Max engine RPM

[Rick Merz]

A crank scraper or a windage tray in a motor with a cam that is designed to produce power in the 4,000 to 7,5000+rpm range will remove too much oil when the engine is operated at a low rpm range to supply sufficient splash oil to the roller bearings, that is why it is not a good idea to run these engines at 1,500 to 2,500rpm all of the time, they are meant to be run at higher rpm’s that is where the cam was designed to produce max power. Remember, I am talking about a steel cam with heavy springs and solid roller lifters (which require more splash oiling). A hydraulic roller cam with lighter springs (which require less splash oiling), can be run from idle to 2,500rpm all day every day and still go to 6,500+rpm that is why they are more desirable for most engine builders and the weekend warrior. I have had a couple of steel cam high revving V8's and V12's and I loved them but they do require more maintenance (valve adjustment), and IMHO need to be operated at higher rpm ranges, after all that is where they were designed to be operated.

 

[Gary Gibbs]

I agree with Rick on this one. If you contact most of the solid roller cam manufacturers they will steer you away from their use in low RPM situations (street driving, etc.) because the rollers will not get enough splash oil. There are a few soiid rollers on the market (last I saw for SB Chevy) that have roller bearings that are pressure fed from the normal hyd. galley. This would appear to be a great idea. Solid roller setups almost always have more spring pressure, more imact load due to lash and no hyd cushion, and more force on the roller.

 

Great info, thanks. It's this kind of info that is hard to pick up from a retailer.

 

[Ian K]

Thanks for all the opinions/info guys - didn't mean
to start a religious war.

I hear plenty of good about DSS, and I may go that way, their
special lightweight hydraulic drivetrain sounds like it will
fit the bill.

Ian

 

[Lynn Larsen]

On the statements above, I and all the engine builders and engineers I have talked with feel that this is not an issue with my motor. I have a solid roller cam and lifters and my springs are ~150lbs on the seat and ~420-450lbs open and they have no issue with the fact that I am running both a windage tray and scraper. Virtually all have said that one would be hard pressed to keep oil off of the cam and lifters even if you were running a vacuum pump on the crankcase. Now, could you run springs that were so damned strong that there could be an issue? Yes, you could run rediculously strong springs that might cause issues. I also think that to automatically equate solid roller cams and super high pressure springs is no longer valid (it may have been at one time, but I think the science behind cam profiles and spring metalurgy has changed that.)

The actuality is that more of the oil on the cams and lifters comes from the oil gallies and run down from the heads, I believe, than from splash. If splash were an issue, you would not see dry sump engines in race cars. Think about it! The goal in these engines is to keep the crank case as absolutely dry as possible and they run 500 miles and sometimes 24 hours flat out with out destroying a cam or the lifters. Another thing to think about: with the decreased friction attained by using roller lifters, just the mist of oil in the crankcase, regardless of wether it is dry or wet sump, is enough to adequately lubricate the cam roller interface. Theoretically at least, there should be no slippage at this interface: it should be just like a tire rolling on the road in a 1:1 between the two. If you are concerned about the bearings in the lifter's roller, get the HPPO oiling option with crower or the comp rollers with the oiling slot cut in them.

There could be some confusion between solid flat tappets and solid roller lifters. With flat tappets that are absolutely dependant on a constant film of oil on the cam to keep the lifter floating on the oil film it, lack of oil could be a problem. That said, if there were a problem, the flat tappets (and of course the cam) would be destroyed in a matter of minutes, not years or thousands of miles. While there is a kernel of truth in all of the opinions expressed in this thread, I think the error comes in the estimation of the extent of the effect these observations will have on an engine.

No one here is building a 10K rpm Formula 1 engine, at least that I am aware of, so as long as you use some reason in the components you are using and don't let your dreams of being like Mike overload the realities of what you are doing, you will be OK.

BTW, no one has ever tried to steer me away from the solid roller cam I am using and they know full well that my car is a mostly street car with just occasional race days; and I have discussed this engine and its components with everyone from people with Masters degrees in automotive engineering to NASCAR engine builders to several race car machinists with years of experience.

