Cam intensity question
 

Got a couple cam questions, or basically looking for some results from some of you guys. I noticed the trend lately with some guys is Lift is increasing, spring pressures are increasing, rpm's are increasing etc. Recently been seeing some of the spring pressures of 550-575-600 open on hyd roller setups.

I had always thought, that increasing lift, netted a penalty in spring life, guide wear, etc. Not long ago, it seemed as if you were running a bbc cam, with .370 lobe lift, that was considered a substantial amount of valve lift (.630 with a 1.7 rocker). Now, I am seeing custom hyd cams going in pleasure offshore engines, with lobe lifts of .400 or even larger (.680 lift).

The understanding to me was, that for endurance stuff, as duration grows, so can valve lift. But, short duration cams which we often run in boats, with high lobe lift, make for a very steep lobe. When the lobe becomes so steep, you now have the concern of lofting the lifters over that steep nose. To prevent that from happening, you need lots of spring pressure on the open side to control the valvetrain. So that may explain these nearly 600lb over the nose hydraulic setups I've been seeing, and the demand for very rigid pushrods, and lifters that can handle all that pressure.

I've been paging thru master lobe catalogs, and there is certainly not one lobe design for all applications. In other words, a profile that works well in NHRA, certainly may not be the profile you want in your marine engine hoping to get 300 hours from your valve train. Aggressive lobes can obviously make great dyno numbers, and open and close those valves extremely fast, but, at the expense of beating the crap out of the rest of the valvetrain. That is certainly something I am not interested in for my engines.

Is there anyone running these .400+ lobe deals with 250-300 hours without issue on a typical bbc journal with .842 lifters? My next cam's I am considering going with more lift, but not sure I want to accomplish that with a larger lobe, or a smaller lobe cam designed for 1.8 rocker ratio, and possibly not need solid roller type spring pressures for a 6,000RPM endurance build.

Best thing to do is call some cam grinders maybe ones with spintron machines. If it was me I would run a solid roller I think with less moving parts might make it more reliable plus you can monitor part failure like a lifter wheel starting to go south. And you have more choices of lifters to go with maybe a .937 lifter for long life. And a 55mm cam core. This is just my thought.

Joe, you really aren't going to gain much with the smaller cubic inch blower stuff moving up to a larger lift cam. Why not just speed up the blower a little and make more power. You are 100% correct more lift = more work for the valvetrain which means more maintenance. I've spoken to a builder that has an engine package with over .800 lift and they have nailed down the valvetrain maintenance to valve springs and lifter inspection at 120 hours. This is using a big cam core and .937 lifters which drastically reduces the pressure angle on the lifter. A 1.8 ratio rocker on a BBC is a bad idea in my opinion. What ends up happening with the higher ratio rockers is the pushrod, lifter and cam loose the leverage from the rocker arm this in return puts an immense amount of pressure on the cam side of the valvetrain. I had the numbers months ago it would blow your mind just how much more pressure it puts on everything. It's always better to have more lift at the lobe than stepping up to a higher ratio. From what I've been told when it comes to a BBC valvetrain guys usually over spring on the seat and under spring over the nose. My new cam has a .462 lobe we are trying to get an oppointment for the spintron right now. Was told with my setup we should end up somewhere around 160 closed and 675 open. This is a solid roller setup.

Joe, Obviously I am no expert and I know I will get flack for saying this. But, first thing I would do is get your heads on a flowbench and see how they perform and what they like. Use someone that you trust and knows how to interpret how the heads react. (I know a flowbench is an archaic tool and has no relevance in the modern era) If you flow 380 cfm @ .0630" and 382 cfm @ 0.680" is the extra lift worth the 2 cfm and maybe cost valve train stability. I know when my heads were ported they were ported to to get the most cfm of air around 0.650" (404 cfm on ~310cc heads). I have seen similar heads flow 420+ over 0.700" but that is not in the usable lift range that I wanted. That engine runs a mild HR cam with 1.85 intake rockers and 1.80 exhaust rockers and has over 200 hours on the engine.

Just my uneducated $0.02

Also, I run 1.8 and 1.75 rockers on 0.380" lobes with solids on a HR cams. I do all things wrong... :)

Your build just seems wilder and wilder every time I read about it. This is going to be cool when complete.

Joe. who is running 600lbs on hydraulic lifters? I was told anything over 500lbs will sink the best of them. I was always told that; more then needed spring pressure = short valve train life, and will rob power.

