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  #31 (permalink)  
Old 09-23-2012, 04:33 PM
How fast is fast enough?
 
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Originally Posted by Daubers View Post
soooo if I am keeping this beast of a carb, what do you guys recommend as a starting point for tuning it street friendly. If its set up right now for upwards of 950 that is going to be too much i think. One thing that I do not understand is how much play I have to change the cfm thru tuning on a carb. Being as it was originally a 750 could I get it closer to there with a jetting change? Forgive my ignorance guys, first time dealing with a carb that I didn't just take out of the box and tune from there, and many thanks! I am learning alot.
you need to find the stock settings to start with, or someone that is VERY familiar with that carb. jetting for cfm is a HUGE error as the air signals and fuel signals depend on a lot more than cfm.

two identical holleys could require two different jetting settings if the emulsion tubes are different, or the boosters, or the venturi shape, or many other things. MANY things attribute to jetting requirement.

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  #32 (permalink)  
Old 09-23-2012, 04:37 PM
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PJ,relax,remember what you told me the other day,lol...
and yes you probably could technically take out the metering rods,especially in a carter and run the carb with a big jet change.
IMsport,maybe change from wouldnt to shouldnt? then explain why in details so that people wanting to learn,then will understand rather than get distracted by other users arguing over grammar/spelling and other subjects some of us might not be that good at.
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Old 09-23-2012, 04:45 PM
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This can give you a few good tips!

But to change C.F.M. rating you would really have to change the carb! The Cfm is a rating of air that a carb can have flow through it at a particular rpm! Its like blowing through a soda straw and then blowing through a 1 inch pipe the pipe flows more air, and then trying to reduce the one inch pipe to the size of the straw! its easier to buy another straw and put the pipe away till you need it!! Thats as simple as I can explain it without writing an essay LOL

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  #34 (permalink)  
Old 09-23-2012, 05:10 PM
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Originally Posted by painted jester View Post
You two braineacs should learn to read!!! the statement says "for the street its fine"!!!!! > and "My competition carbs have no power valves"!!!!!!" (The word is COMPATITION)!!!!!! and "I dought if his B.G 4779 stage 3 has one"!!!!!!!!

Now you 2 brains tell me where I told anyone it was ok to run without power valves on the street !!!!

Jester
Even as a brainiac, its impossible to tell exactly what you were saying, much less implying.

The myth of removing PV from any carb needs to be pointed out as false at every opportunity. I buy racing carbs from one of the top carb tuners in the nation and every one has a power valve in both ends, but all my experience is in road racing and stock cars.
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  #35 (permalink)  
Old 09-23-2012, 05:15 PM
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Originally Posted by ap72 View Post
you need to find the stock settings to start with, or someone that is VERY familiar with that carb. jetting for cfm is a HUGE error as the air signals and fuel signals depend on a lot more than cfm.

two identical holleys could require two different jetting settings if the emulsion tubes are different, or the boosters, or the venturi shape, or many other things. MANY things attribute to jetting requirement.
you mean stock as in before barry grant modified it?
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  #36 (permalink)  
Old 09-23-2012, 05:34 PM
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Daubers : you would be better off getting a smaller carb to match the way you drive and what rpm you think you'll hit and do minor tuning (basics)and put the BG carb on a shelf! Do your every day or weekend driving with the smaller carb and when you go to the track or want to play a little put on the BG! many rodders do just that, Im one who does, I have 6 carbs set up for different uses !!! Its easier then changing jets and pulling power valves and retuning for different situations! its only 4 bolts,linkage and line!

If you decide to take this advice youll need to know how to store the BG holley dont just put it on shelf!

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  #37 (permalink)  
Old 09-23-2012, 05:45 PM
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Originally Posted by lmsport View Post
Even as a brainiac, its impossible to tell exactly what you were saying, much less implying.

The myth of removing PV from any carb needs to be pointed out as false at every opportunity. I buy racing carbs from one of the top carb tuners in the nation and every one has a power valve in both ends, but all my experience is in road racing and stock cars.
I race 1/4 mile we're talking 2 different worlds!

I was implying his BG is a 1/4 or 1/8 mile drag racing carb that may not have a power valve.
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  #38 (permalink)  
Old 09-23-2012, 05:52 PM
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Daubers,if you do not want to use the BG holley,then pickle the carb for storage.
If you want that car to still have close to max power consider getting a new 750 hp.They can be ordered pre set up for under $600.00,or if you want tire melting throttle response and dont mind giving up some top end,buy a 650 double pumper. Those are my first 2 choices,after the BG of course but thats more race ready than street friendly.either way that little car will be a hand full.
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  #39 (permalink)  
Old 09-23-2012, 06:18 PM
How fast is fast enough?
 
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Originally Posted by painted jester View Post
Im one who does, I have 6 carbs set up for different uses !!! Its easier then changing jets and pulling power valves and retuning for different situations! its only 4 bolts,linkage and line!
May I ask, what 6 different uses?


And I meant stock BG settings, the stock "pre-modifed" settings are next to useless.
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  #40 (permalink)  
Old 09-23-2012, 08:31 PM
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@ 2 holley 450's with power valves LOL milled chock horns & vacuum secondary's for when the wife drives the Vet around cruising or at shows. When I drive around I run 2 Holley 650 double pumpers no power valves milled chock horns, ported venturie's, and for the track 2 950 3 barrel Holleys milled chock horns no power valves ported venturies.

