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Ok so I have a comp cam p/n 249-35-351-8, gt40x turbo swirl heads, crane 1.72 roller rockers and I need to know if the stock push rods are too long? The lift is .512" intake and exhaust, duration 270/276, with a 114 degree lobe seperation. I think the push rods are too long because the valves are not closing all the way to build proper compression. With 1.6 rockers there are no problems. Has anyone else ran into this problem before? If so, what size push rods are you using?
Many factors come into play here. It all depends on if the block was resurfaced the heads were resurfaced, head gasket thickness. ETC. I would buy or borrow a pushrod checker that way no mather what is going on in your engine you can dial in the correct pushrod length and get the most power out of the engine.
Call Comp Cams (1-800-999-0853 Cam Help) and tell them exactly what you have they may have an off the shelf pushrod to get the job done. Too many times a guy will put an engine together using a mis/mash of parts and the clearances are all over the place. This is one area you want to be right on so that the valve train stays together. Hope this suggestion works for you. Good Luck.
The block is stock, I used fel pro gasket set for a stock 302. I was doing some research and I think since there rockers are pedistal mount, I may have tightened the bolt too tight? I was reading turn 1/4 to 1/2 turn past zero lash. I will try to properly tighten the hold down bolts first and if that doesn't work, I will buy or borrow a pushrod length checker. Thanks fellas.
I tightened the p### out of them. With the cam set up and 1.72 rockers there is very little clearance on the valve springs from keeping the valvs open. I think they are just too tight keeping just enough tension on the valve springs to keep the valve open. I hear air out of the headers on the exhaust side, but when I put my finger over the spark plug hole no air comes out.
how would you tighten the bolts too tight? they torque to 24fp....YOU NEED TO MEASURE!
+1, you want to tighten the bolts to ~20 ft. lb.; nothing more, nothing less. The 1/2 to 1-1/4 turn equates to 0.020-0.060 in. of preload on the lifters, which is what you want.
+1, you want to tighten the bolts to ~20 ft. lb.; nothing more, nothing less. The 1/2 to 1-1/4 turn equates to 0.020-0.060 in. of preload on the lifters, which is what you want.
Don't mean to hijack here but I don't want to needlessly start a new thread since we're already on this topic. My trickflow pushrod length checker has little white dashs on it. The instructions say that every time they line up while you're unscrewing the checker is equal to .050". Couldn't I get close enough using that method combined with checking the contact pattern on the valve stem? I'm using scorpion 1.6 pedestal mounted roller rockers now so I should be able to see the pattern better then with the factory stamped rockers. I don't have a set of 8" calipers so that's why I'm asking.
+1, I'd probably trust Trick Flow's denoted measurements. Just be sure you know where you're starting (if you're starting at 5.950 in. or 6.000 in. etc.).
With pedestal mount rockers the contact pattern is second hand, and you don't have a lot of room to adjust it. At least the way I see it, it's almost fixed (correct me if I'm wrong). Pedestal rockers usually have a few shims you can change the height they're mounted at, but they are small measurements (0.090 in. max for my case) and that's it.
If you have a pushrod length that gives you 0.020-0.060 in. of preload on the lifter while using no shims, one shim, or maybe even two shims under the pedestal your contact pattern better be good.
I say this for two reasons:
In the instructions that came with my Crane 1.7:1 roller rockers they didn't not say anything about checking the contact pattern
Given the adjustability (when compared to stud mount rockers) it makes perfect sense to me
Ok so further checking, I loosened them and retourqued to proper spec, it fired off but ran like crap. It turns out that I am experiencing coil bind. I am going to just sell the 1.72's and get some 1.6's. It's cheaper to replace rockers than the springs, pushrods, etc.
89 Mustang Pushrod length question 
