[Greg from Aus]

Originally Posted by Ron Sutton

Nice !




You don't want to measure to the front of the collector. With your collector, the individual primary tubes continue on for a several inches inside the collector assembly.

Even though you bought a collector assembly ... technically, the collector doesn't start until the individual primary tubes stop.

So, measure your collector. Measure from the "front" where the primary tubes enter ... until the primary tubes inside the collector stop. You will see a point where all four primary tubes end inside the collector. That is where the primaries end & the collector starts.

You're going to add the lengths of the primary tubes you have built ... to the length of primary tube inside the collector. Don't forget to subtract any overlap where the collector assembly slides over the tubes. (Just so you have an accurate & true length.)

When you figure this out ... post again with the primary tube lengths.

Before, when I didn't know what you had for an engine ... I was "assuming" you had an LS or SBC putting out 450-550 hp. In that case, 27" primaries was my suggested minimum length.

Now, knowing more about the engine you have, I "think" your optimum primary length will be around 27". You could go a little shorter if you need. I say, I "think" because I don't have all of your engine info.

I'd be happy to help you work out the optimum header dimensions ... and optimum exhaust system for you, but you're going to need to provide me with a LOT of specific engine data. Just let me know.

Thanks for the info Ron,
I re measured and it is 28".

I don't have all the engine specs as it's being built at the moment.