Rumble in the Header

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Rumble in the Header

Postby Biscayne John » Thu May 23, 2013 1:13 pm

Hey Guys,

I finally seem to have the bugs out of 0718. I put the webers on and the car is a lot of fun! I did not notice this before when I had the EFI on the car, but now when I am on the trottle (say 4,500 in 3rd gear) and back off the throttle I hear a noticeable popping in the header, sort of what you hear on the small circle track cars. Everything seems fine and drives nice, timming is on, is this common?
John Mahoney
Long Island NY/Ocala FL
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Re: Rumble in the Header

Postby hammerdown7 » Thu May 23, 2013 10:13 pm

John,

Is the pulse air still on the car?

Dick
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Re: Rumble in the Header

Postby Biscayne John » Thu May 23, 2013 10:27 pm

No
John Mahoney
Long Island NY/Ocala FL
AACA
VCCA
CVOA
BCA
The Fleet
1954 Chevrolet BelAir sPort Coupe
1960 Chevrolet Impala 2 door Sport Coupe 348/340HP (AACA Grand National Winner)
1962 Chevrolet Impala 2 door Sport Coupe 409/409HP(the last one to do)
1962 Chevrolet Biscayne 2 door Sedan 327 Auto (AACA Grand National Winner)
1977 Monza Mirage 4 speed
1988 Celebrity Wagon (was my mother in laws since new 42K miles)
2011 28' Bendron Titan Enclosed Trailer; what they travel in when we go
2018 GMC 2500 Sierra Diesel Crew Cab; how we get them there without sweating
2015 Cadillac CTS
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Re: Rumble in the Header

Postby hammerdown7 » Fri May 24, 2013 10:00 am

When the P/A was removed the previous owner may have left the extension tubes in the header. Pull one of the block-off plugs from the header, the tubes, if they are there, will be right below the plugs. They have a slight curve to them and end close to the exhaust valve. You can remove them with the header in place.

Another possible reason for the noise may be that the carbs are a little rich. It may make a difference if you set the initial timing at 15-16 degrees instead of the factory 12 degrees. What size are the carbs?

Dick
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Re: Rumble in the Header

Postby Biscayne John » Fri May 24, 2013 1:13 pm

Dick,
Those tubes are in there, are not really looking to be removed.
The timing was way over advanced when I adjusted it, it was also happening then...
More to come
John Mahoney
Long Island NY/Ocala FL
AACA
VCCA
CVOA
BCA
The Fleet
1954 Chevrolet BelAir sPort Coupe
1960 Chevrolet Impala 2 door Sport Coupe 348/340HP (AACA Grand National Winner)
1962 Chevrolet Impala 2 door Sport Coupe 409/409HP(the last one to do)
1962 Chevrolet Biscayne 2 door Sedan 327 Auto (AACA Grand National Winner)
1977 Monza Mirage 4 speed
1988 Celebrity Wagon (was my mother in laws since new 42K miles)
2011 28' Bendron Titan Enclosed Trailer; what they travel in when we go
2018 GMC 2500 Sierra Diesel Crew Cab; how we get them there without sweating
2015 Cadillac CTS
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Posts: 475
Joined: Thu Dec 27, 2012 7:29 pm

Re: Rumble in the Header

Postby beakerztoyz » Wed Jul 03, 2013 5:50 pm

I have heard that a popping in the exhaust like that may be caused by header's that are not perfectly sealed.. it may not be enough to cause any sounds that you would expect from an exhuast leak but under the conditions you describe the leak allows air to be pulled back into the system. both of my motorcycles do this and apparently it's fairly common on bike's because the pipes never like to seal properly. If you aren't running rich this could be the problem and really it's nothing to worry about
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If I woulda known then what I know now....I never woulda got an h body
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Re: Rumble in the Header

Postby monzajer » Wed Jul 03, 2013 10:51 pm

In some circle track cars the "popping" noise generally happens at the end of a straight, when the engine has reached as much RPM as it can before backing off the throttle, generally around 5500 to 6000. The reason for the "popping" noise is when the valve springs have reach their pressure limit and they start to bounce on the seat. This is known as "valve floating". Increasing to proper spring pressure stops this. Of course, this is assuming you are not referring to a rev limiter, which sounds different, but can be confusing to some who don't know. As said above, a leak may cause this as well.

You mention 4500 in 3rd...that isn't much RPM, but ya never know.

Some of the straight line guys may be able to shed some light.

Let us know what you find.

Good luck and have fun.

Cheers, Jer :mrgreen:
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Re: Rumble in the Header

Postby Biscayne John » Fri Jul 05, 2013 5:18 pm

It has that real Cool circle track sound
John Mahoney
Long Island NY/Ocala FL
AACA
VCCA
CVOA
BCA
The Fleet
1954 Chevrolet BelAir sPort Coupe
1960 Chevrolet Impala 2 door Sport Coupe 348/340HP (AACA Grand National Winner)
1962 Chevrolet Impala 2 door Sport Coupe 409/409HP(the last one to do)
1962 Chevrolet Biscayne 2 door Sedan 327 Auto (AACA Grand National Winner)
1977 Monza Mirage 4 speed
1988 Celebrity Wagon (was my mother in laws since new 42K miles)
2011 28' Bendron Titan Enclosed Trailer; what they travel in when we go
2018 GMC 2500 Sierra Diesel Crew Cab; how we get them there without sweating
2015 Cadillac CTS
User avatar
Biscayne John
 
Posts: 475
Joined: Thu Dec 27, 2012 7:29 pm

Re: Rumble in the Header

Postby MonzaRacer » Mon Jul 08, 2013 7:49 pm

It is raw fuel that is un burned when you close the throttle still going through engine and lighting off in hot exhaust as it gets to a more O2 rich environment. No worries EXCEPT if your running way rich, then it CAN collect in mufflers and blow them up. But if its not too severe and plug color is medium to light gray or brown, leave it alone.
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