[DeTomaso] An engine-bay shot from Japan
MikeLDrew at aol.com
MikeLDrew at aol.com
Wed May 12 20:05:59 EDT 2010
In a message dated 5/12/10 16 29 7, kirby.schrader at gmail.com writes:
>
> So, wow!!!! That yellow thing will have some HP now!
>
Yeah, for a change!!!! The dirty little secret about my Pantera (which I
really made no secret of) was that although it sounded bad-ass, it had NO
power. I sent a listing of my original engine's components to Dan a couple
of years ago and his assessment was that it was the worst 351C ever
built--this despite the fact that each of the individual components was of excellent
quality.
I probably could have gotten away with a simple camshaft change, but
instead elected to go whole hog and have a 408 stroker built with CHI 4V heads.
Dan sold me a block (which actually he purchased from Steve Liebenow many
years ago), I bought the stroker kit and bare heads, and Dan designed a
hydraulic roller cam. Oh, and I had to buy Crane/Ford Motorsport hydraulic
roller lifters, and new valve springs. But every other part of the engine, from
front to back, was reused from my existing engine--valves, timing gear
drive, oil pump, flywheel, intake, rocker arms, carburetor (actually my Larry
Stock 700 double pumper, a really excellent carburetor, is being stripped
and the pieces joined with a new Holley 750 center section, by Bobby Oliver),
etc. etc. etc.
I purposely made some design compromises when planning this engine out.
As John Christian so aptly states, "You can't drive a dyno!" and to that end,
I avoided the temptation to go chasing after a peak horsepower number at
the expense of any number of other things, including practicality and
driveability. I wanted this to be a very low-key engine, and keep the stock engine
screen, which ruled out the vast majority of performance intake manifolds.
That, plus the cost factor, drove me to the CHI 4V heads as opposed to the
admittedly superior 3V heads.
Dan designed the camshaft to maximize the area under the torque curve,
rather than generate more power at the top end. Dan also factored in the
restrictive ANSA GTS exhaust system (even though mine is gutted, it still robs
considerable horsepower), and designed the cam around that restriction. A
freer-flowing exhaust system would have allowed different cam specifications
which in turn would have generated a fair bit more power, presumably.
However, if one used that cam with my restrictive exhaust, the results would have
been considerably worse than the results achieved using the cam I have now.
Dan will have to do all the mojo math magic to reveal the results. Dave
McLain's home-made dyno has been repeatedly demonstrated to be 5%
pessimistic. He has participated (with considerable success) in the Engine Masters
competition several times, and in each case, when his engine was installed on
their super-duper calibrated dyno, the results were 5% higher than his dyno
showed. Also, Dave runs his engines through rather restrictive Mustang
headers (which have a sharp downturn right at the exhaust ports) and mufflers,
both of which adversely impact the numbers generated.
Dan doesn't account for the losses associated with the sub-optimal dyno
exhaust system, but factoring in the 5% pessmism issue, my engine made 527
(529?) horsepower at 5900 rpm, I believe. What really impressed me was the
torque curve, which wasn't curved at all. It was a perfectly flat line at
just under 500 ft/lbs, straight across from 3000 to 6200, with almost no
variation at all from one side to the other.
The incredible thing is that Dan is using the new Dynomation software, and
the difference between the software prediction of my engine's performance
and the actual output was only 2-3 hp, well within the range of statistical
error. That software is really, really good. It's not so good at
predicting torque however; demonstrated torque output is consistently lower than the
computer predicts.
Right now, my engine is about to be tested (just for giggles) with a pair
of Autolite in-line four-barrel carburetors on an independent runner intake.
With no other changes the software is predicting about a 40-50 hp
increase.
Tried to upload a photo of the engine in that configuration but my POCA
album went crazy, and won't let me in now. :<(
Mie
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