Help! 84 vette engine noise

[HailBob]

I have a 84 corvette crossfire, not sure about the mileage, it says 50+ thousand. To me that is a little hard to believe for a 31 year old car! The problem now is it is making a noise from the engine. No it's not a exhaust leak. My friend thinks it could be a lifter or cam problem. It sounds like a lifter. Could it be from worn out exhaust seals? He wants to tear it down and pull the heads. If it is the cam/lifters what should I put back in. I am not really looking for more power, happy with what I got. It is a manual trans 4+3.

 

[Hot Rod Roy]

Pretty hard to guess what the noise is, based on your description! Is your friend a competent mechanic? If he is competent, he will do some further exploration before he tears the engine apart! If he suspects valve/lifter/cam problems, he will start with a compression check, then will probably want to pull a valve cover to look for loose rocker arms or bent pushrods, before removing your heads!

 

[Wavedoggie1]

RE; The actual mileage: The odometer motor seizes up in the dash module. See if the odo actually changes when you drive it.
As to the sound, is it a knocking (bad) or a clicking (not so bad) or a light "tikka tikka tac tikka" sound? (normal for the fuel injectors-they have a rhythm at idle)

You could try and change the oil and add some lucas or marvel oil modifier and see if it changes. Another trick is remove the belt and run the engine (briefly) to see if it goes away.

 

[HailBob]

eng noise

Tried Seafoam and ran it awhile and then changed oil to Valvoline 20w50 and added a additive for noisy engines, noise still there. my mechanic is very competent. Has been working on my cars for 20+ years. The biggest problem I am finding is nobody likes working on them. The noise is pretty loud and increases when you rev the motor. Not like a rod bearing noise more like a lifter. Could it be worn exhaust value guides? Hate to tear it down but will if have to. Don't mind spending money on it as I will be keeping it for a while. I guess it's better to pull the motor out of the car to work on it? What do you think, thanks

 

[DonB]

I did the 350 in my '90 C4 this past spring/summer. Mine was ticking and knocking too. I figured it was easier to rebuild it before it came apart. It is MUCH easier to work on the engine when it is on a stand out of the car. It's also a great time to repair any wire harness issues, power steering, brake, fuel and cooling lines that need attention. If it's an automatic trans do the front pump seal too(if not a trans job).
Send the heads and the block out to the machine shop. Jegg's has some nice rotating assemblies for the engine reasonably priced too. I'm very happy with my results. I'd be glad to steer you in the right direction if you need specifics.
Be forewarned though. These are NOT easy cars to work on. Everything is crammed in there so it's going to take some time and patience. That is why everyone charges an arm and a leg to repair them. I'd recommend getting a factory service manual from Corvette Central on CD and take pictures for reference as you take things apart, because there are a million parts and you will never remember how they all go(the first time anyway,) together again. I've found,..Most of it comes apart in a specific order and must be re-assembled in the opposite order. It does give you a great feeling of accomplishment and respect for the car when you are finished.
Good Luck
Don.

 

[Hot Rod Roy]

Tried Seafoam and ran it awhile and then changed oil to Valvoline 20w50 and added a additive for noisy engines, noise still there. I guess it's better to pull the motor out of the car to work on it?

I thought you said you have a good mechanic! Was the 50 wt. oil PLUS STP(!!) his idea? You don't even know what's wrong with the engine, and you're talking about pulling the engine? You need to find some GOOD help!

 

[DonB]

Before even thinking of pulling the engine you should isolate the source of the current noise. Otherwise you are guessing and doing a "shit-load" of work and expense, possibly for nothing!

 

[DonB]

At this point I think you should pull the valve covers and check the rockers and pushrods and adjust as needed. Id also put a thin oil in the engine with about a half of a quart of either trans fluid(ATF) or Marvel Mystery Oil and run it for a while. Hydraulic lifters have been known to have the tiny oil hole in them clog(or varnish up) and then they don't "pump up" enough and the valve train for that lifter becomes a bit loose and starts ticking.
As HotRod said, "You need some competent help," that knows engines and how to diagnose them.

