Purple Shaft Cam Specs??

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mopowers

mopowers

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I've got a Hydraulic flat tappet cam that was in my 340 when I bought it (installed by previous owner) and barely has any miles on it. Just trying to ID it so I can at least write it down on the box if I use it down the road or if I give it to a buddy or something.

In mocking it up in an assembled shortblock, I'm getting lobe lifts of .315" (int) and .313" (exh) which equals .473" and .470". That makes me think it's the 280/474 cam (P4452992), but the .050" durations I'm getting with my degree wheel are 232* intake and 234*. According to the victory library specs, the 280/474 cam should have @.050" duration of 238/238. For what it's worth, I measured a LSA of 110, so that seems to line up at least and all of the measurements I've taken are repeatable.

Has anyone degreed one of these Mopar cams? How close to published @.050" duration specs were the actual durations?
 
My last purple shaft install was a 509 in a 383. I distinctly remember it being off from the advertised duration but the number was the same between the intake/exhaust. Advertised is something like 248/248 and actual measurement was more like 242/242.
 
mopowers said:
I've got a Hydraulic flat tappet cam that was in my 340 when I bought it (installed by previous owner) and barely has any miles on it. Just trying to ID it so I can at least write it down on the box if I use it down the road or if I give it to a buddy or something.

In mocking it up in an assembled shortblock, I'm getting lobe lifts of .315" (int) and .313" (exh) which equals .473" and .470". That makes me think it's the 280/474 cam (P4452992), but the .050" durations I'm getting with my degree wheel are 232* intake and 234*. According to the victory library specs, the 280/474 cam should have @.050" duration of 238/238. For what it's worth, I measured a LSA of 110, so that seems to line up at least and all of the measurements I've taken are repeatable.

Has anyone degreed one of these Mopar cams? How close to published @.050" duration specs were the actual durations?
Click to expand...
M/P P4452992 seems likely, and there has been much discussion about the "accuracy" of the M/P's claim to use "advertised duration x .85 for @.05 duration numbers."
 
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How close to published @.050" duration specs were the actual durations?
Click to expand...

That’s the thing…….there are no published specs for .050” lift.
They only put the 85% of advertised to stop people from continuing to ask for the .050” specs.

How I remember if from my measurements is……
The Hyd cams seemed to come up short on the .050” numbers compared to the 85% math.
The only two solid grinds I measured were the .590 cam and the .620 cams, both of which measured more duration than the 85% math.

I don’t really care what some paper says they are.
I measure the cams I use, and trust my measurements to determine exactly what they actually are.

Edit- it appears I misspoke about no published .050 numbers.
I even have a MP catalog that shows them……but they’re waaaay off(so far off I blocked them from memory?)
They show the .050 numbers for the replacement hp/340 cam as 228/235(which is right in line with the 85% math).
Whereas the chart in post#10 shows the specs as 210/220 for the same cam.
 
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I loved the 280-474 cam in the big blocks. I loved the 272-455 as well. With a little more compression,gear,and converter the 474 comes to life. The 455 was great for a heavier car with 3.23 gears.
I don't see why they wouldn't perform the same in small blocks.
 
PRH said:
The Hyd cams seemed to come up short on the .050” numbers compared to the 85% math.
Click to expand...
This was kinda what I was figuring. Thank you.

I never realized the .050" numbers published for MP cams were calculated and not actuals. This is all making so much sense now. I remember having a similar question when I had the 268/272,.450/.455 cam as well. That one came up about 8-10* short of the calculated .050" numbers for duration if I remember correctly.

Thanks again, I'll write P4452992 on the box along with the actual measurements.
 
mopowers said:
This was kinda what I was figuring. Thank you.

I never realized the .050" numbers published for MP cams were calculated and not actuals. This is all making so much sense now. I remember having a similar question when I had the 268/272,.450/.455 cam as well. That one came up about 8-10* short of the calculated .050" numbers for duration if I remember correctly.

Thanks again, I'll write P4452992 on the box along with the actual measurements.
Click to expand...
They did that to keep the actual specs on their junk proprietary. It sure worked, too.
 
The paperwork that came with my MP cam…

IMG_9669.jpeg
 
Yall keep in mind too, those ain't the ONLY purple cams that were available. There were also PILES of what they referred to as "circle track" cams that had totally different profiles.
 
abodyjoe said:
i thought this was the "hemi" grind

A Eng. P4286630 D.C. 280-110 280 60 .474" 106 Zero
Click to expand...
No.
The 3690213 is the street hemi grind.
I bought one new in 1977 out of the direct connection catalog at the local dealership.
I also got one in a car I bought right around the same time.
 
OldmanRick said:
Sounds like the "old" Hemi grind .471/.474 109cl #3690213. My buddy had one years ago in a 70' Duster 340 that was all stock, factory converter, and 3.23's. A little soft down low, but went a hair over 100mph in the 1/4.

Mopar Engine Cam Chart
Click to expand...
Yeah it moves the rpm band up a bit. Not bad with deeper gears in an automatic. Went fine in my swinger with 3.55's and a 4 speed.
 
so, this begs the question: how many "hemi" grinds were there?

asking for a guy i know who bought a project car that came with a 360 and a "hemi grind" cam...
(that may be totall inappropriate for the build and now's the time to swap it out)
 
I believe one, then it was replaced with the later 284 cam, but not called street hemi grind. It's original purpose was to work with stock 340 valve train for street performance. It was not wild enough to require better springs and not start poking pushrods through the rocker arms.
 
junkyardhero said:
so, this begs the question: how many "hemi" grinds were there?

asking for a guy i know who bought a project car that came with a 360 and a "hemi grind" cam...
(that may be totall inappropriate for the build and now's the time to swap it out)
Click to expand...
The first and original Hemi grind was the dual pattern listed above in post #17 I believe.
 
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