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Holley Street Demon 1901

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I've got the go-ahead from the boss, about to click on this one:

 

6c4ac5e97986ecbc9d24f1bf1e0089f3.jpg

 

I've reached the end of the line trying to get some sort of economy out of my 4011 Holley. Don't get me wrong, I like its performance, especially its midrange but twice the fuel of my Mrs' Aurion and yet still slower has me cursing every time I slurp fuel into it.

 

The Street Demon design is a resurrected Thermoquad with bits of Rochester thrown in. I've read shitloads of reviews and have come away with the impression that it is a brilliant street carby on a mild or moderate small-block. Loads of people comment on its bolt-on and go capability and snappy off-idle response.

 

This is a factory refurbished one that they say is (more often than not) a return that has nothing wrong with it. They're stripped, inspected, then re-assembled and flow tested just like the new ones but are US$100 cheaper.

 

Also this one has the resin bowl instead of alloy, normally a bit more expensive than alloy but there's no price difference between the refurb ones.

 

I can land one here for $360, not bad compared to what they go for normally. I dunno why Hume Performance hasn't come on board with these as they're a Holley agent.

 

As soon as I get it, I'll do a review as I'm sure many would be interested in its good/bad points. If it doesn't improve economy, I'll be pretty disappointed.

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looking forward to the review, i was advised to fit a rochester carb to My clevo 20yrs ago to keep it pollution legal and good performance.. never did, ran it on LP gas instead..

why are they better for fuel economy, i would have thought if the mixtures are right it should be very similar at cruise speeds

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looking forward to the review, i was advised to fit a rochester carb to My clevo 20yrs ago to keep it pollution legal and good performance.. never did, ran it on LP gas instead..

why are they better for fuel economy, i would have thought if the mixtures are right it should be very similar at cruise speeds

 

The difference is atomisation. If only a percentage of the fuel is being atomised properly, you need to jet up to compensate. Then whatever isn't atomised is wasted.

 

These have lots of features to promote efficiency in the primaries:

 

Small 1-3/8" bores: high velocity = better atomisation.

 

"Triple stack" venturi (like a Rochester)

 

Metering needles instead of a power valve (more precise)

 

Idle blowers below the idle ports to stop fuel trickling down into the manifold

 

Plastic body to keep the fuel cool and stop it boiling/percolating.

 

Simple emulsion/bleed circuit, compared to Holleys, which can be finicky.

 

A Rochester would be a fine choice if it's in good condition. If they need any tuning past stock calibration, specialist info is needed. They are hard to get parts for due to not being made for more than 30 years now.

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That looks awesome greg so that bolts up to your average Holley 4 barrel manifold I'm assuming?

 

 

 

 

 

hey is it a spreadbore ?

 

It has a dual bolt pattern and although the primaries are much smaller than the secondaries, it has the bore spacing of a square, meaning it will fit either.

 

I've read one review where a guy tried one on a manifold made for a rochester and had issues with mismatched faces and vac leaks but a 1/2" spacer would fix that.

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the Edlebrock carby's also use metering rods,

Over your old style 4011 holley nearly just grab a cheap 1850 and give it a go, theres 3 on ebay under $100 & a kit is $50

& put a quick fuel 34-2 or 34-3 metering plate kit on, for interchangeable rear jets.

 

I've been thinking of changing jets, or putting another carby on my 302 as it easily uses 23lt/100km on the highway (rich & 4.11 gears),

I have Holley 465(1848) & 600(1850) Vac sec plus a new Quick fuel Slayer 600 VS(sl-600-vs), but haven't had time to try yet.

& about to start maintenance & upgrades for the AFF Drag Nats.

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the Edlebrock carby's also use metering rods,

Over your old style 4011 holley nearly just grab a cheap 1850 and give it a go, theres 3 on ebay under $100 & a kit is $50

& put a quick fuel 34-2 or 34-3 metering plate kit on, for interchangeable rear jets.

 

I've been thinking of changing jets, or putting another carby on my 302 as it easily uses 23lt/100km on the highway (rich & 4.11 gears),

I have Holley 465(1848) & 600(1850) Vac sec plus a new Quick fuel Slayer 600 VS(sl-600-vs), but haven't had time to try yet.

& about to start maintenance & upgrades for the AFF Drag Nats.

 

Give us a follow-up on the QuickFuel, sounds like a nice piece. I think I might take the advice of many old car nuts and steer away from Holleys if I want half decent economy. Mine gets about 18l/100 around town no matter what I do. Jets, bleeds, float level, emulsion holes, idle feed, I've fucked with them all.

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I've just found out that they're out of the model I want. Bloody paypal taking their sweet time clearing money from stuff we've sold days ago, now i've friggin missed out. Pricks.

