Wiped Cam on 84?
Thread Starter
Instructor
Joined: Feb 2006
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From: Tx
Wiped Cam on 84?
Have 84 with carbureted 350. Heard ticking noise on engine. Identified cylinder, but could not get rid of noise. Went in and replaced all lifters with new ones, replaced 3 slightly bent pushrods. and replaced all of the nuts on the rocker arms. Now engine won't idle, runs rough, backfires at times.
Could I have finished off camshaft? Original lifters did not appear to be bad.
Could I have finished off camshaft? Original lifters did not appear to be bad.
Last edited by dc6902; Sep 28, 2017 at 07:53 PM.
Zen Vet Master Level VII
Joined: Mar 2016
Posts: 5,218
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From: Southlake, TX
IMO Wiping the cam is pretty extreme.
However, you have A LOT going on right now; fuel, spark and air.
My first thought is (if you put the lifter, push rods and tightened rockers correctly) you have air leaks as the L83 is very prone to those. The back fire is a hint that you have a lean condition caused by excess leaks.
Really, tough to tell unless you can "remove" a few items off the "coudl be F'd up list."
However, you have A LOT going on right now; fuel, spark and air.
My first thought is (if you put the lifter, push rods and tightened rockers correctly) you have air leaks as the L83 is very prone to those. The back fire is a hint that you have a lean condition caused by excess leaks.
Really, tough to tell unless you can "remove" a few items off the "coudl be F'd up list."
Le Mans Master
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From: Clearwater Florida
Race Director
Joined: Apr 2003
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From: moraga ca
New lifters on an old flat tappet cam is usually not a good combination. Cams and lifters will wear together as a pair. Break up the pair and you're looking at a new cam pretty soon. Multiple bent pushrods usually mean someone messed up with the valve adjustment or the timing chain slipped a few teeth.
Melting Slicks
Joined: Jan 2009
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From: folsom california
if you have the valve cover off, measure the rocker arm movement; all the intakes should be the same and all the exhaust should be the same; if there's an odd ball (or two or three) then you may have found your problem.
Safety Car
Joined: Sep 2004
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From: Mission Viejo CA
This is a tricky test, because as you turn the engine by hand, and the pushrod is rising, the hydraulic lifter will collapse as the valve spring puts pressure on the lifter. This will give you a changing dial indicator reading, even though the engine (and camshaft) is not moving. You have to wait until the lifter is completely collapsed to get a reading. As you rotate the engine past the cam lobe, the lifter will return to its full extended height. A bit confusing!
Safety Car
Joined: Aug 2009
Posts: 3,752
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From: Melbourne, Victoria, Australia
Hi
Did you prime the new lifters with oil before installing them?
Note some aftermarket lifters need less than the factory one full turn from zero lash, i found that out with my new engine it would not idle and backfired. Turned out low compression on a few cylinders because the valves were not closing fully. Half a turn was all those lifters needed.
Note the early 84 -85 corvettes had known camshaft lobe wear issues,
my old 85 engine had definite camshaft lobe wear.
The easiest technique to set the lifters is when the particular cylinder piston is at the top of its stroke,
rotate the pushrod with thumb and finger until you cannot turn it that is zero lash.
Then turn the rocker nut 1/2 or one turn clockwise depending on lifter manufacturer,
you will have to start from scratch hopefully the lifters have primed by now.
Undo each rocker a few turns and start again, go via shop manual at what ones you can adjust at crankshaft position or each piston at top of its stroke.
Did you prime the new lifters with oil before installing them?
Note some aftermarket lifters need less than the factory one full turn from zero lash, i found that out with my new engine it would not idle and backfired. Turned out low compression on a few cylinders because the valves were not closing fully. Half a turn was all those lifters needed.
Note the early 84 -85 corvettes had known camshaft lobe wear issues,
my old 85 engine had definite camshaft lobe wear.
