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Sat Jul 23, 2016 4:16 pm

I have a 2006cc with a 78mm crank,110 cam 90.5 pistons and 42x37heads.If I were to buy new idf or hpmx carbs,should I go with 40mm or 44 mm.I see people running the 40's on 1600's with success so wouldn't these be too small on a 2006 with the above specs?

Sat Jul 23, 2016 4:27 pm

Either size will work running 34 venturis. That's a mild cam/head setup. (unless someone has worked the heads over)

I would buy the 44s and run the 34 venturis they come with. It should be real close out of the box. The 44s will come in handy when you want more power/CC's and need to to run 36 or 38 venturis.

Sat Jul 23, 2016 4:40 pm

The 44's come with 36 vents.

Sat Jul 23, 2016 7:14 pm

I would get a set of 40 hpmx's. Order some 32 Vents and jet accordingly. That cam is small for 2007 and your rpm will probably be 5500 max anyway. From idle to that 5500 the 40's will feel snappier. My opinion.

Sat Jul 23, 2016 7:49 pm

Would not the choice depend on the where you want the top end RPM to be. Maybe the 44's for a race or drag engine. But for good bottom end torque the 40's. But with those big valves and depending on the cam your running you may already be committed to running the 44's.

Sat Jul 23, 2016 8:57 pm

sullydog93 wrote: Either size will work running 34 venturis. That's a mild cam/head setup. (unless someone has worked the heads over)

I would buy the 44s and run the 34 venturis they come with. It should be real close out of the box. The 44s will come in handy when you want more power/CC's and need to to run 36 or 38 venturis.

I was thinking the same thing. Most likely that cam is the limiting factor.

With that size engine, i would rather have bigger 44mm throttle plates opening up and get more "Venturi" effect out of the same size vents as compared to what the 40's can do.