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I'm about to start building my type 4 engine, waiting to get the parts back
from the machine shop. I will use AN heads with 41 x 34 mm valves. Haven't
bought the cam yet but it will have 290 dur. and 0.535" lift at the valve.
Will this cause coil bind with H.D single springs? Also will the head be
able to flow this much? It will be mildly portet and with a 3 angle valve
job.

Hmmmmm. I think you should step up the exhaust valve size to a 36 or 38 and run 42 intakes. Also not knowing what the lift is @ .050 makes it hard to really tell much about the cam, but it sounds like its a pretty wild cam. Most cam recommedations for a street T4 will be in the 250 @.050 range.

About the coil bind concern, you will have to check the figures and set the springs at a best educated guess, then doulbe check them when the heads are assembled and installed onto the engine. Now people that build a lot of engines and use the same brand and pt.# parts regularly would have a very good idea of what to shim the springs to. But a one off needs to have everything double checked. BTW, dual springs would probably be needed with a cam with that lift and duration due to really fast ramps.

Hope this helps ands I'm sure some more cam knowledge will pop up here soon for you.

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Tom Notch