swag

You all have been really helping me out a lot on the issues with my corvette! Thank you all!

So, I'm working through my list of issues and I have a challenge for you.

I "think" I might know what it is; however I would like your opinion.

So, I have a link to a video where you can hear my engine running.

What do you think that knocking sound is?

Thank you!

https://www.dropbox.com/s/prlymd537v...33721.mp4?dl=0

Big2Bird

All I hear is an exhaust leak. Of course, this is on my dumb phone.lol

0Willcox Corvette

This noise could be an exhaust leak but it sounds like a rocker arm issue to me. The clacking sounds like a loose rocker arm from what I can tell. To eliminate this as the issue, remove the valve cover and adjust the rockers... if the noise persist the I'd look elsewhere.

I always adjust the rockers (on hydraulic) in the following manner:

Bumper the engine over and look at the intake rocker on number 1... when the exhaust rocker moves downward, adjust the intake to zero lash. Once the intake is done then when the intake rocker moves downward adjust the exhaust.... Do this the same on each cylinder. If the intake/exhaust valve is moving downward there is no chance the opposite is on the lobe so that is the perfect time to adjust. You can also use the GM method of adjusting per TDC.. but i prefer the method above because I know if the opposite valve is moving then then I'm off the lobe.

Willcox

swag

Yes, actually, I was talking about the knocking sound. That's what I thinking the issue was. Kind of wanted to test my skills since I am still learning.

I've seen a youtube video where the guy adjusts them while the engine is running. Unscrew until the knocking starts, then tighten 3/4 a turn.

Hopefully, that's all it is and not worse problems! Saving up for an engine rebuild.

For the other issue, I have some exhaust manifold gaskets to hopefully solve the leak.

One problem, the previous owner used metric bolts on the aftermarket headers and they keep coming loose. I got some bolt locks so hopefully that keeps things tight.

Thanks

fishslayer143

I use the copper header gaskets.. no leaks in 9 years ..if you adjust valves hot and running, use a shield to deflect splashing oil or you may start a fire

gcusmano74

Yes. Slight variation. Easier than waiting for each lifter to automatically adjust.
With the engine running, and cardboard placed to contain the oil splash, adjust ALL the rockers to ZERO lash on one head. Shut off the engine, and dial in your preload on all the rockers. Then button it up, go to the other side, and do the same thing.

AirBusPilot

Hmm, actually I believe you adjust the exhaust valve when the intake closes (compression stroke), not when it begins to open (intake stroke). Reason being is when the exhaust is scavenging, it's pulling the intake charge into the cylinder. IOW, when the intake valve is starting down, the exhaust valve is still open, somewhat (on the lobe).

larrywalk

It's an exhaust leak. Time to replace the header gaskets!

swag

Thanks!

I want to replace it with something long term. I think the previous owner put metric bolts in the header and they keep coming loose. Might be part of the problem.

While I was adjusting the rocker arms I noticed that there is a gasket already there.

Also, to make things worse, they put aftermarket headers.

What do you all recommend for a good gasket?

@fishslayer143, you recommend the copper gasket? Which brand and part?

Thank you all!

jb78L-82

Sounds like an exhaust header leak...ask my how I know?

swag

Sure jb, how do you know? Is there something on the video?

jb78L-82

I tried to load a video from when I first had the L-82 355 running after the rebuild but had issues. The sound from the engine was VERY similar to your video...not quite as loud but more like a lifter/rocker sound...it was the exhaust gasket leaking pretty good....

swag

Ok, good. I did purchase some high quality head gaskets. Hopefully, I don't need to change them again.

Do I have to unbolt the whole exhaust or is there enough room to unbolt from the manifold and squeeze them in?

Another issue, the previous owner used metric bolts and they keep coming loose and then probably have the head gasket fail and it starts all over.

Without having to check them frequently, is there a good way to get these to stay tight?

I want to do an engine rebuild in the future and I'll fix all these problems; however, I just want something for now.

jb78L-82

No you do not have to unhook the exhaust to pull the header back from the heads to change gaskets.

FWIW-The Shorty Header flanges on my 78 warped over time and the exact same thing happened on the BBK shorty's on my 94 Mustang GT. In both cases, I bought 2 sets of gaskets and used High Temp ATV sealant to seal them together for each side...all exhaust leaks were eliminated and never came back. If the header flange distorts even a little bit, the cheap crap thin header gaskets which almost all are will not seal properly.

I doubled up on the gaskets for these 1 3/4 inch beauties when I put them on in November as well.

As for header bolts, I have found that any high quality grade 8 bolt after a few tightening cycles will not loosen up....

swag

ok, not taking the exhaust off will make the job a lot easier to do.

I'll get me some of that sealant. The gaskets I got are supposed to be thick and they claim that you won't have anymore leaks after they are on.

I was talking about the bolts that go into the exhaust manifold to the engine. Sounds like it is common practice to use metric when one of the bolts get stuck and break.

Thank you

Gale Banks 80'

It would be a lot of work to put Metric Bolts in a Cylinder Head that came with SAE Bolts. The only way I could see that happening is if the Threads in the Heads were striped out and somebody re taped them in Metric. Most Header Gaskets come with the end Bolt Holes open. Remove the Bolts in the middle. This way You can leave the end Bolts loose and just drop the Gasket in from the top, and you don't have to line anything back up.

swag

Hi, I finally have a nice day to work on my car. So, I replaced the gasket on one side of the car. About to start the other side.

The mystery on the bolts being metric is solved. So, the heads were metric but the threads were american. Odd combo!

I suspect they got the bolts from the aftermarket exhaust manifold.

So, my question? The original specs for tightening the bolts were 20ft/lbs. Since this is an aftermarket exhaust manifold should this be different?

Thank you.

Going back out there to install the other side but keep my phone nearby.

swag

I ended up just replacing the passenger side gasket. There were a couple stuck bolts on the drivers side and I never heard any noise there.

So, I fired up the engine and all the clacking sound is gone. Yeah!

Here's a video of it after:

https://www.dropbox.com/s/x20zrtyfcp...15714.mp4?dl=0

It sounds nice to me but if you all can hear any other issues, please let me know.

Thank you all!

midigike

[QUOTE=swag;1594021691]I ended up just replacing the passenger side gasket. There were a couple stuck bolts on the drivers side and I never heard any noise there.

So, I fired up the engine and all the clacking sound is gone. Yeah!

Here's a video of it after:

https://www.dropbox.com/s/x20zrtyfcp...15714.mp4?dl=0

It sounds nice to me but if you all can hear any other issues, please let me know.

Great Job! Time for a cruise! The only thing I see is the spark plugs should be pulled away from the headers so you don't run into a ignition problems. They sell protective socks that slip over the wires

theandies

If you keep having header gasket leaks don't mess around with crappy gaskets and get some of these:



Earls, they also make collector gaskets.