Cam sticky?

**daveb91** · 02-08-2006, 05:54 AM

Can someone make one this is the first time I have ventured into this internal forum. I was looking for some info and there are just too many posts asking the same thing. maybe have some info about cams with hp outputs, whats good DD cam, whats good for A4 vs M, whats good with stock head whats good with mod heads....... Just seems like it would clean some of this up I guess. Good advice? Or flame away! I can take it!

**Sarge** · 02-08-2006, 09:55 AM

I'll work on one...good idea man....

**Street Lethal** · 02-08-2006, 06:43 PM

Good idea... it's long overdue.

Originally Posted by daveb91

Can someone make one this is the first time I have ventured into this internal forum. I was looking for some info and there are just too many posts asking the same thing. maybe have some info about cams with hp outputs, whats good DD cam, whats good for A4 vs M, whats good with stock head whats good with mod heads....... Just seems like it would clean some of this up I guess. Good advice? Or flame away! I can take it!

**Sarge** · 02-09-2006, 04:16 AM

The beggining draft....special thanks to Hughes Engines man....I am working on a graph that shows various lift/duration cams and their power/torque curves.....

There are some basic principles that are universal, apply to all brands of camshafts and must be understood. Even Zboner can understand it..........

Camshaft size: Bigger or smaller is based on duration, not lift, more specifically duration @ 0.050" tappet lift. Advertised duration figures are not reliable numbers when trying to compare one brand to another for these reasons: first, advertised duration numbers include clearance ramps, which have no positive effect on performance. Second, advertised duration figures are not always checked at the same point with every brand, so the same cam can have several advertised duration figures depending on who or how it is checked. Third, using the duration @ 0.050" is a reliable way to compare cam size from one brand to the next, a good apples to apples comparison.

When selecting any camshaft for your engine/chassis combination, the size must be determined by the duration at .050" tappet (lifter) rise. Using a 1.5:1 rocker ratio this equals .075" valve lift. Any duration less than this has no positive effect on power.

Understanding the duration at 0.050" may seem confusing but the important thing that must be remembered is: as the duration at 0.050" gets larger the camshaft gets larger and vise versa.

The lower (or shorter) the duration at .050", the lower the RPM use, such as RV’s, towing, stock engines, etc. As the duration at .050" increases, the power increases, however, the power band also moves up in the RPM range. This requires additional engine and chassis modifications to work best. One cam will not do everything well, you may have to make "tradeoffs". In other words, if you want to drag race with a cam that pulls at 6800 rpm, don’t expect the engine to lug a trailer around at 2000 rpm or vice versa.

Cams have power bands, "sweet spots" or RPM ranges that they work best in. This power band or "sweet spot" does not mean that the cam will not work above or below this range. If, for example, the sweet spot is rated at 2000-5700 RPM, the engine will still produce power above 5700 RPM (at least ours will), but above 5700 RPM, the next larger cam will produce more power. By the same token, cams will produce power below their sweet spot, but the smaller cam will have more power there (see power curve graph).

The cam size (duration at 0.050") determines where the "sweet spot" will be. All brands of cams of the same size will produce sweet spots in approximately the same rpm range.

The "sweet spot" will be determined for the most part by the size (duration @ 0.050") of the intake lobe. Other factors such as the lobe separation angle, center line and exhaust lobes have some effect, but these are usually for custom cam installations.

A change of approximately 5° duration @ 0.050" is considered one (1) size or step.

The power in the "sweet spot" is determined for the most part by the rate-of-lift or how quickly the valve is kicked open. The quicker the better (ours are the quickest).

The best engine combination is when the sweet spots of all the components (camshaft, cylinder heads, intake manifold, carburetor size, compression ratio, headers and exhaust size) are in the same RPM range. For example, an RV torque cam with a large, single plane intake is a very poor combination.

If you collect a very poor combination of "sweet spots" (also know as mod parts) and then try to pick a camshaft, you leave the cam supplier with an impossible job. Don't try modding your LS1 with a bunch of bolt ons....and the last thing you choose is a cam.....The first component you should pick when you build your engine is the camshaft. Add the other parts to compliment it, not fight it......

**jrp** · 02-09-2006, 10:58 PM

Originally Posted by Sarge

that graph is circa 02-03

Camshaft size: Bigger or smaller is based on duration, not lift, more specifically duration @ 0.050" tappet lift. Advertised duration figures are not reliable numbers when trying to compare one brand to another for these reasons: first, advertised duration numbers include clearance ramps, which have no positive effect on performance. Second, advertised duration figures are not always checked at the same point with every brand, so the same cam can have several advertised duration figures depending on who or how it is checked. Third, using the duration @ 0.050" is a reliable way to compare cam size from one brand to the next, a good apples to apples comparison.

for our intents and purposes (genIII/IV engines) with hydraulic roller cams, all but crane use .006* for advertised duration. crane use .004*

duration @.050 doesnt tell you shit about a lobes profile and how agressive it is. you can have 3 lobes with 224* @.050 but all have different durations @.006, .020, .100, .200, ect.

case in point:

GM hot cam

tr230/224 (224 lobe used for illustrative purpose)

note the durtions of the "smaller" 224 lobe compared to the "larger" lobe of the 228 past .050*

When selecting any camshaft for your engine/chassis combination, the size must be determined by the duration at .050" tappet (lifter) rise. Using a 1.5:1 rocker ratio this equals .075" valve lift. Any duration less than this has no positive effect on power.

genIII/IV use 1.7 ratio

Understanding the duration at 0.050" may seem confusing but the important thing that must be remembered is: as the duration at 0.050" gets larger the camshaft gets larger and vise versa.

The lower (or shorter) the duration at .050", the lower the RPM use, such as RV’s, towing, stock engines, etc. As the duration at .050" increases, the power increases, however, the power band also moves up in the RPM range. This requires additional engine and chassis modifications to work best. One cam will not do everything well, you may have to make "tradeoffs". In other words, if you want to drag race with a cam that pulls at 6800 rpm, don’t expect the engine to lug a trailer around at 2000 rpm or vice versa.

Cams have power bands, "sweet spots" or RPM ranges that they work best in. This power band or "sweet spot" does not mean that the cam will not work above or below this range. If, for example, the sweet spot is rated at 2000-5700 RPM, the engine will still produce power above 5700 RPM (at least ours will), but above 5700 RPM, the next larger cam will produce more power. By the same token, cams will produce power below their sweet spot, but the smaller cam will have more power there (see power curve graph).

The cam size (duration at 0.050") determines where the "sweet spot" will be. All brands of cams of the same size will produce sweet spots in approximately the same rpm range.

The "sweet spot" will be determined for the most part by the size (duration @ 0.050") of the intake lobe. Other factors such as the lobe separation angle, center line and exhaust lobes have some effect, but these are usually for custom cam installations.

valve events determine your "sweet spot" and most importantly the IVC where this dictates the basic RPM range at which the engine will try to run its best.

If you collect a very poor combination of "sweet spots" (also know as mod parts) and then try to pick a camshaft, you leave the cam supplier with an impossible job. Don't try modding your LS1 with a bunch of bolt ons....and the last thing you choose is a cam.....The first component you should pick when you build your engine is the camshaft. Add the other parts to compliment it, not fight it......

um no, the last component you should choose is your camshaft. explain how you can choose a set of cylinder heads around a lobe and VE set. heads are where you power comes from; valve sizing, cross sectional area, port volumes, chamber size, ect cant be chosen to fit around a camshaft for optimal results. you use the cam to open and close the valves to fill the cylinder in the most effiicient way.

-daveb91 check the cam guide in my sig.