exhaust popping

[jdl71]

What are the most likely causes of this?

http://www.youtube.com/watch?v=-ACbqf2uHK4

This is a 230 with a rochester b, and now has hei. Was doing it with the points distributor also. Timing is set around 8*, firing order has been checked several times. Stuck or sticking valves? Seems to smooth out under load, but has a fair amount of popping on decel.

[TopFuel1966]

Probably sticking or burnt exhaust valves. Set each cylinder on TDC and connect a compressed air supply. If you hear an air leak at the end of the tail pipe you have found your problem. It could also be a problem like a vacuum leak in the emissions system, if you have one.

[jdl71]

No emissions but could a vacuum leak at the manifold to head surface cause this?

[Kenfuzed]

The video (audio) shows the truck at idle which would be different than decel pop. Often decel pop or crackle is related to an exhaust leak drawing in cooler air during deceleration and that cooler air collides with the hot exhaust at the port. If it is indeed decel pop then my first action would be to seal up any leaks at the manifold to head and collector with some reliable gaskets. The video kept starting and stopping for me so hard to tell if there is a miss.

[WOLFMANmike]

im going with Vacuum leak thats what ide check first

[jdl71]

Originally Posted by Kenfuzed

The video (audio) shows the truck at idle which would be different than decel pop. Often decel pop or crackle is related to an exhaust leak drawing in cooler air during deceleration and that cooler air collides with the hot exhaust at the port. If it is indeed decel pop then my first action would be to seal up any leaks at the manifold to head and collector with some reliable gaskets. The video kept starting and stopping for me so hard to tell if there is a miss.

It is doing both. I've had trouble sealing the manifold before, but I didn't have that popping at idle so I wasn't sure if I should look at that as a cause. I have ordered another remflex gasket and will see if that improves things. Thanks for all the advice.

[TJ's Chevy]

Under load it goes away? That is valve and or fuel related in my experience. No plug wires crossed? Valves set at 0 plus .5 turn?

[jdl71]

Yes under load it seems to go away. No plug wires crossed. I have not pulled the valve cover yet, but I have not fiddled with the valves and it used to not do this. Pretty sure I'm having intake/exhaust gasket issues (again). Ordered another, but I may rethink spending much more time on it, since last night I found this:

http://columbiamo.craigslist.org/pts/5742032231.html

[TJ's Chevy]

That's not a bad deal, even if that motor wasn't rebuilt. I'd look for a 292 though. lol

[jdl71]

Yeah I know but I thought just that header was a couple hundred bucks. Seemed like it was well worth it. I sent him a text last night and he said he thought it was sold.

[TJ's Chevy]

Originally Posted by jdl71

Yeah I know but I thought just that header was a couple hundred bucks. Seemed like it was well worth it. I sent him a text last night and he said he thought it was sold.

Just re-read It....well worth the money if all that has been done. haha How does he Think it was sold? Must not be the actual owner?

[jdl71]

I guess someone said they'd take it but hasn't actually produced the cash yet. He said he'd keep my number in case they backed out.

[Kenfuzed]

Looking closely at that ad I don't think it is the actual manifold that is a Clifford, but rather the adapter they have on there to fit the Holley onto the stock single barrel manifold. Not sure if the headers add that much value considering the engine is still only a 230 and not a 292. Even a newer model 250 would be better.

Personally I would seal up any exhaust leak for now and save my pennies for a small block 350. There's simply no replacement for displacement

[TJ's Chevy]

Originally Posted by Kenfuzed

Personally I would seal up any exhaust leak for now and save my pennies for a small block 350. There's simply no replacement for displacement

ANYTHING is better than a dang 350! If your gonna go for displacement then it is time for a 454 or Bigger. But 350? That's a little old.

[Kenfuzed]

Originally Posted by TJ's Chevy

ANYTHING is better than a dang 350! If your gonna go for displacement then it is time for a 454 or Bigger. But 350? That's a little old.

That's a little old??? We're talking about a truck that's 50 years old right? Then again so am I

Suggestion for a 350 was because the OP has a straight 6 and a 350 is an easy upgrade, plus can be done inexpensively for some modest power (mine is 330hp while still street friendly). A properly built 6 can be a great ride as well if done right. Perhaps I'm biased since my current truck started out with a worn 6 and I dropped in the 350. Over the years I've installed probably a hundred of these so I guess I've become an "old" creature of habit. Big is certainly one way to go but I didn't think he was looking for that. JMHO

[jdl71]

Originally Posted by Kenfuzed

That's a little old??? We're talking about a truck that's 50 years old right? Then again so am I

Suggestion for a 350 was because the OP has a straight 6 and a 350 is an easy upgrade, plus can be done inexpensively for some modest power (mine is 330hp while still street friendly). A properly built 6 can be a great ride as well if done right. Perhaps I'm biased since my current truck started out with a worn 6 and I dropped in the 350. Over the years I've installed probably a hundred of these so I guess I've become an "old" creature of habit. Big is certainly one way to go but I didn't think he was looking for that. JMHO

I've done the 350 swap in past trucks. And trust me I've considered it more than once while trying to sort out some of these issues. Nothing wrong with it, just seems like the easy thing to do and what everyone else does. No offense meant, just my opinion and personal preference.

And BTW, in your case I would have done the exact same thing. I don't think a straight 6 has any business in front of a automatic.

