Frequently Asked Questions

Manifold Questions

Q -

I have a question re: DCOE manifold choices.

Should I use either E cast iron exhaust manifold or 4-1 NOS ipd header (long). I can give more details if you like.
Do I go with long (R-sport clone) vs. shorty manifold for 45 DCOEs? How will manifold length affect low-end and mid-range drivability?
John F
A -
The short manifold with the sharp curves is a problem and will restrict air flow as well as making tuning more difficult, throwing off the air fuel ratio, etc.
The longer manifold is better in all respects regarding power and driveability.  
Once I get the time to switch over to the new computer that is sitting here with the data on it, I can show you a dyno chart that shows the difference.
A problem with the long manifold is that on 1800s the inner fender has to be modified for clearance.
For street use, with an engine that is going to produce less than 200 HP, dual HSR Mikunis on an SU manifold is a much better setup than the webers and does not require the inner fender modification on an 1800.  ( if its going on an 1800 let me know ).
Depending on the exhaust system and other factors, including exactly which header it is, the cast exhaust manifold will probably work better for the street than the 4 - 1. 
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