FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: fryedaddy on March 05, 2018, 08:39:53 PM
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i bought a new 850dp in 1984 and i used it on 2 different 390s and my new 433.it ran great all those years till i decided to replace it last summer.so i went out and bought a new 850dp,manual secondaries and manual choke.the problem is it is not as crisp as the old one.the old one even sounded better idling.is there anything i can do with this new 850 to get it to perform better,or should i get rid of it and go with something else,if so what would i want.the car has 4.11 gears and weighs less than 3000.i will buy something else if i need to,but i would also mod the new one too.the old dp is long gone so its not an option.
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I personally am having carb issues - I'm usually pretty good with the things but lately they have all turned on me. Anyway - every 850 I ever saw somebody use or worked with was "lazy". The throttle bore and venturi sizes are - IMO - too close in size and have issues metering fuel unless it's a fairly big displacement. The "950"s always seem to do better. Depending on what you are doing, I would consider a 650 or 750. The 650 DPs are good carbs, tune well and easily support over 500 HP. Very crisp. I have two here, one is the go-to carb for everything. It ran on the 302, then went on the 393C in the dragster (same ET/MPH as the home brew 800 DP) and is not on the wifes Mustang racer (7.44 @ 90.5 MPH). That's a $40 swap meet carb and you can't buy it from me for love nor money. If you really want to keep that one, you might touch bases with someone like Patrick at Pro Systems.
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i bought a new 850dp in 1984 and i used it on 2 different 390s and my new 433.it ran great all those years till i decided to replace it last summer.so i went out and bought a new 850dp,manual secondaries and manual choke.the problem is it is not as crisp as the old one.the old one even sounded better idling.is there anything i can do with this new 850 to get it to perform better,or should i get rid of it and go with something else,if so what would i want.the car has 4.11 gears and weighs less than 3000.i will buy something else if i need to,but i would also mod the new one too.the old dp is long gone so its not an option.
Do you still have the old 850? If you do have that one rebuilt and use it. Older Holleys have more precise fuel metering which is why I prefer building and using the older Holleys rather than newer ones. Just make sure you address the warpage issues normally associated with these old cores.
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I went through the same thing a couple years ago. Had an old 750 VS that performed very well for over 20 years, but I wanted a new carb for the engine I bought off of Blair for my '70 F350. Purchased a new Holley 750 (same carb I had) and it ran like crap and would hardly idle. I had it apart probably 5 times checking, adjusting and just generally fiddling with it, but never got it to perform worth a damn. I finally gave up and just rebuilt my old 750 and it ran great. I'm not a guru when it comes to emulsion tubes and some of the finer points of carbs, so I never figured out the issue. I've never had an issue getting a carb to run right, but I've always had older carbs. Lots of rumors about Holleys quality going down with all the buy-outs and whatnot, and I tend to believe it after that experience. Carbs are like wives and girlfriends, if you find one that treats you good, NEVER get rid of it ;)
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old carb is gone as mentioned.the car is a street strip type setup.i need a carb for that purpose.when driven on the street i rarely go over 15-20 miles,so drive ability is not a concern.i just want it to perform when i hit the throttle and sound good at idle and wot.engines a 428,.030 over,10.7 speed pro pistons,bbm heads,rpm intake,comp cam hyd flat tappet .244 at ,050,msd dist,box and coil, hookers,arp studs rods,mains,heads. all i need to be happy is a good carb,all input is appreciated.
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Universal carbs expect you to have a massive cam, so large restriction are used as the planned usage won't have high vac to pull on them.
As such it runs rich in most applications, which is safer for the manufacturer and sucky for the owner.
Many newer carbs like to over emulsify as well for some reason which makes initial booster operation shoddy.
If you find a carb you like, pin gauge it and record the calibration, it's easy enough to replicate later if need be on any other carb.
