Hydraulic lifters on solid cam, and vice versa, in this month's Car Craft

[jayb]

In this month's Ask Anything column that Jeff Smith answers, there are some interesting comments about running hydraulic roller lifters on a solid roller cam.  The question was can you run hydraulic roller lifters on a solid roller profile.  My take on this has always been that a solid roller lifter profile has a take-up ramp, to take up the lash gradually before the ramp really starts accelerating.  So, with a hydraulic roller where there is no lash, there should be no problem following this ramp and a hydraulic lifter will work on a solid profile.  On the other hand, if you try to run a solid lifter on a hydraulic cam profile (roller or flat tappet), since there is no takeup ramp you will smash the lifter into the lobe and potentially cause lifter damage.

However, in the column Jeff Smith claims almost exactly the opposite case.  He says that after talking to Crane Cams the issue with running a hydraulic roller lifter on a solid lifter profile is that the uneven ramp acceleration rate due to the solid lifter's take-up ramp causes uneven pressure loading in the oil chamber of the hydraulic lifter.  He says that again, according to Crane, this can cause damage to the lifter and even blow them apart. 

Also, he claims that running a solid lifter on a hydraulic cam can be successfully accomplished if you limit the lash on the lifter.  The number they gave is .004" to .006" for the lash.

I'm not sure I'm buying these arguments, but they are interesting in any case.  What do you guys think?

[cjshaker]

I don't know if I would buy the "uneven pressure loading" in the lifter comment. How would it do that? A hydraulic lifter is always in a state of 'floating' anyway, and the question of speed of the ramp would seem to disappear given vast variables in RPM ranges of an operating engine. To "blow" the lifter out seems to be saying it's building too much pressure in the lifter (unless I'm misinterpreting something here). I would think the faster initial ramp of a hydraulic would have the effect of building more pressure?

As far as making "unequal" pressure, he makes it sound like there are two separate, distinct ramp profiles. One for take up and one for lift. I could understand the reasoning if there were actually two distinct ramps....causing an uneven hydraulic pressure. But the ramps are actually one, it's just the curve getting there. Again, the faster curve of the hydraulic would seem to cause this more than a solid. UNLESS they are saying that the slower ramp is letting TOO MUCH pressure bleed off and causing the internal spring to work harder........thereby failing when it shouldn't. Does a solid have two distinct ramps, one for lash take-up and then one for accelerating the lifter into lift?  I suppose that would make sense then. But STILL, all this is happening SO fast, even at an idle speed, that I find that hard to believe....but not impossible.

At 700rpm a cam is turning 350, so a single lifter is working 5.83 times a second, or once every .171 seconds. Given that a ramp lobe is only working about 15-20* of the 360*.....or 1/18 (figuring 20*) of that .171 seconds before it goes into "lift mode", that's .0095 seconds.....at idle! Less than one hundredth of a second hardly seems like enough time for that to happen. Especially when you consider the major differences in ramp profiles between camshaft makers. Crane has noticeably slower ramp profiles compared to Comp. for example (given similar duration street cams).

On the other hand, I have always liked Crane Cams BECAUSE  of their slower ramp profiles. They are much easier on valvetrain components than Comps really aggressive profiles. I know I give up HP, but I prefer to build my engines for durability\longevity since I don't race on a track. I have often wondered if that is not at least some cause of the problems with modern cam lobe "wiping" problems.......pushing the physical limits a bit too far. Maybe Crane errs on the side of caution? It would be interesting to have a list of all the cams that people have had wiped lobes on, given proper break-in procedures, to see if there is any "common factor" that comes in to play.....such as very aggressive ramps compared to 'softer' ramps given the same duration.

[plovett]

I'm not sure.  Only conjecture on my part. 

Is the acceleration rate on a hydraulic cam constant?  I'm guessing not.  They tend to have less aggressive lobes than solids and I'm assuming that is influenced by the hydraulic mechanism in the hydaulic lifter.

