Question about rattling valves and timing

[shadowfax101]

It only does it under a heavly load, well when I go real heavy on the pedal. I went to a higher grade gas, not much help. I checked the timing. I found that it was on what looked like 7..I moved it back to about 4 and it got a lot better.
What it does is when I set the timing back and I go for the test drive...I floor it and no noise, I floor it again, no noise. about the third or 4th flooring the noise starts back. I now have the timing set to about the 3 mark. I have not driven at this setting, but I tried 5, 2, and the 0 setting. I know the timing chain is good because the marker line is very steady.

I guess my question is why would it not make the noise at first and then start to make it again?

[Franklinstein]

V-8 or V-6?

[shadowfax101]

360 V-8

[Franklinstein]

Sounds like my straight six was doing...the cam was loose. would run fine and act just like yours is at first....thats because the cam seals had swelled while the engine was off but after warming up, the seals would be lubed up and the cam would rattle...didnt help much that my valves were gettin worn out either. just a thought but ya might want to check out your valve lash...thats how i found out about my problem.

[shadowfax101]

that is something I have not thought about. How would I check to see if the cam is loose

[OJTDJPR]

When is the last time you checked your timming chain. A worn chain will do that. You can set your timming and everytime you jump on the pedal, it will strech the chain alittle more and through you off time again. Just a thought.

[Franklinstein]

Well what i did was go to the base auto hobby shop and removed the valve cover. There is a specific proceedure for checking valve lash and one of the mechanics at the auto hobby shop suggested turning the engine by hand to see if the valves rattled or shook. Now dont get me wrong , it could just have easily have been bad valve guides but after playing around with it, we decided to pull the cam, soon as we opened her up, we could see the the seals were screwed up and that the cam was just "jiggling" as it spun.

[shadowfax101]

Well I was told that if the marker line is steady the chain is good, but could it be steady at idle and still need to be replacing..

[Franklinstein]

I would say yes only because at differnt speeds the chain is traveling at different torque and could, logically, be stretching. I have heard of stretched timing chains before and think you might be better off tackling that first before you go tearing up your cam.

[OJTDJPR]

You will have to pull the front cover off for the cam or timming chain. So either way you have to be in there.
Yes a timming mark will stay steady with the light on it. It mostly will move when you hit the gas and let off. That is when the crank has slowed faster than the cam, like a back lash type thing. If you have never changed the timming set, I would say it might be do for it.
But still as said before dont over look cam and lifters being worn.

[tito]

Wonder why it doesn't make noise the 1st or 2nd time you throw the pedal down? Seems a stretched timing chain would happen every time.

Have you checked your PCV and EGR valves? They maybe clogging and the more times the pedal is romped the more carbon is blowing to clog them.

Just throwing out the cheap/easy ideas before timing covers start popping off.

[netbear]

Each time you floor it, the engine heats up
more and make the engine more prone to
pinging. You might try one heat range
colder plugs or change your thermostat to
a 180 if you have a 195 or to a 195 if you
have a 205.

If all else fails, just put mud tires on
your rig and you won't be able to hear the
pinging anymore.

[letank]

may be your vaccum advance is stuck as the engine warms up...... make sure it goes back to specs......

Michel

[tito]

Did you set the timing with the timing vac advance off and plugged?

[Aaron]

Netbear is exactly right. The first couple times you are flooring it, the combustion chamber is cooler. As you do it more, it gets hotter and is more prone to ping.
Did anyone suggest looking at the EGR valve?

[shadowfax101]

Yes, the advance was unpluged and I pluged it.
I am going to check the EGR valve today..