Lynn

 

[DBLDREW]

Back when I was building my motor I was also considering running a solid roller. The only problems that I was told about, is that if you run a solid roller you will have to constantly be adjusting the valve lash, so this was the reason it wasn’t recommended for the street. But I also was told that if I ran poly locks on the rockers it would help cut down on how often I needed to readjust the lash. The problem was I was getting conflicting advice on poly locks, some would say that I wouldn’t need to readjust at all while others say they don’t help at all. So because I didn’t like the idea of constantly having to reset the lash I decided to play it safe and I just went with a hydraulic roller.

So Lynn being that you are successfully running a solid roller on the street, how often do you have to reset the lash?

 

[Lynn Larsen]

Dbldrew,

Actually the motor is just about to go to the machine shop. Its a brand new R302 block, but this was a consideration for me as well since I have a Jack Roush intake which makes valve adjustment an all day job. I was told that after the first few adjustments (2-3) that once or twice a year was adequate. I think that this was not always true and that the knowledge of metals used in the valve train from cam to the valves themselves has made this much less of an issue than it used to be. Or,so I am told. I agree that <u>good</u> polylocks help a lot. Sometimes, people get junky products and then conclude that what they have experienced is the general nature of a given technology. While technology is great, it is the implementation of that technology that makes or breaks it. (literally and figuratively

Lynn

 

Aside from dyno numbers, how can you determine when valves will float? Is it mearly a matter of spring force or will cam profile, rockers, etc. influence it?

 

[Ron Earp]

I can't imagine having to adjust it as much as some say. Motorcycles, some of the older ones I used, had no hydraulic lifters and while they had to be checked, required it 1-2 times per year. Lot more RPM and I used to put 10k per year on mine in those days. Had to lock the lash adjusters down tight though and any one that was not done properly would make noise in a week or two.

 

[Dave Wharran]

Have a turbocharged air cooled VW. Solid lifters as were millions of other VW's. I adjust valves in it maybe twice a year.
It destroys a set of heads every 25K-30K miles. The seats sink into the heads due to valve float. Springs aren't heavy enough although they are dual springs. Some factors that contribute or add up to cause valve float are cam profile aggressivness, weight of valve train components, spring pressure, how well (tight) the spring fits the retainer, and rate of acceleration of the engine. The particular company I purchase parts from found that a spring that fits the retainer loosly as opposed to those that the retainer has to "snap" in, float more easily because of harmonics created by the spring.

In my case, valve float is caused by the rate of acceleration of the motor and the lack of enough spring pressure to control it. Recommended springs for my engine to prevent float were about 150# seat pressure and almost 400# over the nose of the cam. Lifters had to be 1.6 ratio to clear the large diameter springs. Brutal on the small base circle VW cams. Plus, as luck would have it, the industry seemed to be having a rash of bad cam blanks.
Wiped the lobes off the first cam in 10 minutes of running (with the outer springs removed for cam break in!!)destroying most of the engine with cast iron particles. Second cam used lobes that were welded with hard surfaced rod and ground to final profile. It lasted 5K miles. My budget and patience wore out, so I went back to the lighter springs and consider the heads a "consumable" item.
Getting 3 or 4x the HP out of those little engines in a daily driver and having components last is interesting.

Just adjusted the valves in the 1.5L Honda Civic. Although it is overhead cam and the cam lobes actuate the rocker arms directly, it is still the same principle as solid lifters. First time for adjustment on this engine....at 130K miles.

Point of all this is I agree with Ron. With quality components, solid lifters shouldn't be a problem. But, there are always many other factors that have to be considered for the particular application.

That being said, I went with a hydraulic roller in my 40. Didn't need the engine to rev much over 6K. The quietness of hydraulic lifters, ease of setting, and need not to have to adjust them made sense for my application.

