Camshaft Help

[Collectindust240Z]

I hope this hasn't been beat to death. I've searched but not found. I'm looking for a bigger cam. I have the MSA 480/274 and I'm not really happy. I have a F54 flat top, P90 with "the mod", tripple dellorto 40s, MSA header, zx dizzy, Crane HI6, zx 5 speed, 3.90 R200. Any suggestions? I don't care about idle, the nastier the better. I don't want this thing to run out of lungs at 6000rpm.

Brian

[JMortensen]

You can bet I'm going to bookmark this thead and use it to prove my point about the tiny stage 2 and 3!

 

I'd look for something in the .500/300 range. Also run your timing somewhere between 15-20 degrees at idle and that should be about right.

 

Realize that you'll need to swap springs and seals in order to allow the cam to lift any more than your current cam does.

[Collectindust240Z]

If I'm already using the double springs suplied by Schneider, do I have to get new springs? If so, which ones? And new (different) seals?

Thanks, Brian

[JMortensen]

Schneider springs will handle over .600 lift I think. You should be fine there. Here is the detail on the seals: http://forums.hybridz.org/showthread.php?t=90825

[Collectindust240Z]

YOU ROCK!

thanks

Brian

[JMortensen]

[Collectindust240Z]

where should I get a cam from. I checked Isky, Comp, Crower, and Web. None of them have anything in the 500/300 range.

[JMortensen]

Check out regrinds from Delta, American, Webcams, etc. I've used American before. Lots of guys swear by Delta. I think Drax240z had a line on something with just about those specs. He was using it on a customer's autox car. Might PM him.

[1 fast z]

UMMMMMMMMMM, you didnt look at delta and isky hard enough. I have orderd cams from both of those suppliers with those specs. Delta has a .500 296 duration cam, and a 550 303 cam.

[BRAAP]

Rusch Motorsports offers a REBELLO ground cam with .520” lift. The Schneider springs are the recommend springs for this cam, and either IR EFI or Triple carbs complement this cam quite nicely for the racers and the “extreme” hot street enthusiast. It Definitely wont fall on its face below 7000 RPM.

 

Here is a pic of that .520” lift cam prior to installation in a Hybrid Members custom stroker 3.1 that we are building a custom P-79 for. He also plans to run a nice shot of N2O on this combo as well. Should be VERY potent at the strip and on the street.

 

 

 

 

 

The combustion chambers for that P-79 head will kook just like these chambers on a P-90 that we recently shipped.

 

[TimZ]

Here is a pic of that .520†lift cam prior to installation in a Hybrid Members custom stroker 3.1 that we are building a custom P-79 for. He also plans to run a nice shot of N2O on this combo as well. Should be VERY potent at the strip and on the street.

 

 

Wow - what thickness lash pads do you need to run with that?

[BRAAP]

Wow - what thickness lash pads do you need to run with that?

 

 

 

 

Well, it depends on how deep we sink the valves, how much we kiss the valve stem tips. Also, just how much we shave from the head deck surfaces, both top and bottom, and also how thick the head gasket to be used is, will dictate how many, if any, tower shims we need. Then, we will mock up the head with the valves, retainers and keepers to be used, using soft springs and using lash pads from our in house lash pad inventory, (every lash pad thickness available from Nissan), on each and every cam lobe to verify the cam wipe pattern is where it is supposed to be, or where we want it to be on the rocker arm, which is typically cheated to the back side of the rocker with approx .030"-.050” untouched margin. We will then order and install the appropriate lash pads.

The head that will receive this cam may undergo some chamber welding in an effort to gain some more compression, so right now, we don’t know what lash pad thickness we will need, suffice to say, it will be thicker than average and the Schneider retainers do have adequately deep lash pad retention lips to retain the required lash pads.

[TimZ]

Thanks for the very thorough answer. Hope I didn't sound critical - I have no doubt that it will work fine, especially since you are paying attention to all the right details. I'm just not used to seeing the backside taken down that far - probably not a good cam for a novice (from an installation standpoint)...

[BRAAP]

Your question is a great question, thanks for asking, and it was not taken as being critical at all. If you’ve read any of my other posts regarding L-series cylinder heads, you will note that I have a tendency to write novels about rather simple topics. I just prefer to mention all the details that are applicable and could be pertinent to the topic in an effort to answer any other possible questions that may arise. It is just my nature to be “very wordy”, as my lovely wife puts it.