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Looks like I jumped the gun in posting on this carby... They're still out of stock and although I can buy brand new locally, $529 is more than I wish to stretch to right now. On consideration, I'd rather throw that kind of money at an LPG setup.

 

Still, would have been a cool carby.

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Bitches

 

8cefecf8caa93de0c024b4f630fedff4.jpg

 

Oh 4011 Holley... You've served me well but sadly now it's time to be put out to pasture.

 

518f0f1da6e781657b477ffae157f2cf.jpg

 

You can see the unusual goggle-shaped secondaries:

 

7a7a310f356ce10e9fc5f6deb6c52f93.jpg

 

Square vs spreadbore gasket

 

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8374f86904d447f7178b01fdd827d6c9.jpg

 

As you can see, the siamesed secondary valve, while very cool, can be a bit of a headache when trying to match the carby to a spread/square adaptor. The centre divider has an abrupt face that's smack in the middle of the flow so needs to be contoured with a die grinder to transition smoothly to the spreadbore manifold:

 

131cbc0970bfe0cfe44c23a1ab6faf70.jpg

 

Smoothed and knife-edged:

 

ea38b6b4b9508d0a3518e239098aa9c5.jpg

 

3040d493af2db760b17921137ac758e1.jpg

 

A bit hard to see but looking straight down the open throttle into the plenum there's the contoured divider. If anyone is thinking of getting this carby, this is the sort of thing you might have to do to get it right on a split manifold, square or spread bore. Open plenums are no dramas.

 

2e20877f7b5e38e030f0b07da3aff620.jpg

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Ok I promised a proper review so here goes:

 

It's been nearly 2 weeks since the install, and I've pretty much worked out its good and bad points.

 

• it's unbeatable bang-for-buck. I landed it here for a shade under $350 AUD. They sell locally (new, not refurbished like mine) starting at $550.

 

• the low end torque is amazing. I thought my annular Holleys were good but this is like fuel injection (no exaggeration). Driving around town, there's absolutely no need to hit the secondaries, the performance is enough at 1/3 throttle.

 

• although they say that refurbs are returned units that are checked and cleaned, mine showed no signs of previous installation (no marks around the stud holes).

 

• installation was piss-easy with exception to some issues that are peculiar to my setup, ie non-standard throttle cable and spread bore adaptor (outlined above in previous post). It fired up and idled by itself with very minor tweaks, just like they said it would.

 

• the secondaries open with a glorious howl just like on an Edelbrock or Quadrajet, and traction is now an issue that wasn't there before ;)

 

• has a single fuel inlet so no dicking around with t-pieces and clamps, custom fuel bars, etc.

 

• Its float bowls are sealed so no longer has that old car aura of fuel smell after you park it. Also the composite body keeps temps down so much less or no percolation from heat soak.

 

• comes with lots of bits to cater for different setups: 3/8", 5/16" and SAE flare fuel fittings, 4x mount studs and nuts, 2 different ball ends or a clevis pin for the throttle cable, air cleaner stud, metal intermediate plate and 2 gaskets... Oh and 2 go-fast stickers

 

Ok now for the few issues that I've had:

 

• the primary throttle is a bit tight and hangs up a tad, but only when the engine's running. I suspect it's an alignment issue that will probably go away as it all beds in. I fitted an extra return spring that's made the accelerator a bit heavy but it works fine.

 

• The secondary air flap was catching on the housing, making it a bit clunky in operation. I noticed the screws that hold it to the shaft were a bit off from the holes, so I loosened them and tweaked the flap to open and close without catching. I suspect this is a new carby that failed QC due to these issues but I really don't mind, it's not an issue for me.

 

• the linkages are all held on with impossibly small circlips. They are so small that you can't feel them on your fingers when removing/replacing. Very scary if you lose one and wonder if it fell down the carby, etc. I made the mistake of changing the pump stroke in the dark on the side of the road and had all sorts of trouble putting it back on. I plan on removing them all and installing wire pin clips that you can at least change without tweezers. Changing rods requires removing the choke linkage right over the top of the carby with one of these clips needing removal. Again, scary.

 

• Changing jets (primary or secondary) involves stripping the carby apart completely. Not so bad if only your primaries need tweaking as there is enough of a selection of rods to tune them without needing to swap jets. Also primary jets are specific to this carby only. Secondaries are standard Holley jets.

 

• if a carby is sold ready to run out of the box, you can guarantee that it's going to be rich, which this one is. Stock rods are 60/52, jets are 78. Rods and jets are in increments of 0.002". On reading other reviews, I think I might go either 2 sizes leaner (bigger) in rods to 64/56, or one rod size up (62/54) and one jet down (76). Rods are about $10US a pair, jets $5.

