 2700 rpm, you exceed a 1979 Commodore 308 flat out, and a Porsche 928 or 911SC flat out at just 3500 rpm. Peak power exceeds the last 2002 Windsor XR8 Rebel 5 litre Falcon falt chatt.

Second Index.You have 1.41 lb-ft per cubic inch, which is a ballistic figue you don't get on a anything except a twin cam multivale engine modifed or an independent runner engine with fully gasflowed race spec head. 1.39 lb-ft per cubic inch is as basic BDA Escort figure, and you can just about get that on a race preped A-series or Pinto engine with a lot of specialised cam and head work.

Now, back in 1990 a Street Machine article imparted a little of Larry Perkins logic. He said the least rpms to get the most power yielded the best results. I think he said 460 hp at 6700 rpm beats 469 at 6900 rpm. So he was talking a 304 cubic inch race engine, and that implies than an aspirations index of 4421 for 460 hp beats the 4472 for 469 hp.

Third Index.So multiply calculated flywheel rpm by cubic inches, and divde by hp 5200 x 254 ci/304 hp = 4344

Taken from this Aspriations Index perspective, you have a ratio of 4344. A normally aspirated Twin cam I6 or V8 will do about 4800 at best. The lower the number, the better. The Falcon DJR 320 and 360 Modena Ferrari was about 4000, a world record for hp per cubic inch per rpm. Larry Perkins carbed 725 cfm Quadrajet 462 hp at 6700 rpm Group A Commodore 304 took 4400 in 1987. A V8 supercar has a ratio of about 3630, which is the same as a 1984 Cosworth DFV 3 liter 600 hp at 11000 rpm from 183 cubic inches.

Compared to any street engine, there isn't any more extra to come.


On the basis of lb-ft stats, torque is unmatched
On the basis of power through the curve, it's expectional
On the basis of peak power, it is positvely ballistic.

In summary, you have net power eclipsing Leo Lenoards Phase 3 bashing E49 race car (295 hp net), and better than the gross hp rating of Mopars hottest triple Webered 265. Torque is 22% higher than a twin cam XR6, and 14% higer than the gross figue Mopar claimed in 1972.

The fourth index is how much power you have for cfm rated at 1.5"Hg. You have 658 cfm of carburation, and are making 304 hp from 254 cubic inches. I got 375 hp at 5800 rpm from a 750 cfm carb on my mates 351C 2V back in 1988 with his 3000 pound XY Falcon. Aspirations Index was only about 5521.


The fifth index is weight to net flywheel power. You have 304 hp in a 2570 pund Cortina. 5.14 kilos of weight for every kw is like having a 350 kw XR6 turbo in the driveway.

Start smiliing, take it to the drags, and doing sub 12.5 sec standing quarters

Hi xctasy,

thanks for the detailed reply! Only problem is it was 240hp at the flywheel i.e. about 0.95hp/cubic inch with an open exhaust on an engine dyno. If I had 240hp at the tyres or 304hp at the engine I would have been more than happy!

MastangSix, in terms of Lambda on LPG, the engine was too rich in the midrange at 0.75-0.77, it made better power there at 0.85-0.88 on another dyno run. The thing is, even in the high 0.9s at peak power, it made the same figure on a different run with Lambda at 0.86, which I found quite unusual. My only theory is that there is another limiting factor preventing it from making more power than the air/fuel ratio.

After some research and a conversation with ausxb, I am going to bolt it it back in the car, get a custom set of extractors made with at least 1 5/8 primaries, try adding a plenum to the intake manifold and then play with the cam timing to see what can be done.

My oppologies for incorrect power conversion factors. I see what you mean. 240 hp at 5100 rpm from 254 cubes is a 5400 AI ratio. I'd expect about 4600 or better with a reduced volume intake. That would be 282 hp at 5100 rpm, and a small boost in torque by about 10% to around 308 lb-ft at 3500 rpm.

