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PostPosted: Tue Mar 24, 2020 6:23 pm 
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Supercharged
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I had that problem with the '69 dart one time.

Drove it to the Track for TNT.. Shifted to 2nd gear @ ~6200 RPM, boom.. no more bellhousing, back of the the engine block, throwout bearing support or pressure plate. Could not drive it home.

The Droschak's graciously came to pick me up.

Greg

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PostPosted: Wed Mar 25, 2020 6:11 pm 
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Turbo EFI
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Car Model*: 1963 Dart 270, 1980 D150
Spent some time polishing the turd today. Bent up a new fuel line for the 750 Holley. I now have one for the 500 Holley 2 barrel, one for the Edelbrock 1406 and one for this Holley 3310. What are the odds that my junk can go any faster with this bigger carb? Still lots of tuning to do. I see a test drive in my future tomorrow. No real improvement can be proved or disproved until some normalcy returns and I can go back to the drag strip.
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PostPosted: Wed Mar 25, 2020 6:54 pm 
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I bet It won't run.

I tired a 750 CFM holley on my ruster yeats ago and it was too big. The way I understand it the carter CFM rating is not equivalent to the Holley CFM rating.
Find a 750 eddy or carter afb or avs or maybe even a demon street demon 750.

I believe Ron Hamby used a 600 or 650 CFM Holly on his car at one time with desirable results.


Best of luck Brad!

Greg

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PostPosted: Wed Mar 25, 2020 7:12 pm 
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Food for thought.

https://www.speedwaymotors.com/the-tool ... need/28634
My valc's for my engine put it at right around 500 cfm however it did pick up with the carter 750.


Greg

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PostPosted: Wed Mar 25, 2020 7:23 pm 
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Turbo EFI
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Location: Rome, GA
Car Model*: 1963 Dart 270, 1980 D150
Those calculations say I need about 400cfm but the 600cfm Edelbrock runs really well on my engine. I have an Autolite 4100 4 barrel that people commonly refer to as a 600cfm carburetor but when flow tested they seem to come in at the 500-530cfm range. https://www.fordfe.info/Autolite4100Test.htm At some point I want to try it. I ran it on a near stock engine with bolt on goodies and it ran really well. All this is just stuff to pass the time.

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PostPosted: Wed Mar 25, 2020 10:56 pm 
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I have always found the cfm calculator to be way low. I think it is for the cfm necessary to sustain a set rpm. It does not take into consideration that you are accelerating a vehicle.

Try the 750. Worst that will happen is it won't work.

I know Ron was trying a 750 on his. I have a 600 on mine, but have a 650 to try.

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PostPosted: Thu Mar 26, 2020 2:23 am 
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Supercharged
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Yep..it sure can't hurt to try it.

I sure understand the garage quarantine too Brad..


Greg

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PostPosted: Thu Mar 26, 2020 6:42 am 
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Turbo EFI
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Location: Rome, GA
Car Model*: 1963 Dart 270, 1980 D150
Yup, self imposed garage lock down. It could be worse. I am very thankful to have my garage/sanctuary.

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PostPosted: Thu Mar 26, 2020 11:41 am 
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Turbo EFI
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Location: Rome, GA
Car Model*: 1963 Dart 270, 1980 D150
Pile of parts Holley 750 road test results- negative. Starts, idles and runs fine but has a big hesitation when you punch it at any speed, then pulls hard. I noticed the pump shot looked weak. It's adjusted properly and uses a 31 squirter and orange cam. More investigation into the accelerator pump is needed. I will probably set it aside and put the Edelbrock back on for now.
After the test drive I decided to go through the valves since the engine had some hear in it. They required very little adjustment.

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PostPosted: Thu Mar 26, 2020 12:36 pm 
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Holley 4bbls are hard to set up properly on a Slant 6, in my experience. Everyone I've known who tried a 750 Holley on a Slant tried futzing for a while and then went back to a smaller carb. It will be hard to beat the Edelbrock.

Lou

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PostPosted: Thu Mar 26, 2020 3:29 pm 
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I spoke at length with Ron about the 750 and he told me that all the calculators said that he needed less than 600cfm on his car. But by putting on a 750 that he picked up .3 of a second in the 1/4 mile. I tried a used 750 on my car when I was running 13.80's and never got it running right. It may have been a junk carb! But by going from my 600 to the Webers, I have picked up over .4 in the 1/4. I did drop from 4.56 to 4.30's also.

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PostPosted: Thu Mar 26, 2020 3:40 pm 
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My personal theory on carb size and the charts. The charts are for basically street driven cars. Remember the CFM rating of a carb is at a certain pressure drop across the carb (1.5 inches of water for most 4 bbls). That pressure drop proves there is a intake (carb) restriction. That is why a racing engine at WOT normally will work better with a bigger carb (at the expense of low speed driveability). In theory, if you put a sensitive vacuum gauge at the base of the carb, the correct size carb would be at the point where the gauge reads zero (no inlet restriction).

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PostPosted: Thu Mar 26, 2020 4:36 pm 
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I wonder if in Ron's situation it was because of the alcohol fuel he may have used rather than gasoline?


Greg

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PostPosted: Thu Mar 26, 2020 6:43 pm 
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Turbo EFI
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Location: Rome, GA
Car Model*: 1963 Dart 270, 1980 D150
I wanted to try the 750 because I saw an old post by Terry Littlejohn on the Engine Build Matrix I think, where he said on his Duster street car he went from a 500cfm, to a 600, then to a 750 and dropped ET each time. I built this carb from parts and from some old and even used gaskets. I don't think it is 100% as it is and has the potential to perform far better than it did today.

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PostPosted: Fri Mar 27, 2020 3:31 am 
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Certainly the back of the box "calculators" for carb size are not designed for pure drag racing performance. You might pick up a little with a 600 to 750 swap, but if everything is perfectly tuned in both cases, it should be a small gain.

Lou

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