 

[Tim Kay]

Valve train, rockers, lash, springs, cam, hycraulic, solid, ect, ect. Ahhh, the simplicity of a rotory, 3 moving parts - stir, stir /ubbthreads/images/graemlins/grin.gif

 

[Howard Jones]

Lynn, I'm sure that if a motor is built correctly then it will work well. My point is that If given the choice I would build a larger rather than smaller motor and rev in less rather than more with as simple a design as required to produce the desired power.I have never been one who likes to make things more difficult than necessary. If the choice had been between a MK1 and a Mk2 with a 427 in it I would have surely gone for the big guy. Again the gearbox issue got in the way, along with a limmited buget. So I have a SVO 302 with a holley on it. Maybe if I knew more I would build my own but a guy has to know his limmitations.

Good luck to you.
The main thing is that you build your car the way you like it. I sure did.

 

[Lynn Larsen]

Howard,

I do understand and totally agree that there is huge value in the KISS principal and try to apply it when ever and where ever possible!

Now for something completely opposite of that. There is another racer trick that no one has mentioned that can, in essence, totally negate the mass of the lifters in the above considerations of valve trains and their tendancey to cannibalize themselves and the parts around them when pushed too far. That is the "rev kit"; this is a set of springs that fit between the head and the lifter that "catches" lifter, so to speak. While they do, of course, put extra pressure on the cam/lifter interface, they put no extra pressure on the pushrods and rockers. While this maybe difficult to do with a VW, aircooled, jug setup, it isn't rocket science on a typcial pushrod V8. These have fallen out of favor, I would guess, because they do not help at all with hydraulic lifter collapse under high spring pressures, but what they do do is restrict the load on the main springs to only the mass (intertia) of the springs, rockers and the valves themselves, this would by implication include the retainers and locks or oil caps on the springs. This allows you to use lighter main springs, which have less mass, which means less...........

Comments anyone?

Lynn

 

[Gary Gibbs]

The splash that I was talking about comes right off the crank as the oil is exiting the bearings and does not come from the sump. Thus dry or wet sump would have the same volume of oil coming off the crank assuming the same flow rate of the oil pump.

The comments that I relayed concerning the use of solid rollers on the street were from comp cams tech support approximately 1 year ago. Other manufacturers may feel different, and CC could have changed their recommendation policy by now.

Oil drain back from the top is unfortunately concentrated where the oil holes in the valley are located.

 

[Lynn Larsen]

Dave,

Boy you hit that one right on the head! The NASCAR builder, especially, told me that more damage is done with ill fitting retainers than almost anything else. Second to that is failure to positively locate the valve springs and/or dampners. That is to say, a properly fitting spring cup and/or locator, a shoulder that controls location in the ID of the spring, will prevent a LOT of valve train issues. Most people also pay to little attention to the dampners. Some engine builders would just as soon not use them at all! While they do provide benefits, they should be gone over and carefully deburred and smoothed. Dampners are the major contributor to many Ti retainer failures, especially when the the parts are of questionable origin (read Russian or Chinese.)

Gary, you are, of course, absolutely correct about the spray off of the crank. Most builders recommend against high pressure oil pumps, but I am using a high volume pump that will help in that regard I believe. Perhaps I have not had the warnings about solid rollers because I have spec'ed Crower HPPO lifters and I am not using a super aggresive cam shaft. The lift is only ~.6" (actually .589/.602 w/1.6 rockers) and I don't need 800lb springs. Cams and springs are two areas where too many guys think that if a little big is good, a lot big is better and it just ain't necessarily so. Maybe more to the point is my duration, which is only 230/236 @ .050 and the advertised is 268/274. The smaller the difference between these numbers (268-230 &amp; 274-236) means the valves are closing damn near instantaneously (an exhageration of course) and that requires very strong springs. And, that is going to be hard on everything when there is no dampning affect from hydaulic lifters. So, I can see the technical guys advising them to go with hydraulic lifters when they are ordering huge lumpy cams with little to no ramp to ease the valve closed. And, we haven't even mentioned valve bounce, which has more of an effect than most people realize (and its all bad.)