Based on Vizards observations with swann neck intakes in Mini A- series engines, and some work publicised by Leigh from GRA( gas research), and Bob Chamberlain and Phil Irvings discssions on carb to valve cc and length calcs you are likely to be loosing a lot of power. LPG generally looses 15% peak power on a good indendent runner Weber DCOE set-up, so I'd be expecting an Aspirations index of about 4600 for you Cortina with a better intake. Based on the BA LPG Falcon with its large 2.5 liter intake, I'd expect 20% power is lost due to large runners.

The intake is therefore too long, and has invoked a swann neck effect. This is where the intake runner volume and geometery has resulted in a centriguing out of the air fuel mix, and the total volume in this case is too large to respond to the fast rate (300 rpm per second under engine load) power requirements.

I've got a set of tubular intakes to suit the CA225 carbs as a direct mount. It uses the Fiat 2300S type of carb alignment, were 2-bbls merge into three ports each bank of three cylinders. See http://www.fordsix.com/forum/viewtopic.php?f=3&t=27696

Specifically, this is the intake design .

The TC-TE Cortina brake booster before the 1981 TF Girlock brake master cylinder upgrade is dangerous and has a delay built into the booster. So I'd look at an Escort RS2000 master cylinder linkage, or a VH44 booster, or Mustang SN95 (Aussie market 2001/2002) power brake booster.

That would allow you to drop down the intake volume from the approximately 2.8 liters it is now to less than 1.2 litres. The peak power is torque verses a speed factor. Having long intake runners raises the response time over the 3000 rpm mark, and is reducing power. LPG has a cooling effect which then displaces air, reducing the charge density as there is room for the mixture to escape form the gas carb and expand and vaporise further. This means the air fuel ratio is no longer finely adjustable. The carbs ability to respond to air fuel verses vaccum then is insufficient to make power.

Hey any progress since we talked?
cheers

Come back!!!! Not to badger the witness, but Things look pretty quiet. Mon Feb 06, 2012 was his last visit.

I'm a bit ashamed of the advice, given the sub 14 second quarter mile stats his ride would end up with. And he aint been back posting since.

His work was actually ground breaking for an Aussie 250 with Classic Inlines head and the best American Impco carburation around. Ak Miller would be proud of him! Plus, he's hit on packaging the intake runners in a way that lends itself to using the F150 4.9 EFI throttle body and wet gear, solving some of the space limitations tall 250 engines have if they don't have the Classic Inlines carb hat and intake manifold.

For the Americans and Aussies in a metric mood, 73GreenMachines figures of 240.5 hp at 5200 rpm and 273 odd lb-ft at 4100 rpm is specifically awesome for a propane engine. Compared with standout modern OHC sixes, his 179 kw at 5200 rpm and 370 Nm at 4100 rpm, is better power to weight than the 15.3 second AU VCT XR6, and its in a 2750 pound 1250 kilo Cortina.

And the power to weight ratio would be better than a 14.5 second 1/4 mile 2003 BA XR6 Turbo with 322 hp (240 kW) and 3692 pounds (1675 kilos), and its torque per pound or kilo is better than a 13.6 second Falcon F6 Typhoon.

Objectively, given the current package constraints, that Alloy head Cortina is as good as it gets.

I've looked at all the other combos, and especially the suggested alternative we suggested. 82CapriRS, a 1973 Maverick owner, showed an example on the FourEyed Pride website, with a Craiglist sale of a world record 1970 Ford Maverick 2-door with experimental pre production Bosch injected 170 engine, used for a170 cubic inch class Land Speed assault on Bonnville.
Yes folks, its the old Aussie 2V 250 head 1 year before it showed up in the M-code 170 HP 250 1971 XY Falcon GS and Fairmont.

So the Aussie head really was an all American show case, and with Mikes Classic Inlines head, it still is today!





If its ported AU to FG style LPG injection, this would certainly be the arrangement to tick, with a power brake booster or Works Escort style Triton brake set up which would make the space for it all to fit on in.

The other thing is that the LPG manifold 73GreenMachine has made is perfect for an F150 4.9 EFI throttle body, eliminating the hood clearance issues.



And on a turbo charged 250's, like Georges old Crossflow, his F150 4.9 EFI twin bore throttle body got him into the 10's.