headers vs HP manifolds

[GoMangoBoys]

I am planning to run HP manifolds on our 383 that we stroked to 478.  We are also running the 906 cast iron heads.  This was all accounted for when the stoker kit/cam was designed by Hughes Engines.  When I started this, I was led to believe that the HP manifolds were nearly as good as headers.  Clearly, some people think otherwise.  How much performance improvement is there in headers vs these manifolds?

[anlauto]

I know when I had my Superbird with a basically stock 440, I bought it with headers and removed them for the stock manifolds and could not believe the negative effects of the performance...

[HP2]

The 906 heads, even if ported, are more restrictive than many other aftermarket offerings. Even if ported, the HP manifolds may not be as great a mis-match to these heads if designed to work together, than headers. However, headers have often been the best bang for buck improvement on a vintage big block. Depending on design, you may be giving up 20, 30, or even more horsepower.

Big block test in 427 inch range:
https://www.motortrend.com/how-to/headers-dyno-test/

Small block 355 inch claimer race engine test:
https://www.motortrend.com/how-to/ctrp-0806-exhaust-header-dyno-test/

[MoparLeo]

A good set of headers give you equal length, tuned head pipes. You can get different lengths and tube diameters based on what your build/application are.
Stock manifolds can only be ported/improved not redesigned.
Why would manifolds even be a consideration on a stroked, performance engine ?

[GoMangoBoys]

@MoparLeo   The HP manifolds were chosen over headers because someone told me that they were nearly as good as headers and I do not know any better.  There are a lot of non-performance-related advantages to manifolds.  If we are talking 10 HP difference, then I am not worried about it. If we are giving up 50, then I might worry.

[HP_Cuda]

Even HP Manifolds are restrictive versus headers.

You really got to think about flow when choosing heads and headers.

More flow, more bang, more power.

[chargerdon]

Very interesting question.   What matters the most is flo.  I would love to see a lab testing showing flo and backpressure of our HP Manifolds vs Shorty Headers, multiple brands of Long tube headers.   Also, how much "flo" is needed for a big block designed for 400 hp, 500 etc,   My personal guess is that unless we are looking at 450+ hp you would never notice the difference in the seat of the pants between them. 

[RUNCHARGER]

The bigger the CI the bigger the difference. We used to see an actual increase in performance on a stock 383 engine using headers. Funneling the exhaust a 478 produces through the same manifolds and changing to headers is going to be even more of a gain. Without more information on the camshaft etc. I would expect at least a 40HP gain on a 478 using headers. Easily.

[Mr Lee]

I can understand wanting to keep the stock look. Have you considered extrude honing your originals?   Not cheap and probably
not quite as good as headers but might be a nice compromise


Sent from my iPhone using Tapatalk

[crackedback]

JMO

Either live with the performance disadvantage of the HP manifolds or put headers on it.

I wouldn't spend (IMO waste) money on extrude honing.  Bang for the buck, you might as well give the money to someone that needs it or burn it.    If you were class racing where money is no object and you wanted the small gain for big money, go for it.  Driver car, not a chance with my money

I do love the folks that sell HP manifolds are as good as headers spiel.   

[RJChallenger]

@crackedback  I\m not selling anything, LOL.  But I do remember reading an article in a magazine ( maybe mopar muscle ??) Comparing stock manifolds to HP manifolds and headers many years ago . They claimed on slightly modified motors HP manifolds were better than the cheap headers , but did not perform as well as the better quality headers of the time.

[crackedback]

Plenty of stuff printed over the years that is rough at best.   Headers are better than HP manifolds for performance, all day...   not just at peak.  It's all relative to what is being built.

This one is a stroked B and not likely a "stockish" set up even with 906 heads.  Why someone would sell this poster on HP better than headers...  I don't know.  Ridiculous IMO.

Ask any body that races FAST if they would prefer headers over HP manifolds in those classes to maximize MPH and lower ET.   Extreme case.

Pick your parts, pay your money.

[Bullitt-]

  These old articles using a healthy 440 might give you some insight.
In this one they compare manifolds to headers.
https://www.motortrend.com/how-to/mopp-0106-manifolds-vs-headers/
Here they compare the engine as tested with 906 heads
https://www.motortrend.com/how-to/mopp-0106-how-to-install-ported-stage-v-heads/

[crackedback]

  These old articles using a healthy 440 might give you some insight.
In this one they compare manifolds to headers.
https://www.motortrend.com/how-to/mopp-0106-manifolds-vs-headers/
Here they compare the engine as tested with 906 heads
https://www.motortrend.com/how-to/mopp-0106-how-to-install-ported-stage-v-heads/

Decent head on that engine with a mild camshaft by todays standards, XE274H.  80 HP at peak and a bunch more down low too.  That is consistent with my experience with HP's and headers on a good engine.

Curious of the camshaft choice that was made for the OP.  Hughes is usually pretty aggressive lift to duration trying to take advantage of the lifter diameter with their grinds.  Improved head function with porting? 

@RJChallenger   Nothing personal about people that think headers aren't better for performance than HP's.   If people don't like headers for other reasons and there are some drawbacks, that's fine (appearance, never having to service manifolds).      Selling manifolds on the lack of HP delta isn't usually a good premise if looking for best performance.

[RJChallenger]

I don't think HP manifolds are better than Headers. I just know what I read Many years ago, and that article stated that HP manifolds were better than cheap headers. I guess the purpose of the article was if you had HP manifolds and wanted Headers, be careful which ones you buy. Some headers flowed better than others. Are quality headers better flowing than HP manifolds Absolutely.