Comparison between camshafts: Original 102 (S/S90) and NeuTek SC-200

[Jacques Lefriant]

Hi All
Hi
if you study the tables that Wilhoit provides only the stock cams(Normal +C) and the Tim Biradelly one are smaller than the stock Super/S-90/912. To Ron's comment the major Carburetor issue is the size of the Venturi. Cam selection is a tradeoff even the cams with the identical specifications from the tables will have to be timed optimately and since they are copies of other cams the execution can be better or worse. To play with different profiles on the intake versus the exhaust like the Neutek ones and change the lobe centers the "improvement" will be hit or miss unless many identical engines were evaluated.
j

[Greg Bryan]

Willhoit's WR58 seems to be a copy of the Elgin 6708. I have the 6708 in the C engine I'm currently breaking in and I like it a lot. Torque is better than the 1600S cam I have in the engine I rebuilt for the Conv. D, even though that is a higher compression motor.

I think Elgin grinds all of John’s cams - some of John’s cams are specified with advance from stock which is done with special offset bushings/washers - the WR68 I’m using in my other motor required having the cam drive gear modified to accept the bushings. Then one has to fiddle with them to get the right intake valve closing spec. I struggled the first time I did it but the second time I’m sure will be easier.
John said there is a noticeable improvement in the dyno data with that small amount of advance.
Of course, that’s how modern engines put out so much power having independently phase-able intake and exhaust cams (and 4 valves per cylinder and direct injection etc.)
The WR58 cam has some minor tweaks to it since this chart was made according to the spec sheet I got with it.
PS - Im not trying to be a Willhoit salesman, his shop is conveniently close by my home and he’s very forthcoming with information

[Jacques Lefriant]

Hi Greg
the big issue these days is that there are few custom cam grinders left capable of producing an excellent custom grind for a reasonable cost and there is not the volume/demand to support them.
j
FYI in the past i believe John had Norris grind his cams. one of the cam grinder firms i use did a few for Norris when they were not fully capable of producing them. i have 20 cams on backorder now with a couple of firms. Web seems to be the only firm now able to handle our volume on a timely basis. Until computer generated profiles became available profiles were copied from OEM ones and with a few tricks in the process new ones were generated.

[Martin Benade]

So for a torquey Zenith engine the C cam would probably work better than the WR58?

[Jacques Lefriant]

Hi Martin
the comparison would be a super engine with the stock super 16 cam(the copy WR58) and a C engine with the 15 C cam correcting for the different heads since the carbs are the same.
j

[C J Murray]

"Have I got a camshaft for you!" The best camshaft is like the best oil, no consensus, lots of experts, lots of snake oil, lots of claims, and mostly BS.

There are some indisputable truths and there are some beliefs that are more based on faith than provable fact.

The only real new thing about cam lobe design since they were invented is how the math is done to profile the lobe. Around 40 years ago Crane hooked up with a college professor that developed new mathematical formulas to make better profiles that did not stress the valve train like previous performance cams. Everybody else followed. The other change that occurred years ago is the advent of the Cam Doctor that reads and analyzes the actual lube so you know what you really have.

Increasing duration moves the power from a lower rpm to a higher rpm, truth. To use a cam effectively you need to size the carb venturi correctly. The carb manufacturers want the venturi to be around 80% the size of the throttle plate so you have to factor that also.

Valve lift is good but it is limited by the duration since it takes a lot of duration to lift the valve high without moving the valve too fast and doing damage, truth.

I have measured a lot of cams on the Cam Doctor and the old boring stock cams are very well designed and give very good street performance. The gentle valve movement and the reasonable spring pressures that result are the reason that 356 engines are so reliable.

Some aftermarket cams may be good but some can be very bad and it is likely that you will need to make other changes to get the best result. Don't expect miracles, you still won't out drag a base Corolla.

[Jacques Lefriant]

CJ +10

[Greg Bryan]

All true, but you still have to pick something - maybe it's the lesser of evils, but most of the cams on this sheet that are not the most radical ones will probably give you good service.

[Dave Erickson]

CJ, you don't mention compression ratio as a factor in cam selection, but the Muscle Car folks have it down to a formula. I wonder why 356 engines don't come close to following the formula. Just one example, the chart below says you need 10.5 Static Compression Ratio to run 233 duration, but 1600S cams seem to work fine with 9.0 static compression.

https://www.crankshaftcoalition.com/wik ... patibility

[Martin Benade]

I think everything is moved down a bit on aircooled engines because they run hotter and closer to detonation.

[C J Murray]

CJ, you don't mention compression ratio as a factor in cam selection, but the Muscle Car folks have it down to a formula. I wonder why 356 engines don't come close to following the formula. Just one example, the chart below says you need 10.5 Static Compression Ratio to run 233 duration, but 1600S cams seem to work fine with 9.0 static compression.

https://www.crankshaftcoalition.com/wik ... patibility

When you start an engine project the cam selection is one of the very first selections. Compression ratio is then chosen to fit the camshaft, not the other way around. If you want a higher peak horsepower and you are willing to lose low speed flexibility then increase the cam duration. Because any camshaft duration change changes the dynamic compression ratio, as you increase the duration you should increase the CR to compensate for the later intake valve closing. You could also regain some dynamic CR by advancing the cam to close the intake valve a bit sooner. The differences are very subtle and often can't be felt but some people are obsessed by fiddling with small details and measuring them on a dyno. Some people are in business to "improve" upon the basic stock engine but remember that Hans Mezger was the person that developed the stock engine. How many people are smarter than him?

For street use an increase in displacement is very effective but be prepared to make other changes to all of the other details that increase flow. I have a 2133cc that took me more than a year to properly "tune", including having to make a cam change. No fun really. Then I had to develop an ignition curve that is nowhere near a stock curve. It has 25k miles on it now and I like it but I like my other two stock 1720cc cars equally as well.

[C J Murray]

The link that Dave shared is good and fairly accurate but not completely accurate. The reason that even today engines are developed on dynos even by manufacturers with gargantuan computers and thousands of engineers is that there is no formula that gets them to a final design. They have to build and test various ideas. After they are happy with the dyno results they still have to test drive the car for many miles to see if it has any flaws.

The chart above is probably close to accurate for a small block Chevy but I wouldn't try that with a 356 engine. Do take notice of the power range of the various duration cams. You have to give in order to get no matter which way up or down the duration scale.

I didn't read the whole site but a major factor of choosing a cam and CR combination is the volumetric efficiency of the engine. That is how well the mixture flows through the intake, ports, and valves as well as piston and combustion chamber design. For a given static CR a higher VE effectively increases the dynamic CR but that may or may not be a problem depending on how well the mixture burns due to the piston and chamber. They ain't got no chart for that!

[C J Murray]

Remember, there are many different duration specs for the same cam. Seat to seat, "advertised"(?) .020", 1mm, .050", and .053" lift. You can't compare cams using different lift specs.

[Ron LaDow]

"Have I got a camshaft for you!" The best camshaft is like the best oil, no consensus, lots of experts, lots of snake oil, lots of claims, and mostly BS."

The BS stops when the dyno flag drops.