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I'm using a 455 big block in a Special. The engine came from a 1976 Olds 98, which was in a breaker's yard near London, UK, many years ago. I have had an exhaust assembly made specially for each side of the engine. Each consists of 4 parallel down-pipes from the exhaust ports on the head. They then join together before the muffler. Each muffler then exits just in front of the rear wheel. The two middle down-pipes were cleverly made to mate with the center exhaust port on the block to give the appearance of 4 ports. The problem is that they just don't sound like a big V8 should, especially to those sitting in the car. The sound doesn't have that lovely V8 burble. Various reasons have been suggested - the fact that each muffler exits at the side of the car instead of the rear - the fact that the down-pipes are of different lengths, and the "Siameseing" of the middle two ports.
I'm assuming the engine would've sounded right when it was in the Olds 98 so how can I improve the sound - original cast iron manifolds, equal length down-pipes - exhausts exiting at the rear instead o the sides - or something I haven't thought of?
All replies are welcome. I think I've used the correct (American) terms but, as I'm British, please excuse any language errors. Also, if this post would be better in one of the other forums, please let me know.
I'm using a 455 big block in a Special. The engine came from a 1976 Olds 98, which was in a breaker's yard near London, UK, many years ago. I have had an exhaust assembly made specially for each side of the engine. Each consists of 4 parallel down-pipes from the exhaust ports on the head. They then join together before the muffler. Each muffler then exits just in front of the rear wheel. The two middle down-pipes were cleverly made to mate with the center exhaust port on the block to give the appearance of 4 ports. The problem is that they just don't sound like a big V8 should, especially to those sitting in the car. The sound doesn't have that lovely V8 burble. Various reasons have been suggested - the fact that each muffler exits at the side of the car instead of the rear - the fact that the down-pipes are of different lengths, and the "Siameseing" of the middle two ports.
I'm assuming the engine would've sounded right when it was in the Olds 98 so how can I improve the sound - original cast iron manifolds, equal length down-pipes - exhausts exiting at the rear instead o the sides - or something I haven't thought of?
All replies are welcome. I think I've used the correct (American) terms but, as I'm British, please excuse any language errors. Also, if this post would be better in one of the other forums, please let me know.
Just different words sometimes and not really errors. The V8 burble is more from 2 pipes, but there is some lack of separation, with the center exhaust crossover which gives a unique sound, to other V8s. The type of mufflers used may also effect the sound at idle. I wouldn't worry about it and just enjoy your ride. Maybe other will comment.
Just different words sometimes and not really errors. The V8 burble is more from 2 pipes, but there is some lack of separation, with the center exhaust crossover which gives a unique sound, to other V8s. The type of mufflers used may also effect the sound at idle. I wouldn't worry about it and just enjoy your ride. Maybe other will comment.
Thanks for your reply. I'm not worried but I am concerned, otherwise I wouldn't have posted here. I want to get the right sound. I'm going to attach a couple of photos to show the present arrangement. I'm not sure what you mean by "there is some lack of separation". Are you saying there should be more, and, if so, where?
I am betting you need more camshaft. I noticed a difference even stepping up to 204/214 and 214/214 camshaft's. I went from a 204/214 cammed with 1.72 roller rockers and 9.6 to 1 compression Olds 350 with filled crossover's. The exhaust sounded absolutely amazing. I then went to a stock cammed Olds 260, while it still sounded good but not quite the same. Consider a cam swap, it probably needs a timing chain anyways. Talk to Cutlassefi, he can pick a cam that will sound good and not kill power on your 8 to 1 compression 455.
Thanks for your reply. I'm not worried but I am concerned, otherwise I wouldn't have posted here. I want to get the right sound. I'm going to attach a couple of photos to show the present arrangement. I'm not sure what you mean by "there is some lack of separation". Are you saying there should be more, and, if so, where?
The center exhaust pots talking to each other through the exhaust crossover in the intake changes the sound somewhat.
Lots of thinge effect or can effect or the idle or sound. Cam, compression, idle speed, timing......
Last edited by Firewalker; November 14th, 2018 at 12:31 PM.
Can you post a video of it running holding the throttle partly (say 2500 rpm) open for a couple of seconds. That may help is hear what you are describing.
How big are the down pipes and pipe that goes into you mufflers. They look like 1 3/4 inch. I wonder if since they are the same diameter from the heads to the muffler, you may get more of a mad bubble bee sound, more of buzz than a burble if that makes sense.
You need cyl pressure to make noise. That 455 has maybe 8.25:1, not good for giving you a "rumble".
A single pattern cam on a real tight lobe sep will help but its a band aid at best. I can do one for you if you want but that's your call.
Hope this helps. Thanks.
Can you post a video of it running holding the throttle partly (say 2500 rpm) open for a couple of seconds. That may help is hear what you are describing.
How big are the down pipes and pipe that goes into you mufflers. They look like 1 3/4 inch. I wonder if since they are the same diameter from the heads to the muffler, you may get more of a mad bubble bee sound, more of buzz than a burble if that makes sense.
I tried recording it but the sound on the video isn't anything like the sound I hear! The pipes are 2 inches in diameter.
I appreciate the suggestions made by way of different camshafts etc.but can anyone tell me what the sound from a 455 is like with the original (cast iron?) manifolds? I'm prepared to obtain and fit a pair of those if it means the sound is right, even if the appearance is not as good as at present.
IMHO, your not going to get the sound your looking for with your homebuilt setup. That's not saying a nice sound can't be had, just not the same as a full exhaust car.
Manifolds muffle sound, they will make it quieter. Follow Cutlassefi's suggestion and get a custom on a tight LSA will no doubt help sound, probably needs a timing set anyways. The Olds V8 has a unique, mean exhaust note if done right.
Manifolds muffle sound, they will make it quieter. Follow Cutlassefi's suggestion and get a custom on a tight LSA will no doubt help sound, probably needs a timing set anyways. The Olds V8 has a unique, mean exhaust note if done right.
Can you please explain what the text I've highlighted means? Thanks.
The tighter LSA boosts low end power, the mild factory cams had I believe had a 109 LSA but below 200 duration so still super smooth. If you increase duration it adds a more aggressive sounding exhaust note but too much bleeds off cylinder pressure. The tighter LSA helps with low end power but effects idle smoothness. You want a bit more duration and something like a 106 LSA will help keep bottom end torque. You have a smog motor with low compression, too much duration might sound good but won't get out of it's own way. Cutlassefi will explain it much better and correct anywhere I am wrong .
November 13th, 2018, 03:18 AM
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