I would think the lash ramp on a solid cam might actually help as that would give you a two stage acceleration.  But the second stage might be a doozy on a solid cam.   That is what I think could cause a problem with hydraulic lifters on a solid cam.  I think the acceleration after the hydraulic lifter is past the lash ramp is past could overwhelm the hydraulic mechanism, irrespective of the lash ramp.  If the solid cam has aggressive lobes I think it could be problematic.  If the solid cam has mild unaggressive lobes I think the hydraulic lifter could work well.  Again, I don't think the lash ramp is the issue.   

Going the opposite way with a solid lifter on a hydraulic cam seems worse to me.  Lash ramps are there for a reason, though the slower accelerating hydraulic cam might alleviate that shock some.   I don't like that scenario.

So I agree with you Jay as long as the solid cam has unaggressive lobes. Like I said, just conjecture on my part.

paulie

edit:  Still, the BEST situation is a hydraulic lifter on a hydraulic cam and a solid lifter on a solid cam, in my opinion.

[machoneman]

Now I've heard a lot of engine bullshit, lore and old wive's tales but this one takes the cake: ...."and even blow them apart."

Methinks that the author did quote the Crane repr. correctly yet in recent years the quality of any info coming out of Crane, both before they filed for Chapter 11 (maybe it was 7) and after that motorcycle firm bought the assets, was highly suspect. I'd discount all of what he wrote unless he can back up that b.s. claim with say Comp Cam's tech staff concurrence.   

-However, in the column Jeff Smith claims almost exactly the opposite case.  He says that after talking to Crane Cams the issue with running a hydraulic roller lifter on a solid lifter profile is that the uneven ramp acceleration rate due to the solid lifter's take-up ramp causes uneven pressure loading in the oil chamber of the hydraulic lifter.  He says that again, according to Crane, this can cause damage to the lifter and even blow them apart. 

[afret]

Definitely not a cam expert but I think it's best to just use the lifters the cam was designed for like Paul said.  Cams aren't generally very expensive so just switch to the right cam.

I think if you use solid rollers on a hydraulic roller cam, you need to run very tight lash since the lash ramp on the hydraulic is a lot shorter than on a solid cam.  If you don't tighten the lash,  the valvetrain will probably get hammered.  The cam will now be or act like a slow bigger solid cam compared to a good solid cam design.   That's because the valve will be a lot slower opening and closing with the hydraulic profile compared to a solid.  (I think it does make the "hydraulic" cam smaller than it was with the original lifters though)

If you go the other way around and use hydraulic roller lifters on a typical solid roller cam, you need to get limited travel hydraulic roller lifters or adjust regular roller lifters with the plunger almost bottomed out to act like a solid roller.  You would still need to run the spring pressures of the solid rollers so the hydraulic roller lifters need to be able to handle that.

In either case, unless you have to run the hybrid combos, like when you're looking for max power and the rules state you have to use hydraulic rollers, why do it?

[Joe-jdc]

That is exactly what they told me nearly 25 years ago when I bought 3 experimental hydraulic roller cams for 351W strokers with retrofit rollers.  My only roller cam failure was one of their experimental cams with hydraulic roller lifters.  Engine ran fine for about 10K miles, then a lifter let go and took out the cam, lifters, one piston skirt before it could be shut down.  Joe-JDC

[Marx427]

Well this was a well timed post, as Ive been wondering the same thing for a while..........Way back in 1976 (I was 18)  I bought an Engle solid roller cam set up with Rev kit from a guy who had  worked fro Shelby American 10 yrs earlier ......it was made to run in their 289 Dragon Snake Cobra...in S/S, I believe....he said something about a rule change about roller cams and it was never used........I still have it....has still got the cosmoline and Shelby American/Engle tag attached.........I believe the numbers were around 460. lift /288 adv duration.....Ive never thought of using the solid rollers that came with it, because frankly,I don't think they look up to the task of operating in a street driven car....but I was wondering if I could use it with Fords 5.0 hydraulic roller  lifters in my 68 302 GT Mustang......which currently is bone stock.
Or , do you guys think it would have any more  value to a collector.....as a NOS set up from the Dragon Snake efforts?

