I'm putting a new cam in my 355 this winter while the motor is out of the car, but I need some help choosing one. These 2 seem about like what I'm looking for:
http://www.summitracing.com/parts.aspx?sku=ISK-201292-6

http://www.summitracing.com/parts.as...CCA-CL12-254-3

These look quite similar, but how much differently would they react?

My motor is a 350 bored .30 over, 750 cfm edelbrock w/ choke tower milled down, edelbrock Victor jr. intake, Dart 200cc cylinder heads (good to .620 lift), 1.6 ratio roller rockers, Dyno Don's headers & Y-pipe

Made 440HP @ 5900 RPM and 450ft-lbs @ 4400 RPM with this cam:
http://www.summitracing.com/parts/CCA-12-212-2/


So does it seem like 1 or both of the 2 camshafts listed above would be a good match for the rest of the engine combo? The cam in it now peaks too soon for the rest of the combo I think, but am I pushing it too far with 7000 RPM? Streetability, idle and vacuum are not an issue Thanks in advance for any input you can give me

 

Concidering the typical 350 SBC maximum RPM is 5.5k-5.7k taking it up to even 6 k is kinda pushing it and trying to take it to 7 k is basically suicide. Now granted i know nothing about how your bottom end is put together so i only assume there was nothing worth mentioning but if it is factory stuff accept 5.5k as your max RPM. Ignoring all other factor just looking at it in terms of performance although you might be able to do better with a different cam selecting one to build power outside of your rev range will just make the car slower because your trading off you low end to build power in an area you cant use.

 

the cam you use depends on what the car is used for. if its race only i wouldn't even consider a hyd. flat tappet cam (unless the rules state otherwise) what is the car used for?

 

Sorry guys, didn't mention the bottom end in my build, but it's new, balanced and forged. Shouldn't be an issue right?

As for the car use, it's basically a "budget" rod that sees track and limited street use (Limited meaning far from a daily driver, more of a toy in the summer)

My intake manifold's basic RPM range is 3500-8000
Carb should flow over 750 CFM
200 cc intake runners on the heads
1 3/4 primaries on the headers shouldn't be a restriction

And the basic RPM range in my current cam is 2000-6000

It just seems to me like the current cam is a "mis-match" to the rest of the combination, and a more aggressive one would let the other components reach their potential?

 

the setup you're running is exactly what's on my race only car but it has a .630" lift solid roller. i would recommend a solid or hyd. roller because you can get the lift you need but keep the duration lower for street use. i would find a roller cam with .560-.580 lift 230-240 duration 110 lsa. remember when you use a solid lift cam you dont get the advertised lift because the lift is at 0 lash. use recommend springs and check valve to piston clearance...have fun

 

I can't use a hydraulic roller cam without machine work on my block can I? That's why i was looking at hydraulic flat tappet cams. I'm not sure what it takes to run a solid roller?

And can I ask approximately what kind of power your setup makes skirkland?

 

Well as far as the max RPM is concerned its a complicated matter. Even though its been balanced (balanced to what tolerance?) and is forged (need to consider weight and design for example rods forged H beams forged I beams ect) there's still a lot of factors to concern yourself with. Being thats the case I wouldn't be able to tell you what the max RPM on your bottom end is but still 7k seems like a lot unless you dumped a ton of money into getting good quality bottom end stuff and machien work. Your best bet would be to ask the machinist who balanced your bottom end because they would know a lot better than i would as they have first hand experience with your bottom end and know what went into it. The thing thats really a pain about all this is there's no real max RPM where you bottom end will have an instantaneous failure (not true there is its just not something that is easily attained lol) . This is why a lot of people take there factory SBCs to 7 k and think its ok. The thing is when you over rev your motor you start to enter a rev range where your motor wears at an accelerated rate. The higher the RPM the faster the wear. Also its not like the motor wears twice as fast at 6k as it does at 3k wear grows exponentially. So what i mean by that is say your max RPM was 6k well it might run 160k at 4k rpms continuously it might run 150k miles running at 5k continuously it might last 120k miles running at 6k continuously but running at 7k the motor may only last 50k and running it at 8 k might be a matter of minutes not miles. Although its not quite so simple as that and those numbers are totally made up and not realistic you kinda get what im saying? Your max RPM is basiclly the point where the general wear and tear is considered normal and exceeding that although may not cause instant failure could be thrashing your motor. Although for race cars its ok because theres huge money there and the motors arnt expected to have a long life in the first place that kind of engineering might not to practical for your street strip toy. So what im trying to say is talk with your machinist as to what he thought of your bottom end and play it conservatively with your max RPM especially if your not really 100% sure of its capabilities. Also notice how ive only spoke in terms of your bottom end there is way more to a max RPM than that from oiling the valve train ect. lol even mechanical fans have a max RPM before they fall apart lol. As far as roller lifters are concerned they would be a big plus as that roller tip will allow for higher ramp rates of the cam and solid rollers or just solid lifters will help increase the max RPM. As to if machining is involved? Not really. What i mean is if you have an 86+ block its already machined for roller lifters. If you have an older motor you can get a retrofit kit to install them but because its so expensive you would be better off getting a newer motor unless you happened to be filthy rich with tons of money to throw at this project lol. My recommendation is this if you cant use roller lifters in your block its too much money to retrofit it in with a kit use the flat tappet cam. Some claim that theve done it cheaper by retrofitting factory stuff into older block with some good old fashion back yard engineering but i cant comment on that as ive never done it or heard the details as to how it was done. Use solid lifters unless you don't want to adjust them from time to time in that case use hydrolic as there as "set it and forget it" as is gets. Although as stated hydrolic flat tappet cams for raceing is about the worst you can do. For the street there great but for serious racing no.