Here is a 750 4779 I have that runs freaking awesome:
List number 4779
Type 4150
Primary
Float center hung brass
Booster downleg
Pump nozzle .031
Pump type and cam 30cc blue
Idle air bleed .067
High speed bleed .028
Metering block# 8543
Main Jet 70
Power valve 6.5
PVCR .052
Emulsion 2 @ .028
Kill Bleed .028 in angle channel
Idle Feed restriction .033
Needle and seat .110
Venturi size 1.370
Throttle plate size 1.680
Secondary
Mechanical or Vacuum? MS
Spring color na
Diapghram length na
Float center plastic
Booster downleg
Pump Nozzle .031
Pump type and cam 30cc blue
Idle air bleed .026
High speed bleed .025
Metering block/plate# 6501
Idle Feed Restriction .031
Jet size 80
Needle and seat .110
Emulsion 2 @ .028
Killbleed none, raised feed
No secondary power valve
Notes:
Changed to stepped downleg .152
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Don't buy a Holley, or buy a Holley 950 Ultra. Or Pro Systems, or Quick Fuel.
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Don't buy a Holley, or buy a Holley 950 Ultra. Or Pro Systems, or Quick Fuel.
So if wanting to buy a new carb, what does that leave? In other words, what places would anybody recommend for carb work beyond basic tuning and calibration? The only other place I can think of is AED.
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Drew,thanks for the detailed info.if i decide to go with what i have,i may try some of your info on it.are AED carbs good out of the box.i dont mind paying a little extra if im happy with what im buying.also i have low vac and would this affect carb choice.
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AED is awesome.
Dunno if you can see this, but this is that 4779 on my stockish 390 pickup truck engine:
https://www.facebook.com/AirFuelSParkTech/videos/186653008740105/
Just sold that carb about 5 minutes ago :P Kinda wanted to keep it around, but gotta make more room for new builds.
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Don't buy a Holley, or buy a Holley 950 Ultra. Or Pro Systems, or Quick Fuel.
So if wanting to buy a new carb, what does that leave? In other words, what places would anybody recommend for carb work beyond basic tuning and calibration? The only other place I can think of is AED.
ACFI, AED, Baker, BLP, Braswell, BRE, CFM, C&S, DaVinci, DeVane, Chuck Nuytten
I'm sure I missed a couple.
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Step outside your comfort zone. Go to throttle-body EFI. You'll be so pleased by the instant reaction, the quick start and off-idle drivability you'll wish you'd gone to EFI thirty years ago. My own experience has been with the Holley systems, but I haven't done one recently. Some of the other new brands may be as good or even better.
KS
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With a double pumper, hard to beat AED and a custom build. They really do a nice job and verify everything on a wet flow tester. Not sure where you are, but a phone call and box sent to Richmond can get you some nice tuning, especially if they get rid of the later style IFR
A buddy used them for a pair of 390GT carbs he had on the shelf, and they did great too, but they don't sell any vac secs that I know of. They tend to focus on double pumpers like yours.
Drew could certainly make yours do better too.
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Don't buy a Holley, or buy a Holley 950 Ultra. Or Pro Systems, or Quick Fuel.
So if wanting to buy a new carb, what does that leave? In other words, what places would anybody recommend for carb work beyond basic tuning and calibration? The only other place I can think of is AED.
ACFI, AED, Baker, BLP, Braswell, BRE, CFM, C&S, DaVinci, DeVane, Chuck Nuytten
I'm sure I missed a couple.
Throw APD in there too, just close to $1000.
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Well, unless it's for a WOT race engine, I've read many have the same 'lazy' issue with 850 DP's used on the street as other here have also noted. Bet a stock 750 DP'er would be noticeably better as would a worked one or a worked 950 (750 based) frrm one of the shops mentioned. Must have someting to do with the bowl/venturi area and even the air bleed sizes demanded by thta bowl's flow. BTW, heard the same long ago with the old Holley 3-barrel but methinks that was an issue with pure overcarbing a too small, too mild engine.
