'Myth' of Mopar lifter diameter advantage?
#2678180
07/17/19 08:11 AM
07/17/19 08:11 AM
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Joined: Jan 2003
Posts: 1,761 Windsor, ON, Canada
Diplomat360
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OK, so we have all heard of, read about, perhaps experienced the presumed advantage of the wider Mopar lifter diamater...however, I have to be honest and point out that for quite some time now as I have been looking at various cam listings I have been noticing the Mopar stuff (specific to the small block use - as that is my focus) with much less lobe lift then similar, if not the same, spec'ed cam grinds for the other engine brands. Case in point, I am focusing on the retro-fit hydraulic roller cam grinds from Comp Cams, here are three examples: 1) Mopar Small Block - Xtreme Energy Retro-Fit XR292HR-10Adv Dur => 292/300 Dur @ 0.050 => 242 / 248 Lift => .549 / .544 LSA => 110 RPM Range => 2800-6400 2) Chevy Small Bock - Xtreme Energy XR294HR Retro-FitAdv Dur => 294/300 Dur @ 0.050 => 242 / 248 Lift => .540 / .562 LSA => 110 RPM Range => 2800-6100 3) Ford Windsor - Xtreme Energy XR294RFHR Retro-FitAdv Dur => 294/300 Dur @ 0.050 => 242 / 248 Lift => .576 / .600 LSA => 110 RPM Range => 2500-6500 Alright...so the Ford grinds in particular are something that almost always lists a higher lobe lift. The Chevy...umm...here and there, but in the case of example we have here it is actually a tad higher, not by much, but it is. So, is this because of the roller profile? Even then would you not expect the wider lifter to provide more room for a bigger diameter roller wheel and subsequently the ability to handle steeper lobe ramps? OK, so this is pure theory (reasoning behind why these profiles are what they are), and I feel like too often we (the Mopar fans) like to say we get ignored by the aftermarket, but I find it hard to believe that given the amount of computerized manufacturing the makers like Comp Cams would not design a lobe profile that maxes out the lift. Oh, and btw, if you say this is due to head flow restriction, while true for stock heads I would venture a guess that anyone running this level of cam has probably moved to heavily ported street heads or aftermarket stuff anyways. So what gives here?
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: Diplomat360]
#2678250
07/17/19 10:20 AM
07/17/19 10:20 AM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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OK, so we have all heard of, read about, perhaps experienced the presumed advantage of the wider Mopar lifter diamater...however, I have to be honest and point out that for quite some time now as I have been looking at various cam listings I have been noticing the Mopar stuff (specific to the small block use - as that is my focus) with much less lobe lift then similar, if not the same, spec'ed cam grinds for the other engine brands. Case in point, I am focusing on the retro-fit hydraulic roller cam grinds from Comp Cams, here are three examples: 1) Mopar Small Block - Xtreme Energy Retro-Fit XR292HR-10Adv Dur => 292/300 Dur @ 0.050 => 242 / 248 Lift => .549 / .544 LSA => 110 RPM Range => 2800-6400 2) Chevy Small Bock - Xtreme Energy XR294HR Retro-FitAdv Dur => 294/300 Dur @ 0.050 => 242 / 248 Lift => .540 / .562 LSA => 110 RPM Range => 2800-6100 3) Ford Windsor - Xtreme Energy XR294RFHR Retro-FitAdv Dur => 294/300 Dur @ 0.050 => 242 / 248 Lift => .576 / .600 LSA => 110 RPM Range => 2500-6500 Alright...so the Ford grinds in particular are something that almost always lists a higher lobe lift. The Chevy...umm...here and there, but in the case of example we have here it is actually a tad higher, not by much, but it is. So, is this because of the roller profile? Even then would you not expect the wider lifter to provide more room for a bigger diameter roller wheel and subsequently the ability to handle steeper lobe ramps? OK, so this is pure theory (reasoning behind why these profiles are what they are), and I feel like too often we (the Mopar fans) like to say we get ignored by the aftermarket, but I find it hard to believe that given the amount of computerized manufacturing the makers like Comp Cams would not design a lobe profile that maxes out the lift. Oh, and btw, if you say this is due to head flow restriction, while true for stock heads I would venture a guess that anyone running this level of cam has probably moved to heavily ported street heads or aftermarket stuff anyways. So what gives here? There are other cam companies than Comp. Many companies grind mopar specific lobes. Even Comp does. The MM series comes to mind. Unless you have an in at Comp, good luck getting them to grind a cam with the MM series lobe. The cam I run is very close to the MM lobe. But it's not a Comp because Comp wouldn't do it.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: Diplomat360]
#2678252
07/17/19 10:33 AM
07/17/19 10:33 AM
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Joined: Jan 2003
Posts: 2,094 central texas
krautrock
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you need to look at the shape of the lobe and without getting too deep into it, look at duartion @ .050 and also @.200, you have to find a lobe profile catalog usually. here is an example from Howards. https://www.howardscams.com/sites/default/files/lobe%20list%20email%201-20-2014.pdfit lists regular profiles, fat rate profiles, ford profiles and mopar profiles. just based on a quick glance it looks like the ford .875 profiles are just a tad slower than the mopar profiles...which seem to be close to some of the roller profiles. keep i mind that is still a pretty simple look at things. the nose of the roller profiles could be much different then the flat tappet cams which means more area under the curve.