 

• the secondaries had a pretty bad bog when I first drove it. A 1/2" spanner and a flat screwy is used to adjust the tension in the spring, and you go 1/4 of a turn each time to increase the opening tension. They reckon don't go more than 1 turn tighter than factory but I went 1-1/2 and it's mostly gone now. Even at that, the secondaries still feel a bit lean for my engine, might need a bigger jet.

 

• fuel consumption is pretty shit so far, which goes with being way rich. I also do a lot of short, cold runs which knocks the economy around.

 

Anyway I'll be doing more long country runs in the near future and after I tune the primaries I'll update any progress made.

 

 

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Ok a wee update.

 

I thought I'd do one of those dumb experiments like I always do and blow me down... It worked!

 

I pulled the springs out of the metering rod pistons (like removing and plugging a power valve) and I shit you not, the thing still drives near perfect. Just a slight surge before the secondaries open and a bit flat off idle but otherwise it's like nothing was wrong.

 

This shows how stupid rich they come from factory, in that the cruise jetting is rich enough to accelerate on. The rich step is 52 whereas the lean step is 60, meaning an 8 thou difference in rod diameter.

 

I think these carbs are jetted for an open plenum, cammy engine rather than a stock dual plane manifold and mild-cam one like mine.

 

So I ordered this:

 

4c26dddbe1ce816a466856c42407360e.jpg

 

Gonna be around $135 landed... Ouch! A bit pricey for what you get but I have no other choice. I've just been transferred to another workshop with about 80 km round trip each day so it should pay for itself quickly in fuel savings.

 

 

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Ok a wee update.

 

I thought I'd do one of those dumb experiments like I always do and blow me down... It worked!

 

I pulled the springs out of the metering rod pistons (like removing and plugging a power valve) and I shit you not, the thing still drives near perfect. Just a slight surge before the secondaries open and a bit flat off idle but otherwise it's like nothing was wrong.

 

This shows how stupid rich they come from factory, in that the cruise jetting is rich enough to accelerate on. The rich step is 52 whereas the lean step is 60, meaning an 8 thou difference in rod diameter.

 

I think these carbs are jetted for an open plenum, cammy engine rather than a stock dual plane manifold and mild-cam one like mine.

 

So I ordered this:

 

 

 

Gonna be around $135 landed... Ouch! A bit pricey for what you get but I have no other choice. I've just been transferred to another workshop with about 80 km round trip each day so it should pay for itself quickly in fuel savings.

 

 

Sent from my iPhone using Tapatalk

 

Good work, be good to see it sorted and the results posted, then anybody else getting one has a good starting point.

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Yeah that's pretty much the point NZXD, even after searching forever, I didn't see many honest reviews on these carbs, mostly marketing blurb from magazines, etc.

 

Also, even if nobody on this forum is all that interested, the good thing is that anybody can view this topic from the web. I got my info from other forums in the US that just popped up in a search. Even this one did!

 

 

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Was bored one Saturday night, had the kids at home. So I did this chart that plotted all available jet sizes with all of the rods, calculated jet and rod area, then calculated back to equivalent jet size (in diameter) for each combo, on both rich and lean step.

 

982a7bf25a2f46b337c926411d2daa9f.jpg

 

The 625 comes with 78 jets and 60/52 rods. This equates to a 58/50 jet size rich/lean.

 

Seeing as mine currently drives well on the lean step all the time, I'll go down to the leanest jet (74) with a 50/60 rod, which proportionally, has the biggest difference between rich and lean steps. This makes the equivalent jet size 55/43.

 

This should be the best compromise between cruise economy and performance under acceleration. The kit also comes with some different rod springs (like changing power valves). I hope to use ones in that will come in a bit later (weaker). The stock ones are a tad aggressive.

 

Will post results when the tuning kit gets here

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Ok so anyone who knows me would know that I can't settle for anything without fucking with it so I tried a few different approaches to get it dialled in:

 

Leanest jet (74) with 52/60 rod still had the consumption up around 17l/100, and lacked a little something under power. Then to improve economy, I went to the leanest rod (56/64) had it running ok but obviously more lacking power. Cruise was pretty fine, only had a little surge now and then.

 

So I figured that it really needs the lean step of the second-leanest rod but the rich step of the second richest one, along with the leanest jet.

 

Enter my trusty Ozito "dremel" tool with sanding pad attachment. It was one of those nights that I had the kids asleep at home so I had plenty of time to kill. Using my fingers like a lathe, I rotated the rod against the wheel taking minute amounts off the end, measuring regularly with some verniers, getting down to 0.045" at the tip (down from 0.054") also introducing a gentle taper down to it from where the lean step started much like a rod on a bike carby.