 

Installing “this” cam would be no different than installing any other aftermarket cam, other than it doesn’t come with a recommendation for lash pad thickness. Anyone with good basic mechanical aptitude can do this though, he/she just needs to be sure to check the cam wiping pattern. Most of the time with milder aftermarket cams, the supplied, or recommended lash pads will be just fine, but not all the time. This is especially true if any custom head work has been done, such as extensive surface decking, extensive seat cutting/grinding, new seats installed, larger valves installed, new valves installed, etc. My opinion on the topic of swapping in an aftermarket cam is the cam wipe pattern should “always” be checked no matter what, never just trust the manufactures recommendations for lash pads they either recommend or supplied with that particular cam. I have seen on more than one project where the supplied lash pads allowed the cam to run off the end of the rocker wiping surface, and in those instances, if the cam would’ve been run with those lash pads, the cam would’ve wiped itself out in very short order. In fact, this was true with one of the custom N-42 heads we did for a Hybrid member recently. His cam kit came with lash pads and we couldn’t use any of them as they didn’t work after all the custom work that performed, so we ordered the appropriate lash pads, double checked wiping pattern before we shipped it.

 

If you haven’t already seen the thread linked below, it covers some of the details that goes into building a custom cylinder head and covers cam wipe patterns as well including pictures of the parts and tools used in the process as we built that custom N-42 head mentioned above.

 

http://forums.hybridz.org/showthread.php?t=108398

 

 

BTW, thanks for the "heads up", via PM earlier, I owe you one…

 

 

 

 

Sorry if I got too far off topic here guys...

 

Paul Ruschman

[jgkurz]

Paul,

 

As usual, I learn a lot from your responses. Thanks for taking the time to enlighten us. Couple questions.

 

1) If an aftermarket cam is installed with the incorrect lash pads would it also have an effect on the engine's HP/TQ characteristics? An example might be a cam that was ground from a new billet which was then installed with the stock lash pads. I would assume, maybe incorrectly, that the wipe is close to acceptable. I'm wondering if I could get more out of my cam if I installed lash pads based on proper measurements.

 

2) When you are measuring for the proper lash pads have you seen a need to install unique lash pads for each lobe or do you installed twelve of the same pads?

 

Thanks,

John

[Collectindust240Z]

Just a thought... am I gonna run into piston to valve clearanc problems with Isky's .530 lift cam? Will I realize the potential of the cam with an unported head? Should I just stick with their .495 cam?

[JMortensen]

Just a thought... am I gonna run into piston to valve clearanc problems with Isky's .530 lift cam? Will I realize the potential of the cam with an unported head? Should I just stick with their .495 cam?

I'd be curious to hear the answer to the lift part of this question. What's the duration on the .495 lift cam? If it isn't close to 300 degrees, I'd keep looking.

[Collectindust240Z]

I'm sorry. It's a .490/290 grind. The other one is a .530/306

[RedNeckZ]

I was using the Isky cam 290AS. They have it marked as a 483 lift and 296 duration cam. Had great power around 6000 rpm. Used it on a L-24 with E-31 head, it was overkill for the motor. Thinking of putting it on a L-28 40 over with E-31 head and see what will happen.

[BRAAP]

Paul' date='

 

As usual, I learn a lot from your responses. Thanks for taking the time to enlighten us. Couple questions.

 

1) If an aftermarket cam is installed with the incorrect lash pads would it also have an effect on the engine's HP/TQ characteristics? An example might be a cam that was ground from a new billet which was then installed with the stock lash pads. I would assume, maybe incorrectly, that the wipe is close to acceptable. I'm wondering if I could get more out of my cam if I installed lash pads based on proper measurements.

 

2) When you are measuring for the proper lash pads have you seen a need to install unique lash pads for each lobe or do you installed twelve of the same pads?

 

Thanks,

John[/quote']

 

 

John,

Glad you enjoy my posts.

As for valve lash and HP. Hmmm.. Valve events are a VERY intricate and highly sophisticated part of engine design and development. One could easily spend 10 years in schooling acquiring a Phd and still not know everything there is to know about valve-train dynamics as applied to the reciprocating 4 stroke power plant. I’m no expert nor do I have all the answers, but I will share with you what I do understand, though it may get a bit wordy, and I apologize for that.

