Mechanical vs Hydraulic cams

[Mrturner1]

So if my current comp 280H is .480" lift and 230/230 @.050 on a 110 LSA, will the comp 282s with .495" lift and 236/236 @.050 on a 106 LSA be a tad bigger? How much does the lash take away exactly?

[Mike C]

On the duration it can be complicated to figure because the takeup ramps are different. I would suggest 6 degrees only because that is about the same difference that you see in the Engine Masters video for the two cams that they compare. But the lift number is easy because you just subtract lash number from the lift number.

You can also take cam lift and multiply by rocker ratio and see what number you get (should be the .495) and then subtract that which should have you around .480 if the cam is lashed at .015.

They say the narrower lobe separation moves torque to a lower rpm but I'm no expert on that. I chose the wider LSA on my big block because I want it to sound smooth and breathe through the iron manifolds.

It is still a narrower LSA than GM puts in the 454 HO crate motor.

[Mrturner1]

Well that's pretty cool because I was thinking of doing dyno tests on both cams in the same motor to see what changes and how much. I would be interesting to see the difference between the 106 and 110 LSA with almost exact specs otherwise. The 280H sounds real nice and definetly lopes hard, pulls hard from 2500 to 5800 (I'm sure much further but I've never taken it past 5800 because the tach starts closin in on 5500 and I chicken out for fear of my short block coming apart lol), but it just doesn't come on hard like I wanted. Plus if I'm gonna give up some street-ability for performance I want the idle to hit so hard you can feel it in your chest, with that nice crackle sound. So from what I'm reading the 106 LSA will give me that 2 stroke dirt bike power band feel when the gas pedal is matted, and it will sound like a beast that somebody put some thought and work into, because that was part of my intentions when I rebuilt the top end.

[Mike C]

You can't get something from nothing you know, and in my readings I don't think it dramatic shifts the power band, just tweaks it. I think it is designed to put something else back into place that gets moved on really big cams because that is where you usually see it.

The big cam that was in my motor was a hoot to drive. I figure the motor puts 375 hp to the wheels now or close to it and the other one had to be 425 probably. But it was WAY north of 7000 rpm and as good as the bottom end is, it's not THAT good!

I'm interested in the results if you do the test that's for sure.

[Mrturner1]

Originally Posted by Mike C

You can't get something from nothing you know

I don't know what you mean, you mean I won't get anything from a cam swap? I wouldn't expect a drastic change in power, a shift of power is a sure thing but I'm sure it wouldn't be huge. The sound will be very different though, a 106 LSA is gonna have a wicked idle for sure.

This motor has likely seen the end of performance upgrades, it's time to drive it and enjoy the work. I will do some dyno pulls with both cams and then leave it alone after that. The real power will come later, I want to build an 8-1 compression turbo SBC with around 600hp down the road.

[Mike C]

I mean that you can't make a 280 degree duration cam act like a 260 degree duration cam. Or that you can't make it act like a 300 degree duration cam.

LSA, advance ground into the cam, overall duration all have bearing on how the cam behaves. But mostly a 280 cam will act like a 280 cam. It is not a low rpm cam and you can see that Comp specs it for use with gear and converter.

I had an old Cam Dynamics 284/.480 228 @ .050 in the .030 over large journal 327 in my Jimmy and it pulled 6800 rpm in first with very little torque. The same motor has lived in the Jimmy with a 210 degree Crane 266/.440 cam since 1990 and it is night and day the better choice for the SM465 and a heavy 4x4 vehicle.

[Mrturner1]

Originally Posted by Mike C

I mean that you can't make a 280 degree duration cam act like a 260 degree duration cam. Or that you can't make it act like a 300 degree duration cam.

LSA, advance ground into the cam, overall duration all have bearing on how the cam behaves. But mostly a 280 cam will act like a 280 cam. It is not a low rpm cam and you can see that Comp specs it for use with gear and converter.

I had an old Cam Dynamics 284/.480 228 @ .050 in the .030 over large journal 327 in my Jimmy and it pulled 6800 rpm in first with very little torque. The same motor has lived in the Jimmy with a 210 degree Crane 266/.440 cam since 1990 and it is night and day the better choice for the SM465 and a heavy 4x4 vehicle.

Oh I see what you mean. Don't get me wrong I love the power of a 280 cam, but I think (and Comp tech confirmed) that the 106 LSA will make it hit harder and be peakier, and lope like an SOB when it's idling. That's pretty much all I all wanted that I wasn't getting from the 280H. That, and I wanted to put a solid cam in it because I drive it so little and beat it so hard when I do drive it that I figured checking lash is no big deal really. I am kindof wishing that I woulda had them grind me something in the 240's for duration @.050 BUT, that might have been a PITA to tune for street fun, and I'll go all out on the forged turbo motor later on. It kindof all boiled down to me letting others help pick a cam for my first build, and being too conservative based on them telling me "don't do it don't do it!" lol

To bad we don't have a garage to shoot the crap in, we'd have some good fun I'm sure

[Mike C]

I agree!

I've got a 496 ci big block with a 260/260 @ .050 solid roller in it that's on a stand in the shop. I guess I'll find out at some point if it works in a street car or not!

[Mrturner1]

Originally Posted by Mike C

I agree!

I've got a 496 ci big block with a 260/260 @ .050 solid roller in it that's on a stand in the shop. I guess I'll find out at some point if it works in a street car or not!

That sounds like a fun motor! I wouldn't be able to help myself if it was in my shop, it'd have to go in something. Looks like you have a full lineup already though

I was reading some more last night and I got into some of UDHarolds stuff (I'm sure you know who that is) and he did literally hundreds of dyno tests on SBC motors while he was trying to perfect a few different grinds to put on the market for Comp, and later Lunati when he worked for them. He found that on a SBC with heads from 195cc and up with great flow numbers, a wider LSA (to him 110 is real wide) worked better and made great power compared to everything else, wider and more narrow. But in a situation where the heads weren't big on the intake runner (less than 195cc) or didn't have the great flow numbers of an AFR or any of the high end heads, a 106-108 made more power across the entire useable power curve, and even opened up the useable curve a bit contrary to what most think which is wider LSA = broader power curve. In fact the 106-108 performed best, and next in line was a 114 cam which did better than the 110 he tried. This really shocked me, because so far I've heard the opposite from everyone, but it's UDHarold, 34 years of cam grinding for all the biggest name companies. I'm sure that the reason it contradicts so many people's opinion is because he was intentionally testing 355's with average heads, and guys going with wild cams don't typically use stock or even mild performance heads. He also confirmed that what you were saying is right on the money, a big ole monster cam with loooong duration can benefit from a tighter lobe sep because in a way it counters (bad describing word I'm sure but you get it) the huge duration and makes it useable. So this all is good news for me because I was very conservative when I got heads for my top end rebuild bein's it was my first one and I really didn't know how well it would go. Didn't wanna fire a pushrod into a nice AFR Eliminator lol. I got a set of RHS iron 167cc intake runner heads from a guy who had them layin around, and had them machines for big springs and a the normal head work when you put on a set that aren't brand new. So short story long, based on what UDHarold figured out I might do well with this 282s 106 cam

One more thing, everything David Vizard says about cams and specs in his books, is right in line with UDHarolds stuff. I thought that was pretty cool because David Vizard has some great books. Member Davepl got me hooked on that guys material

[Mike C]

Good stuff. I am a Vizard fan as well. Only one way to know for sure is to bolt 'me in! Good luck and update us with dyno numbers after you do it!