[Jay S]

If your just strictly wanting the title of your thread answered look up profiles from comps dual energy’s profiles.

[ponyakr]

"...amazing how quickly a simple cam question devolves into forceful opinions "

Ain't it so !

Welcome to almost all car forums & FB pages where discussions are allowed !

Almost all engine building questions, even for just a "stocK" rebuild for a resto street/show car will result in guys recommending big cube builds that "leaves nothing on the table", powerwise. So, instead of a low compression 300hp 400, you get recipes for 500hp alum head strokers.

Another thing that car guys are famous for is posting their experience with a car they or a friend had, which, many times was nothing like what the OP is posting or asking about.

It seems that some guy's attitude may be something like: "Yeah you may have that(or want that), but here's what I had. It was great. It was quicker & faster than what you're talkin about. So you probably should build more like what I had than what you are saying you want".

Like Art Linkletter use to say: "People Are Funny".

Just thought about this. Art also said: "Kids say the darndest things". I could say it like this: "Big kids say the darndest things about their car."

[Stan Weiss]

Closest Comp Cams Lobe Profiles to Stock W72 Cam

Let brake this down. Do you want the closest Comp Lobes or the Closet Lobes no matter from who. From what I can find Comp does not have the best selection of lobes for this. From what I have found and posted Howard will have the closest lobes.

Jay I can not find any Dual Density lobe with less than 0.400" valve lift with 1.5:1 rockers. I do see a couple of High Energy lobe.

Stan

[GoreMaker]

I want the most accurate profile info that I can import into DynoSim to try and replicate a stock '77 W72 manual trans engine. It seems like I've mostly got it dialed in using the specs from the first reply. The specs in some of the books I have are pretty similar. The only reason I'm specifically asking about Comp Cams is that the software includes ALL their lobe profiles in very good detail, which tends to give better results. And there's THOUSANDS of them. But I've been unable to find matching ones despite the vast selection.

Playing with this software is fun, and I'm interested in knowing how close I can get to real world accuracy just by inputting accurate numbers.

[Stan Weiss]

Originally Posted by GoreMaker

I want the most accurate profile info that I can import into DynoSim to try and replicate a stock '77 W72 manual trans engine. It seems like I've mostly got it dialed in using the specs from the first reply. The specs in some of the books I have are pretty similar. The only reason I'm specifically asking about Comp Cams is that the software includes ALL their lobe profiles in very good detail, which tends to give better results. And there's THOUSANDS of them. But I've been unable to find matching ones despite the vast selection.

Playing with this software is fun, and I'm interested in knowing how close I can get to real world accuracy just by inputting accurate numbers.

Does DynoSim let you import "S96" files?

Stan

[GoreMaker]

Yes it does

[Stan Weiss]

I don't have DynoSim. But I have played around with DekTop Dyno. In Desktop Dyno in the Cam Manager you can Manual change the Estimated Lifter Acceleration. Have you tried doing this with the specs in post #2?

Stan

[Jay S]

I think pulling files from a compcams library the high energy will be as close as you can find for running a sim to a OEM cam. But close as in horseshoes and hand grenades.

IRC, there are more high energy profiles than what are listed in the catelog, but they all are going to be more aggressive than the original, probably a little more lift, just as you said Stan. The crane cams HP and CCH1 profiles are closer. But I doubt they are on comps data base yet. I think the CCH1 has some slight asymeterical for higher rpms. The HP probably has more dwell than a Pontiac stock grind but symmetrical.

I have a little older dynosim software, 5 plus, it can adjust the cam accel rates from a cam file. But you likely won’t have much luck using the seat ratings converting a comp file to Pontiacs OEM ratings. I think you will have to go back to the .050” rating and adjust the rate from there instead of the seat timing to mimick the Pontiac profile. After you pull the file and change it may average’s the rates on the intake and exhaust, and won’t let you change them individually. Mine version is a little older though, could be they have change it.

I know of a some dynos pulls from a pure stock w72 that had a custom 255/268 dual energy that were intended to mimic the original.

[GoreMaker]

There doesn't appear to be any means of adjusting cam lobe acceleration rate in my version of DynoSim, though by entering all the numbers, it gives me an estimated acceleration rate which seems to be somewhat reflective of real life.

The numbers in post #2 seem mostly sane, but I have doubts that the exhaust lift is the same as the intake lift. My own reference (How to Rebuild Pontiac V-8s) implies that it should have 0.407" of lift on the exhaust side rather than 0.364". Hard to know without having the actual cam in hand, though.

Based on what I've entered so far using numbers I found online and from reference manuals for the cam, heads, intake manifold and everything else, DynoSim 6 tells me that a '77 W72 engine would put out about 213hp@4000rpm and 349tq@2400rpm. That doesn't seem too far out of whack... the power curve tracks pretty well, too, with most of the power gone by 5000rpm:


Again, this is just a fun exercise. But it's kinda neat to see virtual results that mostly reflect real life.

