Just placed my rebuilt (by Air/Fuel/Spark) carbs and a rebuilt (by John Slack) dual spark distributer on our GT500 #906. My exhaust heat riser does not have the butteryfly flapper and hardware on it. Seems like it takes a long time to get the automatic choke to warm the forward carb enough to get it to idle down.
Should the heat riser have the butterfly and hardware and if so does anyone know a source for one of these?
Thanks. Terry Hill
Quote from: nwfire on June 13, 2025, 11:38:51 PMJust placed my rebuilt (by Air/Fuel/Spark) carbs and a rebuilt (by John Slack) dual spark distributer on our GT500 #906. My exhaust heat riser does not have the butteryfly flapper and hardware on it. Seems like it takes a long time to get the automatic choke to warm the forward carb enough to get it to idle down.
Should the heat riser have the butterfly and hardware and if so does anyone know a source for one of these?
Thanks. Terry Hill
Terry, I am not quite sure from your wording if you have the heat riser but with no hardware (gutted with no wheel) or missing the entire spacer. I think that they are a joke when used on a 67 GT500 and if my car I would have one that look correct on the outside but rendered not working (flap open always or no flap). That is if I was pleasure driving the car. If it was for concours I would not go to the extra trouble of modifying for pleasure driving and just put on a working unit and forget it. With that said I have nice used working heat riser spacers and blank ones (no wheel or flapper). PM me if I can help.
Bob: Our car has the heat riser spacer, with no guts in it. Would the carb idle come down faster with the butterfly flapper in the spacer? I drove it the other evening and went probably 1 1/2 to 2 miles and the idle was still not down to a comfortable speed.
Did these cars originally have the space with the butterfly valve when new?
Quote from: nwfire on June 14, 2025, 08:06:11 PMBob: Our car has the heat riser spacer, with no guts in it. Would the carb idle come down faster with the butterfly flapper in the spacer? I drove it the other evening and went probably 1 1/2 to 2 miles and the idle was still not down to a comfortable speed.
Did these cars originally have the space with the butterfly valve when new?
Yes they had a stock heat riser. I would suggest adjusting your choke instead so that it opens faster. If you don't get the results you want default to get one with the guts.
Terry to answer your question more succinctly yes the butterfly that was stock on all GT 500s would help but in reality it probably will still be inadequate. The 500s original design with filter on fresh air tube was poor to begin with. Other single carb systems route the fresh air tube to carb body that creates vacuum that pulls air through rather than just relying on "hot air rises" Other issue is hot air tube is about 2 feet long. On my 65 R code the stove is on drivers side so tube is about 10" and it works great no heat riser at all on those