Head pipe diameter question... : V-Twin Forum: Harley Davidson Forums

Mother · 03-15-2009, 09:50 AM

I believe that there is a perfect pipe for each motor combo and no one pipe fits all combos. A friend of mine who has been in the business end of porting heads and build drag racing/ hot street motors for cars for forty years asked, "Why dont the pipe manufacturers offer 1-7/8" head pipes?". After looking around most are 1-3/4"(for torque) or 2"(for HP). I saw Rinehart offers a 1-7/8" 2into1. Why wouldnt there be more offerings in 1-7/8"???

I have done all I can do until I receive a few more parts to finally get my motor back together. Started bs'n and got bored and now I am asking you guys

pwmorris · 03-15-2009, 11:41 AM

You need a stepped pipe to give you the best of both worlds.
Certain companies and custom pipe makers such as JBV use a computer program that enters all your motor info and gives you the perfect pipe diameter out of the port 1 7/8" for example, then each stepped piece is measure exactly for correct length all the way to the collector and meg.

Hillside · 03-15-2009, 03:16 PM

Paul is correct about the stepped pipes.
We have also seen outstanding results with the Rhinehart 2/1 pipe which has an 1 7/8" headpipe.

Mother · 03-15-2009, 03:42 PM

I am trying the new stepped V&H Outlaw(Indy) stainless 2into1. I was just curious why more manufacturers werent splitting the diff between 1-3/4 and 2".

qtrracer · 03-15-2009, 05:05 PM

If they only made 1 7/8" you would be asking"Why don't more exhaust mfg's make 2 sizes of primary headers?"

Mother · 03-15-2009, 05:32 PM

probably....duh

arealinvestor · 03-15-2009, 06:51 PM

Isn't the D&D Boarzilla a 1 7/8 header????

TXCHOP · 03-15-2009, 08:48 PM

Quote:

Originally Posted by arealinvestor

Isn't the D&D Boarzilla a 1 7/8 header????

Craig, the BZ starts at 1 7/8 and steps to 2 inch.

skidmark316 · 03-15-2009, 09:02 PM

Quote:

Originally Posted by TXCHOP

Craig, the BZ starts at 1 7/8 and steps to 2 inch.

The older ones were straight 1 7/8".

arealinvestor · 03-15-2009, 09:03 PM

Cool thanks Chop!!! Have you installed one(Boarzilla) on an 09 tourer yet????

TXCHOP · 03-15-2009, 09:04 PM

Skid, i had heard that before, do you know when they changed from strait 1 7/8 to the stepped version.

skidmark316 · 03-15-2009, 09:13 PM

I have no idea, but I remember that when they finally put the BZ on their web site, they were all advertised as stepped. They were being sold over a year before that, those are probably the straight ones. I have a straight 1 7/8 bz headpipe on my bike.