Anyone using a Crower 52242 Compu Pro camshaft ..

Talking to the folks on Drag Week that run Brad Penn oil, they say the additive properties of the BP oil break down really fast, like 500-1,000 miles. I haven't looked it up myself, but it was stated by folks that clearly care for their engines and have super high spring pressures. Lots of them change their oil every other day during the week, some change it daily after the couple hundred mile drive.

 

If you have a camshaft with differant profiles & lift figures on the intake & exhust lobes , why don't the valve springs need to be set up to match each lobe lift & profile? seems like it might help with wear & friction.
What say the cam Gods ?

I will take my answer of the air....

Mark

 

I'm also waiting for the cam gods to speak but most of them are not available on the weekends.

In the meanwhile, the spring rates are more determined by the ramp angles that make up a lobe.
Most of the time a set of intake and exhaust lobes are chosen from the same family out of the master lobe list.
This generally means that the ramp angles are about the same within a family.

If a custom cam is made for a some specific application that requires way different type of profiles between the intake and exhaust then the springs need to match each profile and there will be different springs for the intake and exhaust.

Paul

 

Every cam I have installed, custom or over the counter has always had a cam card that states the seat and over the nose spec's What am I missing?

 

You're not missing anything. You go by the cam card spring specs.

The question is: why is there only a single spring spec called out by the cam card when the intake and exhaust lobes are different?

 

I'm going to go with simplicity. The difference between the exhaust and intake shouldn't be radically different and everything I've heard is its much better to be over springed than under. So take the higher and apply to both. Even you Paul have mentioned additional friction on increased spring pressure and my guess is that friction difference is trivial.

 

Nick,

I thought we were talking drag race engines.. If you say that tight lobe center cams work on the mountain, I will defer to your experience, as long as that experience is based on the BBB. The large bore and small cross-sectional heads create rather unique port velocities in this motor. My experience is wholly based on the BBB, I would not be qualified to comment on what works in other makes of engines.
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When sitting in on a seminar given by Lake Speed, former Nascar driver and now spokesperson for Joe Gibbs Driven (oil), during the Q&A I specifically asked if the BR oils could be run for a time period after initial break-in.

I was told yes, that the only difference between the BR and HR series of oils is that the BR has higher levels of anti-scuff/friction compounds, has no detergent, and does not have the engine storage anti-corrosion additive. So using it in a short time period, for up to 500 miles is no problem. In the type of situation that we are discussing here, as Chris mentioned, I think that HR-2 would be just fine.

BTW.. I prefer the BR30. The Standard BR is based on 50wt stock. Considering the rather torturous path for oil in the BBB, I light a lighter weight to reduce the time period after the engine starts, before the cam is up on the "wedge".

We have had great luck with it here, been thru many cases of the stuff. I quit worrying about cam break in w/inner springs on everything but the monster flat tappet stuff a while ago, have had no problems at all. Any flat tappet with bigger than a .340 lobe on it, I will use a special set of break in springs I have.

I am not one of those guys with the drain plug wrench in his hand, while the engine is running during initial break-in. If there is nasty particulate matter in the oil, you have issues that an oil change is not going to solve. After dozens of dyno sessions using my system 1 or oberg filters, and looking at them after break in, I realized that I was spending too much time worrying about contamination during break-in. A good motor is very clean, and the use of a brush after honing really cuts down on the cylinder wall material you will find in the oil. In fact, since we have switch to a brush finished cylinder wall, I have quit using my system one all together. If there is something wrong, the engine will tell me on the dyno. I just screw on a Wix 51258 and worry about other stuff.

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If in fact you had two very radically different I/E lobes on the cam, then yes, your spring package would be different for each one.

But that's not commonly done, typically lobes are picked from the same family out of the lobe master catalog. Each "family" of lobes have similar lifter acceleration rates, regardless of minor lift/duration variations.

This is done for practical reasons.. not the least of which is that springs come in boxes of 16.

But also because there are not many engines that have "really great" intake tracts, and "really poor" exhaust tracts. All you need is an I/E ratio of around 70-75%. So the need for radically different lobes really isn't there. Certainly not for a BBB.

