Strange cam specs

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Earlie A

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I recently purchased a 1979 Dodge truck with a 360 and 727 trans. Block is 1979, hydraulic FT cam and heads are probably 1979 as well. I do know that the engine has been rebuilt and I am quite sure the cam is not stock. Truck had been sitting (indoors) for 10-12 years. Barely ran when I purchased it. I siphoned fuel out of the tank, rebuilt the carb, replaced distributor and coil, checked plugs. Checked compression - it's within factory specs at 112-152 psi. Not great, but within factory specs. Truck does run better now but still does not idle well and no bottom end power. So I pulled the valve covers to measure the cam specs. My set-up is shown below (the picture is from another car). Listed below are the cam specs. I checked them 3 times and repeatability was within 2 degrees each time so I feel pretty good about the measurements. I thought the cam specs were a little strange but I am no cam expert. What do you guys think? Ever seen a cam like this? I thought the intake was particularly weird. I just checked one lobe. Probably should have done more than one while I was at it.

I realize I have a terrible combination of low compression, high duration, retarded timing and stock torque converter. My question is not so much how to make the truck run better as it is just trying to identify a cam or identify a problem with my process.

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.
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Not sure on the cam, but i would check what the heads are.. i'm pretty sure mopar wasn't using aluminum heads in 79...
 
Icetech said:
Not sure on the cam, but i would check what the heads are.. i'm pretty sure mopar wasn't using aluminum heads in 79...
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The picture is from a different car. I just used the picture to show the set-up used to measure the cam. The heads on the truck are iron.
 
Earlie A said:
The picture is from a different car. I just used the picture to show the set-up used to measure the cam. The heads on the truck are iron.
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K.. sorry bout that.. i musta missed it :) Early morning.. i was wondering how you knew to get cam specs but not that a head was alum :)
 
Does the engine have exhaust rotators on it or have the valve springs been updated? I would check a couple things f more lobes just to see what’s really happening there. My gut instinct (FWIW) says that particular exhaust lobe is starting to go away…
 
For starters, if it's a hydraulic lifter engine, there's no way your measurements are correct.
 
All you are going to get is a lobe lift measurement. It's won't tell you a lot.
 
RustyRatRod said:
For starters, if it's a hydraulic lifter engine, there's no way your measurements are correct.
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There is nothing to collapse the lifter, so total lobe lift numbers should be correct. I am directly measuring lifter movement, so these numbers should accurately reflect lifter movement. I realize this is not the same as placing the dial indicator directly on the cam, but it should be a good measurement of lifter movement. Are you referring to something else?
 
Earlie A said:
There is nothing to collapse the lifter, so total lobe lift numbers should be correct. I am directly measuring lifter movement, so these numbers should accurately reflect lifter movement. I realize this is not the same as placing the dial indicator directly on the cam, but it should be a good measurement of lifter movement. Are you referring to something else?
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If you're on top of the lifter plunger, there's no way you can know if it's collapsing some or not. It's an inaccurate measurement. As long as you think it's good, carry on.
 
RustyRatRod said:
If you're on top of the lifter plunger, there's no way you can know if it's collapsing some or not. It's an inaccurate measurement. As long as you think it's good, carry on.
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I posted here because I know you guys have a lot more knowledge on this stuff than I do. I'm not arguing, I'm trying to understand.

The only weight on the plunger is the weight of a carbide pilot (that is being used in place of a pushrod) and the spring pressure from a dial indicator. I'm sure the total pressure on the plunger is less than 1 pound. That cannot collapse a lifter. So why is the measurement inaccurate?
 
Earlie A said:
I posted here because I know you guys have a lot more knowledge on this stuff than I do. I'm not arguing, I'm trying to understand.

The only weight on the plunger is the weight of a carbide pilot (that is being used in place of a pushrod) and the spring pressure from a dial indicator. I'm sure the total pressure on the plunger is less than 1 pound. That cannot collapse a lifter. So why is the measurement inaccurate?
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As long as you're comfortable with it, go for it.
 
My first thought is……assuming the measurements are correct……it would be no surprise to me that a cam with 292* of advertised duration being installed 5* retarded from straight up(or 9* retarded from where I would have put it) is lacking some grunt.

My second thought is that’s a pretty big disparity in lift.
I’d suspect a lobe/lifter wear issue, and would want to verify the exhaust lift on a few other lobes.
It’s certainly possible it’s a custom that someone had done that way to facilitate it being used with the extra short IH & spring situation that goes along with the exhaust rotators being used.

The third thought is…….if it’s a low CR 360 in a truck……and again assuming the measurements are accurate……. There are better options for cams out there available for a combo like that.

Step one for me would be to put the cam in at 105-106.
 
PRH said:
My first thought is……assuming the measurements are correct……it would be no surprise to me that a cam with 292* of advertised duration being installed 5* retarded from straight up(or 9* retarded from where I would have put it) is lacking some grunt.

My second thought is that’s a pretty big disparity in lift.
I’d suspect a lobe/lifter wear issue, and would want to verify the exhaust lift on a few other lobes.
It’s certainly possible it’s a custom that someone had done that way to facilitate it being used with the extra short IH & spring situation that goes along with the exhaust rotators being used.

The third thought is…….if it’s a low CR 360 in a truck……and again assuming the measurements are accurate……. There are better options for cams out there available for a combo like that.

Step one for me would be to put the cam in at 105-106.
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See post #3. He posted photos from a different engine. :BangHead: :BangHead:
 
I’m not sure how the picture not being from his measuring makes any difference in the measurements themselves.
There could be no pictures and the numbers would still be the same.
 
I guess I do need to look at the wear issue. That makes the most sense. If this is a custom cam it sure came out a turd.
 
PRH said:
I’m not sure how the picture not being from his measuring makes any difference in the measurements themselves.
There could be no pictures and the numbers would still be the same.
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Not if the cam he has is different than the one pictured.
 
Earlie A said:
I guess I do need to look at the wear issue. That makes the most sense. If this is a custom cam it sure came out a turd.
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You said the first photo is from a different engine. Is the chart in the second photo from your engine we are talking about?
 
The photo of the engine was used for illustration purposes.

The numbers on the paper are from EA.
 
toolmanmike said:
You said the first photo is from a different engine. Is the chart in the second photo from your engine we are talking about?
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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.
 
“Generally”, the rotator and spring on the exhaust will not accommodate much more lift than the factory cam.

If I’m going thru factory SBM heads, and there is any hint of a performance slant on the build, and the heads have rotators on them………the factory 2 groove valves and rotators get replaced with their non-HD equivalents(at a minimum).

It’s probably not a bad idea to pull an exhaust spring off, measure the installed height, and check the spring in a vice for available spring travel from the installed height to c/b.

I’ve seen it where people have put springs designed for the taller IH of the std retainers, on the exhaust valves with rotators……..which results in very little available spring travel.
 
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PRH said:
“Generally”, the rotator and spring on the exhaust will not accommodate much more lift than the factory cam.

If I’m going thru factory SBM heads, and there is any hint of a performance slant on the build, and the heads have rotators on them………the factory 2 groove valves and rotators get replaced with their non-HD equivalents(at a minimum).
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Do the rotators actually benefit a heavy duty application? I would imagine it is to even out valve/seat wear?
 
Somebody must have thought so.
I believe the IH difference with the correct 2 groove valve and rotator is about .200” less than the non-rotator combo.
Plus the rotators are heavy.

Like I said…….for any type of performance app, I remove them.
 
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.
 
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