Excellent thread! Thanks to this, I was able to understand how the hot air choke works. Mine is the electric assist version and is on a 73 Gran Torino with 302 and stock carb. Picked up a HELP! kit (at local auto parts store) with new tubing and fittings to replace the old one on mine.
This post is great and I'm anxious to see the photos. I just replaced the carb on my daughter's '76 F250 and I was left scratching my head on how the choke actually worked (I'm a bowtie guy so this blue oval stuff is greek to me but I'm learning thanks to you guys!). The 360 in her truck has both the heater hose bracket on the choke and the small heat tube (I don't know yet if it should go to the intake or the exhaust since I just found this post while I'm at work and will need to look at her truck).
Back to the header issue, it seems like I should be able to wrap some metal tubing around the header clamping it with a hose clamp with one end going to the choke connection and the other end to the carb air horn (with piece of rubber hose making the connection) so the choke pulls filtered air.
Now I just need to find that thread about how to fine tune these Motorcraft 2 barrel carbs! I've played around with it and got it close but some directions from the experts would be very helpful! *EDIT* Found the thread for the carb manual!
Last edited by Iowa Guy; 01-14-2011 at 01:27 PM.
Reason: Found the thread regarding carb manual...
Should the vacuum generated in this hot air system be enough to cause an idle problem? With this hooked up on my truck it idles very rough and the truck doesn't run well. If I plug it the idle smooths out and the truck runs much better. I have a 75 F150, 360 2bbl, 4 speed.
Any vacuum leak can cause issues, especially if the engine's vacuum level is low enough. On a completely healthy engine maybe not, but if there are other conditions that could potentially lead to rough idle issues, then one more vacuum leak can be enough to cause a noticeable drop in performance.
What specifically must you plug to smooth out the idle?
Originally I had to plug the clean air line for the choke to make it run. I have since gone through all the vacuum lines and replaced them. I no longer have a problem with the choke circuit. The engine is original with 94k miles. All vacuum line were disconnected except for the distributor and power brakes. The EGR was hooked up but incorrectly. I re-ran the vacuum lines to the EGR going through the PVS valve but it developed a pretty good miss running down the road so I disconnected it for now. I got this truck from my father in law after he died. He had a friend that said he was a "mechanic" who worked on his truck. From what i've seen I don't think he knew much. When I got the truck he had manifold vacuum running to the EGR. Thanks again for the great write up on how the choke works.
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