Topic: Camshafts and Rocker Ratios

[Methodical-1]

I was wondering if anyone has used a different rocker ratio with their cam installation to get more lift?  I believe the standard ratio is 1.6 and I see there are 1.7 ratio rockers available.  Also, has anyone gotten their vehicle smogged after the cam installation.  I live in California where we have to smog every two years.

[sharpxmen]

I was wondering if anyone has used a different rocker ratio with their cam installation to get more lift?  I believe the standard ratio is 1.6 and I see there are 1.7 ratio rockers available.  Also, has anyone gotten their vehicle smogged after the cam installation.  I live in California where we have to smog every two years.

i was wondering the same thing but i didn't see anywhere 1.7 rockers for the 4 banger - where did you see the ones you say are available?

[Methodical-1]

Yella Terra Roller Rockers

http://www.yellaterra.com/products/car-performance/product-detail/part.cfm?partIdentity=37&modelIdentity=23&productCategoryIdentity=4

I think that others may manufacture rockers of different ratios as well (Hesco Inc.) for the 4.0L 6 Cylinder.  These are interchangable with the little 4bangers! 

[Jeffy]

Yello Tera will work with the 2.5L.  I've talked to the MFG. about them.  They said anywhere that sells their rockers can order them.

I think, since the overlap is going to be stock, they should be ok but then you have to have a ending that is running well.  Still, it's hard to say if it will pass or not.  They would be a lot easier then having to pull a cam ever 2 years.

[mrcabinet]

Please excuse my ignorance, but what would be accomplished by using these?

[Methodical-1]

What about some of the RV type grinds?  Is anyone using an aftermarket cam and still passing smog here in California?

Currently I have updated to the 4.0 Throttle body, K&N Cold Air Intake, and have a Lincoln Mark 8 Electric fan awaiting the Delta Controller to arrive.  Don't know what headers to put on yet, but definitely need open up the exhaust system.

[Jeffy]

I don't know anyone who's tried doing a cam and has to do SMOG.  I sold my cam because of this issue.

[sharpxmen]

Please excuse my ignorance, but what would be accomplished by using these?

higher ratio rockers means the valves would be open longer and deeper into the cylinder improving the volumetric efficiency (the percentage beteween the cylinder volume and the volume of air that is absorbed in the cylinder during each cycle). the higher the volumetric efficiency the more fuel per cycle you can have and therefore you make more power. for example if you have a 3.5L engine with an 85%VE would be the same as having 4.0 with 75%VE - they would both be capable of the same power - typical engine is around 80%VE.

[mrcabinet]

I see. So you're essentially getting benefits similar to a performance cam. What would make this more appealing to do?

[sharpxmen]

I see. So you're essentially getting benefits similar to a performance cam. What would make this more appealing to do?

you get more out of a perf cam, but it is more likely to pass smog (or emissions or air-care) with the rockers (the valves will open and close at the same position - they get to "zero" at the same angular position as stock, just the size of the valve opening is larger or if you wish on an wider angle due to the higher ratio), cams are more aggressive and use more overlap (at least some of them).

EDIT: i did not see a writeup about a 4banger with 1.7 rockers - i don't know enough about this motor to make a recommendation, the above statements are general and not about the jeep 2.5L - this is so you know you need a bit more research before making a decision.

[Methodical-1]

Does anyone have the specs for the stock cam used in '99?

[jfrabat]

I see. So you're essentially getting benefits similar to a performance cam. What would make this more appealing to do?

I have a .450 lift 256 duration cam, and put Yella Terra rockers, but they are 1.6; originally, I intended to use the 1.7 rockers with the stock cam, but could not find them and I got a good deal on the MOPAR cam, so I went this route...

[dwtaylorpdx]

I have the Hesco Cam it is the RVOB4,
I also bought the lifters, springs, keepers all the recommended parts.

Oregon has tough smog laws, and I pass with flying colors.
The builder did carefully degree the cam in and it has a couple degrees
retard because he thought it would need it to pass smog, turns out the
mopar computer deals pretty nicely with it and its very clean, too bad
the computer is completely stupid otherwise....

Dave

[dos0711]

I have the Hesco Cam it is the RVOB4,
I also bought the lifters, springs, keepers all the recommended parts.

Oregon has tough smog laws, and I pass with flying colors.
The builder did carefully degree the cam in and it has a couple degrees
retard because he thought it would need it to pass smog, turns out the
mopar computer deals pretty nicely with it and its very clean, too bad
the computer is completely stupid otherwise....

Dave

How is the power with that cam? Is there much difference?

[mrcabinet]

Oregon has tough smog laws, and I pass with flying colors.

Ah yes, I remember the good old DEQ days - waiting in line with a hundred of my closest friends, praying that it would pass. Here in Vegas there's a SMOG check at almost every gas station. I do miss the registration fees though. Is it still $35 for two years? I just paid $740 for my Rover for one year.