Results 1 to 7 of 7
-
08-17-2014 #1
Registered User
- Join Date
- Oct 2012
- Posts
- 219
Engine building philosophy. rocker or cam
All else being equal, for the sake of argument, is it better to increase lift at the cam or at the lifter via ratio?
1980 AMC Spirit
406 SBC ( blown up )
2004r CK Performance
Ford 8.8 rear 410 gears
-
08-17-2014 #2
Registered User
- Join Date
- Sep 2006
- Location
- Southern Indiana
- Posts
- 4,699
build the cam to the engine spec, ie design it right, THEN you use a different roller rocker too tune the engine. See basically you attempt to design an engine as best you can, but you cant cover every contingency, so you use different things to tune.
Lee Abel
AFTERMARKET PERFORMANCE
1977 Chevy Monza 2+2:Project "Cheap Trick"
1978 C10 Long bed , On air and trailer puller
2006 Buell Blast ,Just a bike to ride and for mileage
1966 Caprice 4dr Sports Roof fact.327/now 350/SOON 454???? Project "II Old,,,ZERO BUDGET OR LESS CAPRICE!"
10-25-2014 #3
Registered User
- Join Date
- Jun 2005
- Location
- Grapeview, Wa
- Posts
- 169
I hate to say this, but it depends on:
-The cylinder head
-The valvetrain geometry inherent to the cylinder head
The current theory in many racing applications is to use milder lobes with a higher rocker ratio, but again, it really depends on the head.Tad
'73 Camaro RS in progress.
L-D 3-link (working on the front end, too), SCP spindles, Wilwood brakes. I'll be working on it for A WHILE!
10-25-2014 #4
Registered User
- Join Date
- Oct 2004
- Location
- Illinois
- Posts
- 186
Depending on the engine platform... Most like to keep the cam profile as less aggressive "as possible" and allow the rockers to increase lift.
This is especially helpful in a engine like a traditional pontiac ... where the lifter bore area of the block is not the strongest.
BeebeA link to some pictures of my Firebirds and other toys
http://community.webshots.com/user/ponchoman69
12-05-2014 #5
Registered User
- Join Date
- Oct 2013
- Posts
- 105
Engine building is all about compromises and you make different compromise for different use.
For endurance engine for example, I'd stay low ratio rockers because the higher ratio the more guide wear, valvespeed etc.
If I wanna squeeze every little pony out of it and run 1/4mile at a time I wouldn't mind playing with rocker ratios.
12-06-2014 #6
Registered User
- Join Date
- Mar 2011
- Location
- Ca
- Posts
- 336
like others have said it depends on the engine and its intended use, if you're looking for a more streetable cam but want more lift then i'd use the rocker ratio, but if its a max effort race engine thats going to see alot of sustained high rpm id use a larger cam profile, and don't forget to check for proper geometry after new rocker arms, you probably need to change your pushrods also.
12-07-2014 #7
Registered User
- Join Date
- Feb 2014
- Location
- Memphis, TN
- Posts
- 23
http://www.knowyourparts.com/technic...r-arm-history/
This is an interesting read. When I first read this thread, I thought of which would require less effort to do its job. This is the article I read about it. Seems the higher ratio requires less effort.
Just something else to think about.
Reply With Quote
