After fire poping out headers

[fallguy72]

Any ideas  why my 445 would be popping out the headers?
It's running great other wise.
Timing is set at 34° total right now
750 double pumper is running  a little bigger jets than it came with 73 front 85 back
I opened the little screw at the bottom  for the secondaries a bit more
Vacuum advance has been eliminated on the ready to run distributor
It's running  awesome  starts and idles great just pops a bit when I let off.
Link of my car below
https://youtu.be/gYAUqyNlNpI

[jmlay]

Valve hung open, bent  or needs adjustment. Exhaust leak. Lean mixture.

[sixty9cobra]

I agree on the exhaust leak. Especially with headers on decel.

[Falcon67]

I agree on the exhaust leak. Especially with headers on decel.

X2 -gaskets, header leak.  I just got done replacing the fancy carbon Percy's header gaskets on the Mustang, they leaked like crazy.  Put chunky thick Mr. Gasket ultra Seals (sandwich type) in there, car sounds 100% better and no pops, better ET too LOL.

[fallguy72]

thanks for the reply guys but i just put new Edelbrock heads on and i am sure Remflex gaskets are  sealing. i am running less timing and no vacuum advance because i was planning on a little shot of nitrous. i think it might be rich or lean but i will do more tuning this weekend. What about drilling the carb butterflys? not sure about much right now or if its even something i should worry about.

[cammerfe]

Anywhere that air can be drawn into an exhaust system will cause it to ' lean-pop' on decel.

KS

[Falcon67]

I have yet to find a need to drill any butterflys.  The motor in the dragster is a 393, 11.8:1, decent size solid roller cam, carb is ProForm center with QF blocks and base jetted 74/88, flows about 840.  Just standard idle settings, might have to go up or down two on the back jets - that depends on MPH on the time slip when I get some real test time.  Idle screws (4 corner) had to come out another 1/4 turn from a base 1/8 turn out on a car setting.  Lead is locked at 30 for now.  Should all be ball park.

I thought the super carbon face stainless gaskets were sealing also, until I got the car up on our lift and could see all the soot blowing out the bottom of the ports.

[ericwevans]

I agree on the exhaust leak. Especially with headers on decel.

X2 -gaskets, header leak.  I just got done replacing the fancy carbon Percy's header gaskets on the Mustang, they leaked like crazy.  Put chunky thick Mr. Gasket ultra Seals (sandwich type) in there, car sounds 100% better and no pops, better ET too LOL.

I was going to say exhaust leaks too as I just had the same issue on my truck (although I think pops and flame on decel sound and look cool  ), new gaskets solved it.  I'll give those "chunky thick Mr. Gasket ultra Seals (sandwich type)" a try as I keep blowing out the Hookers.

[fallguy72]

falcon67 so you are saying my idle mixture screws should only be set at 1/4 to 1/2 out on all four corners? btw i had a 67 falcon sport coupe a long time ago. i do have some header extensions that i made ball and socket style that could be leaking but they are only about 6" long, just enough to prevent burning the speedo cable neutral safety switch.

[fallguy72]

changing exhaust gaskets means pulling the motor and trans

[Heo]

I have said it before and i say it again.  I only use silicone as
header gasket, I haven't had a exhaust leak since i started with that
A friend told me that and i...yeaa right....your cheap bastard
Until i had to have exhaust gaskets late one night to my FE fairlane
Used Silicone and they stayed thight as long as i had the car. The gaskets
I bought the next day is still hanging on the wall in my dads garage

[ericwevans]

I have said it before and i say it again.  I only use silicone as
header gasket, I haven't had a exhaust leak since i started with that
A friend told me that and i...yeaa right....your cheap bastard
Until i had to have exhaust gaskets late one night to my FE fairlane
Used Silicone and they stayed thight as long as i had the car. The gaskets
I bought the next day is still hanging on the wall in my dads garage

What are you using as far as silicone, I'll give it a go, already have a leak on the right side so nothing to lose.

[Heo]

I have used that transparent one you use for fishtanks and
that orange form-a-gasket one

[fastback 427]

X2 on the silicone only. The hookers on my fairlane have leaked from day one. Tried filing the flange flat, every different gasket, even anti-seize. The last time i installed them, i cleaned up the header flange and used a small bead of high temp red. No leaks yet, knock on wood. BTW, my fairlane had the same pop on deceleration, no more.

[cammerfe]

The last exhaust gaskets I bought were 'sandwich' type with a core of perforated metal with gasket material on both sides. I used a film of red hi-temp silicone on both sides and bolted 'em up. I used a combo of SS header bolts and SS socket-head bolts depending on accessibility, using a ball-end hex bit for the socket heads. Over the next few days I gave all the bolts an extra bit of 'umph' several times as they were heat-cycled and took a set. They've never leaked and it's now close to ten years on the combo.

KS