My Modified Speed Demon 750DP

onebad82z · 04-09-2010, 05:17 PM

Ok guys here it all done! I drilled and tapped out my carb so I can really fine tune it and have it run it's best for when the WOT closes!

Air Bleeds...

Transfer Slot Restrictors...

Primary Metering Block...

Secondary Metering Block...

And finally re-assembled...

Nitro Dave · 04-13-2010, 11:29 AM

Ok, Give us a detailed explanation on what you did and what it acheives? How does it work?

I have a base knowledge of what you did and why but even I could use the info.
Dave

onebad82z · 04-13-2010, 01:30 PM

D@mn, I didn't study for a pop quiz! lol

Anywhere you see an allen head set screw I drilled the orifice out, tapped it for either a 6, 8, or 10-32 brass set screw depending on maximum size of orifice potentially needed. What this allows is infinite tuning adjustments to every circuit of the carburetor. Last year I had to overfuel some areas of my tune to make up for other areas that could not be adjusted and were to lean. Had I had it modified as it is now I could have tried smaller air bleeds to correctly tune the circuit I was fighting (idle and low speed cruise). But it wasn't as those used to be a fixed orifice. Had I needed to go bigger I could have just drilled it out a touch bigger and I may have had luck. But in some cases you may need to go with a smaller orifice to which a fixed orifice will not allow. With my modifications I can go either way now. A lot of this was due to me having to large of a carb for my combo. But it is paid for years ago, in good shape, and I know the history. So after a ton of research I decided to molest my carb and make it work. I also had it converted to annular boosters as my primary use as a street car will make it much more friendly and makes the carb a smaller cfm size to the motor. Some orifices may be just fine at the size BG made them when the carb was manufactured but I wanted to be able to tune ANY of them if needed and since it was apart for the booster conversion and I did a full rebuild on it now was the time. I bought 50 set screws of each size for under $15, another $35 on drill bits to drill the set screws out to any size needed, and a rebuild kit for $60. So for $110 I converted my carb to a fully adjustable unit much like the ones you can get from the tuner shops at a much higher price. For what I do with my car it was a much smarter move IMHO since the carb itself was paid for years ago.

onebad82z · 05-11-2010, 06:06 PM

Already this modification has proven its worth. I have had to play with idle air bleeds and am just about to start tuning with IFRs as I have a lean transition I need to richen up!

Nitro Dave · 05-12-2010, 10:07 AM

That makes since. I tuned a Cuda a while back using a wideband. It was pretty cool seeing the change on the wide band as I changed air set screws and jetting in the front and back bowls.
Dave

boogeyman · 05-23-2010, 01:03 AM

i wish i had the patience to do what u u did. i bought a ultra HP 850 for mine and sent it to quickfuel. was it worth it hell yes, was it really expensive hell yes. but u just did basically the samething i did for less than half what i spent

04-09-2010, 05:17 PM	#1
onebad82z Hooked on Nitrous Join Date: Mar 2008 Posts: 87	My Modified Speed Demon 750DP Ok guys here it all done! I drilled and tapped out my carb so I can really fine tune it and have it run it's best for when the WOT closes! Air Bleeds... Transfer Slot Restrictors... Primary Metering Block... Secondary Metering Block... And finally re-assembled... __________________ '82 Camaro Z28 1.86 60' / 12.47@110 NA 1.92 60' / 11.94@119 100 shot

04-13-2010, 11:29 AM	#2
Nitro Dave Tech Adviser Join Date: Jan 2008 Location: Hewitt, TX Posts: 1,135	Ok, Give us a detailed explanation on what you did and what it acheives? How does it work? I have a base knowledge of what you did and why but even I could use the info. Dave __________________

04-13-2010, 01:30 PM	#3
onebad82z Hooked on Nitrous Join Date: Mar 2008 Posts: 87	D@mn, I didn't study for a pop quiz! lol Anywhere you see an allen head set screw I drilled the orifice out, tapped it for either a 6, 8, or 10-32 brass set screw depending on maximum size of orifice potentially needed. What this allows is infinite tuning adjustments to every circuit of the carburetor. Last year I had to overfuel some areas of my tune to make up for other areas that could not be adjusted and were to lean. Had I had it modified as it is now I could have tried smaller air bleeds to correctly tune the circuit I was fighting (idle and low speed cruise). But it wasn't as those used to be a fixed orifice. Had I needed to go bigger I could have just drilled it out a touch bigger and I may have had luck. But in some cases you may need to go with a smaller orifice to which a fixed orifice will not allow. With my modifications I can go either way now. A lot of this was due to me having to large of a carb for my combo. But it is paid for years ago, in good shape, and I know the history. So after a ton of research I decided to molest my carb and make it work. I also had it converted to annular boosters as my primary use as a street car will make it much more friendly and makes the carb a smaller cfm size to the motor. Some orifices may be just fine at the size BG made them when the carb was manufactured but I wanted to be able to tune ANY of them if needed and since it was apart for the booster conversion and I did a full rebuild on it now was the time. I bought 50 set screws of each size for under $15, another $35 on drill bits to drill the set screws out to any size needed, and a rebuild kit for $60. So for $110 I converted my carb to a fully adjustable unit much like the ones you can get from the tuner shops at a much higher price. For what I do with my car it was a much smarter move IMHO since the carb itself was paid for years ago. __________________ '82 Camaro Z28 1.86 60' / 12.47@110 NA 1.92 60' / 11.94@119 100 shot

05-11-2010, 06:06 PM	#4
onebad82z Hooked on Nitrous Join Date: Mar 2008 Posts: 87	Already this modification has proven its worth. I have had to play with idle air bleeds and am just about to start tuning with IFRs as I have a lean transition I need to richen up! __________________ '82 Camaro Z28 1.86 60' / 12.47@110 NA 1.92 60' / 11.94@119 100 shot

05-12-2010, 10:07 AM	#5
Nitro Dave Tech Adviser Join Date: Jan 2008 Location: Hewitt, TX Posts: 1,135	That makes since. I tuned a Cuda a while back using a wideband. It was pretty cool seeing the change on the wide band as I changed air set screws and jetting in the front and back bowls. Dave __________________

05-23-2010, 01:03 AM	#6
boogeyman Hooked on Nitrous Join Date: Mar 2009 Location: minooka ill Posts: 110	i wish i had the patience to do what u u did. i bought a ultra HP 850 for mine and sent it to quickfuel. was it worth it hell yes, was it really expensive hell yes. but u just did basically the samething i did for less than half what i spent __________________ Go Go Gadget third gen i who walk thru the valley of death i shall fear no big block thy bottle and thy solenoids they comfort me for thy nitrous is with me.