I took my 308 and added some GT-40Y aluminum take off heads and a comp cam specs are: duration-intake-264-Exhaust-276, Gross valve lift .512, its a Nitrous cam loe seperation is 114. and I used stock rockers arms with the heads and stock length hardened push rods, but the shop says something is wrong that its sounds like the pushrods are sticking or something in the valve train is wrong , I put the cam and heads on my engine myshelf they just put the engine in, My ? is maybe their to short of PUSH RODS or the springs that come with the GT-40Y heads are't strong enough? anything will help, I tightend each rocker arm to 22 Lb of torque when they where at TDC. I followed the firing order.
Got the motor back in car but somethings not right
- Thread starter ZarnAutomotive
- Start date
Michael Yount
Mustang Master
Your set up is very similar to mine - mine has Y heads, 1.7 roller rockers, stock pushrods and a custom cam (ground by CompCams) with specs that are similar to yours. My heads/springs were new - they have no trouble controlling the valves up to at least 5400 rpm (the power peak is at 4900, so there's no need spinning any higher than that).
When you say you installed each pair at tdc -- there are 2 tdc's for each single rotation of the camshaft. You needed to install them at tdc on the compression stroke - when both lifters were on the base circle of the cam. If you installed them at tdc during overlap - both valves would have been open during your installation - don't want to do that. If you're at tdc on the compression stroke the proper procedure is to hand tighten the bolt until they're at zero lash (no gap between the pushrod end or the valve tip end) and then count the number of turns it takes until you hit the 22 lb-ft. torque. You should hit the torque between 1/4 turn and 1 turn of the bolt AFTER zero lash is reached. If it takes more than one turn, use shims to raise the rocker. If it takes less than 1/4 turn, either remove material from the bottom of the rocker fulcrum, or use a shorter pushrod. The ramp rates on your CompCam are much steeper than the stock cam. Even properly installed with correct clearances, they may be a bit noisier than the stock cam was.
When you say you installed each pair at tdc -- there are 2 tdc's for each single rotation of the camshaft. You needed to install them at tdc on the compression stroke - when both lifters were on the base circle of the cam. If you installed them at tdc during overlap - both valves would have been open during your installation - don't want to do that. If you're at tdc on the compression stroke the proper procedure is to hand tighten the bolt until they're at zero lash (no gap between the pushrod end or the valve tip end) and then count the number of turns it takes until you hit the 22 lb-ft. torque. You should hit the torque between 1/4 turn and 1 turn of the bolt AFTER zero lash is reached. If it takes more than one turn, use shims to raise the rocker. If it takes less than 1/4 turn, either remove material from the bottom of the rocker fulcrum, or use a shorter pushrod. The ramp rates on your CompCam are much steeper than the stock cam. Even properly installed with correct clearances, they may be a bit noisier than the stock cam was.