Bottom line is that there are no absolutes. One cannot say that all solid rollers are bad, nor can one say that hyraulic lifters won't turn rpms. There have been huge advances in the ability of hydraulic lifters to stand up (pun intended) to high rpms. I do think the days of solid flat tappets are pretty much over, but they aren't gone yet and probably won't be for quite a while. From a hassel perspective you can't beat hydraulic lifters and I hear what people are saying about putting in bigger higher torque, lower rpm engines to increase longevity - it will work without a doubt!

But, if you want to be able to reach a certain target speed ecomonically, it is cheaper to build an engine that will turn a few more rpm than it is to change the gear ratios of the transaxles that are available to us for use in a GT40 to allow that extra torque to get you to your target speed. If we could change the gears or differential ratios at a whim, like the GT40 race teams could, I would go with a higher torque, hydaulic lifter engine in a heart beat, but I can't. The cost of regearing a Porsche transaxle is just cost prohibitive to someone like me. As far as I can tell, there are no alternate gear/diff ratios available for the Audi which is even lower geared than the Porsche. At least, I have never heard anyone talking about it outside of which gearbox you get in the first place or by buying a used Porsche ?944/928? transmission to get the gears from it. Even at that the ratios aren't hugely different.

So, depending on what the individual wants from his/her car there are trade offs and compromises to be made to get there. But, it can be done and have a streetable, reliable car. As an example, guys who put 347s in a car; not that long ago, they knew it would not last as long as shorter stroked engines. That is no longer a given and there are reliable 347 engines to be had/built with 3.4" stroker cranks and pistons with pins not in the rings and offset to correct the rod geometry. Again, no longer an absolute. Ian, like someone else already said, "build your engine your way!" Just be aware of the different characteristics of different engine types, the techniques to deal with them and the costs associated them. I think that is how this thread started, right? :-D

Regards,
Lynn

 

[Lynn Larsen]

Here is another way of dealing with oiling lifters and cam in low rpm consitions. This is a picture of Comp Cams Endure-X lifters which have a slight groove cut in them to feed oil down to the roller bearings and onto the cam.

The groove can be cut into a standard roller lifter. If you are concerned with introducing stress risers in the lifter, you can use the trick that engine builders have been using for years and put the groove in the lifter bore. There is more than enough meat to absorb what little additional stress concentration this might provide.

If you are concerned with DIY, Crower HPPO lifters can be had for as low as $459 a set. The Comp Endure-X lifters (shown here) should be about the same on the street. Comp also has Gen III lifters that use an internal oil passage for ~$1K.

Lynn

 

[Rick Merz]

Good stuff Lynn, More cam manufactures are making these lifters to address this problem and like you said in the old days engine builders would modify the lifter bores in an attempt to get more oil on the lifter/cam.

 

So....

When I start specing a motor, what is the basic order that I should use to get the performance profile that I want? The issue I'm running into is that part selection is a dependent process with lots of trade offs.

Thanks!

 

[Lynn Larsen]

Ian,

1........Block
2........Bore &amp; Stoke
3........Crank
4........Rods
5........Pistons
6........Balancer/flywheel/timing set
7........Heads
8........Intake
9........Exhaust
10.......Cam
11.......Lifters
12.......Rockers
13.......Valves
14.......Springs (retainers,locks,seats)
15.......Push Rods
16.......Carb/injectors
17.......ignition/dizzy
This isn't set in stone and some sequences can be done in parallel, but you need to know what block and what balance you are going to use up front, then you pretty much have to know the displacement and intake/exhaust profiles before you spec the cam. You have to know the cam to get the right lifters and rockers and you should order the push rods last once you have the valve train set and measured. The carb/injectors you can order once you have the cam defined also. The ignition can be ordered when ever you know what way you are going with that. I would let the machinist and/or builder order the bearings and gaskets with your input once he has measured everything. Waterpump can come anytime after you have the block, rotating assembly and timing set/cover. At least this is my best guess and I'm sure I have left something out.

Lynn

 

Assuming that I'm on a limited budget, what would you splurge on? From what I've read, the most bang for buck is a good set of heads.

What would you skimp on or go with a junk yard scavenge?

BTW, this is one of the most value added threads I've participated in for quite a while. Thanks!