472 cam timing specs

[Gijs]

Hi,

My brother has bought a 68 de Ville Convertible with 472 engine and Im trying to calculate an engine profile (torque/HP) using DynoSim 4.11.

He gave me the following numbers on Cam timing @0.001 valve lift

IVO 18 BTDC
IVC 114 ABDC
EVO 70 BBDC
EVC 58 ATDC

Keying in these numbers gives me a very odd performance graph.
I can correct this in a way by giving this cam about 20 degrees cam advance.

Was this engine used with a none strayt cam? Or can anyone tell me what went wrong?
Ill post the results on the 472 engine(graph)when Ive got all the correct numbers.

Kind Regards,
Gijs Ankoné
The Netherlands

[JIM CLC # 15000]

10-15-05
Gijs, Ill tell you up front that I dont know anything about the 472CID engine. But,I would have to assume the figure you posted (re-cam timing@0.001) must be in error. But, as I said in the opening, I know nothing about these engines.

Good Luck, Jim

P.S. I dont have a solution, but I do admire the problem.

[Nick Campagna]

Here are the specs form the Clevite Catalog.
1976 500cid - will not be too much different
intake centerline  - 117
exhaust centerline - 113
intake dur      seat - .050 lifter lift 312 199
ehaust duration seat - .050 lifter lift 308 203
intake lobe  .267
exhaust lobe .275
rocker ratio 1.72:1 -  I & E

[Gijs]

Hi Folks,

As promised some links to the simulations I did.

Some remarks though I have numbers that say rocker ratio 1.65 > Intake 0.440 lift Exhaust 0.453 lift
and SAE duration Intake 285 and Exhaust 281
These differences result in slightly different graphs

http://www.hyperlinc.nl/plaatjes/Cadillac-472-Std-Forum1.gif TARGET=_blank>http://www.hyperlinc.nl/plaatjes/Cadillac-472-Std-Forum1.gif
http://www.hyperlinc.nl/plaatjes/Cadillac-472-Std-Forum2.gif TARGET=_blank>http://www.hyperlinc.nl/plaatjes/Cadillac-472-Std-Forum2.gif
http://www.hyperlinc.nl/plaatjes/Cadillac-472-Std-Forum-Both.gif TARGET=_blank>http://www.hyperlinc.nl/plaatjes/Cadillac-472-Std-Forum-Both.gif

I hope someone appreciates these graphs.
Anyway Enjoy.

Kind Regards,
Gijs Ankone
Netherlands

My brother @ http://www.hyperlinc.nl/caddy2 TARGET=_blank>http://www.hyperlinc.nl/caddy2

[Michael Stamps 19507]

I assume thats net and not gross.  If so that is about in line with what I expect from a stock non tuned 472.  By non tuned I mean the way the factory shipped them.

Stampie

[Gijs]

Hi I,

Found the reason why Ive got such strange results within Dynosim. I found it in a Dynosim FAQ:

VAnswer There are so many ways that cam specs can be described for cataloging purposes that it’s confusing for anyone trying to enter timing specs into an engine simulation program. Your Pontiac is a classic example of this lack of standards. The Pontiac cam listed in the factory manual is a hydraulic grind with seat-to-seat timing measured at 0.001-inch lifter rise. Because the cam is designed for long life and quite operation, it has shallow opening ramps. This is the reason for the large number of crank degrees between the opening and closing points. In fact, during the first 35 degrees of crank rotation, the lifter rises less than 0.010-inch. If this wasn’t the case and the valve opened and closed at the specified timing points listed in the factory manual, the cam would have over 350-degrees duration, and it’s unlikely the engine would even start! The DynoSim can use 0.004- or 0.006-inch valve rise, 0.007-open/0.010-close valve rise, or even 0.020-inch lifter rise for seat-to-seat timing. [Bold]But the 0.001-inch lifter-rise figures published in your factory manual are useless for engine simulation purposes.[/Bold]

Kind Regards, Gijs