Help me settle an argument

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Very cool of Rob to hook you up. Can't wait to see how she does. Don't forget to look into possibly jetting up some if that's gonna flow 750ish range.
 
I'd start with the 72/84 recommended jetting then move from there.

No problem on loaning it out. It was sitting on the shelf. Give it a good cleaning and get after it!

It should flow in the 800-830 range IIRC.
 
Keep in mind carbs are like anything eles, some work better than others. I have used two out of the box (new) carbs same cfm and one was a tenth faster no mater what we did. When you find the right combo hang on to it. I do agree your lacking in cfm.
 
bsad67 said:
Keep in mind carbs are like anything eles, some work better than others. I have used two out of the box (new) carbs same cfm and one was a tenth faster no mater what we did. When you find the right combo hang on to it. I do agree your lacking in cfm.
Click to expand...

Have you got any kind of a carb spacer under that 650?

By increasing the plenum volume, a 1"-tall spacer will trick the engine into thinking you've got a bigger carb than you have... and, they're cheap.

Good luck!:cheers:
 
sometimes the air bleeds are a little big on those ProForm MBs, couldn't get mine to tune right until I stepped down the air bleeds about4 or 5 sizes then worked great
 
Well I managed to get it on the car. It only took me 30 minutes or so to get everything swapped over and re installed. Initial impressions are good. I haven't fine tuned it like with the other main body (ran and drove like EFI), but it's not bad. I can get the idle and cruise close enough until I get to the track next Friday to tune for WOT.

Thanks again Rob. :blob:
 
Also, as it turns out the 650 main body I replaced is made by Proform. I remember seeing that once before but forgot.
 
Cool. Hope it doesn't have any pump shot bog and WOT tune it.

get after it!
 
Well I couldn't help myself, I had to see if I could get it to cruise like my other main body. A primary jet change (71), idle air bleed swap (71), and a slightly smaller idle feed restrictor (31) makes this thing cruise around like efi. My old setup with the nozzles and cams seems to work like a champ so I didn't mess with them. It only took 4 hours, all so I would get good mileage to and from the track tonight. Hey, gas is expensive. :glasses7:

Dialing in the secondaries shouldn't be too difficult once I make a pass to see where I'm at. We'll see for sure if my 650 was too small. I'm hoping for 1 - 1.5 tenths to make it all worth it. Off to the track, I'll post up the results when I get home.


:burnout:
 
Put a 1" open spacer under the new carb....both of them should net you around 1.5-2 tenths.
Brian
P.S. I've heard Rob is a good guy...but you know what they say about hear-say!! LOL!
 
Results!!!!! Well, not really.

It runs exactly the same as it did before. :banghead:

Yup, no change whatsoever. Exact same 60 ft, 330 ft, 1/8 mile, and 1/8 mph as before. It ran lean at first but once I jetted it up it was in the 12.8-13.0 afr range, which was where it seemed to run best with the 650 main body. I wound up running a whole string of low 7.80's at 86 mph, which is exactly what it was running last week. Maybe I could have played with the jetting some more but I don't think there was a tenth or more in there.

I also tried a couple other things, like taking out the 1/2 open spacer between the carb and intake, running with and without the air cleaner, and manually shifting instead of auto. There was no noticeable change with or without the spacer, adding the air cleaner slowed it down, and manually shifting it did the best mph of the night at 87. Like a dummy I forgot my timing light, but I don't know if that would have made a difference. Would the required timing even change with a bigger carb?

Well that's it, I was hoping to come back with good news but it didn't work out that way. I'm kinda bummed out about it, but that's the way it goes sometimes.........................
 
..........Darn, well atleast u had a goog time and never went backwards....timing may have made some difference....kim.........
 
Jet it up til it slows down. Use the meter to see where it is, but, not as a "this" is the number I should shoot for. Let the MPH tell you. It may be different from the 650dp number. Timing changes can make a difference too.

You know where I believe your main issue lies.
 
I haven't given up yet. I was going to run back out to the track again today but I realized my alternator wasn't charging my battery. I went to start it up today and the battery was dead. I wonder if that has anything to do with it. In any case I've got a new alternator on it and will keep playing with it. I was a little deflated last night but I'm not giving up. I think it's worth another shot but of course that won't be until next weekend.
 
I tryed up'ing my carb with no luck. Was running an 850 on my 400inch small block and went to a 950 Quick Fuel carb. Ran EXACTLY the same numbers, but I still run the 950. Figure if I ever make a change that will need a bigger carb, I've got it. Hope you find the numbers you want. Good luck.
 
