How restrictive are stock type exhaust manifolds?

[SeanMcl]

Just wondering if the stock exhaust manifolds are as bad as they look, or if the water cooling and the corresponding temperature/volume drop of the exhaust significantly eases the back pressure.

I have OMC log style heads, which are probably the worst of a bad situation, but I imagine the principle would hold true for all manifolds.

 

[Bondo]

Re: How restrictive are stock type exhaust manifolds?

but I imagine the principle would hold true for all manifolds.

Yes,...

Lack of dedicated runners, aka; Headers is the problem...

 

[SeanMcl]

Re: How restrictive are stock type exhaust manifolds?

Do the old log style manifolds have flappers in them, or is that a newer development? Mine are from '74. The Seloc manual I have doesn't show them, but I still wonder.

 

[HT32BSX115]

Re: How restrictive are stock type exhaust manifolds?

Yes,...

Lack of dedicated runners, aka; Headers is the problem...

Along with shoving it out through the prop too........

"Flappers" are usually on the "thru-hull's" on the outside, and in the Y-pipe, if installed......