PREDATOR-Z

At -8 degrees overlap it should sound relatively stockish depending on idle speed and exhaust system used. But I would reconsider a bit since the headers are not optimum for RS cam specs,
If I were you I would run more of a traditional split. Something like 214/220 112+1 LSA, -7 degree overlap so still stealth, 38 IVC for early peak.

rubrick1

I see but was thinking that even MACs should outflow the capabilities of the LS1 intake? Maybe a 212/212 on a 110* LSA?

rubrick1

Oh another question for you sir. Do all GM cams have the same lobes and thus ramp rates?

I would love to see a dyno comparison of 3 cams with the same specs as those of an LS1 cam but ground on XE, XER and XFI lobes.

PREDATOR-Z

No, from what I know there are variations between GM cams.
LS1 different than LS6 different than LS7 (That I'm sure of)

TurbopigB4C

iTrader: (5)

You should look at the COMP lobe master catalog in the hydraulic roller section to get a decent idea of how Comp describes the lobes. I believe it goes xe, lxl, xfi, xe-r, ehi, lsl, lsk in that order for how aggressive the ramp rates are. The xe and lxl I believe are both single spring friendly with corresponding coil bind and the more aggressive the ramp rate the more valvetrain noise as well as stress on springs making them have a shorter life. The ramp rate and duration have nothing to do with head efficiency or intake manifold exhaust flow. The mid length headers are not much better than factory manifolds and thus require a conventional split and especially if you are still using cats.
http://www.compcams.com/Technical/Ca...obeCatalog.pdf

rubrick1

I don't know about the 5 RWHP thing when it comes to MAC mids. Plenty of guys have gotten 20+ and back in the day there were quite a few 10 sec cars running MACs.

https://ls1tech.com/forums/generatio...ock-motor.html

rubrick1

Thanks for the replies fellas.

TurbopigB4C

iTrader: (5)

I guess but I would think most of the gains made with Macs would also depend on there being no cats and a nice straight through catback behind it. With stock cats and an exhaust with something like just a direct fit flowmaster muffler swap the macs when compared to factory manifolds would likely make close to the same. I have always been for the 100% emissions friendly builds that give up some power or if I am going to have to do the work to swap back over to my stock stuff every 2 years for emissions and then back again I would want to go all out with long tubes and no cats. With the two piece timing cover changing out cams at emissions time is pretty easy and as long as you are keeping a small duration non emissions cam then you can take the same lobes and duration with a different lsa and swap it in at smog time and not require a retune.

PREDATOR-Z

The MACs Vs LTs is an old topic. IIRC they have shown similar flow in upper rpm but loose trq mid to low range. I ran them on my Z for 3 years but I had a custom Y with Flowmaster merge and had 3 catbacks. Stock, Hooker (best sounding at wot but drony) and Magnaflow (the most compromizing between performance and sound.

rubrick1

So then wouldn't using a RS cam be warranted to help bring the TQ up?

Been looking at a lot of old threads and noticed that some of Lloyd Elliot's old cams were RS but now on his website all his cams are traditional split. Any reason for that or are the cams still RS due to using different lobes on the intake and exhaust?

PREDATOR-Z

You see, a cam functions with the help of all supporting mods. The parameters of the mods will make the cam behave in different ways.
The better the exhaust the more the RS will produce. (in general)

rubrick1

Understood but what I don't understand is why you believe the exhaust will suffer by using MACs? Only reason why LTs make slightly more power is due to their added length and not because they flow more.

My plan is MACs with an H pipe going into true duals under the axle. There is no way a set of LTs with ORY going into any of the widely available Catbacks out there will make significantly more power. I would venture to say my exhaust would actually flow better and make more power.

rubrick1

Any idea why Lloyd changed the cams he sells?

TurbopigB4C

iTrader: (5)

What he was was saying I believe with the Mac headers is that essentially low end flow numbers suffers with them. This essentially tells you that they would hurt in down low efficiency taking away the efficiency effect even more if the cam was a reverse split. If you were going to true duals with no cats with the mids you likely would be able to do a even split with the intake and exhaust duration the same and make good numbers.

rubrick1

I see, thanks.

TurbopigB4C

iTrader: (5)

When you get into exhaust theory from how I understand it long tubes are the only type of headers that provide that awesome exhaust scavenging effect that helps pull the exhaust gases out rather than just pushing them out with flow.

I will be the first to admit its really hard to not use free parts we already have but it just makes more sense with having your heart set on a reverse split to sell the mac headers and buy a decent set of the inexpensive mild steel long tubes and you likely could even find someone selling a used set.

rubrick1

Aside from added cost, unfortunately most inexpensive LTs don't fit so great. I even had a set of Kooks on my former 02 Z28 and I had to grind the steering shaft knuckle and heat and massage one of the pipes for it to fit better and not rub.

Here's a track comparison between MACs and Edelbrock LTs. Now you will also notice that the header swap was not the only thing done for the car to pick up 3.5 MPH in the 1/4. I have a feeling that the addition of Trick Flow heads, bigger cam and a 90/90 intake helped more than going from Mids to LTs.

https://ls1tech.com/forums/drag-raci...nally-10s.html

https://ls1tech.com/forums/drag-raci...-1-8-mile.html

TurbopigB4C

iTrader: (5)

Its too bad Edelbrock stopped making any exhaust products. I have a set of the Edelbrock stepped long tubes that were cheap and fit really great. I only had to grind the factory k-member a little and with my tubular k-member they have a factory like fitment just slip in.

A.R. Shale Targa

iTrader: (2)

[QUOTE=rubrick1;17686568]So then wouldn't using a RS cam be warranted to help bring the TQ up?
PRED is trying to get you to understand that the RS cam works when the exhaust is properly designed and is NOT a crutch for using the wrong header
Duals w/X pipe or 2 into 1 systems scavenge better for mid range torque
which is why they're popular in circle track applications

TurbopigB4C

iTrader: (5)

If fit was the main reason going against long tubes and money was not an issue I have heard the ARH 1 3/4" fit really well and they are only a few hundred more than a set of mild steel.