I notice, the 650 is considered too small!! the fuel flow curve is where it's at.
in stock and super stock, they have to use the stock carb. they go very fast with "small" carbs!!!! the 69 340 cuda set the F/SA record, at 10.73,@ 120 MPH with a "small" AVS car. it's rated at 625 CFM. in super stock, the 283 chev has a 475 CFM rochester carb, the record is 128.11 MPH @ 10.20. they flog and tune , not change parts. just food for thought
 
perfacar said:
I notice, the 650 is considered too small!! the fuel flow curve is where it's at.
in stock and super stock, they have to use the stock carb. they go very fast with "small" carbs!!!! the 69 340 cuda set the F/SA record, at 10.73,@ 120 MPH with a "small" AVS car. it's rated at 625 CFM. in super stock, the 283 chev has a 475 CFM rochester carb, the record is 128.11 MPH @ 10.20. they flog and tune , not change parts. just food for thought
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I'd almost bet that most stock/super stock carbs DON'T flow what they're rated. Those guys massage EVERYTHING. Within the rules though!!:yawinkle::yawinkle:
 
hi you're wrong there, no polishing or any kind of rework is allowed!! only thing allowed is resized air bleeds and jetting. period. these are checked by tech. no maching of venturies, bores are measured. the thing is the fuel curve in carb. engine needs fuel. I run a T.Q., on my stocker, it has NO maching or modifications. only resized air bleeds, rejetted. the fuel curve is very flat, through the whole RPM range.
 
perfacar said:
I notice, the 650 is considered too small!! the fuel flow curve is where it's at.
in stock and super stock, they have to use the stock carb. they go very fast with "small" carbs!!!! the 69 340 cuda set the F/SA record, at 10.73,@ 120 MPH with a "small" AVS car. it's rated at 625 CFM. in super stock, the 283 chev has a 475 CFM rochester carb, the record is 128.11 MPH @ 10.20. they flog and tune , not change parts. just food for thought
Click to expand...


NHRA uses horsepower factoring to adjust the classes for their idea of "parity" in Stock and Super Stock ratings. Eons ago, cars were classified by their shipping weight divided by their advertised horsepower but that was so long ago I can't even remember when they changed to the "factored" horsepower system; probaby in 1972 when all the cars were de-rated to the then-new net horsepower system. For example, the 318 2bbl motor was rated by the factory at 235 in 1971, and dropped to 150 in 1972 with NO mechanical changes. That's a whopping 56-percent!!!

Now, the NHRA assigns motors factored horsepower ratings and the new numbers have a lot to do with your perception of how a car runs, with given equipment.

For example, the 1969 340 is factored to 299 hp, while the 1971 340 is factored to 314 hp, a difference of 15 horsepower, with only a carb change; an AVS vs. a Thermoquad.

But, that 15 horsepower in F Stock means that at 10.5 pounds per horsepower, the 1971 car has to weigh 10.5 X 15 = 158 pounds more than the '69. That's worth a car-length and a half.

So, the reason the record goes to the '69 may not be because it's putting out more power with the smaller carb, necessarily, but because it is legally 158-pounds lighter for the same class.

You can check on the factored horsepower for any engine that's legal for NHRA Stock or Super Stock cometition at NHRA.com. Go to "NHRA RACER" and the site will direct you from there to the "Stock Car Classification Guide."

At the very bottom of each column for the different hp engines, you'll find the factored hp. It's usually different for Stock (one asterisk) and Super Stock (two asteriisks) They have different hp for cars with (allowed) aluminum heads and... get this;
:wack:
the same engine MAY be factored to a different hp in two different bodies (go figure.)

It's a snake pit...
 
perfacar said:
hi you're wrong there, no polishing or any kind of rework is allowed!! only thing allowed is resized air bleeds and jetting. period. these are checked by tech. no maching of venturies, bores are measured. the thing is the fuel curve in carb. engine needs fuel. I run a T.Q., on my stocker, it has NO maching or modifications. only resized air bleeds, rejetted. the fuel curve is very flat, through the whole RPM range.
Click to expand...

As per the rules, you're right, I'm wrong. As for tech CHECKING for those things.......nah. Maybe if you have something obvious or you get torn down. I know more guys that BEND :D the rules on a lot of things in those classes then don't. So please don't preach the "we have rules" thing. To quote a stock racer I know "If you ain't cheatin ya ain't tryin". Just sayin

But what this thread is about isn't stock or super stock, it's about trying a different carb with no rules to bend or break. So change it as many times as you can and log the differences.............if there are any. Good luck!!
 
UOP said:
Yeah, it's a little heavy on the front, but it's not as bad as you'd think. I usually don't have a problem with traction, but it does squat hard on the launch. It's good for pretty consistent 1.68-1.69 60 ft times.
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That is some of your problem there. the a$$ end is pulling a "camaro" on you. eliminate some of the squat and you might improve your times more than a carb change. Which will also help. Just MHO take it as you will
 
Comparing a competitive stock or SS car and what goes into them to the OP's car isn't something I would do.

There's no porting in stock eliminator heads... nope... :)

Any way to stiffen up your rear shocks?
 
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