Has anyone done a compression test? Read the plugs? How much manifold vacuum is it pulling? Is the vacuum reading somewhat steady or is it pulsating? Anyone check for timing chain slop/slap? These are all things you must answer first.

 

[HailBob]

my idea

The 20w50 was my idea. my mech did mention the transmission fluid. Believe me before we do anything I will check with a lot of different people. The car is put up in a garage for winter. Wll be April or May before we do anything. I'm sure he will check everything before he has to pull the motor. Don't think he is looking forward to pulling it. Thanks for the suggestions.

 

[catbert]

If it was me. I'd pull the heads and check them out. I'd clean them out and probably look at a valve job. The car is 30 years old, what could it hurt?

 

[G Winter]

Even a leaking head gasket can cause a knocking sound.An exhaust leak can cause quite a knock type sound.With only 50k on the engine I would find it hard to believe you have a major internal problem unless you have abused it.

 

[wolfuser]

Tried Seafoam and ran it awhile and then changed oil to Valvoline 20w50 and added a additive for noisy engines, noise still there. my mechanic is very competent. Has been working on my cars for 20+ years. The biggest problem I am finding is nobody likes working on them. The noise is pretty loud and increases when you rev the motor. Not like a rod bearing noise more like a lifter. Could it be worn exhaust value guides? Hate to tear it down but will if have to. Don't mind spending money on it as I will be keeping it for a while. I guess it's better to pull the motor out of the car to work on it? What do you think, thanks

Hi,

could you post the noise that would make it easier to 2nd guess whats on. however, I dont think the valve guides are making that noise. if they are THAT worn, than you (or rather the Vette) would be smokin' some oil. and some more.
try that:
- any change in the noise with oil cold or warm?
- looking under the hood: can you locate the noise, i.e. could it be something like the a/c compressor or such?
- idle, car stopped, hood open. rev her slowly! to say 2000rpm, change rpm a tiny bit. if the noise changes, might be con rod bearings.
- driving in say 3rd or 4th, low rpm, increase load. if she knocks then -> main bearings.
- getting any vibrations? engine mounts loose or damaged?
- gear change linkage loose, ball joints worn?
- noise same with clutch on/off?
- if still nothing, I´d remove the valve covers and have a look.

good luck... but dont disassemble the engine without knowing why. it IS a lot of work.
Wolfram

 

[HailBob]

Corvette noise

Hi,

could you post the noise that would make it easier to 2nd guess whats on. however, I dont think the valve guides are making that noise. if they are THAT worn, than you (or rather the Vette) would be smokin' some oil. and some more.
try that:
- any change in the noise with oil cold or warm?
- looking under the hood: can you locate the noise, i.e. could it be something like the a/c compressor or such?
- idle, car stopped, hood open. rev her slowly! to say 2000rpm, change rpm a tiny bit. if the noise changes, might be con rod bearings.
- driving in say 3rd or 4th, low rpm, increase load. if she knocks then -> main bearings.
- getting any vibrations? engine mounts loose or damaged?
- gear change linkage loose, ball joints worn?
- noise same with clutch on/off?
- if still nothing, I´d remove the valve covers and have a look.

good luck... but dont disassemble the engine without knowing why. it IS a lot of work.
Wolfram

I will try and record the noise and post it for you to listen to. The noise is coming from the top of the motor. It sounds like a lifter. I will be checking with as many people as I can before we dig into. I'm not sure about the miles. Have to make sure it's registering miles as I drive. Thanks for the help!

 

[wolfuser]

I will try and record the noise and post it for you to listen to. The noise is coming from the top of the motor. It sounds like a lifter. I will be checking with as many people as I can before we dig into. I'm not sure about the miles. Have to make sure it's registering miles as I drive. Thanks for the help!

Hi,

just a thought, while "waiting for the noise"... if it's comin' from the top of the engine it probably aint a lifter, as those are just above the cam which is somewhat down and center, above the crank shaft. may be one rocker is loose, or something like that... could do no harm do pull the valve covers (get new gaskets....) thats not too difficult. however, make a note what goes where on reassembly.....

good luck!
Wolfram