Strange cam specs

[RustyRatRod]

If it matters, My numbers, gleaned from your chart are only slightly different.
But your numbers are hard to believe that they haven't been reversed. Cuz if you reverse them to make the intake 284 and the exhaust 292, and the lifts become 445/496, then the cam becomes fairly common.
Let's say I'm right, just for a second, then that cam, by your numbers, becomes
284/292/109.5/ 69 overlap, and a Ica of 68, would make the installed centerline to be 106 which is about 3.5* advanced.
In a true 8/1 engine, and at 600 ft elevation, the above 68* ICA, is predicted by the Wallace Calculator, to make 115 psi. cylinder pressure.
Whereas, with your numbers, an Ica of 79*, would generate just 100psi.
I checked my calcs three times so I hope they're right.
However, with your numbers, the bottom end of that combination with a P/V of just 74, it would feel like a tired slanty (P/V of 87).
Whereas at my interpretation, the P/V of 95 is starting to feel like somewhere between a slanty(87) a soft smog 318LA(114).


Also, I see your test apparatus, and am confident in your numbers. I just think that the intake and exhaust numbers somehow got flipped. I have a similar apparatus.

Grant me a moment to opinionate,
At an assumed to be 8/1 Scr, that cam is a terrible cam, for a pick-up truck.
Using your numbers,
To get the bottom end to feel like a half-decent 318, the SCr would need to be boosted to 11.5, to get the Dcr up to 8/1, and the pressure is already close to the limit at 160 psi. I highly recommend to, if your numbers are correct, to throw it away. That's my opinion.
Furthermore, in the current configuration, it would need;
a very hi stall, and
a crazy-high street gears, and
headers with a free-flowing exhaust,
just to get out of it's own way.
More money.

You haven't seen his test apparatus, because he has not posted it. Once again, you get a gold star for not even reading the thread and only trying to glom up the works by showing the world how smart you think you are. If you actually took time out to read the thread, you'd know that's not a picture of anything the OP was doing.

 

[Earlie A]

How about I do this since I've obviously created a lot of confusion. I'll try to re-do the test tonight and take pictures. That way I can show the real set-up, test multiple lobes and verify that the intake and exhaust are not flipped. Just hope there is enough daylight.

 

[RustyRatRod]

How about I do this since I've obviously created a lot of confusion. I'll try to re-do the test tonight and take pictures. That way I can show the real set-up, test multiple lobes and verify that the intake and exhaust are not flipped. Just hope there is enough daylight.

It's not your fault, man. Although the picture was kornfrooshin at first, you said pretty quick after someone said something that it wasn't your setup. All people have to do is read.

 

[PRH]

Fwiw, I took it all at face value that the test was done correctly, and that EA had a handle on what he was doing.
I wasn’t confused by it at all.

 

[Uncle Bob]

verify that the intake and exhaust are not flipped

I spent a couple of long days trying to figure out why my cam didn't match the cam card before I realized I was measuring the exhaust not the intake.

 

[PRH]

The timing events are clearly depicted on the paper here.

The open/close points for both lobes are occurring in the correct part of the cycle.

However, the installed position and lsa seem to differ a bit between the .050 open/close points vs the “centerline” method.

Based on the .050 intake events of 5 and 46, the c/l works out to 110.5.
The exhaust .050 numbers of 10 and 43, the c/l works out to 106.5.
Which would put the lsa at 108.5(217/2).

If the time is spent revisiting these measurements, I’d add a couple of lift points to the test.
Open/close @.100 lift

And what I like to do for the C/L method is check at .050/.040/.030 before/after peak lift, and average the 3 results.

With modern asymmetrical lobe designs, it’s fairly typical to see the C/L point shift 1-2*, based on which method is used and what you’re checking it at.

 

[RustyRatRod]

Fwiw, I took it all at face value that the test was done correctly, and that EA had a handle on what he was doing.
I wasn’t confused by it at all.

Neither was I, but it seemed some were. From all his posted numbers, it's very obvious he has a grasp on what's goin on.

 

[RustyRatRod]

The timing events are clearly depicted on the paper here.

The open/close points for both lobes are occurring in the correct part of the cycle.

View attachment 1716280710

Yeah, so how could anybody really "miss"? lol

 

[PRH]

Yeah, so how could anybody really "miss"?

That’s what I was thinking.

I mean, if you were only checking the C/L of the lobe, then I can see it.
But if you’re checking the open/close points…….. it would be obvious if you were on the wrong lobe.

I’ll slip in an anecdotal story here……
A few years ago a customer brought in an Olds 350 that he wasn’t happy with.
It had been rebuilt a few years before, but didn’t have any grunt at all.
The customer wanted a different cam, so it got a small XE put in it.
It had a Comp 260H which should have been fine, but he wanted something else.
I don’t recall exactly how it went down, but during the degreeing process the builder determined the 260H had been installed a bunch retarded.
They(must have) degreed it off the exhaust lobe…….. because on an Olds, the end cylinders have the in/ex valves reversed from the more traditional layout.
So the cam was set up at 106…….. using the lobe that would be where the intake lobe is on a SBM.
But that’s an exhaust lobe on the Olds.
Intake was in at 114. Oops.

