Posted By: Pale_Roader
Hughes Whiplash cam + Comp Cams springs/lifters? - 02/20/12 12:10 PM
I've got a 67 383 (2-bbl engine) that i'm going to toss some different 516 heads on to. They're very mildly ported, shaved (not sure how much yet, nothing extreme), and will have bigger exhaust valves (have a choice between used stock 1.74 or new 1.81 Ferrea). Basically i dont want the 1.6 valves on there. The guides will be modified for valve clearance too.
I'm sold on the Whiplash RB cam for it. Its gonna be a light, stick car. If i ask Hughes this question they will obviously tell me i NEED their special lifters and springs to go with that cam, but do i need them really? I already have (new in box) Comp 924-16 springs (installed: 115lbs @ 1.900" / Open: 322lbs @ 1.200" / Rate: 296lbs/in). I also have Comp 822-16 lifters, also new. These were bought for a different project that never happened (pretty sure it was the Comp XHL275 cam?)
Will this stuff work normally? I'm REALLY poor right now and would like to make this happen. A $215 cam from Hughes would be a LOT easier to budget than a full $400 kit. I already have the Comp stuff.
The specs on Hughes site for their springs are a bit heavier than the Comp specs for mine (Installed: 150lbs @ 1.880" / 365lbs @ .650). They say their cams need special springs, but the Comp cam i bought this stuff for was the new high-lift lobe cam... Same difference?
What do you think? can i save myself $200+ and have this thing work the way its supposed to?
Posted By: dogdays
Re: Hughes Whiplash cam + Comp Cams springs/lifters? - 02/20/12 05:28 PM
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.
Posted By: BIGSTROKER
Re: Hughes Whiplash cam + Comp Cams springs/lifters? - 02/21/12 02:46 AM
THATS NOT ENOUGH SPRING YOU NEED ABOUT 150 ON THE SEAT
Posted By: Pale_Roader
Re: Hughes Whiplash cam + Comp Cams springs/lifters? - 02/21/12 03:05 AM
Okay, this is where i get confused...
I looked up the Comp Thump'r, there are 3, from a 227/241 to a 235/249 to the big 243/257. The Whiplash is 232/245, yet it has more lift than the biggest Thump'r. Is it the lift, or the duration/ramp profile that dictates the spring needs? The Comp Cams springs recommended are close to what i have. The 995-16 spring (recommended for all 3 Thump'r's), which has the same seat and .550" rates as mine, but an extra 50lbs rated 'rate'.
I assume the Comp is using a less aggressive ramp than the Hughes? Is that why i need more seat pressure?
One more thing. On my box i have right here, the 924-16 spring is rated at 297lbs, yet i just looked on Comp's site and there its rated 347lbs. Which is which? The spring is stronger than i thought it was. Or did they change the specs in the 10 years since i bought these?
Posted By: Junky
Re: Hughes Whiplash cam + Comp Cams springs/lifters? - 02/21/12 07:42 PM
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.
Posted By: dogdays
Re: Hughes Whiplash cam + Comp Cams springs/lifters? - 02/22/12 07:55 PM
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).
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.
Posted By: dogdays
Re: Hughes Whiplash cam + Comp Cams springs/lifters? - 02/24/12 10:53 PM
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.
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.
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.
Posted By: maximum entropy
Re: Hughes Whiplash cam + Comp Cams springs/lifters? - 02/24/12 11:25 PM
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.