Can anyone describe in layman's terms the benefits of the new reverse split cams in light of traditional cam durations?

 

Some traditional SBC cams "crutch" a poor flowing exhaust port by adding exhaust duration.

Some people use more duration on the intake side than exhaust to crutch a poor flowing intake port or intake manifold or restrictor plate. Exhaust is under a lot of pressure and like 1800 degrees though so it works a little differently.

Short track roundy rounders have used reverse split cams in 2 barrel carb classes for at least 20 years.

I'm not sold on them yet for LS1s. Remember that changing the intake port flow to exhaust port flow ratio with ported heads will effect what cam works bestest.

J.

 

Even with our Intake Restriction, most seem to prefer a standard split to the exhaust side for a Supercharger. Any reason why? Why not a reverse split also if they intake is the problem?

 

So...

With the reverse split cams you have more duration, so that the intake valves stay open (for a longer duration), thereby compensating for restrictive flow of the stock intake ports?

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>So...

With the reverse split cams you have more duration, so that the intake valves stay open (for a longer duration), thereby compensating for restrictive flow of the stock intake ports?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">Sounds exactly right to me, but just like crazyquik, I'm not sold on them yet either, I'd rather stay traditional. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

Anybody done a reverse split pattern on a set of heads yet, besides that what-his-name with the LS6 Stage II heads and the X1 cam? I noticed hp was high, but tq was low.

My buddy just installed the new TR230/224 cam two days ago. It really woke that car up. Gonna get it tuned and see some dyno results soon. He's thinkin about a ATI D-1SC to put on top of that. So, how would this reverse pattern cam/ATI procharger combo add up? Any benefits over a single pattern, or regular split duration?

Miah

 

I would think that wouldn't be the best cam to run a supercharger too. I would want a traditional split cam for that application, something with a lil more exhaust duration on a blower motor. Just my .02

 

So which would be a better cam for nitrous, reverse split, single pattern or split pattern. I would assume a split pattern would be best, duration being higher on the exhaust side.

 

Definitly split pattern, you're gonna have hella intake no matter how you look at it... need the extra duration on the exhaust side. You could probably do alright with a tradional single pattern grind too. I just don't think the reverse split would work too awful well for a n20/supercharger application. I could be wrong though, it's happened before. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

Mike, yes, you'll want a regular split pattern for your N20 motor. There has been some discussion on this over in the N20 forum, you may want to try searching there. In general power adder applications are going to want extended area under the exhaust lobe curve. N2O applications will benefit for a wider lobe separation as well.

 

Bingo PSJ.

I've been lookin at advertised durations a lot lately. I like Terry's MMS 229 a lot too.

J.

 

I agree.. We could pretty much say for NA reverse split would work great. NOZ you would want a non reverse split cam. Supercharger you would want a single or traditional split.. Turbo I would think split would be best, but reverse split could work.. I think we are finally finding cams that would work for each application, but I feel that more testing needs to be done.. I am still waiting for my TR230/230..

 

I was talking to a guy with a wicked fast `89 Turbo T/A and he told me that turbo motors love a cam reverse split cam. Must be some truth to it cause that car flew!! <img border="0" title="" alt="[Eek!]" src="gr_eek2.gif" />

 

Mike, with nitrous your intake duration isnt' as much of an issue due to the N20 bringing along its own oxygen to the party. Thats one reason nitrous works better than other power adders in an intake restricted motor.

Some of these new cams aren't really that big. The 230 Thunder Racing lobe has less advertised duration than the good ole trusty T1. I dont know about the duration on the MMS 229 though.

J.

 

I recently installed a reverse split cam and a set of cnc heads in my car and I have been nothing but impressed. The car idles like a beast and sounds incredable. It makes wicked power above 3 grand all the way to 7. I plan on putting a shot on the car soon to see how it does.

 

Blowers like more exhaust duration as the intake port/intake itself is under positive pressure. (Basically overcoming the intake shortcoming until the boost gets to a point where it bottlenecks and only more intake/exhaust CFM will allow more power.) Added exhaust duration isnt necessarily the best case with a turbo car where they are exhaust driven and not rpm dependent from a cog/belt drive like a blower.

However blowers like LSA around 114LSA or the combustion charge can be pushed out past the exhaust valve or into the header itself!! (Bad news) I would like to see a TR 230/230 110 or 111LSA cam dyno in Jasons car to compare against the reverse split cam.

Cheers,
Chris

<small>[ June 12, 2002, 10:18 AM: Message edited by: Chris ARE 360 ]</small>

 

(1) So if the reverse split cams are compensating for our stock intake restrictions, does that mean if you go with ported heads and bigger valves that a split cam starts to loose it's value?

(2) S/E cars can play with duration. Cannot run ported heads. So are they probably running reverse split cams?

(3) Reverse split LIFT vs DURATION cams, thoughts? I had a reverse split LIFT cam last year, Comp 585/560 lift.

 

IMHO the reverse split is compensating for the intake manifold (even ls6) and not the heads.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Pro Stock John:
<strong>(1) So if the reverse split cams are compensating for our stock intake restrictions, does that mean if you go with ported heads and bigger valves that a split cam starts to loose it's value?

(2) S/E cars can play with duration. Cannot run ported heads. So are they probably running reverse split cams?

(3) Reverse split LIFT vs DURATION cams, thoughts? I had a reverse split LIFT cam last year, Comp 585/560 lift.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">1) No, from an engineering standpoint, ported heads would make the intake even more of a bottleneck.

2) S/E are running reverse split cams to the best of my knowledge, with stock lift specs, even though they grind the cams so aggressively that they result in controlled valve float, effectively increasing lift. Cheaters! <img border="0" alt="[devil]" title="" src="graemlins/gr_devil.gif" />

3) Split lift just means you are changing the ramp profile of the lobes, making the exhuast ramp less aggressive.

I recently installed a BIG reverse split cam (230+, 110 LSA). The butt-dyno says holy ****!, but I need to fix my 02 issue before I tune or redyno.

EDIT - Thanks Spelling **** Vince.

<small>[ June 12, 2002, 12:01 PM: Message edited by: TrahnZam WS6 ]</small>

 

Ok...so it would be safe to say SC'ed cars like the traditional split pattern. So do nitrous cars. NA cars like them all.

Why is the tq lower with a reverse pattern than single pattern and split pattern?