Classic Mustangs List Archive

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Mail From: Matt Trostel (email redacted)

> I was told by the mechanic who rebuilt my carburator that my 289
> 4v (it has the original Holley) is not being strangled by the intake (it
> gets as much air as it needs with no problem) but by the _outflow_ of
> gasses. That is, different headers and/or an exhaust system is what the
> engine needs to gain horsepower. By the way, I've got the air cleaner with
> the snout, not the hipo 360 degree cleaner.
>
> Anyone have any experience with this? Would changing to the 360 degree
> filter help? How about the hipo cleaner AND a K&N filter?

It's my understanding that the airflow restriction for most small block
Fords is the heads. This obviously depends on the configuration. My
2v, single exhaust, 289 would certainly benefit from a 4v, headers, and
dual exhaust. That said, unless you've done quite a bit of internal engine
work, the 289 is by no means a high-revving engine. With the horsepower
peak at a relatively low RPM, I imagine any airflow increases provided by
a 360 degree air cleaner and/or a K&N filter would be minimal on a
stock 289. Once you've got a 4v and headers and especially if you build
up the engine and move the power peak and redline up the rev band, the
increased flow of an upgraded air cleaner/filter will return more of a power
increase.

I think your mechanic is right. You'd probably be better off putting the
money you'd spend on the air cleaner assembly and K&N filter into a
pair of headers.

But if your other car is a new car with the horsepower peak at 6500 RPM
and it has one of those small panel filters, the additional flow of a K&N might

make a difference. Not to mention that if you're going to drive it for a few
years, you're going to have to replace the the paper air filter 2 or 3 times
anyway. That's how I rationalized it at least.

Matt
Dallas


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