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The Comp Thumpr cams are the original, the Hughes are their take on the Thumpr. I'd look at the Comp cam, see what they use.
Hughes is notoriously hard to deal with if you don't do exactly what he says and there's a significant difference in the springs. I wouldn't chance it.

R.

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FWIW, I run the Whiplash cam. 229/242 at 0.050, 518 lift, 107 LSA. This is on my 383 with 346 heads milled 0.030, ported/blended, 3 angle valve job, stamped steel rockers. No other mods to the heads. Am using the same springs that I used with the Comp Cam XE262, the one that is recommended by Comp Cams for the 262. Running the Hughes lifters with the cam. The engine runs strong to 6000 RPM. May go higher with no problem, don't know, that's where is shift.

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FWIW, I run the Whiplash cam. 229/242 at 0.050, 518 lift, 107 LSA. This is on my 383 with 346 heads milled 0.030, ported/blended, 3 angle valve job, stamped steel rockers. No other mods to the heads. Am using the same springs that I used with the Comp Cam XE262, the one that is recommended by Comp Cams for the 262. Running the Hughes lifters with the cam. The engine runs strong to 6000 RPM. May go higher with no problem, don't know, that's where is shift.

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Okay, again i am confused...

Just comparing Comp cam/springs to Comp cam/springs here and leaving Hughes outta this...

The springs spec'd for your XE262 cam (either set, there are two options) are stiffer/rated heavier than the springs spec'd for the Comp cam XE275High-Lift cam i bought my springs for. Shouldn't a considerably stouter cam need stouter springs...??? Something's amiss here.

Either way, its looking like a possible go. Not optimal... but doable. The springs i have were spec'd for an aggressive ramp lobe (again, Comp XE275HL - 231/237 @ .050 and .525"? lift). In fact, ALL the high-lift Comps 'recommend' that spring, even the XE295HL (251/257 and .564" lift).

i think i'm overthinking the original question now... especially seeing how well some seemingly mis-matched combos work, but now its the spring recommendation questions that have me wondering. Anyone...???

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Here we go with the cam stuff: The way to get more lift per degree of duration is to have a faster acceleration rate. The maximum acceleration rate varies with the diameter of the lifter. Over the past 10 years or so the cam designers have found ways to use a really fast accel rate on the opening with a slower closing rate to set the valve back down so it doesn't bounce.
The standard of the automotive world, the chevy smallblock, has lifter dia. 0.842". Thus you will find that about 90% of all lobes are designed around that limitation. We call them "Chevy lobes". You can tell this in cam catalogs when the lift and duration at 50 lift are the same for all engines with a 1.5 rocker ratio.

One of the advantages designed into Mopar engines is they have a lifter diameter of 0.904" That means if the cam designer wants to he can accelerate the valve faster. This means more area under the lift vs duration curve and more power. For years Hughes has used what it calls "real Chrysler lobes". These take advantage of the larger lifter. The latest Hughes lobe series is closer to the edge than about anyone else. You can see this when the lift for same duration at 50 is higher on the Hughes grind. So it makes sense that it would take more spring to slow down the faster-moving valve and turn it around. One does not want the lifter to fly off the cam lobe (except in certain very specific cases with lift rules).

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Now onto springs:
There are only a few really pertinent numbers for springs. They are seat pressure at a particular installed height, coil bind height and spring rate.
For example, the Crane 933 springs I am going to use on my 318 project have a seat pressure of 98 lb at 1.700" installed height and spring rate of 328 lb/in. I am going to install them at 1.600" so I have to add the spring rate times the extra compression, in this case it is 328 x 0.100 = 32.8, to the 1.700 seat pressure so now my installed seat pressure is 130.8 lb, perfect for hydraulic roller lifters. Assuming I use a 0.474 lift cam, the open pressure is 130.8 + (0.474 x 328) = 286lb open pressure, in the ballpark for hydraulic roller lifters. Coil bind is 1.08", so 1.08 + .474 + 0.060 = 1.614 which is more than my 1.600 installed height meaning this might not be the spring for the job because one can't run really close to coil bind as it will destroy the spring. In this case I will be saved because my stock rockers come in with less than 1.5 ratio, a 1.45 is more like it, real lift is 0.458 so the springs will have more than the 0.060 minimum clearance between max lift and coil bind.