And just picked up another tunnel ram for the wife to go in her Camaro Im building so she wont drive mine any more! with 2 600s with with Mechanical chokes & vacuum secondary with power valves Heres a pic of the engine I'm building for her! 302 old school

http://www.hotrodders.com/forum/atta...1&d=1348453553

Jester
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  #41 (permalink)  
Old 09-24-2012, 05:51 AM
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I will confirm tonight, I was told they were 78's. Right now it is simply getting too much fuel dumped in, and get's prominent as I adjust the timing. Would like to get it down to a nice idle, not needing 1600 rpms to keep it from stalling out.

Also i do not have access to a jet board.
Set the timing curve up first. If it's set up just for drag racing and you now want to drive the car on the street, it will almost surely need attention in the timing department. The importance of this cannot be over stressed! A race-only engine can often get by on locking the timing at full advance. But for street use, you want to use a timing curve. It will give you good performance at part throttle and better fuel mileage to boot.

Hopefully you have the cam specs. Using them you can estimate the initial timing. The total timing will depend on the compression ratio, fuel, and cylinder head design and material it's made of. If you don't have the specs, you can check the vacuum at idle and give a description of the idle quality (smooth idle, slight lope, very lopy, down right rough, etc.). This will give some indication of what you're dealing with.

If the distributor has a vacuum advance, it may be disconnected for racing. For the street you want to run a vacuum advance that supplies around 10 degrees of advance. An adjustable vacuum advance will allow you to tailor the cut in point of it and that's an important consideration, especially if the vacuum is lower than normal due to the cam specs.

Before going into this any deeper, I'll let you get back to us w/the cam specs, etc. In the meantime, a page w/info on timing is here.
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  #42 (permalink)  
Old 09-24-2012, 06:04 AM
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Set the timing curve up first. If it's set up just for drag racing and you now want to drive the car on the street, it will almost surely need attention in the timing department. The importance of this cannot be over stressed! A race-only engine can often get by on locking the timing at full advance. But for street use, you want to use a timing curve. It will give you good performance at part throttle and better fuel mileage to boot.

Hopefully you have the cam specs. Using them you can estimate the initial timing. The total timing will depend on the compression ratio, fuel, and cylinder head design and material it's made of. If you don't have the specs, you can check the vacuum at idle and give a description of the idle quality (smooth idle, slight lope, very lopy, down right rough, etc.). This will give some indication of what you're dealing with.

If the distributor has a vacuum advance, it may be disconnected for racing. For the street you want to run a vacuum advance that supplies around 10 degrees of advance. An adjustable vacuum advance will allow you to tailor the cut in point of it and that's an important consideration, especially if the vacuum is lower than normal due to the cam specs.

Before going into this any deeper, I'll let you get back to us w/the cam specs, etc. In the meantime, a page w/info on timing is here.
I started setting the timing but plugs were fouled. Decided to try autolite 303's in it and will reset the timing this week, as like you said, it is way off for street. Cams are 285/295 Duration, .507/.534 lift. It's running 10:1 compression. Thanks for all the help
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  #43 (permalink)  
Old 09-24-2012, 06:17 AM
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Originally Posted by Daubers View Post
I started setting the timing but plugs were fouled. Decided to try autolite 303's in it and will reset the timing this week, as like you said, it is way off for street. Cams are 285/295 Duration, .507/.534 lift. It's running 10:1 compression. Thanks for all the help
Do you happen to know the duration @ 0.050" lift? Prolly in the 234-236'ish range... Hydraulic flat tappet, I'm guessing?

I saw that you want it more streetable, being as how the cam isn't that radical (unless the duration you gave is at 0.050" lift!), this shouldn't be a problem- but the carb is definitely on the large side and being a double pumper, it is not going to be at all economical to drive. In this case, a change to a smaller carb could give a lot better mileage and better throttle response at lower engine speeds and smaller throttle opening.

Taking it a step further, swapping the single plane intake for an Edelbrock RPM dual plane can also help its street manners.

What heads are on it?
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  #44 (permalink)  
Old 09-24-2012, 07:06 AM
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Do you happen to know the duration @ 0.050" lift? Prolly in the 234-236'ish range... Hydraulic flat tappet, I'm guessing?

I saw that you want it more streetable, being as how the cam isn't that radical (unless the duration you gave is at 0.050" lift!), this shouldn't be a problem- but the carb is definitely on the large side and being a double pumper, it is not going to be at all economical to drive. In this case, a change to a smaller carb could give a lot better mileage and better throttle response at lower engine speeds and smaller throttle opening.

Taking it a step further, swapping the single plane intake for an Edelbrock RPM dual plane can also help its street manners.

What heads are on it?
I don't know the duration @ 0.050 off hand, but I do have the cam card at home I could look at tonight. Engine also has a Lunati lightweight rotating assembly, 202 camel hump heads. Rockers are 1:5 on intake and 1:6 on exhaust, msd dist and ignition.

They way its looking, i may just sell the BG to get a nice 650 or 750 double pumper. I won't be taking it to the track enough to justify keeping the BG, and cash is really tight unfortunately.
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  #45 (permalink)  
Old 09-24-2012, 07:59 AM
How fast is fast enough?
 
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Originally Posted by Daubers View Post
I don't know the duration @ 0.050 off hand, but I do have the cam card at home I could look at tonight. Engine also has a Lunati lightweight rotating assembly, 202 camel hump heads. Rockers are 1:5 on intake and 1:6 on exhaust, msd dist and ignition.

They way its looking, i may just sell the BG to get a nice 650 or 750 double pumper. I won't be taking it to the track enough to justify keeping the BG, and cash is really tight unfortunately.
flip your intake and exhaust rockers. the exhaust almost never needs more lift and the intake can almost always use it.
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