Comp cams Stage 2 and 3 questions

[Rock36]

Installing heads, cams, forged crank, rods, and pistons is going to seriously flay your wallet unless you are rich.

The cost of labor alone will be huge.....but if you want to eventually run a super charger up to 650 hp you will need the forged internals.

 

[MBDiagMan]

While I agree with the principles that you are talking about, I don't know that a cam adds enough torque in the upper rpm range to significantly threaten the longevity of the rods.

There are many people safely running power adders on the stock rotating assembly. And just about any supercharger for the S197 will produce more torque throughout the entire RPM range than a cammed N/A setup will.

To me, the stress of gaining 20-30 rwtq in the 4000+ rpm range from a camshaft doesn't compare to the stress of a blower giving you 80+ rwtq in the 4000+ rpm range.

I did NOT say that the torque would increase. The torque figure will most likely NOT increase and might even fall off fractionally. Horsepower is a mathematical calculation, not a measured value. The horsepower figure will calculate higher if the torque peak is at a higher RPM.

When you move the torque peak to a higher RPM, you will most likely run the engine much more at that higher RPM. RPM is much more likely to break rods than torque. As a matter of fact, increased engine torque does not really stress the rod that much more. Rods fail on the intake stroke while under tension. At high RPM, that tension on the intake stroke is TREMENDOUS.

Also, I did not mention changing out all internals for forged pieces. Changing only the rods would make a huge difference. The rods are the most stressed component in most any engine. A connecting rod lives a VERY tough life and as mentioned, the life gets exponentially tougher with RPM increase.

You can believe this or not. Your choice and your engine.

Have a great day,

 

[Rock36]

I did NOT say that the torque would increase. The torque figure will most likely NOT increase and might even fall off fractionally. Horsepower is a mathematical calculation, not a measured value. The horsepower figure will calculate higher if the torque peak is at a higher RPM.

When you move the torque peak to a higher RPM, you will most likely run the engine much more at that higher RPM. RPM is much more likely to break rods than torque. As a matter of fact, increased engine torque does not really stress the rod that much more. Rods fail on the intake stroke while under tension. At high RPM, that tension on the intake stroke is TREMENDOUS.

Also, I did not mention changing out all internals for forged pieces. Changing only the rods would make a huge difference. The rods are the most stressed component in most any engine. A connecting rod lives a VERY tough life and as mentioned, the life gets exponentially tougher with RPM increase.

You can believe this or not. Your choice and your engine.

Have a great day,

I'm not sure, but it seems you are taking what I said personally.

I think my statement/question is valid. I believe I understand what you are saying and I certainly understand the whole HP=(torque*rpm)/5252 equation. I just don't see why a cam alone presents any more stress on the rods than a supercharger.

This is what I was thinking for example:

If you are making a peak torque of 320 rwtq at 4500rpm and then a cam shifts that peak 320 rwtq up to 5500 rpm as you suggest, why would that be any more stressfull on the rods than a supercharger making 380 rwtq @ 5500 rpm?

As for RPM, I can understand the added stress on the rods if someone decides that they need to run their car at a higher RPMs all the time. But is that a realistic expectation for a cammed car? I would imagine MOST people who install cams are generally of the racing mind, and only operate under high rpms during drag racing or the occasional spirited acceleration at the stoplight, not because they are cruising along at 55 mph in 2nd gear.

Additionally, I am assuming that Doug at bamachips was giving an honest assessment when he said that the cams (at least the bamachips grind) do not affect the daily driving responsiveness/habits of the car. Therefore, I'm not sure why someone with a cam would be inclined to run their engine at any higher RPM than normal, unless they were drag racing. If they were drag racing, then I go back to my original question of why a cam is more of a threat to the rods than a supercharger. Many shops like JDM are running safe supercharger setups on the stock bottom end.

Maybe I am just missing something. Either way I am only trying to have a discussion.

 

[kooldawg6]

Yeah, I don't understand how you can add cams and get a 30-40 rwhp increase and be harder on the stock internals than say a blower that adds 115 rwhp on the stock internals...Brenspeed has the Paxton Supercharger Package which puts it up to 540 to 565 rwhp and mentions NOTHING about beefing up the bottom end.

 

[kooldawg6]

Just got done browsing BBR's site and the only engine mod they were suggesting was upgrading the valve springs.

 

[billfisher]

the 05 that installed stage 3's in his makes 345rwhp and 332 rwtq with a smooth idle. you can't tell he has cams. until he opens whoop-ass.
he revvs it to 7200 with all stock internals. it makes max power at 6600.

i believe he lost 1 mpg after the custom tune. his torque goes to 300 and stays there for ever. i was there for hid first dynos where it made 334rwhp and 308rwtq. the tune made the rest. his first run peaked at 7200 rev limiter and he added fuel to get to 334. rwtd made ~8 tq across the board with a wicked tune and peaked those 345/332 in the process. for me custom bigger than stage 4. i need more duration than your smaller motors.