I am swapping lifters in my '92, 302, with a Comp Cam 31-255-5 installed and have come across a dilemma or "fork in the road" situation.

I first installed 2 1.7's in the #4 intake and exhaust to check if the rockers would contact the valve cover baffle. Two full crank rotations showed they didn't. I had put a dab of grease on each rocker and neither made contact with the V.C. baffle. That cleared that problem but then another one emerged. I noticed that when I was checking the preload of each lifter with the 1.7's, that I had nearly 1& 1/2 turns to reach 20ft. lbs. torque. So I checked my installed Scorpions 1.6's, and I had 5/8's of turn. Right now using stock 6.881 Comp Cam pushrods. Using my Comp Cam pushrod checking tool, I need 6.840 pushrods to reach 5/8's of a turn (w/1.7's) as I have with my 1.6's.

I have ordered ford racing pedestal rocker arm shim kit. Should be here Tuesday. Can anyone shed some light why the difference with 2 different rockers? I tried searching, but couldn't really find any info as to why the difference.

Also, concerning the use of 1.7's with stock valve cover, I have read that most of the time, you need to grind some away from the baffle as to prevent them from making contact. Has anyone run stock valve covers and not encountered this problem?

Thanks again for looking. I welcome any advice, comments or suggestions.

 

Are you using a solid lifter for these tests? When the engine is running oil pressure pumps them up but without that they may compress slightly and make it look like you have a problem. You can create a solid lifter from a hydraulic by disassembling and adding shims under the bucket. Do a web search and you should be able to find examples of what I'm talking about.

 

I had time to do some checking on the different sizes. I converted a hydraulic to solid and so forth.

Unfortunately, my solid didn't work as well, but found a majority of my problems in the process. I tried a trick I found where I use the adj. pushrod checking tool, get the lifter on the base circle, bolt the pedestal down to 20lbs. ft. torque, and then screw the adj. pushrod out until its snug/tight. Once you get this measurement, add 0.030 for preload. This is what I found..

Cylinder #1 & 2
Int. 6.822
Exh 6.822

With 0.030, that gets me closer to 6.852. Now I had the shims I needed so I added a 0.030 (0.020 mic) and that put me at 5/8's turn. Without the shim, I found I was actually 1 1/8ths turn with my stock pushrods. Now I know why I had so much clatter.

In the process of checking the others, I also found out why I always had a dead/collapsed lifter when cold. #2 Intake and exhaust lifters were bad. I could understand why when I was using the adj. pushrod, I could actually push the cup in the lifter down and it would continue to depress with each turn! #1lifters were. solid, as a solid lifter would be. Maybe they should be easy to depress and I'm looking at this opposite, but it seems I found some problems.

I'd appreciate any advice with this update and if I did read my setup incorrectly, please let me know.

 

i think your problem may lay in not only lifter preload but crane and scorpion are diffrent companies. their rockers have diffrent install heights due to pedestal to trunion height diffrences. also and i dnt know if it was my eyes playing tricks or what not but 1.7 ratios sit higher than 1.6 ratio, or atleast mine did. its kind of like measuring a pushrod. each company measures diffrently

 

I see the height differences between the Scorpion 1.6 and Crane 1.7's. I just need to verify the lift to valve cover baffle now.

I also tried the Crane 1.7's with the 0.020 shim. That gives me just an 1/8th under 3/4 turn. With a 0.040 shim I get just over an 1/8th of turn past 1/2.

With the Scorpion 1.6's, I get 5/8ths of turn with 0.020 shim. With a 0.040 shim, I get 1/2 turn.

Which is best if I run the Crane Cobra 1.7 Roller Rockers? Do you want to be a little past 1/2 turn for tolerance?
In measuring the amount for zero lash, do you want little to no resistance in the pushrods' ability to spin or just a drag?

I also completed my solid lifter, and I still came up with 6.852. So I at least know I'm doing something right.

I completely agree that each manufacturer has a different way of measuring. Just hoping for some professional, sound advice. Really don't mind pulling the plenum, but it sucks pulling the lower intake and I've gotten quite well due to my mistakes.

Thanks again for looking and look forward to any replies.

 

I had to shim my Crane 1.7's too. Keep in mind it's about .060" per full turn, so .020 will affect your preload about 1/3 turn.

 

I would order pushrods that put ~.050" preload on the lifters at torque and shim the pedestals up to spec.

 

I think you're over complicating this. Just bolt em down and run it. If they make any unwanted noise, then start digging into why. The difference in those two may just be from the installed height of the valve stems. I swapped in a set of Cobra's on my 96 E150's 351 when I did the GT40 head swap. I just bolted em down and forgot about em. Zero problems now after several thousand miles. The stock valve covers cleared them fine. I've had this same set of Cobra's now on 5 different engines and never had problems running the stock pushrods.

 

I had no clearance issues on my cheap after-market valve covers. I'm guessing that you'll be good with the stock aluminum covers as Ford used the Crane 1.7's on the Cobra.


The cam your using looks pretty mild.. with a little more lift than stock. With 1.7's, you'll have right at .500 lift. Did you change the valve springs?

 

Yes Ford did use the Crane 1.7 RR's on the 1993-1995 Cobra engines but they used stamped steel valve covers on those engine and not the cast aluminum ones that did come on the same years 5.0 HO engines. This was done so that the RR's had enough clearance and would not hit the valve covers. I owned a 1993 Cobra Mustang for 11 years.

 

The problem area in using aluminum covers is the oil baffles, not the covers themselves. The baffles in the steel covers are located deeper inside the covers. The Cobra rockers don't clear the baffles inside the 83-85 covers either.

 

^This

I have found that to be the case on many occasions for crane/scorpion, etc

 

I installed Crane (Cobra) 1.7 roller rockers in my 1987 Mustang GT's stock 5.0 HO engine, and had no interference issues with anything. I'm still using the stock cast aluminum valve covers. Of course, I'm not sure I noticed much benefits from the the ~6% added lift over the stock rockers.

 

Who can resist the Siren's song of high-ratio rockers...

 

Ford most likely went with steel covers as a "Cover your ***!" method to avoid problems if owners later changed to a higher lift cam. The other reason is the Cobra cam did have higher lift then the HO cam in your engine.