New Clifford 1.7 ratio roller rockers

[Cjmartz2k]

http://cliffordperformance.net/Merc...de=CP&Product_Code=97-5003&Category_Code=JHas anybody else seen these yet? I just linked over from Dino's website. I think these are the only 1.7's out there. It says they will fit under the stock valve cover too. It doesn't say anything about machining the head pedistals or anything, so I assume they are a direct bolt on. I have a Crane 753905 cam with .030 shaved from my head to up the CR to 9.5:1. I also have the upgraded mopar performance springs/retainers for the increased lift on the cam. Would that cause any piston/valve interference? Would these be a good upgrade? I was gonna get the yella terra 1.6 rr, but these might be better.</p>

 

[5-90]

First things first - if you've shaved .030" from your head, you'll want to consider pushrods that are .020-.030" shorter as well. There's no adjustment for valve lash, that's taken up by the hydraulic lifters. They'll probably handle the extra .030" preload, but that should put them right about the bottom of their travel - and that's an issue.

What head gasket are you running? And, any changes to the rods? Crank? The more we know, the better we can help you. I should have a "grind card" for that Crane cam somewhere... - oh, pistons as well, may be important!

I can mathematically model the piston/valve movement with some more input, but that won't take dynamic stresses into account, nor the natural elasticity of the metal parts (crankpin, con rod, gudgeon pin, valve stem, &c.) I'd like to see at least .050" of clearance - static - but the computations won't account for everything in the valvetrain - the best method remains the "clay on the piston" method - and then measure the thickness of the clay at its thinnest.

Also, I'd think that port flow in the heads would be a limiting factor - and extra lift would have a hard time compensating for that. The 4.0 ports are fairly well designed (apparently, a common trait for AMC head designs,) but you'd probably have to do some cleanup work in the ports - especially intake - to complement the increased valve lift.

So, we'd need more information from you to give you more information - in short.

5-90

 

[Cjmartz2k]

Yeah, I'm always telling people "more info needed" too. I already have .050 shims under the rockers, forgot to mention that. I have a felpro gasket which I believe is like .001 thinner or thicker, I can't remember. Off the top of my head, my cam has max lift of .474 exhuast. I'll look it up and double check. The Clifford site says a 1.7 RR would produce a .503 lift with that kinda cam lift. Everything else is the stock rotating assembly. The only exception is #1 cylinder's connecting rod has been replaced with an OEM rod (thanks to a little hydrolocking incedent). And yes, I know, a rebuild would be in order for the above mentioned incedent, but budget was a concern, I fixed it with the motor in it, and it's run 10k miles since with good oil pressure and compression on all cylinders. Basicly, I'm getting all the bolt on stuff now so when my motor need rebuilding, which I'm sure I've already hassened by taking it swimming, I can move all the goodies over to it. I know clay in the cylinder is the best way, but my dad's doing this for me back in the states, and I'm in Iraq right now, and going back to Japan after here, so I won't be back anytime soon. If somebody knows how to do the math, and I have plenty of clearance, I'll go with them. If it's to close to guess though, I'll do the 1.6 ratio. The head has just had the casting cleaned up ,the exhuast runners smoothed, and a slight smoothing of the combustion chambers, but that's about it. I'll probably eventualy go to an aluminum head, but stroker is first, and even though I have most of the parts, it's still a ways away. Thanks for the help!!

 

[Cjmartz2k]

Lift:Intake @Cam2847@Valve456 Exhaust @ Cam3027@Valve484Rocker Arm Ratio1.6

http://cranecams.com/?show=browseParts&action=partSpec&partNumber=753905&lvl=2&prt=5

 

[Dr. Dyno]

http://cliffordperformance.net/Merc...de=CP&Product_Code=97-5003&Category_Code=JHas anybody else seen these yet? I just linked over from Dino's website. I think these are the only 1.7's out there. It says they will fit under the stock valve cover too. It doesn't say anything about machining the head pedistals or anything, so I assume they are a direct bolt on. I have a Crane 753905 cam with .030 shaved from my head to up the CR to 9.5:1. I also have the upgraded mopar performance springs/retainers for the increased lift on the cam. Would that cause any piston/valve interference? Would these be a good upgrade? I was gonna get the yella terra 1.6 rr, but these might be better.</p>