[machoneman]

Don't think so, at least not a duplicate of Ford's 5.0 setup with the spyder, dog-bones and OEM hydro rollers.  Using a OEM Ford dog-bone style hydraulic lifter (ala' the 5.0 and late 5.8's) in a early block requires a SBC (small base circle) camshaft. This is due to the short lifter bores as later 5.0 blocks and late 5.8 blocks have longer as-cast lifter bores.  You could check it but as the cam was designed for early solid rollers it can't be a SBC profile.

OR.....one could purchase the more current 'drop-in" hydro roller lifters for any early or late 5.0/5.8 engines, forget the whole SBC camshaft issue, and use your cam or a hydro. This set-up would allow you to use the early block (the shell of the lifter has been modified) with your cam. I do see (link) that the previously outrageous prices for a set ($600) has come down a lot in recent years. Lunati btw is only one seller.

http://www.lunatipower.com/Product.aspx?id=2556

[Joe M]

Although I've been reading Car Craft for more years than I care to think about, I always take what any mag prints with a grain of salt.  If it don't sound right it probably isn't!  As proof, on page 93 of the September issue, they refer to a 64 Falcon's original engine as a "260-inch inline six"!  Never heard of that one!

[jayb]

True enough, they are always making those kinds of errors; see the post below:

http://fepower.net/simplemachinesforum/index.php?topic=827.msg6687#msg6687

Nevertheless, Jeff Smith is pretty on the ball, so seeing that written up in his tech column gives it some credibility, IMO.  I worked with Jeff briefly when I wrote the Low Buck 390 article for Car Craft, and he's a car guy first, and no dummy.  I guess he was just passing on what the guy from Crane told him, but it still sounds questionable to me...

[Barry_R]

If I get the opportunity I'll give Jeff a call...

I've run hydraulic rollers on solid cams in several EMC entries without a problem.  Actually my favorite package.  Ran a special short travel lifter and adjusted about .010 off the bottomed out position.  Seems to be glass smooth beyond 7000RPM.

[Marx427]

I wasn't aware of the smaller base circle cam..........Been away from Small blocks for a long time....haven't kept up since..........well,  along time ago.  Also thanks for the Lunati info.   MP

[hotrodfeguy]

I look at it this way what would a MFG have to loose if there was a bunch of failures? But people buying a bunch more stuff? I see a can of worms being opened up. Just my take, on it. Just not worth the money saved. Just buy what ya need and be done with it.

[RICK LAKE]

Here's my take on this question, the wheel follows the profile of the camshaft lobe. The profiles may be a little different at base. If the materials are of the correct hardness. I see no real problem, all things beening equal. Here's where a I think a problem may happen, Lack of lube pressure or splash between roller and camshaft. Too high of a spring pressure. Is this not the reason some guys went to a .904" lifter? Over revving or banging the rev limiters is not helping. Valve float IN my opinion is more of a failure cause of hydro rollers than anything. I have run a set of hydro crane rollers for 9 years. No problems or failures. Have also run high oil pressure in the 70-85 psi range. I know alot of guys don't agree with this high pressure. Also limit of motor rpms to 6,200 has prevented problems. I am building another shelby motor in the 498 range with hydro rollers and a .650" lift camshaft. TWM 58MM throttlebodies. I see no reason or problem with running hydro rollers and beehive springs again. Another 10 years of abuse and no major failures would be nice. Small side note with lifters now pressurizing oil to the pins or oil holes directly over the roller wheels, I can't see why you would have a roller lifter blow apart unless debrie, no lube, or slop in the valve train would cause the roller to freeze up, or bang on the camshaft. JMO  Rick L.

[cammerfe]

FWIW, it was very common to 'solidify' hyd. cams 'back in the day'. They sold kits for the purpose. And beware of the 'Roger Huntington syndrome'. Roger was a very prolific writer some years ago, but he was confined to a wheelchair and a great deal of what he offered in print was something he was told or something he thought he heard. There were massive amounts of B-S disseminated because of his limitations. If you report on what you did it's all good but you must, as a reader, question whatever a writer 'heard'. JMO!!

KS