I have a 350 with edelbrock 1000cfm EFI, comp cams 280h cam (230* at .05 lift) trick flow heads, and various other goddies the problem is that when the engin is cold the exauast sounds like a popcorn poper at partal throttel once it warms up it runs fine but it's annoying letting it warm up for 15 min to take a 2mi ride across the airbase. anybody know why it dose this and a fix for it???

 

anybody?

 

Popping noises out the exhaust sounds like you're floating valves. I assume you had your valve springs matched to your cam and rockers, right? When it does this, is there a miss at high RPM? Could be weak springs...
Is it doing this when the ECM is in Open loop and goes away at Closed loop? Could be a timing problem in the closed loop program. How much timing do you have dialed in at open loop?
Keep us posted and good luck.

 

It dose it when I first start the engine and it lasts for about 10 min. if I floor it it dosen't do it only when I try to keep the same speed (25mph on base-about 2000RPM) once It warms up it stops- but not warm enough for it to go into closed loop. Could it be the lifters or the rocker arms? I have crane variable duration lifters and summit roller rockers. the valve springs are the ones that came with the heads wich are the higest seat pressur ones that were avalible and there brand new so I don't think I'm floting the valves(I don't have my summit catalouge handy-I'm at work) I was also wondering could this be related to my header gaskets blowing out alot recently? Thanks for your help.

 

When I had a burnt plug wire and when the car was cold if I gave it too much gas I would get a backfire thru the carb.

 

no it's not that because it's doing small backfires out the exaust but thanks anyway

 

Thanks for the great typo!!!!! I've heard of shoving a potato in the tailpipe, but poping? That would hurt if you lost your balance!!!!!! LMFAO!!!!!

I know you didn't mean it, but it was a very needed laugh!!

Kinda reminds me of that dog that Conan O'Brien has on his show.

"That's a nice exhaust you have...... FOR ME TO POOP ON!!!!"

Thank you,

AJ

 

Is it coming from the back of the car, or up by the collectors? You could try moving the timing up or back by say 3* to 9* to see if that has an effect. If that helps it would be a good indication that the timing maps are off at that load RPM. I wouldn’t drive with the timing advance or retarded by that much for long as it may cause other problems.

 

It's comming from the headers. I already tryed to play with the timing and fuel curves alerady and it had little effect. I also just blew out another header gasket last night I was also wondering if it could be exaust restriction - I have 1 5/8" primaries that go into a 3" collecter that y into a 2 3/4" intermeadiate pipe and ends in a flomaster muffler-, that is going to be changed to true duals (2 3/4") with no cats when I get my taxes back.

 

just returning this to the top:hail:

 

Other then header ping I’m out of ideas. Header ping is usually not that loud though.

 

change your distributor cap, mine did the exact same thing.

 

GM High Tech Performance had to change there springs to Comp ones for the same reasons, on their 396 Lt1. It this is the case, than you may have toasted your pushrods as well. Check them against a straight edge, if you need to change your springs.

 

I just stoped the problem the #7 spark plug had backed out and I thought it was a header leak I found it when it still ticked after the gasket change- the poping stoped (still don't understand how) but I have a new problem that I am about ta start a new thred about.