Cstraub

iTrader: (1)

Ed,
7 years ago when we first met on the corral I do believe Ed.

Chris

rodent

iTrader: (1)

When I called Comp Cams to get a custom cam for my turbo they suggested a split Reverse Pattern. I did some searching on other applications (dsm, gn's) and found other turbo cam's to be a reverse pattern so I would think turbos like a split RP. If I was doing a supercharger or nitrous, I'd go with a traditional split.

Another_User

The hotcam was designed for stock heads, so yes. On stock heads a normal split works out very well. The rest...well not many people boost or push nitrous in "small" amounts.

PREDATOR-Z

I shoot 200 dry (~160 wet) on my reverse with no problem. Wouldn't go any higher though.
We all agree that cams are application specific. So as turbo specific heads exist so do reverse cam/heads exist. Which means that a head flowing 200>210 cfm on exhaust side will definitly do worse than a head which flows 260 on the exhaust.
That said, a reverse with a 300 intake and 250>260 exhaust is the way to go for reverse splits IMO. (like TEA's)
Also there is big reverse +4* and short reverse. That make a difference also.
The ramp rate plays a major role.The more radical the better.
So combo, combo, combo

Ed Curtis

There's that damned over-used word again...

Ed

black_knight

iTrader: (1)

First... um, citing the hotcam as proof that a standard split works well on stock heads is hardly a strong argument. It's the hotcam. The hotcam.

Second, you can't just say that it works well on "stock heads." That fails to account for what headers/exhaust/intake/gears, and most importantly, goal of the customer. Also, stock what heads? There are 98-00 heads, 01-02 heads, and LS6 heads...

My point? Avoid blanket statements like that. Combo, combo, combo!!!

Cstraub

iTrader: (1)

Stock cam spec's for the GTO. . .
207/196 .479/.467 116 Lsa

Hmmm, maybe GM of Austraila is on to something. Let's see reverse split and more lift on the intake. Must mean the heads have good exhaust and don't need exhaust duration or lift to crutch the exhaust side.

Okay, what Ed and I have said about I/E % must not mean anything.

Chris

Geoff

iTrader: (3)

We were one of the first companies out there to create an 'off the shelf ' cam for the LS1 utilizing the reverse split concept. Certain vendors have since come out with look-alike cams that sometimes don't work at all. A lot of the look alike cams don't work because the 'cam designer' doesn't understand the concept of how the reverse split works and this has given the concept a black eye.

Since then a few vendors have come out with normal forward split cams that do perform quite well. It is real easy to pick valve events from the Comp catalog that do work OK. They are conservative choices that while not being optimum aren't so far off as to really get anyone into trouble. As others in the know have said, it is all about combination what is going to work well. It seems to me that in reading this board that some people think that because a cam has a forward split it will give you more high rpm power or more bottom end torque or more sex appeal or more money in the bank or even fresher breath.

IMHO it is wrong to compare to cams power and torque output based solely on the type of split it has. Some people here are preaching valve events and they are absolultely right. Using 'typical' valve events may make for a safe choice, but they are rarely optimized for what a particular motor wants.

To let everyone in on a big secret about reverse splits: As soon as you open the exhaust valve on the power stroke of a 4-cycle engine you aren't going to get any more useful force to push the piston down with. The catch to all of this is that there is a balancing act between taking energy to push the piston down and taking that same energy to push the exhaust out of the pipes to scavange the cylinder. A reverse split does not make torque or horsepower in a different RPM spot than a conventional cam assuming all other valve events besides exhaust opening, such as intake opening, intake closing, exhaust closing, overlap stay the same. The only affect of the reverse split if all of the other valve events are optimized is that you will have a later exhaust opening point which will delay blowing the cylinder pressure out of the exhaust pipes. Will this make more power? Again it depends if the exhaust system is up to the task of properly scavanging. We have tested all of this and know it works.

To put this into another perspective look at 2 different cams:

Cam#1 243/252 @ .050" lift Intake opens 13 degrees BTDC, Intake Closes 50 degrees ABDC, Exhaust opens 54.5 BBDC, Exhaust closes 18.2 degrees ATDC.

