Valve Train Noise?

[twild]

I'm a new GN owner and figured I'd ask a few questions before I start on an un-educated wild goose chase.

My car is an 87' and i have no idea what internals the engine has. Peaking in through the oil filler hole in the valve cover, it appears to have stock rocker assemblies. It has quite a few mods to it, bigger turbo (6776), alcohol injection, larger intercooler, MAF Translator, boost controller, etc... On cold start up, the valve train on the left (driver's ) side seems quiet but the right (Passenger's) side is noisy. On hot start up, the right side makes a bunch of noise which to me sounds like a couple of lifter not pumping up, and after about 4-5 seconds it quiets back down but it's still more noisy than the left side. Either hot or cold, the right side makes more noise that to me sounds like valve train noise (as compared to the left side, which seems quiet).

I haven't checked the oil pressure yet but the oil pressure light appears to be working properly.

I'll say this, after driving mine for the first time, I understand why people are so passionate about their GN's. To step on the gas at 45 mph and have the rear break loose is pretty damn exciting!

If anyone has any suggestions on where I might start in tracking down this issue, please chime in.

Thanks,

Thomas

 

[turbofabricator]

Could be cam going flat. Or just bad lifters.

 

[twild]

Thanks Ken. I'll be checking it out next week, it would be nice if it was just a few lifters.

 

[dank GN]

It concerns me when I hear that you have all these bitchin mods , but you don't have the basics like a oil pressure gauge , scanmaster or way to monitor knock . How do you know the oil pressure light is working ? Just about every GN I've seen has had the oil pressure switch by passed or removed .

 

[fastblackracing]

The valvetrain noise can come from many
Places..... These engines seem to be very
Sensitive to the type and brand of lifter used as well as the amount of preload on the
Hydraulic plunger.

Sometimes adjusting the preload can reduce plunger noise but with stock rockers you would need adjustable pushrods to accomplish this.

It is also possible that you have a roller cam in the engine which throws another noise source from the link bars into the mix.

Also the rate of lift from the cam lobes can have an effect as a slower ramp cam will usually be quiter than a fast ramp cam.

Make sure that you are using an ac pf52
Or equivalent oil filter that has an anti- drain valve in it to help keep the system full so that on start up you have oil pressure faster.

And most of the replacement camshafts up until recently have the front cam bearing journal grooved and this grooved front journal really wears into the front cam bearing which causes an oil loss at this point which is critical since the driver side lifter bank gets its oil from the front cam bearing.

The stock GN 109 block transfers the lifter oil from a groove in the block behind the bearing and the 4.1 and stage blocks get this oil from the grooved journal or special bearings or other means.

So any excess leakage can cause the drivers side lifter to struggle for oil.

I would pull the intake to see what the lifters look like and weather it's a roller cam or not. If it is lifters you may have caught it fast enough to save the rest of the engine.

 

[twild]

It concerns me when I hear that you have all these bitchin mods , but you don't have the basics like a oil pressure gauge , scanmaster or way to monitor knock . How do you know the oil pressure light is working ? Just about every GN I've seen has had the oil pressure switch by passed or removed .

Well thanks for commenting and I wish it had an oil pressure gauge as well but I just bought it and it didn't have one. The car actually does have a Scanmaster (It's listed by my signature) and for now It's what I'm using for monitoring timing retard. Also, the oil pressure switch is present and hooked up. When I go to Key on, engine off the oil pressure light is on. Once I crank the vehicle, the oil light goes out. It's my understanding the light goes off when the switch sees 4 psi of oil pressure. The previous owner did all the mods and I'm trying to get everything working like it should.

 

[twild]

The valvetrain noise can come from many
Places..... These engines seem to be very
Sensitive to the type and brand of lifter used as well as the amount of preload on the
Hydraulic plunger.

Sometimes adjusting the preload can reduce plunger noise but with stock rockers you would need adjustable pushrods to accomplish this.

It is also possible that you have a roller cam in the engine which throws another noise source from the link bars into the mix.

Also the rate of lift from the cam lobes can have an effect as a slower ramp cam will usually be quiter than a fast ramp cam.

Make sure that you are using an ac pf52
Or equivalent oil filter that has an anti- drain valve in it to help keep the system full so that on start up you have oil pressure faster.

And most of the replacement camshafts up until recently have the front cam bearing journal grooved and this grooved front journal really wears into the front cam bearing which causes an oil loss at this point which is critical since the driver side lifter bank gets its oil from the front cam bearing.

The stock GN 109 block transfers the lifter oil from a groove in the block behind the bearing and the 4.1 and stage blocks get this oil from the grooved journal or special bearings or other means.

So any excess leakage can cause the drivers side lifter to struggle for oil.

I would pull the intake to see what the lifters look like and weather it's a roller cam or not. If it is lifters you may have caught it fast enough to save the rest of the engine.

Thanks for the information and suggestions. My initial thought was to pull a valve cover and see if I have a broken rocker shaft or try and check cam lift with a dial indicator. I agree that pulling the intake would be a good idea, so it looks like that's what I will be in the near future.

I'm just guessing since it has the stock rocker setup, it may still have the flat tappet lifters. Any suggestions on a brand for replacement lifters?

Thanks again.

 

[TurboTGuy]

Where are you located?

Some pretty knowledgeable guys are scattered all over the country and two heads are always better than one. Maybe someone can look at it with you or you could take it to one of the T/R guru's out there for a look-see.

 

[earlbrown]

Thanks for the information and suggestions. My initial thought was to pull a valve cover and see if I have a broken rocker shaft or try and check cam lift with a dial indicator. I agree that pulling the intake would be a good idea, so it looks like that's what I will be in the near future.

I'm just guessing since it has the stock rocker setup, it may still have the flat tappet lifters. Any suggestions on a brand for replacement lifters?

Thanks again.

Popping the valve covers off and starting it is a quick and easy test. I would pull the rocker shafts, replace the plastic buttons while they're off and put a dial indicator (since it sounds like you have one) on each of the pusrods and write down the lobe lifts.

If you have a broken shaft (very common) you've found your problem. While the rocker shafts are off roll the pushrods on something flat to make sure they aren't bent and look for any evidence of contact to the head.

 

[twild]

Where are you located?

Some pretty knowledgeable guys are scattered all over the country and two heads are always better than one. Maybe someone can look at it with you or you could take it to one of the T/R guru's out there for a look-see.

I'm located in Louisiana.

 

[twild]

Popping the valve covers off and starting it is a quick and easy test. I would pull the rocker shafts, replace the plastic buttons while they're off and put a dial indicator (since it sounds like you have one) on each of the pusrods and write down the lobe lifts.

If you have a broken shaft (very common) you've found your problem. While the rocker shafts are off roll the pushrods on something flat to make sure they aren't bent and look for any evidence of contact to the head.

Thanks Earl, I plan on doing that today, weather permitting. I'll post what I find.