[JLMounce]

I've been tuning on the 455 in my 1969 Firebird today and one thing I've noticed is that after WOT runs the engine makes sort of a washing machine type noise during low rpm cruise.

kind of an rpm dependent wooshing sound.

The only thing I know about the valvetrain in this engine is that is has that stampled Comp Magnum roller rocker. Other than that I don't know what cam it has in it or what or type of lifters.

I did note that at idle around 700 rpm (in park) the engine only wants to make about 10" Hg. This was taken from the manifold vacuum port on the carb.

I'm not sure if this is something I should be concerned about, or if the engine has a noisy valvetrain.

Any thoughts?

[shaker455]

Post a good Youtube vid & lets see.

[JLMounce]

Originally Posted by shaker455

Post a good Youtube vid & lets see.

I'm going to take the car out this evening for a cruise. I'll see if I can strap the gopro under the hood for a short bit and capture the sound.

It's not a tick like valves hitting the seats, it's more of a soft chugging/whooshing.

After doing a little bit of research the fact that my vacuum needle rapidly vibrates at or near it's vacuum level does sound like I may have some valve guide issues. I wonder if that might be part of the sound here.

Or maybe I'm just paranoid...

[Lee]

Are you running a roller cam with the stock valley pan?

[JLMounce]

Originally Posted by Lee

Are you running a roller cam with the stock valley pan?

I couldn't tell you. The previous owner had this engine built and all I can surmise is what I can see with my own eyes. I haven't had the valley pan off so I don't know if it's running flat or roller lifters, hydraulic, solid etc.

I do believe that it is using a factory valley pan however.

I do vaguely remember hearing the original owner say something about a roller valvetrain. I was 16 at the time and wasn't paying nearly as much attention as I should have been.

[steve25]

Untill you at least pull a valve cover a and look at what you have every thing is a guess!
With one of the covers pulled you can also look down into the lifter valley at some points and see if you have roller lifters or not .
I would not fire the motor up again untill I did this check plus pull t he oil filter and cut it open to look for bad stuff!

[shaker455]

Sounds like what the other guys said.

Possibly roller lifters contacting a EGR style valley pan.

If you can get your hands on a automotive camera you can stick it down in the lifter valley to see what you got.

Start paying attention Jason...lol

[JLMounce]

I'll do that this week. I've had the valve covers off so I do know it has the comp roller rockers. I wasn't aware there were sight lines down to the lifter galley. I'll get my snake camera out and see what I can find there.

The car had a very recent oil change and there was no debris on the magnet nor on the filter element. I'll do another oil change and check again.

[JLMounce]

Here is a quick clip from a drive last night. I tried to isolate a good section where you can kind of hear what I've been talking about.

https://youtu.be/2gHj-5diUsk

[ponjohn]

It sounds like:

Vacuum leak
Exhaust leak
or a miss

[shaker455]

Originally Posted by JLMounce

I'll do that this week. I've had the valve covers off so I do know it has the comp roller rockers. I wasn't aware there were sight lines down to the lifter galley. I'll get my snake camera out and see what I can find there.

The car had a very recent oil change and there was no debris on the magnet nor on the filter element. I'll do another oil change and check again.

Okay, what did you put in for oil? did you add a zinc additive?

[JLMounce]

Okay here are some photos of the valvetrain and I got a couple down in it's belly from my snake cam.

Clearly it's a flat tappet cam/lifter. I couldn't get the snake positioned well enough to make out clearly what brand lifter is being used. Everything that I can see looks to be in fairly decent condition. The engine should only have a couple thousand miles on it.













All the rockers on the passenger bank are tight without any slop in them.

The engine has a fresh fill of Mobile 1 10w30 with ZDDP additive and a Wix filter. Probably about 20 miles on the engine since oil change.

Exhaust leak and vacuum leak did cross my mind. Considering the low vacuum reading I was getting with the vacuum gauge, that may be something to look at.

The carb has the transmission vacuum line hooked up to manifold vacuum, the PCV line from the valley pan to front of the carb and a vacuum line from the rear of the carb to the power booster. Distributor is a mechanical advance only so ported vacuum has a plug.

I'm wondering if it wouldn't make sense to grab some new intake gaskets and reinstall the intake.

[grivera]

I don't see a link bar in pic so lifters appearto be hft. Rockers are CC roller tip. What heads and intake? Some years head/intake combination? Depending on year and improper install may be a source of a leak. Has it made the sound since you acquired it?

[JLMounce]

Originally Posted by grivera

I don't see a link bar in pic so lifters appearto be hft. Rockers are CC roller tip. What heads and intake? Some years head/intake combination? Depending on year and improper install may be a source of a leak. Has it made the sound since you acquired it?

It's a XJ coded 455 block with #62's. Intake is an edelbrock P4B square bore version.

Since I got it on the road this year is always made this sound. When I purchased the car back in 1999 it had an offy dual quad manifold on it. The P4B was put in place about a week after I brought the car home.

It's probably prudent to reinstall the intake to rule that out. I've also discovered a fuel delivery issue at cruising speed so I think the mechanical pump is bad.

[gtofreek]

What's up with the pushrod? That's not an adjustable pushrod is it? Those are only for checking pushrod length, not for running.

From what I can hear, it sounds like something related to engine rpm. Like flexplate rubbing on a plastic flexplate cover, maybe. I know some GM cars came with plastic covers, and if they weren't put into place exactly right, they would rub the flexplate.

[JLMounce]

It could be a shadow. Hard to tell though. The previous owner cut quite a few corners on this car. I've been fixing those cut corners now for 16 years.

Sadly part of that cut corner us the current lack if a flex plate cover. I do need to get one of those on order.

[steve25]

The motor may have been built with Rhodes lifters.

[Half-Inch Stud]

Windage tray scraping a rod big end?

Or worse yet said clearances closing up because the engine oil pan is resting on the subframe.

Hey it happened to me in my 455- laden Firebird . once HIS

[pugslyx234]

Too me it sounds like valves are too tight !
Giving it that miss or make sure sure firing order is in order. Ah low vacuum?

[Firebob]

That vac line runs down to the modulator on the trans. They are exposed to a lot of wear. You might want to check that end as well.