I am setting up a tall deck Desoto with a Donny Johansen solid roller cam. This is my first roller and am trying to get it right the first time. This is a mild street motor in a 3600 pound '50 Merc. I have had nothing but trouble with the flat tappet regrind and available hydraulic lifters. I have read that running loose clearances can cause the rollers to hammer on the cam lobes and cause failures. Donny's cam card calls for .020 but he says .015 would be fine. Anyone running tighter clearances? I have seen writeups of people running as tight as .006. Anyone using the mousetrap style rev kit on the rocker shafts to preload the rocker/pushrod/lifter parts to keep the roller in contact with the cam lobe? I have found pictures of these springs and I can make them if I cannot find them to buy. Does anyone know of a source for these? Thanks, Billk
Good timing. I am working on shaft mounted springs for forum member desoto and should have something in the near future.
How soon and how much, about, on the rocker shaft springs? I visited your site and it is very informative. Billk
desoto and I are working on the final details for the springs and pieces, but like every endeavor, we can't sit on $$$$$ worth of inventory so the question of the day is: just how many folks would actually use this system? Yes, I know, everything runs on dollars and some would not invest much unless they absolutely-positively knew it would make magic....but the reality is that these will offer some stability to the valve train and will offer the option to run more spring pressure without any major drawbacks. Hot flat-tappet cams would benefit from this as well as all of the rollers. Send a PM to either Skip or myself if you have any interest in a 'better mouse-trap'..... Gary
First thing I'd say is trust Donnie on the clearances - he ground the cam, knows the profile, etc.. As far as putting a rev-kit on it . . . not a bad idea, but kind of depends on what you're doing with it. Is this a street engine? Is it naturally aspirated or blown? What are the cam specs? What rocker ratio and what are your current thoughts on spring pressure on the seat and open? Having a little bit more to work with isn't a bad idea (information that is).
Rev kits are most useful with big cams and solid lifters, either flat tappet or roller, and do their job in a slightly different manner than the 'usual' valve spring. The "rated" valve spring stack load (in lbs.) is only true at the valve. The short side of the rocker arm (tappet, pushrod, adjuster) will see a different rate due to the rocker ratio. If your spring is rated at 100 lbs. closed, 250 lbs. open at the valve, then with 1.5:1 rockers, the lifter will 'see' 150 lbs. closed and 375 lbs. Back in the 'old' days, it was quickly found that trying to run big enough springs to control those heavy roller tappets was tough: • really big springs not invented yet • big spring OD, and equally big retainers, didn't clear the underside of the rockers • high valve pressure pounded on the seats and would pull the locks through the retainers • and, of course, EarlyHemi exhaust rockers don't like big spring pressures A rev kit, either mouse-trap (torsional) springs (shaft mounted), or a more complex, inside-the-valley package (springs in-line with the lifter) applies extra spring load only to the tappet and pushrod, With these, the valve seat's load doesn't change so giant springs are not required. Example: same 100 lbs. closed, 250 lbs. open with 100 lb. rev kit keeps the valve side at 100/250, but the tappet gets 250 lbs. closed and 475 lbs. open. The rev kit simply changes the balance of spring load between the 2 sides of the rocker. The torsional springs that Skip and I are working on are fairly straight forward and are similar to some 1960's Milodon pieces. .
I'll bump this for the mid-week crowd.... I am a bit surprised at how little interest has been shown in these springs considering how much traffic a thread gets when discussing roller cams in EarlyHemi engines. If you have a roller cam planned in the next year or two you just might want to consider these. .
Bored&stroked, This is definitely a street motor. 330 +.030 Desoto in a 3670 pound 50 Merc. It has a tko600 5 speed OD and 4.11 rear gears. 212/212 @ .050 with about .470 lift. The seat pressure is about 145 (per Donny's suggestion) and I don't know the open pressure. If there is a lack of interest in the mousetrap springs it might be because of the price of admission on a roller setup.