 

Okay, I see what you're saying. I suppose I should probably tone down my max RPM goals (I'm glad you mentioned the mechanical fan, forgot about that lol)

This is a low mileage car (Under 5,000 miles a year) although it's driven pretty hard, but wear is really not a huge issue.

But you're saying all 87+ blocks are already machined for a roller cam? That would include mine then, being a 1pc rear main seal.

I guess I'm just not sure what I want to do now exactly...
-I want a higher RPM, and I think it would match the rest of the engine better, but I suppose a hydraulic flat tappet isn't the way to do that
-So I'm not sure if i want to convert to roller, (if the block can), or keep the cam I have, or get a more aggressive hydraulic flat tappet that isn't unrealistic

 

Well the thing is its all what you want from it. To explain what i mean by that ill try to explain why rollers are popular and you can decide if thats important to you or not. So heres the deal. The big advantages of a roller cam is A. eliminates the cam wear issues associated with flat tappet cams and B. allows for cams with higher ramp rates. What are ramp rates and what is the importance of ramp rates? (BTW if you already know i dont mean to be insulting just trying to explain if by chance you dont know or to thoes that read this and dont know I dont mean to dumb it down its just me explaining things). First ideally valves would be open or closed like a light switch. However practically this can not be done obviously the cam lobes cant be square the have to be kinda like a half oval. Ramp rates are a way to describe how steep the oval is essentially the closer to a square lobe being better. Now because of the design a roller lifter can have a higher ramp rate than a flat tappet cam. Now that we kinda have an understanding as to what a ramp rate is now lets talk about why its important. Im sure youve noticed that heads have flow rates that vary with the lift of valve. Again ideally if the valves acted like a switch just open or closed it would be just 0 flow (valve closed) or max flow (valve open). However because this dosnt happen you spend some time at .1, .2, .3, .4, .5 valve lift. So the overall amount of air that can flow into the cylinder is the combination how much air can flow in at .1 lift and then at .2 lift ect. Obviously the more time you can spend at max lift the better. This is commonly refered to as the "area under the curve." In translation as to what this mean in terms of flat tappet vs roller if both cams had the most aggressive ramp rate that they could operate at reliably 1 of 2 things would happen. If you wanted to maintain the same duration on both cams, the hydrolic roller cam would have the potential to have a higher lift. The second scenario if you wanted a certant amount of valve lift the flat tappet cam would need a longer duration to do it. The final piece that puts it all together in terms of what this means to your car is this basic cam theory states that the larger the valve lift the more power you will make across the board and the longer the duration the higher in the rev range the peek power will be. What this means it typically because we pick cams with the idea of a certain power band in mind and that power band is related to the duration for any given duration a hydrolic roller cam will be able to get more lift which will equate to more performance across the rev range than a flat tappet cam. If your not a serious die hard drag racer this benefit might not out weigh the expense of going to a roller set up however if possible the advantage is clear. Its not that you cant make a high reving flat tappet cam just that in terms of performance the roller can do what the flat tappet cam can do but better.

 

the car runs 6.80 1/8 i'm guessing about 550hp all motor. car is completely gutted with 6 point roll bar. i didn't have to do any special machining for the roller. have to use bronze dist. gear and a timing chain with a thrust bearing behind it and a roller button on the front of the cam. you don't want the cam walking, and because the solid lifters are much heavier than hydraulic lifters a much stiffer spring is required to keep the lifter on the cam

 

Skirkland, your car is so much like mine it's scaring me man ... Pretty cool to know I could run a time close-ish to that if I had a decent rear end and tires.


And Rolling Thunder, what you are saying makes sense. I "blueprinted" my motor off a crate engine that I liked the specs on at the time, but now unfortunately I wish I had just spent the extra cash and fitted it with a full roller valvetrain. Unfortunately, being a "budget" rod I can't justify swapping all that out again at this point... I'm gonna stick with a hydraulic flat tappet for now.


But do you guys think something like the Isky cam linked at the top would be too much? I probably want to stay away from the comp cams one, I don't want piston to valve clearance issues. Thanks for the help guys

 

Well if you like the Isky cam go for it but you will still have to check the clearances as you may still have trouble. To me its kinda a toss up in terms of which is reallt "better." The both operate over the same basic RPM range despite different durations and this is partly due to the lobe separation angle. The Isky cam is a bit tighter than comp cams. Basically the differences in lobe separation are as follows:

Decreasing lobe separation:
1. narrows the power band
2. dyno results will tend to be more peeky and drop off quickly
2. shifts the power band lower
3. makes more peek power
4. pumps up the mid range
5. Also as a side note creates more overlap for that classic choppy idle



Increasing lobe separation
1. widens power band
2. takes away from the mid range
3. produces less maximum power
4. Broader flatter torque curve

 

the main difference is my compression ratio is 12:1 and the cam is huge. even when my car was 10.5:1 it was running low/mid 7s. you may not have valve piston clearance problems. you never know until you check it. if your timing marks on your balancer are accurate, check exhaust clearance 10 degrees before tdc on exhaust stroke and intake clearance 10 after tdc. set up a dial indicater on the valve retainer and use a large pair on channel lock pliers to check distance from the valve to the piston. but i recommend the big cam those heads will thank you.

 

Well I've been thinking about it, and I think I'm just going to stick with the cam I have now. It's got a relatively broad, useable powerband which is what drew me to it in the first place, and driveability is pretty decent. I would probably be happier keeping the cam and getting a dual plane intake manifold more in my powerband, instead of vice versa. When I really decide I need more power, I'll build something myself with bigger cubes (Or forced induction ) so I can keep the driveability and reliability

Thanks a lot for the input though guys Good info from both of you