Better ratio rocker arms?!

Johnnie Walker

Johnnie Walker

Piece of Fish!
NAXJA Member
Location
WA state
What is the stock rocker ratio and are there any swapable better ration rockers? For example, when I had my dakota, they had 1.6 RR, and there were 1.7 RR available as a swap. Is there anything like this for out 4.0L?
 
I remember looking into this and I don't think i found any. maybe some will work but i didn't find anything specifically marketed at the 4.0 L.

hesco make a bunch of vale train products. I found some adjustable roller rockers on their site, but its a tad pricier then just swapping out the stamped steel ones or a different ratio.

http://www.hesco.us/shop.asp?action=cat&catID=7758
 
I'm wanting to recall that the OEM RR ratio is 1.6:1, so you'd need 1.65:1 or 1.7:1 (unless I'm wrong. I haven't thought about that end of things for a bit...)

Note that going with higher-ratio RRs generally does require a change of valve springs, so you don't "go solid" before you get to full valve lift - then end up breaking something really important!
 
According to mopar(mopartsracing/jeepconnection.com), the stock valve springs are good up to .43" lift max(P4529215 are the replacements for 88-02). Now Mopar recommended their use for the P4529228AB cam(.43 lift) and the P4529229AB cam(.44" lift, which is more than the max lift they rec), but not the P4529230AB cam(.45" lift, they recommended the P5249464 springs, good for .525"). So how do the lifts change when you go from 1.6:1 to 1.7:1? The 87-95 cams are .424" lift on both intake and exhaust and will now be .457". The 96-01 cams are .408" intake and .414" exhaust and will change to .434" and .44" with the 1.7s. I used http://www.wallaceracing.com/rockercalc.php to calculate. So the question is if you use the 1.7s on stock springs, when will they bind? It seems that it'd be safer to try on the 96+ cam since the lift is less, but I'd be wary what happens come 4500+. Maybe someone who has used the 1.7s can chime in with their experience and setup.
 
Well 400$ is obviously more than I'm willing to pay just for RR's Are the stock rockers roller or standard rockers?

gradon said:
According to mopar(mopartsracing/jeepconnection.com), the stock valve springs are good up to .43" lift max(P4529215 are the replacements for 88-02). Now Mopar recommended their use for the P4529228AB cam(.43 lift) and the P4529229AB cam(.44" lift, which is more than the max lift they rec), but not the P4529230AB cam(.45" lift, they recommended the P5249464 springs, good for .525"). So how do the lifts change when you go from 1.6:1 to 1.7:1? The 87-95 cams are .424" lift on both intake and exhaust and will now be .457". The 96-01 cams are .408" intake and .414" exhaust and will change to .434" and .44" with the 1.7s. I used http://www.wallaceracing.com/rockercalc.php to calculate. So the question is if you use the 1.7s on stock springs, when will they bind? It seems that it'd be safer to try on the 96+ cam since the lift is less, but I'd be wary what happens come 4500+. Maybe someone who has used the 1.7s can chime in with their experience and setup.
Click to expand...
He said he has some, waiting for a response. Unless the valves are really that close, I do not see why a little extra lift is bad. It made a world of difference on my dakota.
XJ Wagon said:
Stock is 1.6:1. I put the Yella Terra in mine 1.7:1.

http://www.yellaterra.com.au/produc...37&modelIdentity=23&productCategoryIdentity=4

Ordered them from Patriot Performance.

https://www.patriot-performance.com/xcart/product.php?productid=139&cat=60&page=1

I don't know how much it gave me. I did the exhaust, header back, Throttle body, K&N FIPK and gears all at the same time. Big difference all together, but don't know what each one seperatly did.
Click to expand...
What year is your XJ, did you change valve springs?

5-90 said:
I'm wanting to recall that the OEM RR ratio is 1.6:1, so you'd need 1.65:1 or 1.7:1 (unless I'm wrong. I haven't thought about that end of things for a bit...)

Note that going with higher-ratio RRs generally does require a change of valve springs, so you don't "go solid" before you get to full valve lift - then end up breaking something really important!
Click to expand...
I swapped 1.7s in place of 1.6s on my 92 dakota with a 318, and no issues. I know the 4.0L is different, but do not really see them being affected that much.
 
Harland Sharp Makes a real nice set of full roller rockers for 4.0s. Keep in mind your biggest benifit will be the reduced friction. There is lots of spring pressure to keep the valves shut and that in turn creates tons of friction (obviously). Just think the the valve pushes up on the rocker and the push rod pushes up on the other side so the pivot in the middle has lots of tension on it, not to mention the rocker tip doesn't push down but it swings on a arch and drags back and fourth on the valve. Keep in mind if you get stock ratio BUT get full roller rockers you'll benifit more from the reduction in friction then the lift will give you. Also if you increase the ratio then you have to keep in mind piston to valve clearance AND push rod length. I think Push rod length would be more of an issue then the small change in lift. In my opinion Id go with stock ratio full rollers and just make sure to cross your Ts and dot your i's when you install. Personally no matter how involved or how complicated something is I go for reliability. Its better to make a careful selection the first time and install it to your best ability then do it a second time.
 
Johnnie Walker said:
I swapped 1.7s in place of 1.6s on my 92 dakota with a 318, and no issues. I know the 4.0L is different, but do not really see them being affected that much.
Click to expand...

Note I said "may." It depends on what springs you would have, and at what lift height they'd "pack solid" on you.

If they'll support the higher lift, you're fine. If they won't; the first time the spring packs, something will break. Period.
 
The non adjustable 1.77 YellaTerras fit under the valve cover and as far as I know the Harland Sharp adjustable and non should need a valve cover spacer and t-stat housing spacer as well. Keep an eye on the spring solid height, piston to valve (not a big deal as you have plenty of room even with a higher lift cam installed straight up), and push rod length (which, again shouldn't be that big of a deal if you are just swapping rockers). The setup is expensive in the $400-$600 range though.
 
5-90 said:
Note I said "may." It depends on what springs you would have, and at what lift height they'd "pack solid" on you.

If they'll support the higher lift, you're fine. If they won't; the first time the spring packs, something will break. Period.
Click to expand...
Thats why I want someone to chime in on the spring compression height at 'x' ratio stock and how much farther the spring will compress.
 
Johnnie Walker said:
Thats why I want someone to chime in on the spring compression height at 'x' ratio stock and how much farther the spring will compress.
Click to expand...

If I had a spring test or lift test jig, I could tell you - at least on three different heads so far (2685, 2686, 0630.) Chances are fairly good that at least the 2686 and 0630 use similar valvetrain parts, but I haven't worked on verifying this yet.
 
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