The apparent disinterest can, probably, be attributed to the proliferation of hydraulic high performance cams. Years ago, when we wanted performance, hydraulic cams didn't cut the mustard so we were stuck with flat tappet cams. Flat tappet cams, with their required valve lash, caused the pushrod to wear into a point as they worked their way into the rocker arm. Since nobody's been running flat tappet cams for any length of time (something more than just in and out of the trailer), everyone's forgotten the problems. Now, people are starting to jump on the bandwagon and actually DRIVE cars with flat tappet cammed hemis and they're starting to notice that they have to keep lengthening their pushrods to get rid of tappet noise and loss of performance. When you stop and think about it, Chrysler already knew this was an issue because they used an entirely different setup for their solid lifter cams in the 300 and industrial/marine engines. Back in '66 I installed a Milodon rev kit on my hemi but there was a problem with the installation. The ends of the springs contacted the inside of my stamped steel '58 Imperial valve covers and the chrome-moly retainer rings that link the springs to the tips of the rockers quickly wore out and broke on a number of rockers. The result was a set of pushrod ends that were destroyed on the valves with the broken retaining rings. The valves that still had intact rings were all within tolerance, lash wise. This all happened in the span of 311 miles. I had to order another set of pushrods and another rev kit.....right in the middle of a UPS driver's strike. I lost half a summer's worth of driving waiting for my parts. When you look at it, you realize how simple it is. The spring lifts the tip of the rocker off the valve stem and puts tension on the entire valve actuation system, thus, mimicking the zero tolerance found in a hydraulic lifter set-up. 8 intake valve springs 8 exhaust valve springs (slightly longer) 10 small hose clamps and 16 chrome-moly retainer rings. ....and a length of 1/2" square stock with a slot near one end that fits into a 1/2" socket wrench extension that you use as a lever to wrap the spring down over the rocker tip to install the ring. I dimpled my Imperial covers and installed the new rev kit and pushrods and eliminated the pushrod tip wear issue. 51 years and nearly 300,000 miles later and it's still running well and not eating up pushrods. I ran a set of Donovan valve covers for a number of years and they cleared the rev kit as do the O'Brien Truckers covers I've had on there for the last 22 years. One of the things I mentioned to Dennis when he was designing these covers is that he needed to make them tall enough to clear the Milodon rev kit.
FWIW, I am involved with 2 hemi flat tappet (non roller) cam issues right now. Both owners are wiring customers of mine that are experiencing frequent tappet clearance issues. One car has been on the road for a couple of years now and was so bad the clearance was 0.090" on some valves when it was set a hundred or two miles prior at 0.018". The other is a fresh engine that won't stay within tolerance and still has very low mileage. I've been promising both guys that a solution is in the works but it takes time. I don't have the connections locally or the marketing network to get it done and then distribute the product.
Another customer of mine had a re-ground hydraulic cam in his hemi but he stayed with stock, non-adjustable, pushrods. Some of the pushrod ends wore into a point and the lifter noise got real annoying. He, on my recommendation, replaced the pushrods with adjustable ones and the problem went away years ago. The re-grind process decreased the base circle enough that, on some lifters, slack occurred in the valve train and he ate up those pushrods. When you re-grind a cam, you need to seriously think about adjustable pushrods because your stock ones will be too short and on a hemi, that can sell disaster.
Skip, thanks for the bump on this subject. Sadly, I still haven't had the time to continue work on the "inside-the-valley" rev-kit ***embly and lately I am having so many demands on my dwindling supply of 'time' that I haven't finished the bits-n-pieces for the mouse traps....I do have another Mopar trans adapter for the Forward-Look crowd but that is another very long story....... In some fashion or manner, the rev-kits will happen. It is just a matter of time. If there is a dedicated EarlyHemi nut that needs a project, contact Skip or myself and we can talk. .
I'm interested, because of my never ending lifter noise, inspite of many push rod adjustments. Keep up the good work 73RR, and let us know when they are available.
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