Needless to say, with the new even shorter duration XE cam…….. properly degreed in to 106……. The low end power was greatly improved.
A burnout was now possible.

 

[Earlie A]

So here’s some new numbers and pictures of the real set up on the real truck. Looks like there probably is cam wear. I’ve noticed that the dial indicator stays flat around max lift for 20-30 degrees. Also looks like way too big of a cam. As AJ said, it feels like a worn out 6 cylinder. No throttle response at all.

 

[PRH]

Looks like the #1 ex lobe is .035” shy on lift compared to #3.

As I recall, a lifter can be retrieved out of the valley thru one of the open areas of the head.
Id pull the one out of #1 exhaust for a peek at the bottom of it.

.332 x 1.5 = .498
That’s a big ask out of the springs that go with rotators.

 

[Earlie A]

Looks like the #1 ex lobe is .035” shy on lift compared to #3.

As I recall, a lifter can be retrieved out of the valley thru one of the open areas of the head.
Id pull the one out of #1 exhaust for a peek at the bottom of it.

.332 x 1.5 = .498
That’s a big ask out of the springs that go with rotators.

I pulled #1 exh lifter with a magnet but the drain back hole is not big enough to pull it out. I was able to rotate it around. It actually did not look bad. It certainly was not chewed up.

 

[Newbomb Turk]

I spent a couple of long days trying to figure out why my cam didn't match the cam card before I realized I was measuring the exhaust not the intake.

Wait until you get a head on the flow bench and spend 5-6 hours trying to figure out why the intake port lost 50 CFM.

Once I jerked my head out of my butt I realized I was testing the intake port backwards.

I learned a ton from it. Not the least was LOOK at the bench BEFORE you turn it on.

I’ll skip all the bone headed crap I do on the dyno.

 

[Bewy]

If the measuring technique is accurate, it is a reverse pattern cam [ less exh duration ]. I have been using them for 25 yrs...
More & more people are using them, or pseudo RP cams by using std cams with lower ratio rockers on the exh. Jon Kaase won the engine masters contest with a 246/238 @ 050 RP cam in a 400 Ford that made 660 hp.
Some turbo cams are also RP.
No power. Could be many things...

 

[PRH]

I pulled #1 exh lifter with a magnet but the drain back hole is not big enough to pull it out. I was able to rotate it around. It actually did not look bad. It certainly was not chewed up.

On the SB heads I have here to look at, the cavity by cyls 3/6 looks to be the largest.
Just work the lifter rearward to that hole and it should fit thru.

Nonetheless, it seems as though you’ll be doing a cam swap.

 

[PRH]

If the measuring technique is accurate, it is a reverse pattern cam [ less exh duration ].

How do you explain the .035” lobe lift difference between #1 and #3 exhaust lobe(.297 vs .332)?

Also, duration @.050 for #3 is 238/241.

 

[AJ/FormS]

You haven't seen his test apparatus, because he has not posted it. Once again, you get a gold star for not even reading the thread and only trying to glom up the works by showing the world how smart you think you are. If you actually took time out to read the thread, you'd know that's not a picture of anything the OP was doing.

Seriously, that's your takeaway? .
And once again you get a gold star for being a grumpy old man, having to run your mouth.
OP said;

Yes. The chart is from the truck. The picture of the engine is just demonstrating the set-up for measuring the lifter movement. I meant to take a picture of the set-up being used in the truck but I forgot. I used the same set-up a few months ago on another car so I posted that picture. Sorry for the confusion.

You read much?
Op says he used the "SAME SET-UP.... on another car", and posted that picture; which was, by the English used, of "the same set-up"..
Com'on Rusty, rein in your tallons; Your judgement is interfering with your understanding.

 

[Bewy]

PRH,
To answer your questions:
[1] Worn lobe
[2] Inaccurate or wrong measuring technique.

 

[HSDemon]

I have seen this a thousand times, the truck has no low end power as the cam is way to big for what you have. I would be willing to bet that the truck has a stock converter, stock highway gears and the factory 8:1 (if you lucky) compression. I used to own a speed shop back in the 80's and 90's and people thought that the bigger the cam, the more power they would make, and nothing can be further from the truth. With the right combination of parts a bigger cam will usually make more power, but in a stock smog era engine it will absolutely kill all the power the engine has. If you have a stock carburetor it will also be difficult to make it idle correctly. The cam may have some worn lobes to boot, but that is not the issue, the issue is that the cam is just way to big for what you there. Only easy solution is to change to a very mild performance cam, something like a stock 340 cam.