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OT: Replacing Cam in 350 oil pressure

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JoeBob/IN

04-12-2008 15:07:24




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Well, it finally went kaput! Been running rough for about a year and I didn't really diagnose it too much 'til just yesterday. Tore valve covers off of my '95 Chevy with the 350 and found out why it has been running rough. Appears as the cam is bad. Looks like several of the valves aren't opening all the way. Another strange thing happened at the same time. It lost oil pressure according to the gauge. Now either the gauge/sending unit is bad or that Amsoil is really fantastic oil cause I decided if it was shot and lost oil pressure I would drive it the last mile home 'til she fully died. Surprisingly I made it and it still starts easily and runs! So, where can I tap into with a gauge to check oil pressure and while I am doing it what aftermarket cam would be a good one? Would like a bit more umph and/or mileage out of her. Oh, and it is a farm truck so that keeps this post semi legal!

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Rootsy

04-13-2008 08:19:33




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 Re: OT: Replacing Cam in 350 oil pressure in reply to JoeBob/IN, 04-12-2008 15:07:24  
Fact of the matter is. A roller lifter cannot "turn" unless the tie bar holding the adjacent lifters in proper orientation breaks or comes off. In order for that tie bar to come off the spring steel retainer or spider must come unbolted or one of the arms has to break off...
Since a sbc lifter has an oil groove all of the way around it there is no way for it to block oil to the bearings by rotating in the bore. The lifter galley is the first place to get oil in a sbc (yes even before the mains and rods). The oil passes through the lifter galley and is then distributed to the mains which then supplies the rods. Oil feeding the lifters is sent to the top end via the push rods. Thus as long as the pickup is taking in oil and the pump is putting it out and it's going through the filter the lifters will get oiled first. There are screw in plugs behind the flywheel flexplate in the block and press in plugs behind the timing chain with small holes in them. If one comes out it'll lose oil pressure. If you roll an engine over by hand a half dozen times you will begin to collapse hydraulic lifters.

If you wipe a camshaft lobe the fine particulates will wipe out the main and rod bearings and oil pressure will drop. Hence whenever an engine eats a camshaft or lifter you pretty much have to totally disassemble it, thoroughly clean all parts and oil passages and rebuild with new bearings. and in some cases have rods resized and the crank turned...
I've seen sbc roller camshafts eat themselves a few times. Easiest way to tell is to pop the intake, and remove the lifters that aren't opening the valve... you'll know right away if you have a bad lobe. I've also seen lifters that won't pump up...
A few years ago I had a customer bring a brand new Hi-perf marine engine to me that ate a roller camshaft... GM or Mercruiser had installed BBC roller lifters in the mouse which have flats 90 degrees to a sbc roller lifter... hence the roller was sliding over the lobe instead of rolling... engine lasted a total of about an hour before it died...

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Rootsy

04-13-2008 08:25:38




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 Re: OT: Replacing Cam in 350 oil pressure in reply to Rootsy, 04-13-2008 08:19:33  
Standard GM roller camshaft setup showing the tie bars and spring steel retainer...
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Jiles

04-12-2008 18:43:17




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 Re: OT: Replacing Cam in 350 oil pressure in reply to JoeBob/IN, 04-12-2008 15:07:24  
Chevrolet has had a cam problem since 1955! I have replaced more then I care to remember. In my 45 years as a mechanic I have never seen a Ford or Dodge with wore out camshaft, reguardless of mileage. It has to do with lubrication, When adjusting valves on a running engine, ever wonder why oil squirts over the fender.



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jose bagge

04-12-2008 17:15:11




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 Re: OT: Replacing Cam in 350 oil pressure in reply to JoeBob/IN, 04-12-2008 15:07:24  
since it's a roler motor, it more than likely "turned" one or more lifters and that's what ate the cam. The turned lifter probably blocked the oil galley and that's what's causing the shaky oil light. I'd plug a cam, lifters and probably a new oil pump/screen into it and let in eat.
Check with Summit for the best deal on cam/lifter packages for that engine. While your replacing the pump, ya might just pull a main cap and have a look at a bearing just to make sure that this is all just limited to the cam- infact, I'd pull the pan and have a look before i ordered any parts (just in case)

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Bob

04-13-2008 01:25:56




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 Bagge, you're FUNNY! in reply to jose bagge, 04-12-2008 17:15:11  
You posted: "The turned lifter probably blocked the oil galley and that's what's causing the shaky oil light."

NO WAY. Crapped out it's roller, fell down, ate the cam, WHATEVER.

However, it's IMPOSSIBLE for it to BLOCK the oil gallery in a way that would cut off oil to the other lifters and/or affect oil pressure!

If you don't believe me, take a look at a SBC block, and notice how the oil gallery runs BESIDE the lifter bores, and cannot be BLOCKED by what goes on IN the lifter bore..

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teddy52food

04-13-2008 08:13:03




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 Re: Bagge, you're FUNNY! in reply to Bob, 04-13-2008 01:25:56  
I agree with Bob.



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jose bagge

04-13-2008 05:17:11




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 Re: Bagge, you're FUNNY! in reply to Bob, 04-13-2008 01:25:56  
shi-yat, I dunno- maybe it OPENED the damn lifter galley and allowed pressure bleed down and that's what's giving the shakey light.
My point was that I think this started as a lifter issue, ate the cam as a result, and that the OP problem will probably be corrected when the lifters are replaced. I don't think OP was the problem to begin with.
Hell, bring me the peices and I'll figure it out.

And... I am a hilarious dude to be around. Just ask my wife!

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Bob

04-13-2008 09:30:30




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 Re: Bagge, you're FUNNY! in reply to jose bagge, 04-13-2008 05:17:11  
My wife thinks I'm funny, as well. Well, maybe not FUNNY.



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El Toro

04-12-2008 16:54:17




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 Re: OT: Replacing Cam in 350 oil pressure in reply to JoeBob/IN, 04-12-2008 15:07:24  
You should have an oil pressure sending unit near the rear of the intake manifold. I think those hydraulic lifters would become noisy if there's no oil pressure. The last cam that I installed in a Chevy was a Wolverine Blue Racer kit that included new lifters. Hal



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marlowe

04-12-2008 16:29:27




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 Re: OT: Replacing Cam in 350 oil pressure in reply to JoeBob/IN, 04-12-2008 15:07:24  
had a 94 and a 95 in the shop both had bad cams. plus rollers were bad also Chevy had some real soft cams



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Erniedd

04-12-2008 15:48:22




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 Re: OT: Replacing Cam in 350 oil pressure in reply to JoeBob/IN, 04-12-2008 15:07:24  
So if you wiped some of the cam lobes off, the pieces of metal went through the oil pump and open its clearances up. Some chips may be holding the pressure relief valve open.

Amsoil is good, but it won't replace metal.



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Aaron SEIA

04-12-2008 15:44:31




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 Re: OT: Replacing Cam in 350 oil pressure in reply to JoeBob/IN, 04-12-2008 15:07:24  
If I remember right, that engine has hydraulic lifters. If it ran out of oil, the lifters would collapse and the valves wouldn't open fully. Maybe the run bad is oil burning related. I'd check the dipstick and see if it's low. I ran mine low once (forgot to tighten an oil cooler line) and it started running rough.

Aaron SEIA



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big fred

04-12-2008 16:16:39




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 Re: OT: Replacing Cam in 350 oil pressure in reply to Aaron SEIA, 04-12-2008 15:44:31  
I would agree, a '95 should have a roller cam, and cam lobe wear should be the last thing that happens. If you lost pressure, I'd bet your lifters ain't pumped up.



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