If you think about it, the same spring can have many different seat pressures depending on installed height, which could explain the different ratings on the same spring.

R.

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Now onto springs:
There are only a few really pertinent numbers for springs. They are seat pressure at a particular installed height, coil bind height and spring rate.
For example, the Crane 933 springs I am going to use on my 318 project have a seat pressure of 98 lb at 1.700" installed height and spring rate of 328 lb/in. I am going to install them at 1.600" so I have to add the spring rate times the extra compression, in this case it is 328 x 0.100 = 32.8, to the 1.700 seat pressure so now my installed seat pressure is 130.8 lb, perfect for hydraulic roller lifters. Assuming I use a 0.474 lift cam, the open pressure is 130.8 + (0.474 x 328) = 286lb open pressure, in the ballpark for hydraulic roller lifters. Coil bind is 1.08", so 1.08 + .474 + 0.060 = 1.614 which is more than my 1.600 installed height meaning this might not be the spring for the job because one can't run really close to coil bind as it will destroy the spring. In this case I will be saved because my stock rockers come in with less than 1.5 ratio, a 1.45 is more like it, real lift is 0.458 so the springs will have more than the 0.060 minimum clearance between max lift and coil bind.

If you think about it, the same spring can have many different seat pressures depending on installed height, which could explain the different ratings on the same spring.

R.

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Man... i used to know all this stuff... its been a looong time since i had my head in the cam books...

Anyways, so what you're saying is that as long as i can stay further than .060" from coil bind, i can shim the springs i have for a bit more seat pressure?

The 924-16 spring is a dual-spring. With an installed ht ov 1.900", and coil bind at 1.175", that gives me .725" to play with... minus .060", so .665"?

IF i install it at 1.800" (by my handy-dandy Comp catalog here), the 924-16 is now 137lbs... closer to the 150lbs Hughes springs seat at. That also brings the pressure at .500" lift to 311lbs. The Hughes springs are 325lbs at .500" lift. I assume this means my 'new' coil bind is .625"? Since the lift ov the Hughes cam is .518", that still gives me lots ov room.

Am i close? or is the math not so linear in all this...??? I'm just trying to understand the math now.

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There are three different things going on here.
First, the Comp Thumpr cams came out at least 6 months before Hughes' Whiplash. I believe that the Whiplash was a response to the Thumpr and in typical Hughes fashion they did it just a little better. As you yourself noted the Hughes "real Chrysler" cam has more lift per degree of duration. It sounds like the Comp is one more Chevy lobe on a whatever core.

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Also, the quicker rate of lift for larger diameter lifters is not a Hughes secret, it's an early Machine Design principle. So to say that the Comp is in any way a ripoff of Hughes is laughable. It just took Comp a little longer to see the market for the lobe, they probably let Hughes do their market research for them. Again, this is common in the competitive world of industry.

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Okay, now on to second point, you may have old springs where the part number stayed the same but the spring itself was changed slightly (upgraded) over the years. So I'd believe what's on the box they came in. And yes, springs are blessedly linear and your math looks right.
Third, I am about as cheap as they come and the more I think about this the more I think you will be all right without spending the extra $$$$. Keep in mind to break the cam in to Hughes specs, including removing the inner springs. Then be careful in the upper rpm ranges where the springs might possibly allow valve float or bounce earlier than a stiffer spring.
As for the lifters, they all come from just a couple of places, as long as the oil doesn't come squirting out around the lifter it should be OK.

Keep us posted on your results...
R.

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my chiropractor urged me to avoid whiplash cams. just get a purple shaft (which is what everyone is emulating here) and be done with it.

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