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Old 04-24-2010, 12:54 PM
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Push rod / valve not moving GM 400

1978 Pontiac Trans am 6.6 litre 400
Car was out of commission for several years, had a couple of collasped lifters prior to down time that were replaced. Oil flushed and replaced and ran fine for several years after before going in storage.
Problem: Cylinder 1 intake valve is not moving at all, pushrod is not even twitching while running, no noise or movement from rod even when rocker is removed and engine is running. There may have been a few hundred miles put on car in this condition with lifter not moving at all. not sure?
I cannot see how this would be a collasped or even damaged lifter, I would expect it to be flopping all around if that was the case, and the alternative I am not ready to think about, so I thought I would run it by someone else before I jump off the deep end. Help! Could it be simply a lifter collasped?

Thanks

Mark
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Old 04-24-2010, 01:49 PM
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sandman61,

SORRY but the cam has gone flat.

Scholman
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Old 04-24-2010, 04:22 PM
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If a tree falls in the forest do I have to admit my cam is shot?

Yeah......I know......just hoping for some miracle explaination other then
cam......I guess I could look at this as an oppurtunity for that performance cam and headers that that I've always wanted. I'm bummed because this is the model with the stock performance cam and the entire car is still stock. I'll start looking for an original replacement and go from there. Thanks.

Anyone have a possible "how it might have happened" explaination.

Mark
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Old 04-24-2010, 06:23 PM
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Hopefully the lifter stayed in the bore and didn't get kicked out, an internal oil leak would be the result if it was ejected. If the p-rod is still in place, that likely didn't happen.

A couple thoughts for the future:

The added zddp needs to be fully integrated into the rest of the oil that is in the engine, not just poured in before start-up. I would suggest mixing it into a gallon jug of the break in oil before being poured into the engine for priming.

The lube that's wiped onto the lobes and foot of the cam has to be "stiff" enough to stay put. I prefer the black moly cam lube that stains the hands, but w/o the "grittiness" of some of the black moly lubes- that actually feel gritty between the fingers. The 'grit' does not help and will only clog the filter after being slung off the cam.

Only use the moly lube on the lobes, lifter feet, cam/distributor gears and fuel pump push rod (if used). Do not use it on the lifter body- the lifter must not be hindered from spinning as soon as the engine turns over. The lifters should all be witnessed before start up to be rotating in their bores when the engine is turned over by hand. If they're not, you may find the lifter bore(s) are varnished up and might just need to be vigorously swabbed out w/a brass bristle wetter w/lacquer thinner or acetone. Lifter bores seldom ever need to be honed to any degree- if you decide they DO need honed, go lightly!

The engine has to be correctly assembled, fueled, timed, plumbed and wired to start up IMMEDIATELY. If there's a problem (fuel, oil or water leak, running hot, whatever), shut it down but do not idle it. It will do much more harm to idle it before it's time than shutting it off and dealing w/the problem.

The cam- to survive- has to have splash oiling provided by the crankshaft windage. This means that the speed has to be varied, but not less than 2000 RPM for any extended length of time. If the engine speed isn't varied, some lobes might be getting all the oil in the world, while others will be starved by comparison.

To this day, I believe some lifters are supplied w/overly aggressive finishes. If they're not chucked up and finished w/a solvent wetted piece of 600 grit, they WILL smooth themselves- at the expense of the camshaft lobe itself.

The geometry needs to be correct from the start, not corrected later on after it's noticed. This includes proper clearances between everything in the valve train.
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Old 04-25-2010, 05:41 AM
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still there

Yes my push rod is still where it should be, if that can be thought of as " good news". Thanks for the tips, looks like I'll be needed them!

If anyone is familar with the W72 series of the 400 and has a recommendation for a replacement cam that gives compareable performance with the stock carb, intake and headers, let me know. I am still trying to keep it stock if possible, but the original W72 cam is no longer available.

Or if anyone has had 1st hand experience with a better cam I may think about
moving past my stock obsession!

thanks
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Old 04-25-2010, 06:25 AM
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Putting a new lifter onto an old cam wiped out the lobe. With original lifters/cam, once they're worn in together, they'll be fine. Replacing an old lifter with new one onto a "worn" cam might very well wipe out a lobe...
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