1000cc 4cyl, primary diameter.

I am looking for outside diameter measurements of exhaust header primarys. Both stock and aftermarket.

Thanks!

pm OMR.....hes working on some......

If anyone with a set of headers could take a quick measurement, would be great.

1.5" O.D. is the norm on the majority of after market 4-1 header designs in the risers (head to collector)....

There's a reason for this in exhaust designs... Tunable (steering) of the desired power band... Pipe wall thickness also plays into the equations. Then there's the length of the risers/exhaust end, collector and baffle designs as well for performance gains.

Now before everyone jumps my case here, displacements, cam/P&P head/valve, carbs is where the true power gains are made.

Basically there's a whole slew of variables required in the design that come into the mix...

Can't say for stock for I don't have a stock exhaust to measure from. I would think 1.25" to 1.5" is ~ right.

OMR

Thanks OMR.

I work for an exhaust manufacturer (cars), trying to see it we have the tooling for the bender, I had figured appx 1.5" would be the max. The smallest we have tooling for is 1.625.

1.625" may be ok.... at least to fit into the head port.
The riser to head tubing is normally slightly flanged to seal on the port exhaust gaskets.

Get a cut piece a couple inches long and size to port...

Just to give you some insight...