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Discussion Starter · #1,363 ·
I haven’t done much to the car over the winter. One thing I did finish today was removing the 750 double pumper to try a 650 Demon with vacuum secondaries. I paid too much for the demon as it was misrepresented on FB marketplace. I went through it, fixed someone’s previous mistakes, put a fresh kit in it and it now works well and I’m happy with it. The throttle response is snappier at lower rpms than the 750 was.
 

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Discussion Starter · #1,365 ·
It’s not a dumb question. The demon line was brought on the scene by Barry Grant. The top of the throttle body has a smoother transition into the Venturi and it has a billet base plate and metering block. Holley jets, power valves, gaskets and other small parts work on it. Holley bought the demon line and still sells them. This carb had an electric choke but I removed it
 

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56 BelAir 2 door hardtop. Small block 400 with TH 350 9" Ford rear end.
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I have always had better performance on the street with vacuum secondary carbs. A double pumper sized correctly and tuned perfectly will probably out perform one but for ease of tuning and drivability give me a v.s. every time.
 

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Discussion Starter · #1,367 ·
I’ll agree with that. On almost the whole car I have run whatever secondhand parts I got a deal on and the double pumper is in that category. It would be a good drag race carburetor and I was a little surprised that I have enough motor to handle it. Most of what I do with this car is cruise and so far the 650 seems much crisper at lower speeds. The gas mileage might get better too. I have no idea what it is now. Really haven’t cared.
 

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Discussion Starter · #1,368 ·
I’ve been trying to sort out carburetor problems. My Demon has a hesitation in it at around 2 grand that I haven’t been able to work out of it yet. I bought a wideband air fuel gauge that came with a defective oxygen sensor. I’m currently waiting on a replacement to be sent. I’ve also purchased a bench seat shifter handle and assembled a shifter to work with my upcoming bench seat.
 

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Discussion Starter · #1,372 ·
it’s almost like the pump shot is not lasting long enough to let the carb get from off idle into full throttle.
I had thought about that but it only does it under light acceleration in a certain spot. If you go ahead and throw the coals to it, it goes. I may have a little too much jet in the front because it loads up a little if it idles for more than a few minutes . I discover little things the more I mess with it.
 

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Discussion Starter · #1,373 ·
I messed with my carb yesterday and I think I have most of my hesitation problem worked out. I think the genius that jacked up the rest of the carb messed with the accelerator pump adjustment bolt too. I know you are supposed to measure the clearance between the accelerator pump arm and the bolt with a feeler gauge but I forgot the measurement. You could visually see that it wasn’t squirting as soon as it should so I kept backing off of the adjustment nut until the car ran better. The car needs gas in the tank and the closest 93 pump is 20 miles away so I quit until I get some more gas. I also removed the 68 front jets and put 66 in place of them. That seems to have taken care of the loading up at idle.
 

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Don't you just love what some so called experts can do to mess up things. They always seem to think they know more than the people who design and build things. Thers is much misinformation on tuning a carb on the web.
 

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56 BelAir 2 door hardtop. Small block 400 with TH 350 9" Ford rear end.
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The reason for the clearance between the pump lever and the bolt is so the linkage won't get bent when the pump is at full stroke. .050 is usually what is called out. I set it there then open the carb to w.o.t. by hand before it has fuel in it to make sure nothing is binding. You can bend stuff with that heavy right foot and never know it.
 

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I guess the next step is to sort out what squirters are currently installed, and what came with the carb when new. Really large squirters shorten the time of the squirt, smaller lengthens. I am still Thinking you have a pump shot/squirter issue at transition. Either a short pump shot, I.e., linkage not permitting a full shot, or squirters that are two large, so the pump shot does not last long enough to get you past the off idle transition and the main system kicks in.
 

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Discussion Starter · #1,377 ·
I guess the next step is to sort out what squirters are currently installed, and what came with the carb when new. Really large squirters shorten the time of the squirt, smaller lengthens. I am still Thinking you have a pump shot/squirter issue at transition. Either a short pump shot, I.e., linkage not permitting a full shot, or squirters that are two large, so the pump shot does not last long enough to get you past the off idle transition and the main system kicks in.
It’s a 31. I believe it came with a 31
 

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Discussion Starter · #1,378 ·
The new oxygen sensor that Autometer sent me arrived yesterday. I installed it and it made no difference in how the gauge acts. It is still stuck on 17.0 which is as lean as it’ll go
 
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