Engine break-in issues
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Junior User
Joined: Sep 2009
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Engine break-in issues
Hello, I just dropped a 390 into my truck that I completely rebuilt, scat crank, rods, pistons set. Comp 268h camshaft kit, springs, lifters, timing chain. Used all the cam lube, used assembly lube, prelubed with Brad Penn break-in oil. Prelubed it twice. When I went to break it in it fired up after a couple turns of the motor and a pump of the throttle and sounded great, smooth, got the rpms up and about 10 minutes into it it popped out the carb but kept running strong. Towards the end of the 20 minutes it was popping inconsistantly through the carb. Did some reading and figured my camshaft was shot. Took the valve cover off and found that the number 1 intake push rod was down half inch from the rest with the adjuster on the rocker backed off. I had adjusted and tightened. Put a dial indicator on the push rod and it read a little over .30 lift on the cam lobe. Now the 268h cam says .286 lobe lift. I have yet to take the intake off as it started raining on me this evening. I was just wondering if the lifter could have failed or if my camshaft is indeed ruined. I can check everything with the intake off, I just wanted some peace of mind while the rain hinders my investigation. Thanks
Elder User
Joined: Jan 2011
Posts: 831
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From: Tanilba bay NSW Australia
hate to say it but it could be either or both, and if so, you are up for a new cam and lifter set regardless. For your sake I hope not. I did read correct where you said you only had 30thou lift so you are ruling out a bent push rod?
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Junior User
Joined: Sep 2009
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I have since found the problem. Two of the lock nuts backed off and one adjuster backed out far enough to where the push rod jumped out of the lifter and hit the retaining clip for the plunger, allowing the push rod to fall back down inside the hole. Got a new lifter and dropped it in and haven't had the issue since.
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