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: krautrock]
#2678255
07/17/19 10:38 AM
07/17/19 10:38 AM
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Joined: Jan 2003
Posts: 10,735 North Dakota
6PakBee
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I have no scientific data to present, just to point out that Chrysler at one time offered the mushroom lifters that have a larger diameter at the cam then the stock versions.
"We live in a time when intelligent people are being silenced so that stupid people won't be offended".
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: krautrock]
#2678263
07/17/19 11:40 AM
07/17/19 11:40 AM
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Joined: Jan 2003
Posts: 1,761 Windsor, ON, Canada
Diplomat360
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YES, perfect! This is exactly the sort of information I'm curious about, especially the theory behind things like the nose duration, etc. So given that I picked up a custom ground CompCams hydraulic roller (thus my focus on the CompCams parts, not meaning to ignore the other guys) I actually reached out to their tech folks and asked for the grind card, which they shared. The cam has the 13084 & 3039 lobes, these are the Xtreme Energy XFI rollers: Lobe 13084: .006 dur is 290 .050 dur is 240 .200 dur is 163 Lobe 3039: .006 dur is 300 .050 dur is 248 .200 dur is 169 Now, if I had that same info available for the other grinds I would have happily posted those as well, alas, I do not.
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: Diplomat360]
#2678278
07/17/19 12:18 PM
07/17/19 12:18 PM
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YES, perfect! This is exactly the sort of information I'm curious about, especially the theory behind things like the nose duration, etc. So given that I picked up a custom ground CompCams hydraulic roller (thus my focus on the CompCams parts, not meaning to ignore the other guys) I actually reached out to their tech folks and asked for the grind card, which they shared. The cam has the 13084 & 3039 lobes, these are the Xtreme Energy XFI rollers: Lobe 13084: .006 dur is 290 .050 dur is 240 .200 dur is 163 Lobe 3039: .006 dur is 300 .050 dur is 248 .200 dur is 169 Now, if I had that same info available for the other grinds I would have happily posted those as well, alas, I do not. A hydraulic roller (or a solid roller) is a bit different. But lifter diameter still matters, maybe even more so with a roller. With a lifter bore of .842 the biggest wheel you can get in that hole is .750 and that's pretty small. I can't remember if the .875 bore will let you get a bigger wheel than .750 but I don't think so. With a .904 bore you can get an .815 wheel and that's a big deal. So no matter how I slice it, the bigger lifter bore is always better. Comp and Pro Stock don't use 1 inch and bigger lifters because they want to spend extra money.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: Diplomat360]
#2678316
07/17/19 02:05 PM
07/17/19 02:05 PM
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Joined: Oct 2007
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polyspheric
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The Chrysler mushroom: .970" foot. Why this size? Used on the Ford Model T - no, I'm not kidding, that's how old this is. There's actual math to calculate the possible rate change: V = (tappet diameter - .040”) ÷ 114.6, where .040" is an acceptable safety margin to prevent edge contact. Maximum values by tappet diameter in lift per degree of cam lobe rotation: Engine Tappet OD Max velocity Chev. Gen-3 L6, V8 .842” .00700”/deg.
Ford .875” .00729”/deg.
Chrysler, A.M.C. .904” .00754”/deg.
Oldsmobile V8 .921” .00769”/deg.
Model “T” mushroom .970” .00812”/deg.
Chev. Gen-2 235, 261 .990” .00829”/deg.
VW Type I• 31mm 1.220” .01030”/deg.
Boffin Emeritus
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: polyspheric]
#2678320
07/17/19 02:28 PM
07/17/19 02:28 PM
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Joined: Sep 2014
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The Chrysler mushroom: .970" foot. Why this size? Used on the Ford Model T - no, I'm not kidding, that's how old this is. There's actual math to calculate the possible rate change: V = (tappet diameter - .040”) ÷ 114.6, where .040" is an acceptable safety margin to prevent edge contact. Maximum values by tappet diameter in lift per degree of cam lobe rotation: Engine Tappet OD Max velocity Chev. Gen-3 L6, V8 .842” .00700”/deg.
Ford .875” .00729”/deg.
Chrysler, A.M.C. .904” .00754”/deg.
Oldsmobile V8 .921” .00769”/deg.
Model “T” mushroom .970” .00812”/deg.
Chev. Gen-2 235, 261 .990” .00829”/deg.
VW Type I• 31mm 1.220” .01030”/deg.
Doesn't someone now offer a 1 inch mushroom lifter for the mopar stuff?
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: BSB67]
#2678354
07/17/19 04:13 PM
07/17/19 04:13 PM
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HotRodDave
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most generic shelf cams use lobes desighned for the smallest common lifter, the chevy, so even ford and chrysler with their larger lifters typically get stuck with the smaller lobes because it is easier to just make one small lobe and use it on everything than 3 specific lobes. Also just because a ferd, chuby, mopar use similar part numbers from a common manufacturer does not mean they were made the same, differnet head flow considerations and displacements require different lobes for optimal performance. Also ferds usually use higher rocker ratios so even if they do use the same lobe they will have more lift.
