Fiddly job
Hi Jim,
I did this section a few weeks ago , and found it very fiddly. First off, I would be sure the Radiator with its face plate are in their final position, with clearance for the heater door to fully open and at least specified clearance between the fins of the radiator and the cooler box ribs.
I would cut the cooling duct to the first scribe line, expecting to trim it more later. Drill and cleco the duct in place; the fit around the oval air intake determines where the radiator end of the cooling duct will be. Now see how much space you have between the face of the radiator and the trimmed end of the cooling duct. There needs to be a big enough gap to give the cowl duct interface ? inch clearance off the face of the radiator. The gap is for the rubber duct seal.
I found I had to cut the cooling duct back a lot more than the 5/16? specified in Step 8 on page 49-13. More like ? inch. This is because the plans don?t allow for the thick fillet in the angle of the cowl duct Interface.
Its fiddly as I said, but the dimensions are not critical. There is plenty of overlap between the cooling duct and the duct interface for bonding. Over-trimming 1/8? will not be a problem.
Just don?t do what I did ? let the duct interface move out of position when you bond the duct interface to the cooling duct. You might be up for $27.70 to replace that itty bit of rubber cowl duct seal B!
Best of luck, Rod