[TJ's Chevy]

Originally Posted by Kenfuzed

That's a little old??? We're talking about a truck that's 50 years old right? Then again so am I

Suggestion for a 350 was because the OP has a straight 6 and a 350 is an easy upgrade, plus can be done inexpensively for some modest power (mine is 330hp while still street friendly). A properly built 6 can be a great ride as well if done right. Perhaps I'm biased since my current truck started out with a worn 6 and I dropped in the 350. Over the years I've installed probably a hundred of these so I guess I've become an "old" creature of habit. Big is certainly one way to go but I didn't think he was looking for that. JMHO

My 77 C20 had a 454, replaced it with a 496; and recently a 572. I got my 66 with a tired 292(95 psi and tired cam), put a 4 barrel and headers on it and with flowmasters it would sing to 5000 and sound stinkin awesome. Replace it with a hopped up 292 that will sing 5000 without making me sweat. haha My GMC has a 305 V6 that was a pain in the butt to pull and put back in, kept it cause that motor has tons of torque and pulled a load of wood better than a 350(74 2 barrel 350...gutless pos and I thought my 305 v6 was slow!) could and get the same mileage. Maybe I am the biased one, but that dang sbc is boring as heck....at shows I don't even bother to look at the engines half the time cause they're all the same !

[jdl71]

The Langdon header is what I was referring to, they are $277 new. That's half of what he's asking for the whole thing. I have a 350 on an engine stand, went that route before with other trucks, want to keep a 6 this time.

[Kenfuzed]

Ah I see. Is your current engine also a 230, or a 250 or 292? I didn't realize those header were so pricey, I sold a 250 a few months back with headers that looked just like those pictured and let the engine go for 3 bills since it was missing the pump bracket... D'OH!

[jdl71]

Originally Posted by Kenfuzed

Ah I see. Is your current engine also a 230, or a 250 or 292? I didn't realize those header were so pricey, I sold a 250 a few months back with headers that looked just like those pictured and let the engine go for 3 bills since it was missing the pump bracket... D'OH!

It's a 230. I'm assuming mine probably has never had hardened valve seats put in either, so those two things alone are about worth what he was asking. Add to that a rebuild and cam upgrade fairly recently and it looked like a pretty sweet deal.

[jdl71]

Getting back on track here, I spent some more time driving and fooling with it and the popping really does not go away under load, it just seems to be less noticeable at higher rpms but it is still there. I ran all the cylinders to TDC and adjusted the valves one at a time, zero lash + .5 turn, made no difference. I then went to my way of adjusting valves, with engine running back off until they clatter then tighten till quiet, + .5 turn, popping still there. One thing I did notice is I'm running R44 plugs. There is a reason I did that but can't recall what it was right off hand. Wondering if a cooler plug like that would cause any of this? I guess my next step will be another compression check and pressurizing each cylinder as mentioned in a previous post.

[TJ's Chevy]

Originally Posted by jdl71

Getting back on track here, I spent some more time driving and fooling with it and the popping really does not go away under load, it just seems to be less noticeable at higher rpms but it is still there. I ran all the cylinders to TDC and adjusted the valves one at a time, zero lash + .5 turn, made no difference. I then went to my way of adjusting valves, with engine running back off until they clatter then tighten till quiet, + .5 turn, popping still there. One thing I did notice is I'm running R44 plugs. There is a reason I did that but can't recall what it was right off hand. Wondering if a cooler plug like that would cause any of this? I guess my next step will be another compression check and pressurizing each cylinder as mentioned in a previous post.

On the plugs...is the gap to wide? Any of them look fouled or discolored in an abnormal way?

[jdl71]

They are all gapped at .035. They are a medium brownish color, they have very few miles on them. I also shut the doors, turned the lights off and ran the engine, did not see any arcing anywhere. I've pulled plug wires off one at a time while the engine was running and each time I could tell a definite difference so I believe they are all firing.

[TJ's Chevy]

Good to know, that means you can almost put ignition out of the picture. All wires are in proper order...plugs are firing and in the correct gap range. Valves are adjusted, but have not been tested for leakage? I would assume the valves are ok as it is not back firing through the carb...the only thing it is doing is popping out the exhaust. Does it spit and sputter when you stomp on the throttle? If so you can count on valves not seating or being to tight or a vacuum leak of some kind. I have an exhaust leak on my GMC's 305 V6 at the gasket between the flange and exhaust pipe. Still smooth as silk out the exhaust except you can here poofing under acceleration. I doubt an exhaust leak would cause that major amount of popping. If a cam has gone flat it can cause popping as well. My 292's cam went flat from what I could tell and it popped at idle and when you reved it. Before you do a compression check...fire the motor and let it get hot...then pull the dipstick. If a ton and a half of smoke and air comes out then you know you have problems with the rings. That's the way I've done it.

[jdl71]

It does not spit and sputter if you mean like it's going to lay down, it revs up fairly smoothly. There is still popping. Does not backfire through the carb. It does pop at idle, I can hear it while under load, and when decel it's considerable. I did a compression check on it last year and it seemed ok, but I did not try pressurizing the cylinders. Earlier this morning when I was fiddling with the valves I closed it up and ran into town, and I apparently left one too loose, so I ran through them again with the engine running until I found the one causing the clatter. After that it seems like the popping is worse, but I don't know I may just be imagining it also. I could tell that I was gaining and losing rpm while adjusting them though.