Looking to try out the 1901 street demon 625 cfm for my 65 barracuda. i think there is way too much carb on it now. it runs like a scalded dog right now but issues with idle and start up, plus its about ready for a rebuild. I been looking around for feedback and haven't see much on the good or bad on these, any advice or input be greatly appreciated.
Advice on a 625 CFM STREET DEMON CARBURETOR for 273 commando
- Thread starter mkingan
- Start date
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I have had good luck with a 625 on an 318, when I changed the motor to a 360 it is still on there, starts easy every time hot or cold, pulls good, I would buy another one if I needed it. I got the one with the phenolic body, to cure heat issues in the summer, and it will start first crank when 0 degrees outside.
Also you have to dissemble the entire carb to put the mopar throttle linkage on.
The stock mopar one will not work, you have to give them an extra $20 for that part.
The stock mopar one will not work, you have to give them an extra $20 for that part.
thats great. in arkansas so that will def. help. the motors pretty stout, but my brother built it for more top end then cruise. there is an 850 on it it takes it and asks for more, but low end it seems to stumble. its a rare card from holley ment for 427-454, i want something more lower end and not so troublesome. thats why i was looking at the street demon over another classic holley or edelebrock, am i thinking right?
I know it worked fine on a stock wore out 318, and it also works good on the built 360 I am running now.
In my opinion its a great carb for the money.
In my opinion its a great carb for the money.
can you explain that a little more detail please
The piece that your throttle cable hooks to on the carb.
You have to dissemble the carburator to install it.
Factory one will not work, you have to buy the one from them.
Go to Holley's website, find the installation instructions, it shows you the part number to order.
Its easy to do.
You have to dissemble the carburator to install it.
Factory one will not work, you have to buy the one from them.
Go to Holley's website, find the installation instructions, it shows you the part number to order.
Its easy to do.
ok thanks ill look, find it funny that the price on ebay is same price on holley's web site
I bought one a few years ago for the 360 in my '65 Barracuda. I love it. It was very nearly plug and play for my application. It starts right up every time and pulls and cruises perfectly. I have not one single complaint about the Street Demon 625.
Having said that, 625 CFM seems like maybe it's a bit much for a hot 273. When I was running my 273 I used an Edelbrock Thunder AVS 500cfm and it ran great. Others may disagree, but I was really happy about how easy it was to get installed and tuned. I always use an on-board A/F meter.
Cheers.
Having said that, 625 CFM seems like maybe it's a bit much for a hot 273. When I was running my 273 I used an Edelbrock Thunder AVS 500cfm and it ran great. Others may disagree, but I was really happy about how easy it was to get installed and tuned. I always use an on-board A/F meter.
Cheers.
625 is not nearly too much for it , currently it has an 800 cfm and it will take all that and more. i just think a newer design and better reliabiliy would be better off
pishta
I know I'm right....
625 is max effort with max velocity through the carb on a bench. Your 318 may not even pull the secondary air door past 50%. That would be a good GoPro video of a shot of the carb during a high speed pull ON THE STREET, (or a TPS wired to the air door to a dash gauge) with all its drag associated with a moving car. Remember the air-door style carbs only allow whats being demanded. not like a double-flusher (pumper) that is entirely linkage driven.
ok good info. i think that monster 800 cfm is mechanical secondaries. like i said at full out its awesome but putting around seems to stumble. i'm not going to road race this thing, not after a 7 year restore. thanks for the info i just wanted to make sure i wasn't missing anything going with the demon due to it being a little more unconventional. i like all the new improvements it has so i think ill go with it brand new verses used or reman then ill get a true view of it. thanks
I ran (and still have) a Holley remanufactured 625 Street Demon for my Mustang 289. I wasn't able to tune out a stumble when the secondary air door opened (I followed all the instructions for tuning it) and if I tightened the door too much, it would go dead rich before the air door opened.
I will say, it had a lot of dried gas in it when I bought it, and the accelerator pump wouldn't even work until I had it on the car for 15 miles or so (I'm guessing it dried out from shelf time). I'd buy a new one. With a little accelerator pump tuning I might have gotten the thing working well, but I decided to try something else. I have a Holley 570 on it right now that's working pretty well for me, but I had to do a lot of tuning on that one to make it right too. I've rarely been lucky enough to have a plug and play carb...
I will say, it had a lot of dried gas in it when I bought it, and the accelerator pump wouldn't even work until I had it on the car for 15 miles or so (I'm guessing it dried out from shelf time). I'd buy a new one. With a little accelerator pump tuning I might have gotten the thing working well, but I decided to try something else. I have a Holley 570 on it right now that's working pretty well for me, but I had to do a lot of tuning on that one to make it right too. I've rarely been lucky enough to have a plug and play carb...
69_340_GTS
Well-Known Member
Hardly "the entire carb". It's a 10 minute job. I had one.
I even called Holley tech, and said "you have kidding, a brand new carb design, and this is the best you guys can come up with"?
They said they were aware of the problem and working on it, I bought one of the first ones when they came out, maybe they changed things a little, but I doubt it.
It is not hard to do at all, if you have ever had a carb apart.
is the 1901 worth it? or just stay with the 1900, unfamiliar with the thermoquad
Last time I checked, the 1901 wasn't much more expensive, and from what I've read, the phenolic body does make a difference in fuel bowl temperatures. I think I'd go for the 1901 if I were buying a new one, but I haven't used it myself.
thank-you, on holley there the same price , i can get a discount (about $40) ordering it from advance auto parts with codes and discounts but i can't get the 1901 just the 1900, but i'm in arkansas so guess it be worth it
Buy the one with the plastic bowl, it took care of my heat issues, the Holley I had on it had.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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As to how many cfm your carb will pull, it hardly matters what size 4bbl you put on it; That is to say, if your engine is only capable of pulling 390cfm, then any 4bbl will supply only that much.
