I made another shroud with changes to the #1 #2 side but didn't get the results I wanted . still about a 15-20C temp difference . . Also still didn't get the fan clearance right . I modified it to get fan clearance and have a bit more clearance than my other shroud . The funny thing is it gives a distinct almost blower type whine that the other shroud doesn't . I'll leave the R&D on the shroud for now , One I don't like working with fibreglass it's a PITA to work with and I don't know if the temp difference is just something with this engine ,even though the compressions are even . If I had cheap dyno excess I'd run it up without the belt and see what the difference is with load .
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I moved on to trying to make the car nicer to drive , the exhaust has always droned and been loud and after an hour on the freeway is not nice . Since I couldn't buy a muffler to fit where I wanted to put one ,I decided to have a go at making one . Pretty happy with the results. I'll make another one for the other side but with just straight tube .
custom muffler 1.JPG
custom muffler 2.JPG
custom muffler .JPG
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great work Wreck! interested to know how many decibels you have reduced with your own muffler? its always hard balance to get right with limited supply of exhaust parts for the Type 4. Ill no doubt build my own also.
The DIY muffler replaced the little resonator in the pic ,it's fibreglass packing had burnt away . It was quieter but still droned , I removed the big triflow muffler and fitted a resonator , that has removed a lot of the drone ,I plan to make a straight through muffler and then a resonator running behind the engine with the exhaust tip in the centre near the collector . It's 2 1/2 inch system .
Gabbi underneath . .jpg
I have let the car idle without a belt and the temps are still different , I'd like to run it under constant load off the idle circuit . With 4 CHT's you can really see how much idle mixture and carby balance plays with head temps ,even when driving . I know the thermocouples/gauge is accurate because after running turning off and checking the temps 10 5 minutes later they are even .
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Merry Christmas Forum Folks , I wish you a safe and merry Christmas and fantastic New Year .
an update on the custom shroud .
I made a small concave shape change to the back (#1) section of the shroud causing the airflow to move more to #1 cylinder added a small vane and now have what I was hoping for . All 4 cylinders with in 10C all the time . Most of the time they are with in 5C of each other .
The picture is the CHT's after a 14km 30 minute peak hour commute in 30C ambient temps . The thermocouples are attached to the spark plug boss in the heads .
Not bad for an air-cooled engine with over 200 flywheel HP .
This shroud would be easy to use in a Joe Cali style conversion and may be made available to buy either by itself or with the cylinder covers depending on demand .
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. Also still didn't get the fan clearance right . I modified it to get fan clearance and have a bit more clearance than my other shroud . The funny thing is it gives a distinct almost blower type whine that the other shroud doesn't . I'll leave the R&D on the shroud for now , One I don't like working with fibreglass it's a PITA to work with and I don't know if the temp difference is just something with this engine ,even though the compressions are even . If I had cheap dyno excess I'd run it up without the belt and see what the difference is with load . 
