HP exhaust manifolds and FAST cars

[68n70]

Been a long time since my last post...have been preoccupied with kids, work, moving etc. etc.etc.... but have a question:
For about the umpteenth time I've read a post about headers vs manifolds and had a question pop up that may have been answered already, so bear with me!
I know the FAST cars have monster stroker motors with a boatload of tricks to make them as fast as they are, but still they are running exhaust manifolds:  how do they get that kind of performance with em???  I believe they extrude hone them, but it doesn't seem like that would make them able to work as well as they do for that kind of horsepower.   And if I build, say a 470, how could I achieve respectable performance with them as well?
Thanks in advance.

[Rolling_Thunder]

porting of the exhaust ports, gasket match to manifold itself, extrude-hone the manifolds....   

[firefighter3931]

The camshaft selection is the key to making big power with manifolds. The idea is to widen out the LSA to reduce overlap as much as possible which in turn limits reversion. It's a bit of a science, no doubt... but it can be done.    None of these FAST engines are running on pump gas either and the heads are heavily worked as well. 



Ron

[68n70]

Thanks guys for the responses...
So given the scenereo of a 470 build with a decent set of heads, if I choose my cam correctly and work the manifolds as described and everything else being equal, how much do I give up vs a good set of headers?  Would I be wasting my time building a 470 (w/ manifolds) or can I get most of the performance out of it still?   If it's only a tenth or two, maybe 3, I can't see any real reason to run headers unless you are racing every weekend.
Waddya think?
   

[tecmopar]

It partly depends on how the car is driven, once a week to a cruise or show, or many times a week to enjoy it. I've never been a fan of headers, the fit, leaks, noisy, hot and getting in the way of everything to name a few plus with the corks on there for the street you lose some of the scavenging effect. I am a fan and user of ported and extrude honed iron manifolds for a long time now, how long, well they used to cost only 250 a set but now thier up to about 5-600. The only 2 cars, a BB and a SB I ever bothered to track test the differences, with very similar conditions showed a lose of around .2 and 4-5 MPH which for a kinda quieter and easier to work on street car didn't bother me at all. If your gonna do it right and only race at the track, seeing how today street racing is more dangerous, really frowned upon, and none of us do it anymore ( wink wink ) then by all means get a good set of headers, but for me I'll stick with iron pieces, good luck.

[firefighter3931]

Thanks guys for the responses...
So given the scenereo of a 470 build with a decent set of heads, if I choose my cam correctly and work the manifolds as described and everything else being equal, how much do I give up vs a good set of headers?  Would I be wasting my time building a 470 (w/ manifolds) or can I get most of the performance out of it still?   If it's only a tenth or two, maybe 3, I can't see any real reason to run headers unless you are racing every weekend.
Waddya think?
   

Personally, i wouldn't bother extrude honing the manifolds. The money would be better spent on a good x-pipe exhaust system and free flowing mufflers. The x-pipe will help with scavenging by creating a venturi effect which pulls burnt gases away from the heads rather than having the engine push them out. On a manifold type exhaust the x-pipe is a no brainer.


As for power loss, it really depends on the build and cam profile. A tight lobed cam (106-108 lsa) will lose a lot of power with a restricted exhaust while a wide lobed grind won't suffer as much. 



Ron

[68n70]

Thanks Ron, that makes sense...
So one could build a stroker and enjoy most of the benefits that come with it (mainly torque) and run manifolds...
If I could ask for more info on the cam, as I'm not at all knowledgeable about them:  what, if any, is the downside of running a wide lobe cam?