Hello, I just joined and own 1970 Maverick with Grabber appointments! I have some technical questions and will post soon. I will also post a picture of it. Black with black original interior. 302 roller motor with a C4. I have a hobby business of rebuilding carburetors and tuning! I am 71 years old and bleed Ford blue if you cut me. Also own a 1967 Mustang. Also black. Rob Campbell
Welcome to the forum Rob! Where is Bremerton; Washington? It just so happens I'm dealing with an intermittent engine missing issue under heavy acceleration. Once it starts, it keeps going and it will eventually smooth out. I replaced a 120 gph Carter fuel pump that has been in service since 1991. The pump wasn't the problem. The Carter pump was obsolete, so it took me a day to install a different pump having to replace fittings and bend new fuel lines etc. On top of that, having to deal with the current crop of parts store counter people that had no clue about brass fittings, metal or rubber fuel line. They wanted to find what I needed based on my vehicle year, make, model, and engine. I tried to tell them the parts I needed were not associated with my vehicle. I ended up walking out of the store. My Mighty Demon 650 may be the culprit. When that carburetor is running right it is a beast! I'll try replacing it with one of my lesser high-performance known quality carburetors.
Bremerton is about 30 miles due west of Seattle. As the crow flies! Give me a call at (564) 229-9967. I talk way faster than I type! I have many questions to ask about your engine and such. I bet I can help you!
Rick, I think I would go after the ignition system. first ensure you have 12 volts to the system from the key. Many times I have ran into voltage drop on the power wire due to age. Not sure if you have the ability to swap out the dizzy? Even to an old points dizzy. Don't run it long with the cast iron gear. Just enough to test for missing. The other thought is high float level. I have cured many a problem with Holley and Holley clones with a simple needle and seat change. And you can do it on the engine! Rob
I want to know your rear tire diameter? The 3.80 gears with 25 or 25 diameter tire would be better at the traps for your car?
Rob, I have 26" tires on the car; I know that puts me way too low in the rpms going through the traps with a 3:80 gear ratio. I mention that fact in one of my videos in my "Garage" post. As I also stated in my "Garage" post, I built the car to be street and highway driven never trailered. It is not a race car A Gear Venders overdrive in combination with a much lower rear gear might be nice. Note to self, "It is not a race car". Thank you for the written advice on my engine misfire in your previous post. I corrected my engine issue by installing my Speed Demon 750 vacuum secondary carburetor. My Comet runs really hard again with no misfires. I'll go about diagnosing and fixing the Mighty Demon 650 that was on the car. I'm thinking power valve.
Rick, Under full throttle the power valve will be sensing zero vacuum and be wide open. A ruptured power valve will cause very rich idle mixture and drive you out of the garage. Most modern carburetors have backfire prevention installed in the throttle plate assembly. Not as many problems and Holley offers a kit to install in their older carbs. 125-500 is the part number and an easy install. I would look at the needle and seats. Holley has .110, .130. and .150 sizes. Bigger is better! Demon experienced some quality control problems early on. They are better now. I ran a supercharger Demon carb and it worked great! Rob
Rob, Thanks for the guidance. I remember replacing the power valve in my 20+ year old 650 Speed Demon for the very reasons you described. I'm well aware of the quality control issues with the Demon carburetor line when it was still under Barry Grant management. Have you noticed the newer Demons have smaller bowl vents than the older units? I'm of the belief that was to reduce the amount of fuel evaporation in those huge Demon fuel bowls. I noticed my old Demons would lose bowl fuel if the engine had to set a month or two without starting. Fuel bowls would be low or empty. I'll get started working on my Mighty Demon one of these days. Again, thanks for the advice; not too many carburetor experts around anymore. Rick