What I have heard, in regards to lift, mainly on the intake valve......and it may not be true, but

lets say your heads only flow 400cfm at .700 lift, and 402 CFM at .750 lift. One may assume that there is no point in going with .750 valve lift, because the CFM gains arent there on a flow bench. However, on a running engine, the valve is only at peak lift, for a very short period of time. So, by going with the .750 lift , you will see a power gain, because now the valve see's a longer duration of time, around .700 valve lift. This is sort of why low lift numbers are just as, if not as important as peak lift numbers. This is where the flow bench vs running engine gets fuzzy as far as picking a cam...

I think it is pretty rare, to see a power loss, on a bbc with good flowing aftermarket heads, by going from .630, to say .700 lift on the intake. Of course if you got some old truck peanut ports, thats a whole different story. Exhaust, not as important when it comes to lift. This is why, the trend has been going with cams with more intake lift, than exhaust lift, and why usually most bbc's respond better on the dyno, with a higher ratio on the intake only.

Another area of camshaft stuff I am learning, is that there are many factors that can go into designing a lobe. A lobe should be designed with the rocker ratio, lifter body diameter, lifter wheel diameter, as a package. As well as, the application it will be run in. The way I understand it, as far as lift vs duration goes, is a lobe with .400 lift and 240* @ .050, will be a more aggressive lobe, than .400 lift, with 260* @ .050. Theres obviously alot more to a cam design, that just .050 numbers, lsa numbers, and lift numbers.

For a guy like me, with a small cubic inch deal, a 260* duration lobe, just doesn't fit the bill for an engine that isn't going to exceed 6000rpm. . So, if I was to go with a 236ish lobe @.050, and wanted a .400 lift lobe for a 1.7 rocker, I'd have a very steep lobe, and need more spring pressure to control the valvetrain. Seem's to make more sense, if I went with a lobe with less lift, and 1.8 rocker ratio, I'd be able to run less spring pressure because my lobe is gentler, and have a setup that's easier on the lifters, less side loading of the lifters, etc etc.

Black Baja, I get what you're saying about mine just turning the boost up a bit. This question is more along the lines of , when I tear down, if I am gonna be buying cams, or making changes, just like any build, we all want the best power and best reliability. Plus it also pertains to some friends stuff I am always involved in. What I don't want, is a drag race profile, that beats my valves off the seats, excessive spring pressures, and a valve train that barely can make 100 hours, but looks good on a dyno. I was under the impression from what some of the nascar car guys are doing with extreme rocker ratios, is that less lobe lift and more ratio takes stress off the pushrod side of things, allows them to turn serious rpm with minimal spring pressures, and still get their big valve lift?

Good tech talk guys

I understand what you are saying. It gets into piston speed, time at each lift interval, dwell and other stuff. I know mid lift #'s are important but all of that other s#it plays a role that I leave to the experts. I love this engine build stuff, but I am a polymers engineer and deal with the flowability of non-newtonian fluids not air. lol

I think nascar is limited to flat tappet camshaft that's why the will run around a 2.0 rocker ratio they can not get a lobe to do what they want in a flat tappet.
What kind of power you make now at what rpm CID?

Joe, if you can get your hands on a 1.8 & 1.7 rocker. Hold them up next to each other. Where the difference in ratio comes into play is the pivot point of the rocker. The higher the ratio the closer the pivot is to the intake side. Try to think of the rocker as a pry bar. When you pry on something in order to get more leverage you need the pivot point closer to whatever you are trying to move (in this case the valve) the closer the pivot point is to the valve (1.7) the more leverage the cam lifter and pushrod have. 1.8 rockers on a BBC with a hydraulic lifter are a nightmare (for me) my hands are so beat up calissed up it's difficult to get any feeling on the pushrod. With a 1.8 rocker the pivot is so far back to the intake side you really can't even get you fingers on the pushrod to spin it and feel for resistance. It's not bad with the intake manifold off but with it on good luck. Also when you move to a 1.8 you have to machine the pocket on the guide plate deeper (exhaust if I remember correctly). Just some words of caution and things to think about. If you really want reduced pressure angle stepping up to a 55mm cam is the way to go. The larger diameter lifter with bigger wheel helps but only a couple percent compared to the larger cam core. With the larger core it puts the lifter up in the lifter bore and keeps it there very well supported. I was wrong on the lobe lift in my last post of my cam it's .472 [email protected] with the .937 lifter .850 wheel it gives it 3 degrees of duration. So the intake would actually be [email protected]. This is for a 632ci motor. As the cubic inches and air volume demand increases so does the ideal lift of the cam. With AFR 385's the motor actually wants .941 lift at the valve. I don't know about you but that scares the u know what out of me and with the 55mm cam and any more love lift on the cam I don't think I would have any connecting rods left on the even side of the motor. I had to get into the rod bolt pretty good to get the rod to squeeze by the cam and that was using rods designed for extra cam clearance. My buddy that builds very large cubic inch motors always told me its not a real motor unless you have to use an angle grinder to build it.