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Cam gods Paul?... Thankfully there are none on the site that I know of.. if you ask me, the camshaft is the one component of the engine that is tremendously over-analyzed. Sure it's an important piece, that dictates engine operational characteristics. But unless your talking radically different lobe sizes and timing, or changing to a different lifter style (flat vs roller) then the actual differences between two similar size cams are rather small.

I think discussions like this one are valuable, as long as the reader takes away the fact that the cam is just one component in a bigger picture, and as long as you stay within defined parameters based on engine usage, stay away from the latest sales gimmick, and install the thing correctly, then your build will be successful.

By far, the greatest number of cam related issues in performance engines has nothing to do with selection and lobe design.. and everything to do with improper installation. While I would like to think that you could trust a component to come out of the box and be exactly what it is suppose to be, that's just not the world we live in.

Select the proper cam for your application, and degree it in, and you will be happy. It really is that simple.
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JW

 

I think one also needs to remember that you are talking about two distinct differences in weight between the intake and exhaust valves so many times the two distinct lobesay still work with the same spring . Assuming the intake is given priority . I agree with you Jim W that the inlet tract of the BB Buick presents some different circumstances but torque is what is lacking up here so I would want to play to its strong suit when it was cammed . Good stuff here folks

 

So I asked a friend of mine that has been drag racing a long long time if he ever used different spring pressures for the intake and exhaust or knew of someone that did and his answer made sense. He told me a friend of ours does on his big block Chevy, but it has been on a spintron (and he winds it up to 8,600rpm!) so he knows exactly what the valve train is doing at that rpm and thus has used different spring pressures. Where as the friend I asked said he has always ran the same pressure across the board because he never spent the money to get the spintron work done and rather be over sprung than under.

So I guess the answer would be if you could quantify the the needed change there is no harm in running two different pressures, but as JW stated, they come in boxes of 16 :TU:

 

Good deal Ick
Hope it runs well for you
Oh ,and if it does ,does this mean fast ramp cams are ok again?p

As well as the Lunati cam that was ran 30-pds light on spring psi in Larrys' engine , may have been a different outcome with the correct springs tooo No:

 

NickEv, I used a"fast lobe" cam back in the early 80's, Mark Hefington of Cam Dynamics Ground me two cams for are Super stock pull trucks.Under load they made outstanding power even though they turned about 500 rpm less than the cams we had been useing. Torque talked!

Mark

---------- Post added at 07:36 PM ---------- Previous post was at 07:21 PM ----------

 

NickEv

Well I got the chance to test the springs that I shimmed .030 today . A little background this cam is a adv 270 / 290 - 226*/240* @.050 113lsa .505 / .484 lift. This cam hits like a sledgehammer of idle & pulls hard to 5000 rpm -anything over that & the valvetrain seemed to flutter & wave. Now after shimming the springs .030 I retested & was somewhat surprized to feel the valve train breakup & float @ 5100 up (worse that ever ) I don't think the lifter can take the extra spring load .

What do you think would be the risk of swaping mech lifters on to this cam ,has less than 50 miles on the engine.


Mark

 

Up Date , I removed the .030 valve shims & left the preload as it was before shiming springs . Went out for a test drive pulls strong to 5100 & then flattens out to 5500 rpm ,but does not float the valves. I think the lifter just could not preform with the extra spring presure @ 330 open & 130 seat.

Another thought that I have is @226* dur intake it's not a very big cam... and others with specs like this cam have power in the 2000 - 5200 range get, all being ground on a 112 - 114 maybe with my set up this is all I am going to get (& I will say this camshaft has outstanding power from the 1500 - 5100 rpm) with my gearing it pulls top end right on 5000rpm. I am sorry if I have bored anyone with this thread ,but if I did'nt think this cam was worth the effort I would not have posted in the first place.

In closeing I shure would like to hear from users of this 226*/240* H13 Scott Brown camshaft . How does it preform with there set ups ?

Mark Campbell

 

If it's better w/o the shims maybe they were coil binding.

Also, make sure your fuel system is up to snuff. That can cause similar nosing over on top end......

 

BQUICK,

Here is the set up on the springs 115# @ 1.89 this cam calls for 125# seat & 300# open
305# @1.39
coil bind @1.150

Do you feel they are to close to coil bind ? I thought .060 was the min spec . Cam lift is .0505 & .484


Mark