Piston to valve clearance could become an issue if you go for the 1.7 RR's. You've already reduced the clearance between the piston and the intake valve by 0.062", and the clearance between the piston and the exhaust valve by 0.090", so you probably don't have much left.
A set of 1.7RR's would increase valve lift to 0.484" intake/0.514" exhaust, reducing piston to valve clearance by a further 0.028" for the intakes and 0.030" for the exhausts. Total reduction of clearance would be 0.090" intake and 0.120" exhaust.
That could be enough to bring pistons and valves into contact.
BTW, the 0.030" that you had milled from the head increased the CR by 0.45:1 so you're actually running a 9.25:1 CR, not 9.5 (unless you also shaved the block deck).

 

[Cjmartz2k]

Hmmm, thanks for the info guys. I'll be ordering the yella terra's than Wednesday. I guess those RR are more for stock cam 4.0's? Or maybe just ones without so much shaved off the head. O well. Dino, weren't you planning on getting some RR sooner or later?

 

[Dr. Dyno]

I was toying with the idea of getting the Yella Terras but now that I've found out about the Clifford 1.7 ratio units, they've got me interested. Only thing is I don't have an extra $500 lying around at the moment.

 

[Cjmartz2k]

I think you also have the 753905 cam--can you run these with no trouble, or are you going to do the clay mock up? Did I just shave to much off the head for them to work, and do you think they would even make that much more of a difference than the yella terra's? I'm toying with the idea of still ordering the 1.7's, and getting a head to port/polish, then putting on the 1.7's. I just don't want to go through all the trouble if there isn't a big difference from the 1.6's. Also, do you think that would be enough to make the computer go bonkers?

 

[Dr. Dyno]

The difference in HP/TQ between the 1.7's and the 1.6's is likely to be small (maybe 4-5hp) but since the 1.7's only cost $59 more than the 1.6's, they might be worth going for. I don't think the computer will care about the extra valve lift.
In your case, you've probably shaved too much off the head and left too little piston to valve clearance for comfort to go for the 1.7's, so it might be worth your while getting another head to port & polish.
Piston to valve clearance isn't a problem for me because with my stroker set-up, I have a 0.045" deck clearance and a 0.088" quench height. I didn't shave the block nor the head. Plenty of room for an extra 0.030" of valve lift and yes, I do indeed have the same Crane 753905 cam as you.

 

[brent]

so big question, would I have problems running these 1.7 rockers, I'm currently running a hesco stroker kit, bored .30 over, the cam came with the kit and not sure the lift or duration , didn't deck the block and the head is the hesco aluminum one. also running the 62mm TB and spacer, banks cracked header, high flow cat and flowmaster hooked together with 2.5" pipe. so with clifford stating I'll get 20% more touque, thats like 420ft lbs............... seems a little stretched to me

 

[Cjmartz2k]

Well, you have a long rod stroker, so you don't have the extra clearance like Dino, but if you didn't shave the head/deck, and the fact that it's an aluminum head..............Dino?:compwork:

 

[Dr. Dyno]

The Hesco cams have a valve lift of 0.468" on both intake and exhaust, so with 1.7 RR's that lift would be increased to 0.497". Deck clearance with Hesco's stroker kit is probably zero or thereabouts so yes, that's 0.045" less clearance than I have right there. I don't know how much difference the aluminium head would make to the piston to valve clearance but the only way to find out is to do a clay mock up.
The claimed 20% increase in torque is obviously BS. Take away the zero (i.e. make it 2%) and that'll be about right.

 

[brent]

posted this up on hesco. they tell me I'd have no problem with either, and the stock stamped rockers are from 1.58 to 1.61 ratio, Dino if I'm lucky I'll see that 2%