New exhaust-now pinging

[dr.flash]

I had a local shop install a flowmaster 40 on my 78. 2-1/4' pipe from the header back and out the left side behind the rear wheel. Now going up hills at highway speed I get pinging. Any suggestions??

 

[american psycho]

my 40 pings when the temperature gets hot - is the muffler/pipe restricting flow and raising your engine temps?

 

[dr.flash]

Temp is right where it's always been, but I did replace the t-stat last week so maybe that has something to do with it.

 

[Colorado Boy-74-FJ40]

Not enough back pressure and in need of a valve adjustment ....maybe?

 

[RockDoc]

If your exhaust has been modded to significantly improve the engine's breathing, it might be worth while to have your carb re-tuned. Although I don't know how significant the influence of the exhaust would be in the intake with the low overlap of the stock cam.....

 

[grant5127]

The ping was there before the new install you just didn't hear it because the old exhaust was well insulated with caked on mud & rust on the outside and soot on the inner.... plus the old tubing is probably thicker than now day cheap s***...... Run through the tune procedures and if that doesn't cure it go to the next colder plug.........

 

[Pin_Head]

Another possibility is that it is an exhaust leak and not a ping. An exhaust leak also gets louder with engine load. An exhaust leak changes frequency directly with engine RPM and pinging is not necessarily the same as enging speed. you need to have an ear for the difference.

 

[Rice]

Before swapping plugs push the timing back a touch.

 

[bsmith123]

lean

When you switch to a header you also lean out the mixture a bit so making it prone to pre-ignition.

x 2 on checking timing first

also could be wrong plugs or carbon deposits which heat up glowing red and ignite the fuel before the spark does


That is what pinging is --ignition before the spark or just spark too early in the process

also make sure you are not lugging the engine in too low a gear uphill

 

[dr.flash]

Another possibility is that it is an exhaust leak and not a ping. An exhaust leak also gets louder with engine load. An exhaust leak changes frequency directly with engine RPM and pinging is not necessarily the same as enging speed. you need to have an ear for the difference.

I'm pretty confident that it's a ping.