 

1) There is no definite “yes” or “no” answer to your first question. Of most importance here is that the cam wipe pattern is actually “ON” the pad of the rocker “entirely” and not running off the end of that pad. As long as the wiping pattern is “on” the wiping pad itself, (and if the intake, exhaust system etc compliments the cam that is installed), the engine will run great. As for optimizing that cam wipe pattern for performance, we tend to cheat the wipe pattern as far toward the back of the rocker as possible, (towards the rocker pivot/adjuster). This is typically referenced as “cheating the rocker ratio” and essentially cheats the rocker ratio from say 1.5:1 to 1.55:1. This is a small incremental gain in lift and duration that can sometimes be gained if the ratio is less than optimal currently, (no way to know that till it is checked…). Also remember that with the cam, no matter how you acquire any gains in lift and duration, this will also come with the corresponding loss in drivability and mileage as well. Think of this process of cheating the rocker ratio as “fine tuning” the cam specs towards the performance end of the spectrum, just as you would fine tune your ign advance curve, or fuel curve at varying loads for max power. If the cam wipe pattern is at the front of the rocker and there is enough “unwiped” surface at the rear portion of the rocker pad, say it can be cheated back .050” or so, on the dyno, you could realize a small but measurable increase in power from that alone, nothing that you would feel seat of the pants. This is only if the rocker ratio is on the lazy side to begin with. But as you fine tune several aspects of the engine, such as rocker ratios, fuel curves, ignition curve, gearing, traction, etc, it is the sum of “all” these things that makes the difference between an engine that just has a bunch of cool goodies bolted on to it that runs pretty good, vs one that has been “fine tuned” or “dialed in” and runs incredible. To back up a little here, ideally you want all of the cylinders to breathe equally so all the cylinders are producing the exact same HP. Hopefully the intake tract and exhaust tract is allowing this to happen, (in our L-series, yeah right), and with this theoretical equal cylinder filling happening, you would want the cam timing “at the valve” to be equal for all cylinders as well. We typically take for granted that all the lobes on a cam that we purchase are ground “identical”, but in reality, there are slight differences in the lobes themselves. If you have an accurate micrometer and are able to get repeatable results, (i.e. you have used a mic regularly), you can measure the lift of all the lobes on a cam vs their respective base circles and you will see what I mean. I’ve seen as much as .010” difference between lobes on the same cam. (this does not take into account valve duration as that would make this already lengthy post an extremely long novel, suffice to say, that any differences in duration from one cam lobe to the next will follow suit with the lift.) In an effort to help equalize the valve events, we can cheat the wiping pattern of individual lobes to help accommodate this equal cylinder filling. Also, not all rockers are created equal and due to manufacturing tolerances, can cause the rocker ratios to be off from one rocker to the next. For the average street bruiser and even the die hard road racer, this is taking “blueprinting” to a bit of an extreme, though a realistic one. I’m sure you get the point. If I lost some of you with this, don’t worry about it as this is splitting hairs. As long as your new cam is wiping “on” the rocker wipe pad, you’ll be well served. For those who would like to learn more on this subject of equal cylinder filling and other extreme engine design and tuning techniques, I strongly recommend a book written by Jeff Hartman called “How to tune and modify Engine Management Systems”. If you’ve read and thoroughly understand the “Frank Honsowetz Datsun Engine” book and also have read various David Vizard books and understand his very in-depth approaches to engine design, development, and tuning, Jeff Hartmans Book is a bit extreme in terms of intake and exhaust design and tuning, none the less it takes all that to the next level. In short, the answer to your first question John is…. Maybe….

 

 

2) The answer to this question is “sometimes”. I’ve used as many as 6 different lash pad thicknesses on one head due to several factors. A couple factors being that the head was severely warped to begin with and I wanted the valve heads to be sunk the same distance within the combustion chamber. Another approach to this same scenario would’ve been to tip the valve stem tips so that the same lash pad thickness could be used. As for which approach is better? 6 one, half dozen the other as to which approach is best. That decision is made case by case. As mentioned in the answer to your question, the real issue is that the cam lobe is wiping on the rocker pad entirely and not running off either end.

 

 

Hope this helps answer your questions without muddying the waters too much…