I am not causing global warming, I am just trying to hold off a impending Ice Age!
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: Diplomat360]
#2678422
07/17/19 07:43 PM
07/17/19 07:43 PM
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Only read your own posts.
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: polyspheric]
#2678463
07/17/19 09:37 PM
07/17/19 09:37 PM
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LA360
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Many have already explained the larger lifter bore is an advantage and not a myth, but shelf cams are never going to push the envelope as far as acceleration etc. They are generic, high volume production camshafts, they only thing they'll tweak is the lobe separations and how the lobes are paired. Comp, Bullet, and Engle do high acceleration lobes for 0.904" as a custom for good reason. The average guy isn't going to correct lifter bore geometry with bushes, and often the bore orientation is out of phase, resulting in lifter or camshaft failure.
Jesel make 1.25" roller wheel lifters for Pro Stock and the like these days for good reason
Alan Jones
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: LA360]
#2678478
07/17/19 10:54 PM
07/17/19 10:54 PM
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Posts: 1,761 Windsor, ON, Canada
Diplomat360
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Many have already explained the larger lifter bore is an advantage and not a myth, but shelf cams are never going to push the envelope as far as acceleration etc. They are generic, high volume production camshafts, they only thing they'll tweak is the lobe separations and how the lobes are paired... OK, fair to an extent...strangely enough somehow the Chevy and Ford grinds end up with the higher lift lobes though...presumably out of the very same lobe catalog I have here, so why isn't CompCams putting the higher lift lobes on Mopar cams??? I mean like you said: "...They are generic, high volume production camshafts, they only thing they'll tweak is the lobe separations and how the lobes are paired..." ...so what is the reason for pairing the lower lift lobes for our small block engines? Is it poor head flow? Is it bad geometry??? That's the depth of an answer I'm looking for... Bottom line being: the "shelf cam" argument here holds no water, as I just pointed out the other guys somehow end up running those lobes...so what gives? That's really what my question is about...would you not expect any manufacturer to want to optimize their sales regardless of what engine their product goes into? Makes no sense to me to want to sell less product...after all, if more lift was a bad thing we'd all be running our stock cams! LOL
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Re: 'Myth' of Mopar lifter diameter advantage?
[Re: Diplomat360]
#2678515
07/18/19 12:59 AM
07/18/19 12:59 AM
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Joined: Sep 2014
Posts: 4,457 Washington
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Many have already explained the larger lifter bore is an advantage and not a myth, but shelf cams are never going to push the envelope as far as acceleration etc. They are generic, high volume production camshafts, they only thing they'll tweak is the lobe separations and how the lobes are paired... OK, fair to an extent...strangely enough somehow the Chevy and Ford grinds end up with the higher lift lobes though...presumably out of the very same lobe catalog I have here, so why isn't CompCams putting the higher lift lobes on Mopar cams??? I mean like you said: "...They are generic, high volume production camshafts, they only thing they'll tweak is the lobe separations and how the lobes are paired..." ...so what is the reason for pairing the lower lift lobes for our small block engines? Is it poor head flow? Is it bad geometry??? That's the depth of an answer I'm looking for... Bottom line being: the "shelf cam" argument here holds no water, as I just pointed out the other guys somehow end up running those lobes...so what gives? That's really what my question is about...would you not expect any manufacturer to want to optimize their sales regardless of what engine their product goes into? Makes no sense to me to want to sell less product...after all, if more lift was a bad thing we'd all be running our stock cams! LOL Don't confuse total lift with the lift rate of the lobe. Two seperate things. The reason all the cams for Chrysler's have low lift is the idea that the port breaks over at about .450 lift. I can make it break over much lower than that. I can also move it up, or at least flatten it out. Put an intake manifold on and it changes everything. I run as much lift as I can get for the valve gear. I'm running (on the street) a lobe that is 281 on the seat at 255 at .050 so it's pretty close to a Comp MM lobe. With a 1.6 rocker I net about .606 at the valve. It isn't hard on parts. It will idle clean down to 700 but I don't idle it that slow. That's hard on parts. I let it idle at 1000 and it's not an issue. As to why the manufacturer doesn't optimize lobes for a Chrysler is there is NO MONEY in it. Most guys to this day STILL buy a cam out of a catalog or worse yet, take a poll on a forum and Joe blow runs cam XXYD in his jalopy and it's the cats ass even though Joe has never done any testing. So they have to have a cam today and they buy that crap. Honestly, 98% of the guys out there won't ever know the difference. It's economics. Simple money math. There are so many companies that will grind a custom cam with a .904 lobe on it for you there is no sense in every buying an off the shelf cam. But, you have to convince the guy on the phone why you need a faster lobe. I bought my cam from Jim at Racer Brown and before he used those lobes we had almost two hours on the phone and flow sheets plus a drawing of the cutter I used used for the valve job.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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