Port Matching N42 Head for Triple Webers

[Duffman]

I have an N42 head/N42 bottom end engine that I added triple Webers to this last year.  I am enjoying them immensely.  I wanted to port match and unshroud the valves to get best air flow and enhance performance.  I believe the N42 head is a good option for headwork, but am wondering if the FI notches on the intake ports will cause any issues on port matching?  I wanted input from those of you that know about this much more than I!

I appreciate your thoughts.

 

Thx,

Stephen

[Pillar]

if the notches are left as is, they will create turbulence by way of a low pressure area which could cause unwanted "tumbling" of the air flowing over that area.  However, depending on how much you are porting, you may not have much of the original notches left (the more you port it out, the less of the original notches will be left over) so the turbulence generated by them may not be that noticeable.

 

If you are worried about it and would rather get rid of the notches all together just to be sure, you could have them filled in and then do your port matching.  

[Pillar]

Oh, and be careful when doing your porting.  If you go to far, you run the risk of cutting into one of the coolant passages. Shouldnt be an issue if you are only doing a little smoothing and mild porting, but again I dont know how big you are going with it.

[Tony D]

Just remember this, optimal face size is 35mm. You can flow 230cfm through that face juncture.

If you are porting so the injector notch isn't showing anymore, you're doing it wrong unless you're running 55 DCOE's. Even then, head juncture is 40-43mm and the notch still exists.

What evidence to prove the flow is hurt by leaving those notches in there? I'd like to see it other than just someone claiming "it makes turbulence" especially in lieu of the fact that dyno numbers show the SCCA allowable "port matching" on the manifold and head 1" either direction of the gasket surface doesn't reap any performance reward, but if done improperly can hurt performance.

The flow is in the bowl and short side radius, not the diameter of the runner or removing injector notches. 35mm is more that big enough to allow most triple manifolds to taper no more than 7 degrees to hit the throttle plate diameter at the carb/manifold flange.

Proper angle-tapered porting of the Triple Manifold is more fruitful, depending on which one you have. Most for L28's now come near 35mm already and have the proper taper from 40 to 35 or 45 to 35 at the head flange.

Edited August 15, 2017 by Tony D

[stav2201]

I agree with Tony D on this, I would not grind out those fi notches. if I recall correctly, on an L28 you can use dcoe40s, but optimal power is with 45's or 48's. so a bit pointless to grind them down. Before you do any work on your head, make sure you have upgraded to some after market headers. no point increasing airflow coming in if you can't get it out properly.