The easiest technique to set the lifters is when the particular cylinder piston is at the top of its stroke,
rotate the pushrod with thumb and finger until you cannot turn it that is zero lash.
Then turn the rocker nut 1/2 or one turn clockwise depending on lifter manufacturer,
you will have to start from scratch hopefully the lifters have primed by now.
Undo each rocker a few turns and start again, go via shop manual at what ones you can adjust at crankshaft position or each piston at top of its stroke.
Last edited by gerardvg; Oct 1, 2017 at 02:56 AM.
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Melting Slicks
Joined: Jan 2009
Posts: 3,482
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From: folsom california
This is a tricky test, because as you turn the engine by hand, and the pushrod is rising, the hydraulic lifter will collapse as the valve spring puts pressure on the lifter. This will give you a changing dial indicator reading, even though the engine (and camshaft) is not moving. You have to wait until the lifter is completely collapsed to get a reading. As you rotate the engine past the cam lobe, the lifter will return to its full extended height. A bit confusing!
Safety Car
Joined: Sep 2004
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From: Mission Viejo CA
Obviously, you'd need to re-adjust the valves correctly before starting the engine!
Safety Car
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From: Mission Viejo CA
Thanks for your many contributions to this forum, though!
Thread Starter
Instructor
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From: Tx
Update:
Someone suggested checking fuel. Found water in fuel tank. Removed and cleaned tank
Adjusted valves at tdc compression and others 180 degrees out. Put valve covers on . Engine starts. Timed to 10 degrees. Went to fine tune valve adjustment and engine won't run or idle with valve covers off. With valve covers on it is difficult to open oil filler cap. Too much suction. Engine vacuum is 17. What is going on? Plus loud sound from carburetor. Engine runs with valve covers on, just has slight miss. Has Edelbrock intake , no egr, just pcv.
Someone suggested checking fuel. Found water in fuel tank. Removed and cleaned tank
Adjusted valves at tdc compression and others 180 degrees out. Put valve covers on . Engine starts. Timed to 10 degrees. Went to fine tune valve adjustment and engine won't run or idle with valve covers off. With valve covers on it is difficult to open oil filler cap. Too much suction. Engine vacuum is 17. What is going on? Plus loud sound from carburetor. Engine runs with valve covers on, just has slight miss. Has Edelbrock intake , no egr, just pcv.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Thread Starter
Instructor
Joined: Feb 2006
Posts: 170
Likes: 6
From: Tx
Melting Slicks
Joined: Dec 2009
Posts: 2,236
Likes: 286
Update:
Someone suggested checking fuel. Found water in fuel tank. Removed and cleaned tank
Adjusted valves at tdc compression and others 180 degrees out. Put valve covers on . Engine starts. Timed to 10 degrees. Went to fine tune valve adjustment and engine won't run or idle with valve covers off. With valve covers on it is difficult to open oil filler cap. Too much suction. Engine vacuum is 17. What is going on? Plus loud sound from carburetor. Engine runs with valve covers on, just has slight miss. Has Edelbrock intake , no egr, just pcv.
Someone suggested checking fuel. Found water in fuel tank. Removed and cleaned tank
Adjusted valves at tdc compression and others 180 degrees out. Put valve covers on . Engine starts. Timed to 10 degrees. Went to fine tune valve adjustment and engine won't run or idle with valve covers off. With valve covers on it is difficult to open oil filler cap. Too much suction. Engine vacuum is 17. What is going on? Plus loud sound from carburetor. Engine runs with valve covers on, just has slight miss. Has Edelbrock intake , no egr, just pcv.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Regarding the crankcase vacuum, check your PCV valve. I'm presuming you haven't had your intake manifold off the car recently?
Team Owner
Joined: Aug 2004
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From: Park City Utah
Sound like you hooked the "breather" side hose from the valve cover to manifold vacuum, rather than the PCV side hose w/the PCV attached to it. OR you hooked the PCV valve hose to manifold vacuum (as it should be) but w/o a PCV valve installed.