Cam design limitations

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Bill Dedman

Bill Dedman

bill dedman
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I am trying to figure out how this works:

I'm told that I can't BUY a short duration, high-lift cam for my slant 6, from anywhere. I am talking about a 210-degrees at .050" lift profile (112 degrees lobe separation) with .530" lift.

The story I get is that to get that much LIFT, I have to have more duration.

That makes NO sense to me.

Why does it make no sense?

Because the implication is, that the lobe profile for the short duration cam is such that there's no material to grind, to get the desired specs.

B.S.

If there's a .530-lift cam that exists with say, 252-degrees of duration at .050" lift, the same blank could be used to create a shorter duration cam wth the SAME LIFT, the lobe profile just wouldn't be as "FAT" through the middle. It would just take some extra grinding... wouldn't it???

The material (on the blank) is THERE... obviously. This new, short-duration cam would have "skinnier" lobes...

What am I missing here???????

Can somebody explain why these cam grinders are so reluctant to grind the cam I want?

I'm stymied...
 
Maybe they're not wanting to grind what you want because they feel they'll have to reduce the base circle so much to get that kind lift that a cam as long as the slant's would twist itself apart.
Have you talked with Oregon Cam Grinders, 360-356-7985
I was under the impression that if you or they had a core with enough lobe height, they would grind you just about anything you wanted.
 
I believe the lobe ramp will be so steep that the edges of the lifter and not the face will be riding on the lobe. You know, the same reason you can't put a Chevy lifter on Mopar ramps. If you absolutely need it, see if they can design you a mushroom lifter camshaft for that application. Or go roller.
 
Exactly IQ. The ramp will become to steep, the lifter has a chance that it will dig into the lobe.

Once before, you barked at me about my sig and made fun of it about roller cams for a 318, which had no place in the argument to begin with, and now, someone else mentions roller cams for a /6.

I guess you ain't shopping around so damn well.
 
Have you tried talking with Dave at Hughes Engines ?? Maybe he can shed some light !!!
 
[email protected] with .530.....and on a 112?



Others may feel diff but...
The closer you are to the speed ur asking for...the shorter life span that cam will have.imo
the ramp can only be so fast/steep in relation to the lifters face area and it will require high seat/mid lift spring psi to control it.... the lobe wearing out will be faster. imo

More @.050 and or narrower cl will get you into reality with a flat tappet.
 
1wild&crazyguy said:
[email protected] with .530.....and on a 112?



Others may feel diff but...
The closer you are to the speed ur asking for...the shorter life span that cam will have.imo
the ramp can only be so fast/steep in relation to the lifters face area and it will require high seat/mid lift spring psi to control it.... the lobe wearing out will be faster. imo

More @.050 and or narrower cl will get you into reality with a flat tappet.
Click to expand...

I need a 116 lobe center spaing, .500"-total lift, amd 210-degrees of duration @ .050"-lift.

With the large-diameter lifters we have in the opars, I was hoping that would be possible, but it looks lke it's not.

Thanks for your advice and good information.
I appreciate it!
 
Call Oregon. They did some pretty tricky grinding on mine. I had picked out a grind similar to what you want.......but it was for an Isuzu diesel and was a roller grind. They called me back and said they could do it, but it would be pointless because it would need to be a roller grind or a mushroom grind. I ended up with like .493 lift and 230 @.050. But they were able to grind it on 105 LSA from the factory 109 and it's not even close to the cam core on the base circle.
 
rumblefish360 said:
Exactly IQ. The ramp will become to steep, the lifter has a chance that it will dig into the lobe.

Once before, you barked at me about my sig and made fun of it about roller cams for a 318, which had no place in the argument to begin with, and now, someone else mentions roller cams for a /6.

I guess you ain't shopping around so damn well.
Click to expand...

No; you're apparently hitting the bottle too much, because you're totally wrong about my problem with your sig line. My problem with your sig line was that you were making a blanket recommendation for people to "get a roller and forget the ZDDP" when that is simply not possible for those of us (and, there are a lot of us) with slant 6's, BECAUSE NOBODY MAKES OR HAS ANY BLANKS FOR THOSE CAMS. NOBODY... and yes, I have shopped around... a lot.

Talk about IQ...

