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General Engine Performance Questions
#1
Hey all,

I just recently became an owner of a 1971 Mach 1 Fastback back in April. I've been going through a few repairs and just generally getting to know the car and thought I better ask the community for some of their wisdom.

So for starters, my Mach 1 has an aftermarket "Performance" Edelbrock 429/460 motor in it that was installed by the previous owner. I am also assuming that the intake manifold and carburetor are also Edelbrock, but to be honest that might be dangerous assumption to make. So question number 1. How can I figure out exactly what engine, air intake manifold and carb I have? Is there a standard location for serial numbers? I've tried searching on Edelbrocks website without much luck. I just want to make sure the combo works together well.

To reference my original reason for posting, I recently ran into a problem that I would like to nip in the bud. I think it is a "tuning" issue with the carb but it could be something else. So recently I had one of the rubber hoses in the fuel line go bad. At first it was just a small leak, but I think it was causing my motor to run lean and it was overheating a bit. Eventually it reared its ugly head and the leak finally got bad enough to prevent fuel from getting to the carb. I wanted to make sure everything in the fuel system was good so I took it to some local buddies who own a shop to get it it fully checked out (I thought the in tank filter might have clogged). Found the bad part of the fuel line and replaced it as well as the filters while we were there. They also did some "tuning" of the carburetor. Afterwards the idle has been really great and it honestly has felt like it is running well and the overheating issue is all gone. 

However, when I'm on the highway if I'm going ~80 mph and I want to accelerate, I seem to lose power somewhere around ~83 mph (I'm not flooring it or anything either). When I back off the gas the power seems to come right back shortly there after. Before this overheating and fuel leak issue appeared I had def hit 110 mph before without any problem (I know I probably shouldn't but it's hard to resist and I don't sustain that speed, it's just for 1 stretch of straight highway that's probably 3 miles long). Also semi-flooring it at low speeds doesn't seem to be a problem. So my obvious thought, having just dealt with a fuel issue, was that the engine isn't getting enough fuel, but honestly I don't know enough about carburetor based engines to make that call. I thought maybe the bowl was running dry, but then I also thought what if the bowl/fuel is too rich and doesn't have enough air? Do you guys think this is a Fuel/Air ratio issue? Or a fuel flow issue?

I also ran into vapor lock this past weekend so I am considering installing an electric fuel pump in parallel with the mechanical one and putting a switch in the cabin so I can turn it on and off at will. Thoughts in this?

Thanks in advance!
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#2
as for the intake... keep looking for some number stamped on it somewhere... i'm running a edelbrock also and i don't recall one but maybe i looked wrong place. for the carb the number (memory serves me right) is stamped on the front of the mounting flange.
[+] 1 user Likes delawarebill's post
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#3
A couple pictures would help for quick identification.

Carburetor should have a part # stamped on the front of the passenger side base plate.

[Image: 44932d1051772333-vacuum-line-timing-edelbrock-temp3.jpg]

I'm not a fan of Edelbrocks and sold all mine years ago, but if it's too rich on your high speed blast, it'll be leaving a trail of black sooty smoke. My guess is it's too lean and probably running out of fuel.

Regarding the booster pump, that is a possibility, but Edelbrocks are known for heat soak issues. Put a good phenolic spacer under the carb and eliminate as much rubber in the pump to carb line as possible with steel.


[+] 1 user Likes Hemikiller's post
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#4
The two biggest reasons for vapor lock are fuel line too close to exhaust pipe and/or a restriction in the fuel line.

Vapor lock occurs between the fuel pump and fuel tank and is caused by the vacuum created by the fuel pump, which due to the low vapor pressure point of gasoline basically causes the fuel to boil, creating the vapor.

The sock in your fuel tank may be clogged or the short sections of rubber hose that connects the fuel line to the tank or fuel pump may be weak and collapsing, or the fuel line may be contacting the exhaust pipe.

Your engine lack of power problem sounds like fuel starvation and the reason for it is likely to be associated with your vapor lock problem.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
[+] 1 user Likes Don C's post
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