I currently have a 7747 with good results on a Chev Corvair. Im using twin TB's and no problem... I love this freakin car w/FI and DIS. The trouble seems to be with SA. Because of the Air-cooled engine's wide engine temp variation SA is a challange. Im using Oil temp as the Coolant Temp right now, but Its been if different places with the same result. The one constant source of ping on this engine is external temps. If the temp outside stays at 75-85, the car runs perfectly and no knocks....even under heavy load. When the outside temp goes to 90 and above, spark knock starts and the higher the temp...the more knocks. Heavy load increases the engine temp, but very slowly and before the 7747 can reduce the SA with coolant temp table. Since the 8746 as IAT and the 7747 does not, would I be correct in saying, the 8746 will act just like the 7747 except I could use the IAT on the 8746 to reduce SA based on outside temp? I know I could use other PCM, etc, but I do love the simplicity of the 7747/8746 and all I would have to do is add one wire. Thanks Ted www.browndata.com/projects.htm

I would use a real cold air kit to achive a better result. I assume your TBI unit is 5.125 inch where AC would bolt up. Spectre sells a bonnet and flex ducting that may work.

It being air cooled I can see that as tempermental. My newly installed IAT this spring on cool day shows at times a 100-90 deg diff from coolant to where sensor is located next to air filter at end of duct. On a hot day I see 40-50 deg diff.

Good luck!