The problem comes when the carb gets to be too big, then you have other issues as you have discovered.Mostly related to driveability and starting,just as you have discovered.
It is doubtful that your engine normally aspirated can even top out a 500. So if you want a 650 have at it, but something closer to 500 will be a dream at lower rpms, where it might pull 80 to 250 cfm under various conditions, and under 4000rpm, all depending on load, altitude, temperature, and volumetric efficiency.
If your engine only is able to pull 390 cfm, and you pull it through an 800 carb, it will still only pull 390 cuz that's all the engine can do. The difference is the velocity thru that big carb is about 1/2 of what the carb was designed for, and so you get to mess with all the circuits to optimize it.
If you bolt on a 250 cfm carb it will perform perfectly up to the rpm where your engine is able to pull more than 250. At that point it becomes a restriction. For a 273, this could be around 4000rpm. The engine will continue to pull more cfm thru the small carb, it just can't pull the full 390 to make as much power as if it had the correct sized carb.It might get close if it was held at one rpm long enough, but that would never happen on the street.
So, most of the time you want the secondaries to come in after the engine is able to accept them. This is usually around 3000 rpm or a bit higher. For you this might be 165 cfm,on the primaries. but if your engine power-peaks around 5000 and you rev it to 6000, on account of your automatic has that powerband requirement, then your total cfm might be 390cfm. With an exceptional set-up pulling 85% VE your total cfm requirement might be 403.
With a bigger size cam peaking at maybe 5600 and shifting at 6500, your total requirement might be 436 to perhaps 450cfm.
Remember that these are full-load WOT requirements.
And most of the time you will be on the primaries, so small primaries are a good thing.Since most 4bbls are square bores, a 450 would be well able to pass 225 on the primaries, thus extending your low speed operation to 4000, if the secondaries were disabled.But since the secondaries usually begin opening at about 65%, the primaries are actually gonna only have to work to about 2700 at which time the vacuum secondaries may be triggered.
But if you want to bolt on that 650, it will work. The velocity thru the primaries will just drop a tad as the secondaries open. And so you get to mess with the jetting again. And the primaries may not be as crisp as they could be.
Me personally,I would bolt on a 500 as a maximum. This might be good to 8000 rpm, at 80%VE.
800s are really for over 400 cubers. mean think about it; what size carbs did the factory put on 340s/ that's right 580s IIRC. Those are good to 5900at 100%.
A 750 might feed a 367 to 7000@100%VE. I ran a 600 on my 367 for a while with a 270*cam and it wasn't that doggy.At lower rpms it was actually pretty crispy.A 600 is good to about 7000@80%VE
'Course I am a big fan of 4 speeds and DP carbs, but only cuz my engine can spin the tires pretty much anytime,with those,lol....Lots of pumpshot seems to cure the sag
The problem comes when the carb gets to be too big, then you have other issues as you have discovered.Mostly related to driveability and starting,just as you have discovered.
It is doubtful that your engine normally aspirated can even top out a 500. So if you want a 650 have at it, but something closer to 500 will be a dream at lower rpms, where it might pull 80 to 250 cfm under various conditions, and under 4000rpm, all depending on load, altitude, temperature, and volumetric efficiency.
If your engine only is able to pull 390 cfm, and you pull it through an 800 carb, it will still only pull 390 cuz that's all the engine can do. The difference is the velocity thru that big carb is about 1/2 of what the carb was designed for, and so you get to mess with all the circuits to optimize it.
If you bolt on a 250 cfm carb it will perform perfectly up to the rpm where your engine is able to pull more than 250. At that point it becomes a restriction. For a 273, this could be around 4000rpm. The engine will continue to pull more cfm thru the small carb, it just can't pull the full 390 to make as much power as if it had the correct sized carb.It might get close if it was held at one rpm long enough, but that would never happen on the street.
So, most of the time you want the secondaries to come in after the engine is able to accept them. This is usually around 3000 rpm or a bit higher. For you this might be 165 cfm,on the primaries. but if your engine power-peaks around 5000 and you rev it to 6000, on account of your automatic has that powerband requirement, then your total cfm might be 390cfm. With an exceptional set-up pulling 85% VE your total cfm requirement might be 403.
With a bigger size cam peaking at maybe 5600 and shifting at 6500, your total requirement might be 436 to perhaps 450cfm.
Remember that these are full-load WOT requirements.
And most of the time you will be on the primaries, so small primaries are a good thing.Since most 4bbls are square bores, a 450 would be well able to pass 225 on the primaries, thus extending your low speed operation to 4000, if the secondaries were disabled.But since the secondaries usually begin opening at about 65%, the primaries are actually gonna only have to work to about 2700 at which time the vacuum secondaries may be triggered.
But if you want to bolt on that 650, it will work. The velocity thru the primaries will just drop a tad as the secondaries open. And so you get to mess with the jetting again. And the primaries may not be as crisp as they could be.
Me personally,I would bolt on a 500 as a maximum. This might be good to 8000 rpm, at 80%VE.
800s are really for over 400 cubers. mean think about it; what size carbs did the factory put on 340s/ that's right 580s IIRC. Those are good to 5900at 100%.
A 750 might feed a 367 to 7000@100%VE. I ran a 600 on my 367 for a while with a 270*cam and it wasn't that doggy.At lower rpms it was actually pretty crispy.A 600 is good to about 7000@80%VE
'Course I am a big fan of 4 speeds and DP carbs, but only cuz my engine can spin the tires pretty much anytime,with those,lol....Lots of pumpshot seems to cure the sag
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