This year they switched to roller cams for the big tracks and still flat tappet on the street courses. I was told when they made the change they had all kinds of trouble getting the valvetrain stabilized because the acceleration rate of the roller lifter is so much greater.

You guys want to wrap your heads around something? Check out in-rad (inverse radius) cams, the lobe actually looks like a penut. Made AMAZING power, but at the sacrifice of valve train life.

There are three different pneumatic/electro magnetic systems in development and testing. That will be the ticket for making an engine live with obscene ramp speeds and lift numbers. If they can make the systems last that is. Unfortunately, the millions that had been invested into these systems in years past had all been geared to high rpm longevity and not a life span with regard to hours or years of service.

There are a lot more out there in use than people would think. Including some that have them in their engine without even knowing. Many hot street cars even. If I'm not mistaken, even some HR's.

I know they have some inverse radius solid rollers , they make them in hydraulic now ?

I believe so. So that's not 100%. I could swear I remember someone saying Jones (and some others) does some that way. Again, don't quote ,me.

Oh, you can quote me that some diesels use IR. Obviously, those don't rev high.

No, only SR, and that technology is 20 years old. We were working with Crower in the development of those cams back when Menard was still running V6 Buicks at Indy.

But it seems like some people read a tech article about "new technology" and the real pros are the ones that have been helping develop and test it for the past 5 years.

yep...merc 377 scorpion motors run a can like this..easy on the valves,,sets them down nice and easy..

Did a quick search, and Here's an old thread with Harold Brookshire and Mike Jones responding to someone asking about IR cams.
Jones does mention use in HR's

http://speedtalk.com/forum/viewtopic.php?t=8711

Just bought my cam/valvetrain a few months back.

55mm solid roller
Isky tool room springs.
Jesel rocker arms
Morel lifter (.904 with an .810 wheel)

Closed psi- 195
Open psi-540

Cam is 720 lift and mid 200's @.050 ( I can't remember the exact duration but it's in the 250 range)

and in the same year,,Isky says this.:D

http://www.iskycams.com/tech-tips-2000.html#2007

heres an idea,,stop using drag race cams in a marine motor.unless your gonna run your engine 7-10 secs at a time,then your ok.

you guys can do the math,top sportsman sbc,(sbx) 1.1" lift,425lbs seat,1195lbs over the nose,,springs are good for 1 season ~12 events.aluminum rods are good for 2 seasons.And I check the springs every week on the car.

And a little earlier Isky said this: .:D

http://www.iskycams.com/tech-tips-2000.html#2003

The problem is, most guys don't know the difference between a drag race cam, or an endurance cam profile. The average guy looks at a "marine" cam, as one that has no duration, and can be run with wet manifolds, as being the only difference between a BBC "boat" cam, and a 1/4 mile cam. So, they look at the duration numbers, and LSA, and think its all good for a boat.

It be nice to see cam cards from cam companies putting duration numbers other than at .050 and .004 on their specs.

.

Exactly why I didn't jump on the higher pressure bandwagon when replacing the springs on my 525. Mercury's choice has worked fine.

Looking thru comp cams master lobe catalog, they have specific marine lobes. These are their basic marine camshaft lobe profiles....for a cam duration like mine for example of 236*, it has a lobe lift of .357. and .607 valve lift with 1.7 rocker.

Then their is their "high lift" version of their marine hydraulic rollers. A 236* lobe for their high lift version, has a .360 lobe lift, with .612 at the valve with 1.7. While I certainly don't think comp cams is god, they aren't new to the cam business, marine, endurance racing, etc. They have quite a bit of a knowledge base on camshaft lobes. Also, when looking thru cranes literature, I have not seen anything with a "marine" useage or endurance useage, with anything near .680-.700 lift with a 1.7 rocker, even on the longer duration stuff.

Also for those who have a Dyno-Sim program plug in a more aggressive cam profile, see what the HP/TQ gain might be and decide if the gain is worth the reliability issues that are associated with the profile when used for marine long term usage! I'll bet it is not worth the grief.