If someone is willing to spend $1,000.00 up front to get a roller cam BLANK ground, they're off to the races, but then, they have to pay for the cam grind, which is a can of worms because there are no "masters" that are roller tyappet, "slant-six-specific," to use for grinding the lobes. They'd probably end up with a small-block Chevy roller profile, which might work... but probably wouldn't be optimum.

Those cam blanks would have no center gear to drive the distributor OR oil pump; a different ignition system would have to be built (crank trigger???) and an externally-mounted, belt-driven oil pump would have to be installed.

A hell of a lot of negative factors, (to say nothing of the money involved) JUST to get a roller cam.

THAT was the situation that engendered my comment about your sig,; it was a blanket statement that seemed not apply to everybody... but didn't say "if it's feasible.'

Maybe you didn't know all that when you installed it as a sig line. If that's the case, I apologize; i'm sure you're intentions were good...

I have another car ('72 Valiant) with a 360 Magnum (factory roller) engine with a Hughesengines roller cam in it, and I love it!!!

So, I really agree 100-percent with what your sig line says; it just doesn't fit everyone's circumstances.

I don't know anything about cam/profile/rate-of-lift limitations, and I appreciate your comments on that score... I'm learning.:violent1:

Oh; my other vehicle is a stock, '93 Dakota 318 Magnum (roller cam) pickup... I wouldn't have mentioned it in my rant about your sig... Like I said; I LOVE those rollers!!!

Thanks again for the good info!
 
twofosho said:
Maybe they're not wanting to grind what you want because they feel they'll have to reduce the base circle so much to get that kind lift that a cam as long as the slant's would twist itself apart.
Have you talked with Oregon Cam Grinders, 360-356-7985
I was under the impression that if you or they had a core with enough lobe height, they would grind you just about anything you wanted.
Click to expand...


From what I have learned here, it seems to me that the problem in grinding what I think I need is the lift rate for accomplishing a total lift of over .500" is just what Rumblefish said it was... the necessary angle generated by that accelerated lift rate would cause the edge of the lifter to gouge the lobe of the cam and destroy it in short order.

I had never considered that...

I learn something every day...:violent1:
 
Bill Dedman said:
No; you're apparently hitting the bottle too much, because you're totally wrong about my problem with your sig line. My problem with your sig line was that you were making a blanket recommendation for people to "get a roller and forget the ZDDP" when that is simply not possible for those of us (and, there are a lot of us) with slant 6's, BECAUSE NOBODY MAKES OR HAS ANY BLANKS FOR THOSE CAMS. NOBODY... and yes, I have shopped around... a lot.
Click to expand...
Innnn cooorect.


Talk about IQ...
Click to expand...

If someone is willing to spend $1,000.00 up front to get a roller cam BLANK ground, they're off to the races, but then, they have to pay for the cam grind, which is a can of worms because there are no "masters" that are "slant-six specific," to use for grinding the lobes. They'd probably end up with a small-block Chevy roller profile, which might work... but probably wouldn't be optimum.
Click to expand...

Do some more homework on the ramp profiles before making ignorant comments.
Those cam blanks would have no center gear to drive the distributor OR oil pump; a different ignition system would have to be built (crank trigger???) and an externally-mounted, belt-driven oil pump would have to be installed.
Click to expand...

You lack imagination.

A hell of a lot of negative factors, (to say nothing of the money involved) JUST to get a roller cam.
Click to expand...
Sometimes ya gotta pay if ya wanna play.

THAT was the situation that engendered my comment about your sig,; it was a blanket statement that seemed not apply to everybody... but didn't say that
Click to expand...
Actually, I do believe you did. While you run that course, it didn't make sense because it was in my sig, not part of the comments being made. Taking someone sig. into commentary as part of it is only belittling yourself while twisting up the convo while trying to make someone look bad by entering such a statement as if it part of a testimony of what they said.

Maybe you didn't knoiw that when you installed it as a sig line. If that's the case,
Click to expand...

You are so full of SH%^&( your eyes are brown, even your hair. I made mention of it at least twice (IIRC) during it all and you continued to ramble on and attempting to bash me further.

I apologize..
Click to expand...
NOT accepted



So, I really agree 100-percent with what your sig line says; it just doesn't fit everyone's circumstances.
Click to expand...