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Well, unless it's for a WOT race engine, I've read many have the same 'lazy' issue with 850 DP's used on the street as other here have also noted. Bet a stock 750 DP'er would be noticeably better as would a worked one or a worked 950 (750 based) frrm one of the shops mentioned. Must have someting to do with the bowl/venturi area and even the air bleed sizes demanded by thta bowl's flow. BTW, heard the same long ago with the old Holley 3-barrel but methinks that was an issue with pure overcarbing a too small, too mild engine.
There is truth to that statement..I ran a 950 3bbl on a std. bore/stroke 427, a reproduction "D" cam, F 427 manifold in a V-drive Hondo flat. That carb was one of the best all around carbs I've ever run. Idled smooth @ 800 RPM, good low-mid range power and pulled well to 7K RPM with no bogs, hiccups, flat spots, lean outs or any other issues throughout the RPM range. 3bbls got a bad rap because "If big is good then more must be better" thinking. Usually they were installed on much smaller and/or milder engines. So your statement of overcarbing an engine is very true. In a more friendly environment and properly built they were great carbs. The 3 3bbls I have [2 950s and a 1050] were due to people who couldn't get them to run right and gave up, lucky me...I usually got them for next to nothing or were free.
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According to everyones responses, if you want a new carb that is for a fairly mild street oriented type build (you know, 80+% of the builds out there, or at least outside this forum group), you're basically screwed. Or your only recourse is to purchase a new Holley and then spend another $300-$400 ungrading the metering blocks, boosters and metering plates, modify the carb bodies, buy a bunch of air bleeds, then spend a bunch of time calibrating, adjusting and guessing at what your combo needs.
Got it >:(
This is why I hate company buy-outs!
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But if one buys a new carb from one of the mentioned Holley carb tuners/experts after giving them all the relevant engine/use details, they aren't really that much more. Besides, most can be plopped on and run like the devil!
According to everyones responses, if you want a new carb that is for a fairly mild street oriented type build (you know, 80+% of the builds out there, or at least outside this forum group), you're basically screwed. Or your only recourse is to purchase a new Holley and then spend another $300-$400 ungrading the metering blocks, boosters and metering plates, modify the carb bodies, buy a bunch of air bleeds, then spend a bunch of time calibrating, adjusting and guessing at what your combo needs.
Got it >:(
This is why I hate company buy-outs!
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Carbs are getting into the price range where a person could buy one of the less expensive electronic fuel injection units.
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But if one buys a new carb from one of the mentioned Holley carb tuners/experts after giving them all the relevant engine/use details, they aren't really that much more. Besides, most can be plopped on and run like the devil!
Point being, a carburetor shouldn't cost upwards of $800 or above. And everyone seems to be ok with the fact that Holley can't produce a carb that performs as good as the ones they made 50 years ago.
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Agree those prices have soared which is why good used carbs (see Drew!) have drawn a large following. There must be 10,000+ used Holleys just laying around the country waiting for a home somewhere. My cousin still has a heavily worked 4500 Holley I gave him years ago, like new, and formerly used on a 351C Pro Stock engine (bought 2 for IIRC $200 in 1978!). I'd take the plunge on a good used Holley if the price was low.
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Well.... I can't speak for the big time carb tuners out there, who are in a totally different league than a hobbiest like myself. I'm gone 6-8 months a year so obviously my experience is stunted due to this.
But I can buy a 750 dbl pumper for $100-$125
Strip it, make metering adjustable, rebuild, redye, and replate the carb so it looks like new.
Test it on an engine for any weirdness, go for a ride with the O2, make a few adjustments, and sell the carb for $400-$500 which is pretty close to what a brand new "mystery calibration" carb would cost.
It's far more depressing to have to do all this work to a carb that cost $600 new!
This is why I'm stockpiling old style Holley's with any money I make with this hobby.
I dunno, if it was me, I'd find someone willing to do that sorta work local to you and tune it on the engine.
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I dunno, if it was me, I'd find someone willing to do that sorta work local to you and tune it on the engine.
Sorry for getting the OP off track.
I haven't had a problem that wasn't pretty easily solved on any older carb. I'll stick with them. I just wanted a new carb for the engine in my tow vehicle, but that's the last time I try that!