Very true. From my experience with my engines, and a few friends engines, that have had lobe lifts of .370 range or less, with duration numbers of 235ish to 245ish, have seen good life from the valvetrains. Not talking 1000 hours, but 200-300 hours isnt out of the question, with moderate spring pressures. What concerns me, is a few buddies who've got custom cams for their marine engines, that have similar duration numbers, std bbc journal, std .842 lifters, but are sporting .400-.410 lobes. The cam guy they use doesnt provide them with duration numbers at .200 on their cam spec sheets.

I guess time will tell how their valvetrain holds up, and if the extra little bit of power, was worth it or not for them.

From the little I am learning on this stuff, is there is no getting around increasing lobe intensity increase, if duration doesnt grow with the lobe size. So, while most think they are simply adding valve lift, they are also increasing lobe aggressiveness..?...

Would it be wise to assume, keep gentle ramps, keep lobe lift down, run enough, but not excessive spring pressure, and make your power in other areas of the build, if long valvetrain life is what you want. Especially on forced induction marine stuff.

i am thinking about building a 15-1 compression ratio,huge cam,big chief headed n/a engine for a 24 foot baja that is for sale on ebay,it should make 1000 hp and need valve train maintenance every 25 hrs but who cares about little things like that.i am going to use neo oil in the alfa drive so it should hold up well.i am going to run it on e85 so fuel won,t be to expensive.the ebay add said the transom is soft but i think some super glue will bring it back to snuff.my question is will the 23 pitch aluminum prop that comes with the boat work or will i need one of those high priced stainless steel 4 blade props.one more question,will my s10 pickup pull my new boat ok?i only live about 40 miles from the canal i plan on running it in.

I agree 100%,

Tony, you got me playing with the sim software.

Just for chits, I built a 540ci, 10:1, Dart 335 headed engine with a dominator carb and single plane. With a Crane "651" cam, 244/256 114lsa, .632/.632 lift cam, 1.7 rockers, the sim came back with 685HP peak. Changing nothing but making the lobe larger, going from .371 to .410, which netted .697 lift, the horsepower 702HP. 17HP gain. What did change, was the auto calculation feature, that displays lifter acceleration. It doesnt give specifics, but basically categories. It moved the stock setup which was between "oem and aftermarket street", to the larger lobe moving it between "aftermarket street" and "limited street".

I then changed to the famous "741" 236/244 .610/.632 112lsa crane cam everyone loved lol. This combo netted 647hp. Again, by going to a .410 lobe, and increasing lift at the valve to .697, the HP jumped to 662. 15hp gain. Again the lifter speed increased, to a higher point than it did with the longer duration 651 cam.

According to the sim software, those lobe changes certainly didnt put it into their category of "all out racing" or "pro stock", but it did increase it further from "oem performance " and "aftermarket street performance" closer to "drag and limited street". Although this information is just from a simulator, it seems to coincide with what companies like crane, comp, have in their lobe catalogs for "marine endurance" as far as lobe lifts go. Of course their is probably many many variables, like when getting into 55mm cores, larger lifter diameters, etc etc. Its more standard bbc stuff.

Being that in a boat like mine, 15-17hp gains, will barely net me 1mph in top speed gain, I'd much rather go with the lobe thats easier on parts.

I think you would be better off getting into a LS based engine that will get you into a much better valvetrain.

If I was gonna make a change, I'd simply go with larger cubic inch. The most power I'd consider installing in my boat would be twin 1000hp. And that is an easy goal with a mild valvetrain BBC with a Whipple and low boost, or even the right roots.

I know Eddie young has 1000hp deals like that running around that have exceeded the 300 hour mark plenty of times before coming in for a refresh. I also know his valve lifts are not in the .700+ range, and his spring pressures are not nearly 600psi open on a hydraulic. I kinda want to take a page from his book .

The LS stuff is really cool, and no doubt a better design, but not into spending all the money to ditch my twin stelling exhausts, engine mounting , accessories ,and all that other stuff. The BBC is capable of my goals all day long, as long as the valvetrain isn't designed for a drag race engine .

What about going solid roller to lower valvetrain mass for lower spring pressures with the benefit of more accurate lift? I know solid roller lifters are lighter. Has anyone did any research on mass of valvetrain components from brand to brand, and different materials? I am sure the nascar guys scrutinize this stuff. I would think a lot of performance and longevity could be gained from mass reduction.

There is a bennifit to a lighter valvetrain, but at the expense of routine maintenance. You have to ask yourself, "Do I own a race boat, or a boat to drink Bud Light on?" Most here own the ladder. I own both, but will only run HR. I cannot justify the added time required to maintain my hobby vs. the small amount of power gained.

Joe, Good stuff!

I'm building a coates cammed engine so I don't have to worry about all that valve train junk.:D

Cool,so you can port the 'valves' right ?