Cam#2 243/237 @ .050" lift Intake opens 13 degrees BTDC, Intake Closes 50 degrees ABDC, Exhaust opens 38.5 BBDC, Exhaust closes 18.2 degrees ATDC.

These two cams have the exact same amont of overlap based on the lobe design and have it the exact same spot in relationship to TDC. Additionally the intakes are exactly the same in design and opening and closing points. The only difference between these two cams is the exhaust opening which affects scavange time. Does it work? Sometimes very well depending on application. With the wrong exhaust it might not do any better or worse than Cam 1 or it could be worse. I will say that in my opinion with the right choice of exhaust Cam #2 can definitely have the potential to make more power. That is why you pay someone who has tested it and knows based on your combination of parts. I will say that Cam#2 is in a well known member of this boards car and it runs quite well for what is in the motor.

Just remember that you can't make a blanket statement that Cam X makes more bottom-end or top-end than Cam Y based on just the fact that it has forward or reverse split without knowing all of the other valve events that go along with it.

Sport Side

iTrader: (6)

I like it...but would you mind explaining why you use a 4* advance in cam-timing on alot of the TR grinds? Isn't this working against what was just covered?

Geoff

iTrader: (3)

I am just putting the valve events where I think they are needed to achieve a certain result. All of the cams we sell have a slightly different purpose. I will also say that what we tried a lot of different things in the last several years. Some of the original cams we have done still work very well so there is little room for improvement for their intended application, but everyone out there wants bigger and better so that is where we are trying to focus and get the last available ounce of performance.

Sport Side

iTrader: (6)

.......and

Care to give a more detailed reasoning on why?

Another_User

GM has far less in mind than squeezing every last horsepower out of that engine. Sometimes I find myself wondering exactly what GM was thinking a lot of the time. GM is influenced by far more than horsepower when they do things like that. They are worried about fuel economy, emmissions, and making sure that the mid-level cars don't compete with the vette. I'll admit, I don't have all the facts, but I am sure about one thing: a lot of people buy reverse splits because somebody said they were the best, and they are not always. And just because you use one with good results, doesn't mean you wouldn't get better results with a different cam.

Sport Side

iTrader: (6)

don't you feel informed now chris

Ed Curtis

I know I do...

BTW...

Here's a few more...

GM GrandAm Cup is 239*-251-106*
GM Hot Cam is 219*-228*-112*
GM ASA Hot Cam is 226*-236*-110*
97-99 Stock LS1 207*-199*-117* with 113* ICL
2000 Stock LS1 is 209*-198*-115.5 with 112* ICL
01-03 Stock LS1 is 207*-196*-116* with a 117* ICL
01 LS6 Stock GM is 211*-204*-116* with a 114* ICL
02-03 LS6 Stock is 218*-204*-117.5* with a 115* ICL

The .006" - .100" and .200" are even more interesting...

... sorry, just couldn't resist ...

Ed

MNR-0

I thought it was the other way around, in that the split is exhaust biased not intake biased. Or am I reading this wrong?

196=intake
207=exhaust

Cstraub

iTrader: (1)

Thanks Ed.
MNR-O
No they are reverse from the factory, more duration on the intake side.

Another User
You are preaching to the choir. Cams are to be combination specific and just because one guy has a cam in his engine doesn't mean it will work with yours.

Chris

Another_User

I think I got contradicted with data that backs up my point, since those are all normal split cams. It is not my fault they put them in the books backwards so people think they are reverse split. They are regular split, with more exhaust, because stock exhaust ports and manifolds flow like crap.

Cstraub

iTrader: (1)

I'll go with what Ed posted. . .one thing he has is good info.

Chris

Another_User

:puts book with specs for most of the cams listed above away and smiles:

jrp

iTrader: (16)

not my cam

https://ls1tech.com/forums/generation-iii-internal-engine/260159-98-00-cam-pro-data.html