I did a quick search on this topic and didn't come up with anything so I figured I would throw it the question to you guys. When the engine is cold the exhaust rap is awesome and super snappy but that goes away after the engine is warm and almost no rap exists. I did what I thought were all the tricks to make it happen but I must have missed something. Here's the specs -Chevy 292 inline 6 -Stock manifold split with a block off plate welded between the front 3 and rear 3 banks with a 1/2" hole drilled in it -1 1/4" exhaust -12" gl***pack on the front bank located under the drivers seat area running all the way out the back -Straight pipe on the rear bank running all the way back Any ideas on what's making it stop rapping? NAES
...that generation of Chevy 6's did not have the quality of "rap" as did the 62 and earlier 6's. even with a true split such as yours,...not sure why....don't know why yours acts as it does, but most engine "talk" much better when they are started up "cold" than after they're "warm"...maybe someone here will have an answer. ,,,what vehicle is this engine in?
When it warms up everything tightens up. When the engine is cold it does not burn the fuel as efficiently either. part of your "rap" comes from unburnt fuel in the exhaust system, it ignites at some point. Here is an example that you probably won't understand any better if you didn't get that. I run a stock high performance cam shaft in a lot of my V-8 builds. When my engines are cold even running not chokes they are lumpy as hell. Once the warm up they have a tendency to smooth out. When they are cold everything is still loose and everything in the engine is hunting its place. once warm everything tightens up and stops hunting.
Its very easy there is a Mouse in your Exhust.! & when its Cold you woke him up & he or She Scramble's to get out thus causing the Rap Noise as soon as he or she finds his way out the Rap stops. just my 3.5 cents Live Learn & Die a Fool
I'd start over ... Weld up the hole in the blockoff, & put a pair of 22'' steelpacks as far forward in the system as room allows using 1 7/8'' tailpipes. Then adjust the valves & tune it ...
I would say it sounds different when cold because if the choke is on it is running richer, choke goes off when it's up to operating temp. Also fuel doesn't burn as well when the engine is cold.
In 1954, the older guys (with 59A flatheads) put pennies in the block's heat riser ports, under the intake. Zowie, did that make a 'backrap'! So I imitated that 'free tip' on my 296", and man...that was the most COLD blooded thing for 15 minutes of driving imaginable! Pulled the intake, removed the pennies...and my 4 jugger became 'almost driveable'! With straight linkage, natch.
I have a 292 with 2.5" exhaust with 3" Chambered tube mufflers and 6" exhaust tips. It always raps all the time, hence my HAMB name. Get Langdon's split header system. The one you have is too restrictive for rappin'
yea rappin is pretty wide open, liberal is an understatement, no restrictions at all. "I'm a dog with a bone Just tryin a fine a home Like ta run like ta play like to lay aroun all day ta da ta da ta da da da . . ." We be rappin holms
Thanks all for the replies, I do appreciate the input. Everything tightening up once warm seems to make the most sense. It's just odd since I followed the same formula as the lowrider guys do to get the exhaust to rap, albeit without earlier inline 6. Engine is in a '64 C-10 Definitely not starting over, I'll happily live with it. NAES
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