[Stan Weiss]

Does DynoSim let you say whether to use SAE J607 or SAE J1349. While I believe SuperFlow gives you the option almost every dyno sheet I have seen uses SAE J607. Pontica used SAE J607 until about 1972. They then changed to SAE J1349. So What does this mean? SAE J1349 HP will be less than SAE J607 for the same engine dyno pull.

Stan

[GoreMaker]

Yes, it defaults to J1349 but allows to set J607 and a few other variants

[Stan Weiss]

Originally Posted by GoreMaker

There doesn't appear to be any means of adjusting cam lobe acceleration rate in my version of DynoSim, though by entering all the numbers, it gives me an estimated acceleration rate which seems to be somewhat reflective of real life.

The numbers in post #2 seem mostly sane, but I have doubts that the exhaust lift is the same as the intake lift. My own reference (How to Rebuild Pontiac V-8s) implies that it should have 0.407" of lift on the exhaust side rather than 0.364". Hard to know without having the actual cam in hand, though.

Based on what I've entered so far using numbers I found online and from reference manuals for the cam, heads, intake manifold and everything else, DynoSim 6 tells me that a '77 W72 engine would put out about 213hp@4000rpm and 349tq@2400rpm. That doesn't seem too far out of whack... the power curve tracks pretty well, too, with most of the power gone by 5000rpm:


Again, this is just a fun exercise. But it's kinda neat to see virtual results that mostly reflect real life.

Looking at the DynoSim manual this looks just like what is in DeskTop Dyno 2003.

Stan

[GoreMaker]

Yeah I have that but it's not adjustable. It's just an indicator that changes to display an estimation of valve acceleration based on the numbers I enter manually

[Stan Weiss]

Originally Posted by GoreMaker

Yeah I have that but it's not adjustable. It's just an indicator that changes to display an estimation of valve acceleration based on the numbers I enter manually

There should be 2 radio buttons on top of it. If you click on manual then you should be able to move the slider.

Stan

[GoreMaker]

Originally Posted by Stan Weiss

There should be 2 radio buttons on top of it. If you click on manual then you should be able to move the slider.

Stan

Nope



'twould be nice, though. Not sure why it's not there.

[Jay S]

Desktopdyno, uses .006” timing events for the seat. Before the standard SAE cam ratings cam out, PMD used their own seat rating method, close to .003” tappet, I don’t remember the exact method they used. Maybe Stan does.

End result is the seat ratings you are using (274*, 298*) are roughly 25* to large on the intake, 30* plus on the exh, and will be giving the sim software a negative bias for HP. I checked one of the w72 cams, intake is mid to upper 240s @ .006” tappet, exh is upper 250s to lower 260s @.006”. Sorry, i don’t remember the exact numbers, that is the best I can recall.

Most factory cams this era and older had longer seat timings on the exhuast, much longer at .004” tappet and below. It was to drop the combustion temp for emissions at an idle. It really does not effect anything on the performance…. Other than making the exh manifolds glow red on a hard run…Lol

[Stan Weiss]

Jay,
I don't remember where Pontiac rated them. This is from an old H-O publication. Note that they look to have the stated seat duration but the lines have not gone to zero.

Stan

PS Let me add if you look closely at the H-O plots you will see that the closing side down low is not symmetrical to the opening side.

[pastry_chef]

Originally Posted by Jay S

PMD used their own seat rating method, close to .003” tappet, I don’t remember the exact method they used

The smallest Comp High Energy lobe 5224 is 256 @ .003

From Harold in Sept 2009,
- duration at .004", where the SAE has decided that hydraulic durations begin and end.


High Energy 5200 is 270 @ .003, 255 @ .006 and 206 @ .050

Dual Energy was mentioned above. lobe 5310 with .271 lobe lift is 265 @ .003

With no binding rules, for performance in a 400 my smallest aftermarket I'd go would be around 265 @ .006 , 210 @ .050 around .440 valve lift. (1.5 rocker).

Attached dyno results for a low compression 350 Chevy, on the top end the still mild test 2 cam had 100 horsepower over test 1 cam.. just a small increase in duration and vacuum still great. 400 Pontiac with 3.75 stroke, technically would want more valve seat and more area under valve lift curve.

[GoreMaker]

See this is why it would be great to have an actual measured profile I found a bunch of Pontiac cam profiles throughout the Internets that other hobbyists have directly measured, but none of them are specifically the 549431

Cam profiling stands are too expensive. With the proliferation of Arduino boards and cheap rotary encoders, it must be possible to build something for less than a couple hundred bucks that's just as accurate as the $2k+ stuff...

[Stan Weiss]

A thread from many years ago on PY.

https://forums.maxperformanceinc.com...d.php?t=386047

Stan

https://studylib.net/doc/18630019/w7...--original-h-o

Page 23 to 26 might be good read