popping exhaust

[wally05]

My 68 with 302 runs strong, but seems to pop loud whenever I let off the gas fast. Which stinks b/c switching gears is annoying, haha. I'm thinking it's a timing issue as all cylinders seem to be doing okay and everything else looks good. I'm going to pull the plugs, check them and do some other checks, but then I was going to do a full timing adjustment and such. What do you think? I'll try to get some vid of it up on here soon.

 

[franklinair]

Definitely check the timing & carb adjustments. I believe your car has dual exhaust. Does it have the "H" pipe coming off the L & R exhaust manifolds? Very important to keep the exhaust pressures balanced & equal.
Neil

 

[wally05]

Yeah, it's an aftermarket H-pipe and such. I'm going to check the headers and such for leaks, but it looks pretty tight. Everything is pointing towards a timing adjustment. If that doesn't work, where should I look next?

 

[joedls]

I had this happen when a couple of sparkplugs weren't seated correctly. Two cylinders were running very lean from sucking in air.

 

[wally05]

Yeah, I could see that as being a problem. I always make it a point to do a plug check and probably replace when I get a car. This will be Thanksgiving break's project. It could be pretty much anything ignition also, correct? That's just the gist I get from my troubleshooting guides.

 

[BroadwayBlue]

We felt this was a timing and possibly carb adjustment as well. Was on the to-do list just didn't get around to it yet.
It improves some as the car warms up.
As Korey said everything else seemed to be OK which led us to look to a timing adjustment as well.

 

[rvrtrash]

Do you have a vacumn gauge? That will give you a lot of info as far as timing, leaky valves and such.

Steve

 

[Mosesatm]

If you have a dual port vacuum advance make sure the correct hose is connected to the correct port. The hose connected to the front port should have little or no vacuum at idle but should increase as RPMs increase.

 

[wally05]

Thanks for all the help, guys. I'm hoping to look at it a little tomorrow and get a better idea. I'm loving this car, I'm just trying to dial it in for a little more driving before the snow.

 

[robert campbell]

Is it running a stock carb?? Vacuum check as mentioned earlier is a great start. I have had a couple of those stock 302 4-barrel carbs apart and they are weird dudes. I rebuild many types of carbs for people and I even had one of these on my car when I first got it. Has a huge Styrofoam coated float that over the years can sink slowly and raise your float level. This will “enrichen” the high-speed circuit in the carb.

Whether you have a stock carb or not, do you feel it is running a bit rich or fat?? Excessive unburned gas in the exhaust can cause this pop. Signs of this is the car runs great when cold and worsens noticeably when hot. If you ran it through the gears stone cold, does it pop? Really bad gas mileage? All plugs a bit on the dark side?? Hard to tell on a car that gets short drives all the time.

Follow on to Steve and the vacuum gauge is a quick compression check to eliminate a burned exhaust valve.

The other culprit is an exhaust leak between the manifold or header at the engine. You were already on that

Rob

 

[PNewitt]

No doubt, it's one of those pesky "Idaho TEST Potatos" wedged in the left tailpipe.

A California Potato won't make problems, it's just something about those 'daho spuds!!