Do other {cyl head vendors for}brands of cars-motorcycles go thru
the BS of offering cylinder heads with several different
intake port volumes, in what otherwise would be
just one offering? {seen on SBC ,Ford, no others}

If someone owns a one liter Honda bike, how many different cyl head volumes,
can one choose from?
For SBC vendors offering varying volumes,
my suspicion is, the 'big' one is their correct design,
the small volumes are their low price monkey models.
I realize that the intake port is a continuation of the
intake manifold. I find it troubling that vendors do not publish the cross-section-area of their product
{exception, Edelbrock race}
I just don't trust someone's,, good-better-best,
stage 1 stage 2, driving style suggestion,
pile of BS, for recomendations.
Keep in mind that, should the engine guy for some
race team think that the intake port is too large,
the narrow part of the combined intake tract could be put
in the intake manifold.

 

Here are a few reasons.

1. The SBC is the most popular engine ever produced & due to this there, has been extensive research & also the buyer market to make producing different sizes feasable. The BBC & Fords also have a similar popularity. There is not a price advantage to any size head.... small ports may have thicker walls or the sand casting is larger to allow a bigger water jacket. This is minor in the cost of the head, so the small ones are not cheap knockoffs. The cost is in the machine work & also the technology behind the ones making the best power.(manufacturers have to recoup this R&D as well)

True Chrysler has lagged behind in the aftermarket, but there are companies out there making excellent heads (such as Indy) for these engines as well. Also look at Larry's work (Maxracesoftware) He knows how to make a little iron cylinder head make power... seems almost impossible to make so much power with little ports.

If you have a bike, you are usually stuck with the stock parts, but they are already race quality to begin with. You cannot make 150hp/liter with junk. Looking inside my R1 with 5 valves per cyl., it is a definite quality piece. True, it can be ported here & there, but, you will not see much for the many hours spent improving it. You could easily gain 50hp on a typical car by doing heads, but a strong bike will not generally see 10hp unless the entire package (cam, carb, exhaust & compression) is all altered at the same time to optimize it.

Any additional work is up to the porter to make the required size. Many heads that are a 1 size fits all, have the required wall thickness to adjust the size to suit. The off-the-shelf option allows for less port work & also allows some to bolt on standard castings with good results.

2. The cc volume is only a rough guideline so it is a pretty safe term. Port dimensions are somewhat guarded to prevent unqualified comparisons from being made. Remember flow does not necessarily mean HP & port dimensions do not necessarily give accurate indications to the flow capability. High flow with fuel separation in the chamber will not make power, but can look good on the flow bench. Dimensions at 1 spot in the port do not give all the details. The pinch point can have a positive impact on power as well.

Basically in simple terms, HP should be the best comparison of 2 heads & only in the manner that you intend to use them. The one that makes the most a 8000rpm is likely not the best head for your 6000rpm car.

 

{LP, thanks for responding to my post}
.
Consider a thought experiment.
You possess a million different ‘intake port shapes’,
for the SBC, they fit for port location, pushrod holes, etc.
You test them for power in an engine,
not for 1 psi {28 inch water} steady flow.
You pick two, one ‘best power’ at 6000 rpm,
the other, ‘best power’ at 8000 rpm.
Then, test these two for 28 in. steady flow.
My guess is that the ‘6000’ would ‘flow’ better.
anyone else?

 

The intake is not usually the restriction as there is much more freedom to accurately size the intake, whereas the heads have multiple bolts, water passages & physical size constraints to deal with in their design.

Here intake runner length also comes into play for "ram" tuning, they could flow the same amount, but the length could be tuned for optimum power at different RPM's.

Converesly, for the same engine the higher RPM will require more flow so the intake should flow more for more high RPM power.