Help! Gt40p Valvetrain Chatter

Michael Yount’s valve adjustment procedure

Here's an easy way to determine this. Start with the #1 cylinder. Rotate the engine with a ratchet on the crank bolt clockwise. Watch the #1 pushrods. First the exhaust pushrod will rise and fall signaling what would be the exhaust valve opening and closing if the rocker were on. As it closes the intake pushrod will rise -- keep rotating clockwise until the intake pushrod falls and is level with the exhaust pushrod - both at the same height. Both lifters are now on the base circle of the cam - both valves would be closed if the rockers were on.

Now, install both rockers. Tighten the bolts with one hand while rocking the rocker with the other hand - continue until you reach the point where you can't 'rock' the rocker any more because there's no gap on the valve stem end or the pushrod end. You are at zero lash - i.e. - no gaps. Stop tightening just as you reach this point.

Now, put your torque wrench on the bolt and tighten it to 18-20 ft-lbs while counting the number of turns it takes to reach the torque. You should hit the torque within 1/4 to 1 turn of the bolt. If it takes more than 1 turn, use a shim to raise the rocker -- each .030" shim will reduce the number of turns to torque by about 1/4 turn. If you reach the torque in less than a 1/4 turn, or you have trouble reaching zero lash even at full torque, then you'll either need longer pushrods, or to CAREFULLY remove some material from the bottom of the rocker fulcrum. Using the procedure described above, you will work through the remaining 7 pairs of rockers. If you follow the firing order, it will minimize the manual cranking you have to do to get the lifters on the base circle of the cam prior to installation of the next pair.

When I first went through mine, 13 of them took no shims; 3 of them took 1 .030" shim. Upon cranking it up, one or two of them sounded a bit noisier than I thought was right, so with the engine hot, I pulled the upper off, and the valve covers, and went through the installation procedure again. That time, 11 of them took no shims; 4 of them took one .030", and one of them took one .060" shim. And they were very quiet running.

Good luck with it.
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Michael Yount - K'ville,TN 82 Volvo 242w/5.0L; 2000 Suzuki Bandit 1200

tmac3439 said:

1988 mustang gt, 5 speed, mass air conversion, bbk unequal length headers, off road h-pipe, explorer intake, explorer 65 mm tb, 70 mm pro-m mass air meter, gt40p heads with comp cam springs.
I just finished swapping my e7's for the gt40p heads. I was told the springs were comp cam spring upgrade for these heads from a local mustang enthusiast. I had to use the pushrods and rockers from the e7 setup. First i torqued the rockers to 18-20 ft/lbs at tdc on compression stroke, valvetrain sounded awful. Then i tried the spin the pushrod until it stops then turn bolt one full turn, still, sounded awful. Then i tried it with the engine running and broke a rocker arm bolt during the procedure. What am i missing?

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I am not a mechanic, but I have almost the same mods, even the same headers and h-pipe! But I am using 1.7 rockers, 75mm pro-m meter, 70mm tb, 93 Cobra intake with ported lower, original pushrods, and stock gt40p springs. The only valvetrain noise I had was from the oil baffle inside the valve cover coming loose! My mechanic used screws that were too small. Once that was fixed It sounds normal (and bad ass)! By the way I am running 24lb. injectors and Aeromotive 340 fuel pump. What are you running?

Re-read my post - you need some shims for the rockers...That's why you still have noise...

tmac3439 said:

Would my local Ford dealership have the shims? If so, how many should i get? Sizes?

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Local ford dealer should have the shims. Read the tech note and work from there. Use a mechanic's stethoscope to locate which valves need the shims. Harbor Freight has them on sale - See http://www.harborfreight.com/catalogsearch/result?q=stethoscope for $5.

tmac3439 said:

jrichker, hats off to u sir. Did exactly as u said but i also took apartall my lifters, cleaned them and reinstalled them. I only shimmed #7 intake .030 and #3 exhaust .020. Im assuming the chatter im still hearing, which is 1000 times better, thank you again, is the rockers that were torqued to 18 ft lbs and reached 1 turn past zero lash. Where should I be aiming for, quarter to three quarters? Eighth to a quarter?

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According to Michael Yount's tech note, the shims are to be used in .030 increments. You should hit the torque within 1/4 to 1 turn of the bolt. Anywhere in that range is OK.

Use the mechanic's stethoscope to go back and isolate any remaining noise you have.