GM L31HD and cam choice

[Supercharged111]

I believe lift to duration ratio is a good indicator of lobe aggressiveness and a decent way to guesstimate if you'll have valvetrain noise. Another is comparing advertised (usually @ .006") vs .050" durations. This is kinda why lift and duration, to an extent, do increase together as slowburb pointed out. The duration gives you an idea of how quickly that valve has to open to peak and slam shut again.

 

[rangrayy]

Aside from the obvious similarites (metallurgy, bolt patterns, etc.) there is nothing similar between swirlports and vortecs.

.... I know they’re different heads. That is not what I meant by “similar to...” you need to reread the posts a few times before responding. The similarity was referring to how the swirl ports drop off after a certain rpm(airflow capability). In a similar fashion(still with me?) the vortecs have the same issue, so it would be silly to install something that exceeds those limitations.

 

[Supercharged111]

No the Vortecs drop off after a certain lift, not RPM. Totally different.

 

[rangrayy]

No the Vortecs drop off after a certain lift, not RPM. Totally different.

Okay similar concept then between them.

 

[Supercharged111]

Okay similar concept then between them.

Dude any heads drops power after a certain anything, that's not a valid comparison.

 

[slowburb]

.... I know they’re different heads. That is not what I meant by “similar to...” you need to reread the posts a few times before responding. The similarity was referring to how the swirl ports drop off after a certain rpm(airflow capability). In a similar fashion(still with me?) the vortecs have the same issue, so it would be silly to install something that exceeds those limitations.

No, I don't need to reread anything, I'm actually quite good with reading compression. I didn't need to read this more than once:

You’re right, I don’t understand.

Chill man. Just relax and reread everything posted here a couple of times.

 

[98 Nitro]

I’m looking for the best cam possible without machine work on the heads. Although if I’m purchasing a crate motor it probably wouldn’t be too much more to pull the heads and have them machined, gasket matched. Or just buy a short block, if they still sel them, and buy better heads but that’s getting into more money than I’m ready to throw down on this pickup currently.

This is what angers me about GM. They no longer sell the vortec short block. With the old short block you could save some money and pick your cam and heads.

 

[Supercharged111]

That long block is still a killer deal, how cheap was the short block?

 

[98 Nitro]

The short block was about $800 cheaper and I agree the long block is a good deal but I just think it was better when GM gave us more choices.

 

[davkenrem]

Hello, any progress on this build? I just took shipment of a new L31-R HD yesterday and I too am looking for a cam. I'm looking for off Idle torque to 4-5000 rpm in a 97 Suburban on 35" tires and 3.73 gears. I've read this several times and I think what I understand is that the GM# 14097395 HT838/Marine cam is the choice for no cylinder head machining and new springs? If that is correct, would this combination benefit from roller tip rockers?

Thanks in advance?