[DeTomaso] Dynomation as a Dyno Lie Detector

Sat May 15 20:33:15 EDT 2010

Increasing CR moves the entire curve up on a % basis.

Increasing from 9.8:1 to 11:1 might move our Honda only 6 or 7hp, but that's
probably a 20% increase.  ;-)

I don't know the %, but I'd bet 5-10% per point.

In practice, it depends greatly on the camshaft though.  Use the CR that
your camshaft was designed to work with.  If you use too low CR with a cam
with too much overlap, it's going to run like a pig at low rpm's.

-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com] On
Behalf Of Will Demelo
Sent: Saturday, May 15, 2010 7:16 PM
To: Daniel C Jones; Pantera REALBIG forum
Subject: Re: [DeTomaso] Dynomation as a Dyno Lie Detector

Increasing the compression from 9.8:1 to 11:1 only made 6 or 7 more 
horsepower? I would have thought that more compression would have made more 
power. Why would someone take the chance on detonation for only 7 more hp?
Will
----- Original Message ----- 
From: "Daniel C Jones" <daniel.c.jones2 at gmail.com>
To: "Pantera REALBIG forum" <detomaso at realbig.com>
Sent: Saturday, May 15, 2010 6:37 PM
Subject: [DeTomaso] Dynomation as a Dyno Lie Detector

> That suspicious Powerblock 351C buildup has re-surfaced in March 2010 
> issue of
> Muscle Car Review magazine in an article entitled "Cleveland Hall of
> Fame".  The
> article has a picture of the "finished beast" without distributor, water 
> pump,
> balancer, thermostat housing, etc. and claims it was dyno'd at 466 HP and 
> 471
> ft-lbs of torque but no RPM values are provided.  It also claims a 
> compression
> ratio of 9.8:1, though the Edelbrock Performer RPM 351C-2V cylinder heads 
> are
> nominally 60 cc's and Keith Black KB177 flat top hypereutectic pistons
> are used.
> Those pistons have a 1.67" compression height and valve notches of 2 cc's 
> and
> are listed by Keith Black as providing 11.07:1 compression ratio with
> 62 cc heads.
> I ran it through a compression calculator that I wrote, assuming 60 cc 
> chambers
> and a Fel Pro headgasket of 0.041" compressed thickness and got an 11.1:1
> compression ratio.  Not even close to 9.8:1.
>
> The article states the camshaft was a Comp Cams part number 32-000-5 which

> is
> a generic core part number.  I believe that to be a typo and the part 
> number is
> actually 32-600-5 which is the smallest 351C Thumpr cam:
>
> http://www.compcams.com/Cam_Specs/CamDetails.aspx?csid=1477&sb=2
> Grind Number 279TH7
> Thumpr Series hydraulic flat tappet, high performance street, stock
> converter ok,
> best with 2000+ converter and gears, choppy/thumping idle, 2000-5800 RPM 
> range
> 278/296 degrees advertised duration
> 226/241 degree @ 0.050"
> 107 degrees LSA, installed on an intake centerline of 102 degrees
> 0.506"/0.493" valve lift
> 0.300"/0.291" lobe lift (appears to be a typo on the lobe lift or
> assuming short
> than 1.7 rocker ratio)
>
> 0.006" valve timing is given as:
>  int open  39 BTDC
>  int close 67 ABDC
>  exh open  80 BBDC
>  exh close 45 ATDC
>
> The specs listed in the article are hydraulic flat tappet with:
>
> 278/296 degrees adv. dur., 0.491"/0.476", 107 LSA
>
> but the lift assumes the 1.7:1 rocker ratio of the Comp Cams Magnum
> roller rockers
> used in the build.  Still, the lift numbers don't quite match up to
> either the lobe
> or valve lifts from the Comp Cams card.  If you assume the valve lift
> in the Comp
> card is with 1.73:1 rocker ratio, the lift with 1.7:1 would be
> 0.497"/0.484".  If
> the lobe lift is correct on the Comp cam card, the lift would be 
> 0.510"/0.495".
> Let's be generous and use the largest lift and assume cam specs of:
>
> 278/296 degrees adv. dur., 0.510"/0.495", 107 LSA
>
> Edelbrock cylinder heads 2.05" 1.60"
>
>
http://www.edelbrock.com/automotive_new/mc/cylheads/ford/cle_perf_rpm.shtml
>
> Lift     Int    Exh
> 0.100  058 054
> 0.200  120 105
> 0.300  180 138
> 0.400  227 151
> 0.500  260 161
> 0.600  265 165
>
> Flow numbers as tested on Edelbrock's SuperFlo SF-1020 flow bench.
>
> Inputting everything optimistically and using Edelbrock claimed flow data
> with open headers and 9.8:1 compression ratio:
>
> 422 HP @ 5000
> 470 HP @ 4000
>
> Increasing compression to 11:1:
>
> 429 HP @ 5000
> 476 ft-lbs @ 4000
>
> With TMeyer independent flow bench data on Edelbrock 2V heads and 9.8:1:
> 416 HP @ 5000
> 472 ft-lbs @ 4000
>
> With cylinder head flow from Cleveland Confidential magazine article:
> 419 HP @ 5000
> 471 ft-lbs @ 4000
>
> In my experience, when fed accurate data (actual cam timing specs, flow 
> bench
> data from Dave's conservative bench, minimum/maximum port areas, etc.),
> Dynomation has been close on the HP but optimistic by 20 to 30 ft-lbs
> on torque.
> The above simulation is likely optimistic since the minimum port sizes are
> assumed to be the same as an unported iron 2V head.  The simulation is 
> quite
> sensitive to the minimum intake port area.  A slight increase in that can 
> drop
> the HP prediction by 10 HP.  The simulation is less sensitive to larger 
> minimum
> exhaust areas (at least for a relatively large port engine like a
> 351C).  In any
> case, I'll buy the Power Block engine made over 400 HP (assuming it was 
> ever
> dyno'd which I see no evidence of) but not the claimed 466 HP.
>
> As a point of reference, Edelbrock claims:
>
> 456 HP @ 6000 RPM
> 445 ft-lbs @ 4500 RPM
>
> for a 4.04" bore by 3.7" stroke, 9.75:1, Cleveland with RPM Air Gap intake
> and flat tappet cam with specs:
>
> 312/322 degrees advertised duration
> 234/244 degree @ 0.050"
> 112 degrees LSA, installed on an intake centerline of 107 degrees
> 0.571"/0.589" valve lift
> 93 degrees overlap (seat)
> 0.050" valve timing is given as:
>  int open  10 BTDC
>  int close 44 ABDC
>  exh open  59 BBDC
>  exh close 5 ATDC
>
> With the above entered into Dynomation, along with Edelbrock's claimed
> flow bench data and 750 CFM of carb flow, the predicition is:
>
> 434 HP @ 5000 RPM
> 460 ft-lbs @ 4600 RPM
>
> With 800 CFM of carb flow, that increases to:
>
> 444 HP @ 5600 RPM
> 463 ft-lbs @ 4600 RPM
>
> for the headers assumed.  The Edelbrock numbers are much more believable.
> The Power Block build reads like fiction.
>
> Dan Jones
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