Instead of a Cam swap

[Backwoods Rambler]

Could someone simply get different ratio rocker arms, or perhaps custom length pushrods? If so, what would be the recommendation for each assuming you're compensating for not purchasing this cam:

CompCams #68-231-4 206/214 degree camshaft ......

.....in this stroker combo:

Jeep 4.2L 3.895" stroke crank
Jeep 4.2L 5.875" rods
Speed Pro H825CP +0.030" bore pistons
9.6:1 CR
CompCams #68-231-4 206/214 degree camshaft
Ported HO 1.91"/1.50" cylinder head
Mopar/Victor 0.043" head gasket
0.081" quench height*
Ford 24lb/hr injectors with stock 49psi FPR for '96 and later engines
Est: 265hp @ 4900rpm, 325lbft @ 3500rpm

Obviously the duration won't change, but would a simple increase in lift alter performance at all? Also, how would the lack of change in duration effect the estimated HP and TQ?

[SilverXJ]

I know that at least one person here is running 1.7 Yella Terra rockers without issue. They also went with a cam with less lift (mopar 30AB) and MP valve springs. Your push rods have no effect on your rocker arm ratio. All they need to do is fit basically (proper preload and proper valve stem contact). Only thing wrong I can see with your build is the quench, its too large.

[Mgardiner1]

I can't give any before and after impressions on the 1.7 YT RR. I calculated out lift with my 30AB should be a .481, and the accelleration of valve lift should also be ever so slightly increased as well. Definitely no clearance issues. Not to mention they look sexy during the build process My main reason for picking up a set was the stock rockers were very worn, and i didn't want to invest money into "just another set" of stock rockers. However, after my entire build is all said and done (not to mention went way over budget), i would most likely not have gone with the roller rockers, as i don't think the cost warrants the gains. I do enjoy knowing that my valve train has less resistence on it because of it. Who knows, maybe the YT are my secret to my axle snapping power LOL

[Backwoods Rambler]

Only thing wrong I can see with your build is the quench, its too large.

That's the 4.6 Low Buck Stroker Combo found here: http://www.jeep4.0performance.4mg.com/stroker.html

I was just using it as an example in case more specs were needed to determine what, if any, effect the change might make.

I can't give any before and after impressions on the 1.7 YT RR. I calculated out lift with my 30AB should be a .481, and the accelleration of valve lift should also be ever so slightly increased as well. Definitely no clearance issues.

So you got a lower lift cam due to your choice to run the YT RR's? Do you think this is a good approach to avoid the cam damage so many experience?

Not to mention they look sexy during the build process

That's reason enough don't you think

[Mgardiner1]

Here, i think this may be more along the lines of what you are asking.....

I am assuming your looking for the following combination:

Your stock 1998 camshaft with 1.7 ratio rockers
Or CompCams 68-231-4 with stock rockers

Don't get hung up on the overall numbers, this is for comparison purposes only!

Stock cam is the dotted lines, compcams is the solid line

[Mgardiner1]

I can't give any before and after impressions on the 1.7 YT RR. I calculated out lift with my 30AB should be a .481, and the accelleration of valve lift should also be ever so slightly increased as well. Definitely no clearance issues.

So you got a lower lift cam due to your choice to run the YT RR's? Do you think this is a good approach to avoid the cam damage so many experience?

No, i sought after the 30AB cam more or less because it was designed by mopar for mopar application. I wanted the wide faced lobe which seems to be something aftermarket cams do not offer. I did not base my roller rockers purchase on the cam, and i did not base my cam purchase on the roller rockers. I went with 1.7's, because they are the same cost as the 1.6 RR's, and i wanted a little "extra" bang for my buck. If i was running a cam that initially had a lift of .500 or more, i would not have used 1.7's.

[Backwoods Rambler]

I am assuming your looking for the following combination:

Your stock 1998 camshaft with 1.7 ratio rockers
Or CompCams 68-231-4 with stock rockers


Stock cam is the dotted lines, compcams is the solid line

You're correct. That's a perfect comparison. I just want to avoid the cam problems others have had and keeping the stock cam, lifters & pushrods seems to be the best way to do that.

So, a taller, more broad HP curve and a lower & broader torque curve....interesting....Let me know if I'm reading into that wrong...the image is a bit fuzzy.

Can you add a stock HP & TQ curve to that for comparison also? Or perhaps drop the comp cams and add the stock info?

[Mgardiner1]

click on this link, it will show you the full size, less fuzzy version


http://i256.photobucket.com/albums/hh18 ... 1/dyno.jpg

[Mgardiner1]

Stock 1.6 vs Stock 1.7

Dotted line is 1.7 ratio. the only difference between the 2 graphs is the overall lift. I did not tamper with the duration (its been said 1.7 rockers add a touch of duration). I did however choose the next step higher lifter acceleration for the 1.7 RR.




and direct link http://i256.photobucket.com/albums/hh18 ... dyno-1.jpg

[Backwoods Rambler]

Ah, for some reason I was thinking that the other specs included the motor layed out above. Not biggie, but it would be fun to see the curves of the motor spec'd out above (with the stock cam & 1.7 rockers) vs a totally stock motor, just to see where in the curve the HP increase is.

[Mgardiner1]

I'm sorry i did not clarify my statement.

The engine specs for both curves i posted reflect for a stock bore, but stroked engine, a 9.0 SCR (you can see all the specs to the left side of the first dyno), pocket porting, stock valves.

Again, don't get hung up on the numbers. The only things that would further affect the seperation of each of these curves when compared to each other, would be things like forced induction, or much larger valves, or different plane intake manifolds.

[Cheromaniac]

Two years ago when my Crane 753905 cam failed after 34k miles, I elected to reinstall my old stock cam with the original stock valve springs/retainers and Yella Terra 1.6 roller rockers. The loss in performance was too small to even notice by the SOTP (only 0.15 slower to the 1/4 mile) and I certainly don't miss the Crane cam. I always had a small degree of valvetrain ticking at idle with the Crane cam/Mopar springs/stock rocker combo but since I went to the stock cam/stock spring/YT rocker combo, the valvetrain has been whisper quiet.