General Category > Quadrajet Carb Talk and Tips

camshaft rules of thumb?

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Marx3:
Hi, I am very interested in cam specs, especially understanding them. I guess you have to have alot of experience over severeal years before you get really hard at determining which cam is better.
In my country ( and in all others countries I guess  :) ) people make the usual mistake when choosing cam: they go for the bigger the better ending up with that lopey 400 hp sound, but in reality they have an engine that is working against itself.

Is it possible to make some quidelines for camchoice? assuming that one always wants the cam that works best for the engine NOT the cam that sounds the best.

CUI vs CR vs VE ? ??

Cliff Ruggles:
Camshaft choice can certainly be a "bundle of snakes".  Most folks get all caught up in the "bling" when it comes to camshafts, and get drawn in to advertisements from companies making cams claiming all sorts of power gains at every rpm.

I've been full circle with cams in the engines we build here, and use and prefer more "tradition" grinds with more off seat duration and wider LSA's.  Pretty much the opposite of what most companies recommend.

I could literally write a book on the subject, but will say that folks should look more at the actual duration when comparing cams, than the .050" specs.  Every moment the valves are off seat are opportunities to move air thru the ports, things just don't start at .050" tappet lift.  Actual specs determine the overlap and intake valve closing point as well, and have a great impact on cylinder pressure in any given application.

As a general rule I think many modern cams leave a lot of power on the table with short seat timing events combined with tight LSA and advanced intake closing points.  These cams are typically "raspy", aggressive idle, throw a lot of power at you early and narrow up the power curve at the same time.  This typically has the user thinking he's making a butt-load of power with the new cam, at least compared to a grind that delivers smooth idle, strong/broad torque curve, and "locomotive" power characteristics.

Here's a clip of my car at the track with it's "boring" smooth idling "tractor" engine.  I actually have to retard the timing 4 degrees and shift at 5000rpm's to stay roll bar legal:

http://www.youtube.com/watch?v=6zVdoLR-VzM

HeathD:
What are your views of roller cams/roller lifters/roller rockers?

Flash bling, strip only or a reliable alternative (albeit expensive).

Nice video too. 8)

Heath

Shark Racer:
I like roller cams a lot. Improved valvetrain life, decreased friction, more lift for the same duration, no need to run any special high zinc oil. A little extra cost up front but it's win win win otherwise!

Ethan1:

--- Quote from: Shark Racer on July 04, 2013, 09:43:09 AM ---I like roller cams a lot. Improved valvetrain life, decreased friction, more lift for the same duration, no need to run any special high zinc oil. A little extra cost up front but it's win win win otherwise!

--- End quote ---


 I do as well and just for those reasons as well. Cost more, but are well worth it, not having to worry about wiping a lobe on FT cam because of lack of zinc in todays common oils.

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