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- Dec 24, 2011
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I have recently mounted a Stroker based on a C85-12 (STC converted to -8 = no accessory-case) with O-200 crank and cylinders. I thought I had done ALL of my homework including talking and dealing with experts on the topic where we all agreed that everything would mount-up and be the same-same (same engine mount, same exhaust, no issues with exhaust-can clearance as I have no starter or -12 clearance issues with oil screen).
To my surprise, the resulting exhaust dimensions were different than the A75 that it replaced. While the exhaust flanges meet/mount to the cylinders as-expected, the whole exhaust system is riding about 5/8” lower the original setup (when measured to the cowl and/or engine mount). I believe that this is all due to the O-200 cylinders (Millennium) having a slightly different dimension on the exhaust port relative to the crankcase/engine-mount. (unless someone convinces me that the C85-12 case, converted to a -8, is different dimension than a true -8).
As a result, I must modify the manifolds (either cut the down pipe and/or angle the rear) or modify the cowl. I’m trying to keep this as original looking as possible. Thus, I don’t want to modify the cowl and would rather tweak the exhaust system.
Before I cut & weld the manifolds, does anyone have any experience with this situation or have better ideas?
For comparison purposes. A75 picture of my original setup and the new Stroker/C85 setup with top cowl only. You will see that the exhaust-to-cowl relationship in the A75 was not dead-center but visually acceptable. The new setup only allows me to show the relationship to the top cowl as the bottom cowl is a no-go without the mods.
For reference the dimensions of the cowl for the exhaust is: 3 3/8", the exhaust OD is 2", the current distance from the top cowl to the OD of the exhaust is 1 11/16". Thus, I need to "raise" the exhaust by a minimum of 5/16"; safer would be ¾’; to be centered vertically in the hole would be 1".
To my surprise, the resulting exhaust dimensions were different than the A75 that it replaced. While the exhaust flanges meet/mount to the cylinders as-expected, the whole exhaust system is riding about 5/8” lower the original setup (when measured to the cowl and/or engine mount). I believe that this is all due to the O-200 cylinders (Millennium) having a slightly different dimension on the exhaust port relative to the crankcase/engine-mount. (unless someone convinces me that the C85-12 case, converted to a -8, is different dimension than a true -8).
As a result, I must modify the manifolds (either cut the down pipe and/or angle the rear) or modify the cowl. I’m trying to keep this as original looking as possible. Thus, I don’t want to modify the cowl and would rather tweak the exhaust system.
Before I cut & weld the manifolds, does anyone have any experience with this situation or have better ideas?
For comparison purposes. A75 picture of my original setup and the new Stroker/C85 setup with top cowl only. You will see that the exhaust-to-cowl relationship in the A75 was not dead-center but visually acceptable. The new setup only allows me to show the relationship to the top cowl as the bottom cowl is a no-go without the mods.
For reference the dimensions of the cowl for the exhaust is: 3 3/8", the exhaust OD is 2", the current distance from the top cowl to the OD of the exhaust is 1 11/16". Thus, I need to "raise" the exhaust by a minimum of 5/16"; safer would be ¾’; to be centered vertically in the hole would be 1".