There's a twist from the last round of talk.

I don't know anything about cam/profile/rate-of-lift limitations, and I appreciate your comments on that score...
Click to expand...

SCORE!??? WTF, were keeping score? LOL. OK, your on, you got it.

Oh; my other vehicle is a stock, '93 Dakota 318 Magnum (roller cam) pickup... I wouldn't have mentioned it in my rant about your sig... Like I said; I LOVE those rollers!!!
Click to expand...

Those lines make no sense to enter in. But what ever floats your boat....
Click to expand...
 
Bill - Is there a reason why you can't run more duration? I think even if Comp was to grind of of thier MM series lobes you're still looking at 15° more at .050. That's assuming that A) the cam could be ground to that lobe and B) you do not have a lot of idle time, and/or can run a lobe-oiling lifter.
 
hey bill they are right as to the lift vs duration issue... now you know why i was looking at cam profiles for the 1" lifter... the lifter ramp gets to steep even for the .904

i will be able to get my .550 valve lift after lash with a measly 252 @ .050 duration... i know its to much for you but its as good as it gets without roller rockers...

now the roller cams i found do have the oil pump gear on them but would need to have a bronze gear on the oil pump which i believe that doug dutra has a couple...
 
rumblefish360 said:
Innnn cooorect.

That commentwas in response for my contention that nobody has any slant 6 roller blanks.

Apparently, you have better information.

Can you let us slant 6 guys know who this cam grinder is so we can stop agonizing over there high-lift rocker arms?

We REALLY need a roller for this engine...

Thanks for any information...
Click to expand...
Click to expand...
 
805moparkid said:
hey bill they are right as to the lift vs duration issue... now you know why i was looking at cam profiles for the 1" lifter... the lifter ramp gets to steep even for the .904

i will be able to get my .550 valve lift after lash with a measly 252 @ .050 duration... i know its to much for you but its as good as it gets without roller rockers...

now the roller cams i found do have the oil pump gear on them but would need to have a bronze gear on the oil pump which i believe that doug dutra has a couple...
Click to expand...


If you know who has blanks that can be ground into a roller tappet compatable profile, please post it here.

I and several other guys would appreciate it.

Thanks for any info...
 
moper said:
Bill - Is there a reason why you can't run more duration? I think even if Comp was to grind of of thier MM series lobes you're still looking at 15° more at .050. That's assuming that A) the cam could be ground to that lobe and B) you do not have a lot of idle time, and/or can run a lobe-oiling lifter.
Click to expand...

Look... I have no experience in building and tuning turbo motors, so I have to listen and pay attention to those with experience in this.

Those voices tell me that 210-215 degrees @.050" is what works best, because when you start getting over 220 degrees, the overlap allows too much of the pressurized, incoming mixture to be blown out the exhaust valve.

THAT is why we run 115 degrees of lobe separation and short duration; with 25 pounds of air pressire blowing the mixture into the cylinder, a lot of duration is neither necessary nor desirable... it just reduces cylinder pressure.

That's what they tell me..
 
Rumblefish360 said:

"You lack imagination."

I have a 360-Magnum powered 1972 Valiant 4-door sedan with a Vortech supercharger driven by a system I designed myself (no "kit" for this app) and TWO complete, autonomous, fuel systems, that runs mid 11s and 118 mph in the quarter mile.

How many of those have you seen lately?

I am building (almost race-ready) a 1964 Valiant, slant six-powered, turbocharged, high-boost, 1964 Valiant 4-door sedan. IF I can get it to run like is should run, it'll be a 10-second car (yet to be seen.)

Do those sound like cars from a guy who "lacks imgination"??

Tell me about your cars; HOW IMAGINATIVE ARE THEY?
 

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Hey bill i read what you posted about lob separation and duration is this for tuning at idle?
So you can optimize boost.if so wont a higher duration help you out in the higher rpm range and if so have you looked in to the rhoads lifter as they allow you variable duration for better idle and pump up around 3000 rpm.I know this is a slant 6 but i use rhoads lifters in my 440 and i have a long duration cam but i idle very well at 800 rpm.just asking if this might help save you a dollar.

http://www.rhoadslifters.com/Pages/PartNumber.html

I just checked web site they dont list /6 but i would call them any way.
 
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