Question about cams..... single pattern vs split

[B3422w5]

Was talking to a guy at Howards cams yesterday about a possible roller cam for my 418/ trickflow project.
They have a cam i think thats close to what i might want. Its 263/273 on a 108. 640 ish lift.
I asked the guy why the 10 degree split. He basically said its a helpful crutch for an exhaust port.
Not sure the exhaust port would be an issue. They could do something custom more like 264/268, closer to what i was thinking.
Guess my question is, when is a split cam needed and not needed?What circumstances would a single pattern work better?

 

[moper]

The difference in lobes is always there for a reason. Without knowing the ramps and timing of the events & any other info you provided him about the package it’s not an easy guess as to why he spec’d that. It may simply be that lobe has other characteristics he wanted too. Although if that was his answer I’d consider it as “high level” at best. That really simplistic IMO.

 

[B3422w5]

The difference in lobes is always there for a reason. Without knowing the ramps and timing of the events & any other info you provided him about the package it’s not an easy guess as to why he spec’d that. It may simply be that lobe has other characteristics he wanted too. Although if that was his answer I’d consider it as “high level” at best. That really simplistic IMO.

Its the only roller they had in the catalog that was bigger than 260@50. I just am not sure that huge split is needed. Know nore when the trick flow heads actually come out

 

[cpearce]

As the ratio of exhaust flow to intake improves the need for split patterns diminishes. Split pattern cams hold exhaust valve open longer to help overcome a weak exhaust port, or possibly a restrictive exhaust system. With good heads such as Trick Flow I can't imagine wanting a big split in durations. My W2 head 408 uses a custom ground cam with a 4 degree split, most shelf cams are around 6. Using a large split with a very efficient head may even have a negative effect of over scavenging the cylinder. Since you are building a custom engine, may I suggest a custom cam ground for your application, this is how I went. We have been very pleased with results.

I am in no way an expert or guru, I just love to tinker with this stuff. If I am wrong here I hope some of the more experienced will chime in on my comments.

 

[moper]

If the heads are not out and tested yet there’s no point in really getting specific. A catalog grind is just that. Most are compromises over a bunch of things, so don’t sweat it. When the heads are tested by your guy, then work with a grinder to get what you need.

 

[justinp61]

Do you have any numbers on the heads yet? I'd make a call to Dwayne Porter or Brett Miller and talk cams.

 

[B3422w5]

Do you have any numbers on the heads yet? I'd make a call to Dwayne Porter or Brett Miller and talk cams.

Just what trick flow has publically posted.
Dwayne has specced most of my cams over the years. Trust his knowledge.
I wont be looking to break any speed records. Just want an ultra reliable low 10’s combo.

 

[justinp61]

Just what trick flow has publically posted.
Dwayne has specced most of my cams over the years. Trust his knowledge.
I wont be looking to break any speed records. Just want an ultra reliable low 10’s combo.

Understood, the cam in my 434 is 266 or 268/271 @ .050 and .711/.719 at the retainers after lash with 1.7 rockers. The lobes don't have very aggressive ramps. My springs are an endurance spring from PAC.

 

[B3422w5]

Understood, the cam in my 434 is 266 or 268/271 @ .050 and .711/.719 at the retainers after lash with 1.7 rockers. The lobes don't have very aggressive ramps. My springs are an endurance spring from PAC.

Yea, Vic Bloomer told me about a 1.46 diameter spring that i can use on my Harland Sharps with a roller cam. I had looked around and nothing was made that would fit that i could find anybody made( needs to be 1.50 or smaller to clear) so i have a way now IF i go roller to do so without buying new rocker gear.
I also might use the cam that is currently in my 360( flat tappet 260/264, 565/565) and just buy 1.6 intake rockers for my HS gear i have. Its too big for what i have going on with the 360( but was on the shelf when i needed it) but would work just fine with the 418 and the extra squeeze.

 

[yellow rose]

IMO there is very little reason to run a split pattern cam. I never look at exhaust flow number. I don't even care what the exhaust flows. I care about how quiet it is.

The only time I run more exhaust timing is on alcohol.

It's a cam grinder trick to do. They think it's tricky. They take intake duration off and then blow the LSA out to make it RPM. It's a bad way to do it.

Either way, they are either adding exhaust duration or subtracting intake duration.

An asymmetrical lobe single pattern cam is what most guys need.


Edit: I also use a split pattern cam on blown or nitrous.

 

[justinp61]

Yea, Vic Bloomer told me about a 1.46 diameter spring that i can use on my Harland Sharps with a roller cam. I had looked around and nothing was made that would fit that i could find anybody made( needs to be 1.50 or smaller to clear) so i have a way now IF i go roller to do so without buying new rocker gear.
I also might use the cam that is currently in my 360( flat tappet 260/264, 565/565) and just buy 1.6 intake rockers for my HS gear i have. Its too big for what i have going on with the 360( but was on the shelf when i needed it) but would work just fine with the 418 and the extra squeeze.

Is your cam from Hughes? I ran their older 260/264 flat solid, IIRC it was .628/.633 with 1.6 rockers. In my 10.8-1 408 it ran 6.57 in the 1/8 on pump 93 at 3240 pounds. Pretty good cam IMO.

 

[yellow rose]

Was talking to a guy at Howards cams yesterday about a possible roller cam for my 418/ trickflow project.
They have a cam i think thats close to what i might want. Its 263/273 on a 108. 640 ish lift.
I asked the guy why the 10 degree split. He basically said its a helpful crutch for an exhaust port.
Not sure the exhaust port would be an issue. They could do something custom more like 264/268, closer to what i was thinking.
Guess my question is, when is a split cam needed and not needed?What circumstances would a single pattern work better?

Now that I read this again, I agree even more with you. You don't need to "crutch" the exhaust port. On the last cam I bought we didn't even discuss exhaust flow. The port is so bad, you can't fix it with anything other than a different head.

The spilt duration thing is a marketing tool.

 

[B3422w5]

Is your cam from Hughes? I ran their older 260/264 flat solid, IIRC it was .628/.633 with 1.6 rockers. In my 10.8-1 408 it ran 6.57 in the 1/8 on pump 93 at 3240 pounds. Pretty good cam IMO.

No, Howards. That cam was on the shelf when i needed one and others had nothing remotely close to what i wanted. It would be 603/603 with 1.6 rockers if i had some
Dwayne and i both agreed it was “ one size too big” but would work with correct convertor.
Its proven to make good power for no more than i have going on

 

[justinp61]

No, Howards. That cam was on the shelf when i needed one and others had nothing remotely close to what i wanted. It would be 603/603 with 1.6 rockers if i had some
Dwayne and i both agreed it was “ one size too big” but would work with correct convertor.
Its proven to make good power for no more than i have going on

 

[rumblefish360]

Now that I read this again, I agree even more with you. You don't need to "crutch" the exhaust port. On the last cam I bought we didn't even discuss exhaust flow. The port is so bad, you can't fix it with anything other than a different head.

The spilt duration thing is a marketing tool.

I disagree with this. BUT! Only to a degree.
A lot depends on the exhaust ports worth as well as the size of the engine. You should pay attention to the exhaust port flow. A little extra exhaust duration could, could help. I’m could, could hurt as well. I’ve seen dyno runs with single and split pattern cams. Engine dependent, one of them does better. There is a good argument for both.