Pushrod bending Cam eating sbc Why? - Team Camaro Tech
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post #1 of 8 (permalink) Old Sep 7th, 03, 08:02 PM Thread Starter
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My cousin has a 350 Chevy engine that has in 190 miles since rebuilt,bent at least 2 pushrods bad and now has a cam with 2 lobes worn off.They were not on the same cylinders that had the bent pushrods on.The story. He called me a few days after he got the truck back from the his mechanics shop.It was running rough.I checked it out.It was missing on 3 cylinders.pulled the plugs,gas run out of the cylinders,because of no fuel filter,and the needle and seat on his new Eldebrock carb stuck open by dirt.I replaced the plugs fixed carb,started it up,dead miss no 3 cyl,pushrod bent and fell down in lifter valley.Removed Intake ,no3 exaust lifter pushed out but no damage to it.I replace the pushrod and re adjusted all the valves and changed the iol and filter.Cranked it up ran perfect for 190 miles,then he called me Saturday and said it was ticking on the right bank but was running good.later that evening he called back after going for a short trip the ticking stopped but now a dead miss.tore back into it,now no 6 intake pushrod bent.replace the pushrod and adjusted the valve,cranked it up and now no 6 exaust valve not moving.His mechanic removed the cam.lobes worn off of no 6 exaust and worn bad no 7 intake.I would like your opinion about what caused these problems.This engine is a 350 flat top with Comp cam 292 H and their lifters pushrods and roller tip 1.5 rockers.601 305 heads.My theory is lack of lube at the top end of the engine,possibly cam bearing not lined up right that caused the damage,most likely lifters seizing up?Whats yours?

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post #2 of 8 (permalink) Old Sep 8th, 03, 01:18 AM
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cam not broke in properly.
valves miss adjusted.
cylinder hydraulic'd due to gas.
valve springs wrong &lt; height/poundage&gt;
just a few guesses w/o seeing or hearing.
good luck.

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post #3 of 8 (permalink) Old Sep 8th, 03, 02:15 AM
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I agree with Doug, I would add: Over revving, and weak valve springs.

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post #4 of 8 (permalink) Old Sep 8th, 03, 08:30 AM
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The retainer may have hit the guide due to all that lift with not enough clearance causing interfearance and the resulting bent pushrods. Bent pushrods can come from interfearance or wiped out lobes either way.

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post #5 of 8 (permalink) Old Sep 8th, 03, 11:01 AM
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Either not enough retainer to guide clearance like Stingr69 said or coil bind.

You need at least .050" clearance between the bottom of the retainer and the top of the valve guide. Same with clearance between coils --- you need at least .050" between the coils (watch the dampener too).

I'd bet your prob is one of those two things.

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post #6 of 8 (permalink) Old Sep 8th, 03, 04:34 PM
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Rockers hitting the valve covers? I imagine you could see witness marks on the inside of the cover and perhaps a dimple.


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post #7 of 8 (permalink) Old Sep 9th, 03, 01:23 AM
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I was going to say that the slot wasn't long enough for using 1.6 ratio rockers, BUT you aren't using them!!

Or maybe the intake bolts may be too long and binding some P/R's???

Otherwise, don't know except as already stated. pdq67

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post #8 of 8 (permalink) Old Sep 9th, 03, 05:48 PM
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One last thing, had springs installed for a Hyd cam and later found out after to two flat cams,

"the springs were for a solid lifter cam, and they were in the wrong box from new!"

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