engine noise

I have just rebuilt my 350 and whenever I am accellerating i get this clatering noise coming from the engine. It only does it when I put a load on the engine, so while cruising there is nothing there but the minute i try to step on the gas ir comes bach for the duration of the time I am on the gas pedal.

I must say that I have blocked the EGR valve port and completely disables the AIR system.

Therev is no noise while the car is at idle or even while sitting and it is accellerated(under no load)

any Ideas,

Thanks:laugh:

 

Sounds exactly like what was happening to me. How is your carb? You might also want to check your timing and distributor. I had my carb rebuilt and my distributor switched to a hei unit the chattering is gone away. More than likely it is your distributor.
Ivan

 

is it like a pinging when the timing is advanced too far??

 

If your motor is the high compression variety make sure you're running high octane gas.

 

It sounds to me like the engine is pinging from what you are describing. You said you just rebuilt the engine. How different is it now from what you had before? Did you change the compression or cam or intake or any thing? My first bet is you have a dis. problem. Are you using a Pertronix module? Do you have HEI? A little more information here and I think that we can figure out this problem. You may just try to disconnect the vacume advance and see if the problem goes away. I know the engine won't run the same but it may just give you a half way point to figuring out the problem.

 

thanks for your input

my car was rebuilt to strock specs with the exception that the pistons are bored .040 over. My distributor is stock with points but the pertronix is in the mail, I will be installing it this week anb see what happens.

I dont know what I would do without you guys

 

My first bet here is the timing. What is it set at right now? what is the base timing and do you know what the total timing is? Also just curious, what carb. are you using?

 

timing

my timing is set at 4 degrees BTC. stock setting

 

thanks

thanks Larry, I will replace the egr valve and use a vacuum gage to set my timing, by the way, can anyone tell me how to do this procedure? the one about using a vacuum gage!!!!

:laugh:

 

Chief a lot of us have been thinking about different pinging problems lately. You may have a bad EGR valve like Larry says, but I would try one more thing before spending any money on this problem. Change your timing to 10* initial. Disconnect the vacume advance and plug the hose. Drive the car down the road and see if you still have pinging. Did the pinging get worse or clear up some. Does the engine run better at idle. If you change the timing and the idle goes above 850 rpm, set the idle back down to 750 or 800. This whole test will only take you 10 min. to set up once the engine is warm. It must be at operating temp. What grade of gas are you using? This can also paly a role with this problem during the winter. If you follow these steps it will only cost you a $1 and a few minuts of your time. Honostly you don't know what is wrong and throwing money at it blindly won't get the problem fixed and just piss you off that you spent more money on it. Do the simple things first. I took the EGR and Air pump off my 72 350 and never had a problem. Most EGR valves don't work to begin with and fail shortly after they are put on. Try this first.

 

Larry I'm not saying your wrong with what you said about the EGR valve. I'm asking you a question here. EGR stands for Exhaust Gas Recirculation. That means it is taking exhaust gases and adding them back into the intake charge. Isn't that raising the tempreture of the intake charge? I was told that the EGR raised the temp of the intake charge to reduce the amount of Hydrocarbons produced by Higher compression engines with colder intake temps. That is why the compression is lowered with the EGR valve to reduce the chance of pre detination that could occure with higher intake charge temps. created by the added tempreture rise from the exhaust gases.

 

egr

interengly enough, the shop manual says that the egr will lower operating temperatures i believe by pre-heating the fuel-air mix.

I think thats what i read

 

What I'd like to know is what kind of carbeurator you're using and what kind of ignition. Fuel quality contributes to ping, but so does quantity. A lean running engine will definately have engine ping at full throttle.

First of all, I think you should read the spark plugs.

Pull the plugs. If they have a slight tan color they're OK. If they're really white, they tellling you you're running lean (which can cause pinging) and you need to fatten your secondaries, which can help get rid of the ping by fattening the mix and quenching pre-ignition. If the plugs have a slight dry black coating on them, you're already running rich, in which case i'd definately bet it's a timing thing.

Here's what I'd do next, although this is a little more time consuming.

Put cheap cas in the car. 87 octane will do.

Check your timing where it's at now, and drive the car around noting when you hear the ping at full-throttle.

Take the car back to the driveway and put a timing light on it. Retard the timing 2 degrees. Give it another full throttle pass listening for the ping.

Keep retarding the timing in 2 degree increments until the ping stops OR you start to notice a definate lack of power.

Turn the timing up a degree.

Fill it up with premium gas next time.

Invest in a good ignition an HEI distributor. They'll help. My pinging all but disappeared when I switched from a points ignition to an HEI and an MSD 6AL ignition.

 

Phil what you recomend requires him spending more money right now. What I recomended doesn't cost him any thing out of pocket. He said he is already at 4* initial timing. That timing setting is to low as it is for todays fuels. If he already runs premium gas and has a problem with pinging then putting 87 octain gas will only aggravate the problem. Turning the timing down any more than it already is will probably make his car not want to run at all. I agree it could be the carb is too lean but to make any changes to it will require more money out of pocket now. If the carb is fine that will be money wasted.

 

adjustments

well i used a vacuum gage to set the timing at the highest vacuum I could achieved and it seems to be working. The pinging got reduced by about 70%, I am now shooting for the EGR valve, I will put it back on and give that a try,

Thanks

you guys REALLY KNOW YOUR S$%^!!!!!

 

:Smarty:
EGR is meant to reduce COMBUSTION temps. Yes it will raise your intake air charge temp somewhat, but what it really does is take the place of combustible mixture in the cylinder. Less fuel/air in the chamber means lower combustion temp (less BANG - all else being equal). Lower combustion temps control the creation of Oxides of Nitrogen (NOx), funky molecules which can only form at extremely high temperatures and pressures.

I don't think that disabling the EGR on a carbureted engine should upset the air/fuel ratio too much because both the fuel and air that is supplied come from the carb, and it has no idea what is happening downstream. On an electronically fuel injected system it really makes a difference though, because the computer wrongly assumes that some of the air available for combustion is being replaced by the inert (non-combustible) exhaust gas, and reduces the fuel to account for this, resulting in VERY lean conditions (this would be bad).

We now return you to your regularly scheduled programming.........

 

Chief what did your timing end up at? Did you increase it or decrease it? If you increased the timing and the ping started going away you have a rich problem. Too much gas and not enough spark soon enough.

 

You could try retarding the base timing 2 degrees, that should fix it. I belive thats what the service manual recommends. Premuim fuel would also help.

I have seen many cars that would ping with a non-functioning EGR valve. I worked at an Olds dealer in the late 80's and we would get all kinds of 3.8's, 260 Olds and 307 Oldsmobiles that would ping like crazy beacuse the EGR passages were plugged with carbon. Cleaning it out almost always corrected it as long as the car was properly tuned and carb and ingnition were in good shape. Alot of these were triple C (early computer carbs) so that may have made a difference.

From what I understand it's the lack of cooling not the change in the mixture that causes it.

 

timing

well the timing is set higher now I couldn't tell ya what it is at because i just used the gage, bur I will check it later and algo do the egr, I am running 94 octane fuel and I pulled my plugs three days ago and they are clean, not yellowish(lean), nor black(rich)