bortous

They do but I was referring to hydraulic as most of us run these camshafts.
It's good that now they have hydraulic lifters that are guaranteed to 7500rpm.
So if I ever upgrade the runners to the high rpm I know the engine can spin safely to they rpm as my other hardware matches.

old motorhead

iTrader: (10)

I'm pretty sure Spin realized that a bigger exhaust event, compared to the intake, would yield more power. A lot of the motivation with these specs was to make good power, yet not have a rowdy rig that would get old quick due to crappy manners. Some are willing to sacrifice a little power for better manners, better fuel eco, etc. 480-490 was probably more common than 500 for this cam with bolt ons. Still enough to be a lot of fun a quarter mile at a time, on a road course, and on the street. Especially in a 3200# Vette. And you can still get reasonably fuel eco in a long trip.

A lot of folks value better manners vs getting that last few HP. Me included. Do a search for "mild cam" here. Those guys aren't the ones getting all the attention though. Hell, I enjoy reading about big cams and big HP. I've done that before. Have no "want" to do it again. My recent build included a cam with "0" overlap that did quite well in the power department. Drives like a dream too.

bortous

Yes but I don't think he realised that having a 12 or 15 degree split for the LS3 head does not make make the engine lazy in the low end as long as the IVC is the same.
It's the only way to get these to hang on in the top end.I notice a lot of people when they cam their LS3 there power drops off earlier than the OEM camshaft and therefore they have a lower red line even though they have more power.

Having 4 degrees of overlap in an LS3 is barely anything. Anything above 9 degrees is where your driving manners will start to become affected. This is with a good tuner.
If you looked at the dyno sheet, of the 230/234 camshaft, peak power peaks at 6100 and falls off 200rpm later.
Torque takes a dive after 5500rpm.
Seeing as though you are an old motorhead, I think you made a good choice with a 0 overlap cam.
Nice and smooth.
I have a 24 degree overlap camshaft in a stroker engine.

Darth_V8r

iTrader: (4)

Typically when I see a cam with low or no split it is focused on midrange power more than top end. Regardless of head geometry

bortous

That's right, low - mid range power it is.
But having a cam fall off the top end faster than a stock cam is not good.
If the stock camshaft revs to 6500 you need one that holds at least the same.

Summitracing

Back in the olden days, durations were spec'd by intake and exhaust flow ratios. Naturally "specialists" initially went crazy with longer exhaust durations to compensate for a "poor" intake/exhaust ratio. Big mistake. Spin was the the first to raise awareness that backflow through low velocity gargantuan intake valves was causing a serious issue with reversion. Everyone owes him a debt of gratitude for bringing the issue forward.

bortous

That's an interesting thought coming from summit. Reversion can happen with excessive overlap as with any head. Some tolerate more than others.
Narrow splits are good for low- mid range power yes.
However without a longer exhaust duration, these engines do not hold up as well up top because you cannot get the EVO and IVC where it needs to be unless you introduce a lot more overlap by increasing intake duration higher to have a narrower split.
The exhaust side flows 65% of the intake so naturally you need 1-1.5 degrees of extra exhaust duration to help the exhaust side and improve efficiency and therefore power.
So you are saying cam motion and Brian Tooley have been doing it wrong?
Brian Tooley's 229/244 113 LSA camshaft makes excellent low end torque in the LS3 while making superior top end power.
Knocking 10 degrees off the exhaust will give you 5 degrees less overlap but also make less power and not pull as high.
This has been tested that larger splits make more power from 3500rpm+ compared to camshafts with less exhaust duration.
If you don't agree, you either have not tested this out for yourself like Brian has or you think he is wrong.
Most LS3 camshaft that perform well all over have 12-15 degree splits.

Darth_V8r

iTrader: (4)

Splits matter less than valve events. Goofy cam spec for illustration but 230/230-117+5

47 IVC. 57 EVO. Way low overlap. You do not need to add duration to get earlier EVO. You can use a wider LSA with more advance. Go to 118+6 and EVO is 59.

Not denying exhaust duration is good for top end power. But adding duration is not the only way to get earlier EVO.

But if you do not bump compression, earlier EVO hurts more than it helps.

old motorhead

iTrader: (10)

The camshafts I spec for me aren't to impress or please anyone but me. High 400's to 500's with perfect manners is a nice place to be. 10 degrees of overlap with a "unicorn" perfect tune isn't real world. Tell someone else that bullshit. It ain't real.

Summitracing

Merely a difference in opinion. Plug the numbers into the Summit Racing cam timer (powered by Cam Motion). The differences in valve events will become evident. You may see the Summit Pro Ls intake valve opening events vs exhaust closing are more friendly to tuners to give them more latitude and less loss of horsepower with typical performance closed exhaust applications.

bortous

I don't think you understand.
This bullshit you assume I am saying is something you need to study and realise that maybe it is you instead who is ignorant.
It's common knowledge that 4-6 degrees of overlap in an LS3 and you still get stock like manners with a good tune. Any more than 9 degrees then your driveability begins to suffer.
If you think otherwise, then please disprove what I have stated.

bortous

I agree Darth but if you spec a cam this way, your overlap is biased to your intake way too much which means power will fall off too soon.
Having less overlap also won't help either.
And yes an early EVO requires more compression to work properly.

bortous

There is nothing wrong with the summit camshafts. They have different way of doing it.
It has just been proven that specifically with the LS3 head an earlier EVO makes more power and carries better. (of course up to a certain point.)
Brian Tooley knows his stuff as stated before.
You should test out his camshafts against your own and see how they compare.

Darth_V8r

iTrader: (4)

I hear you, but I am running 8 degrees split on CNC ls7 heads which are biased worse than ls3 heads, and I peak at 7k and really do not see a noticeable drop until 7700.

Remember the exhaust stroke has this thing forcing all the air out of the cylinder. Unless boosted the intake has no assist.

bortous

What's your cam specs again?

Darth_V8r

iTrader: (4)

248/255. Guess that is 7 not 8 degree split. 114+3

bortous

That works too I guess but with an IVC of 55 you are really trying to get it to rev.

Darth_V8r

iTrader: (4)

Its a solid roller. Loses six degrees of duration warm. It basically runs like a 242/249.

52 IVC is about ideal on a ls7

bortous

Ah yes. That makes sense.
I forgot you were using a solid roller.
Is it one of those low lash versions from cam motion?

Darth_V8r

iTrader: (4)

Yup. LLSR ftw. I doubt if I ever build another hydraulic roller unless it is a mild build.

Like if my wife took a two week trip to visit family and came home to not realize that the Mamo 220 heads and a 218/226 stealth cam were in the car...