 

.... And finally some success!

 

On the primaries, power is smooth and effortless, just as it originally was with the factory (rich) setup but even better. It cruises beautifully and it transitions perfectly from cruise to power. Before you could feel the rich step coming in, much like a power valve.

 

Secondaries needed some richening due to the smaller engine capacity than the carby was designed for, (350 cubes) starting with the standard 80s, moving up to 82s, then jumping right up to a drilled 89 (I had no drills in between that and 82). It pulls quite well from low rpm foot to the floor, but it's best not to nail it before 3000. The air door preload is now set at the factory 1 turn after contact. Initially, with the smaller jets it needed another 1.5 turns to get the bog out if it.

 

The accelerator pump is a whole new chapter that I'll go on about some other time.

 

So in summary, it's a brilliant design of a carby with plenty of potential. The tune of it however hasn't had much homework done by the manufacturer to get the most out of it. The fact that I had to buy a tuneup kit and then modify the rods even further to get where I needed to be shows that their approach is a bit crude and never has the right combination of tuning parameters to take advantage of the efforts they made to design the carby in the first place.

 

So to recap, my Holley 4011 performed well but drank way too much. I was often getting towards 20l/100km. When I first bolted on the Street Demon, I was immediately impressed with the performance but not with the economy. It showed little to no improvement over the old clunker I just pulled off and took a lot of trial and error to get it to where it is now. I'm hovering around 15l/100km with some runs dipping into high 14s. This translates to about 400km to a tank, but being a wagon it's hard to be accurate with such a wide and flat tank. It's very sensitive to what slope you have the car on so you can think you've filled it but it still has a few more litres left in it after the gun has clicked off.

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Hi, I new here and have just been reading this thread. No doubt you'll notice from my screen name that I'm a Mopar enthusiast but rest assured I've had plenty of Fords including a '94 Lincoln Towncar and currently own a G6 FG plus a 2010 Lt Caprice so I've got foot in all 3 camps.  I've just bought a Street Demon 1901 and will be buying a calibration kit soon. It will be going on a mild 318 with 10 to 1 forged pistons, 360 V8 J casting heads with 1.88 intakes a mild cam a bit up from a factory 340 manual. It has a Wiand twin plane and TTI extractors and all shoehorned into a 2 door hardtop 65 Plymouth Signet (basically an AP6).  I'm wondering if your 302 has something similar in the way of mods in the hope that your info would broadly apply to my small block application.  This is a long term project I've just bought last month and is  not expected to finished for 1 to 2 years.  My other car is a 440 1969 Dodge Charger R/T clone that's just about to get a Holley Sniper once the new tank arrives.

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Hi, I new here and have just been reading this thread. No doubt you'll notice from my screen name that I'm a Mopar enthusiast but rest assured I've had plenty of Fords including a '94 Lincoln Towncar and currently own a G6 FG plus a 2010 Lt Caprice so I've got foot in all 3 camps.  I've just bought a Street Demon 1901 and will be buying a calibration kit soon. It will be going on a mild 318 with 10 to 1 forged pistons, 360 V8 J casting heads with 1.88 intakes a mild cam a bit up from a factory 340 manual. It has a Wiand twin plane and TTI extractors and all shoehorned into a 2 door hardtop 65 Plymouth Signet (basically an AP6).  I'm wondering if your 302 has something similar in the way of mods in the hope that your info would broadly apply to my small block application.  This is a long term project I've just bought last month and is  not expected to finished for 1 to 2 years.  My other car is a 440 1969 Dodge Charger R/T clone that's just about to get a Holley Sniper once the new tank arrives.
G'day mate, love the Mopars, maybe start a build thread in Brothers From Other Mothers.

A mate has a stout alloy headed 408 stroker in a VK Charger punching out 530hp at the crank. It gets along nicely I must say. Before that, he had a bog-stock 318 with a 4-barrel bolted on. It was a bit of a chugger. All bark and no bite.

Regarding the carby; even after tuning, I still have some issues with how well it does some things. Although it's been 2 years since turning a wheel, and you do forget a lot in that time, I can remember that cruising was great, WOT was good too, but it still had the occasional flat spot on acceleration off the mark.

I pulled the accelerator pump apart and found that the cup seal on the pump plunger is a bit flimsy and sometimes didn't seal, so I stuffed an o-ring inside it to try and give it some preload against the bore wall, also putting in a stronger spring to try and build pressure more quickly in the chamber. Both fixes were only partially successful. The squirter still has an occasional delay when first hitting the accelerator. I think the circuit also suffers from drain back.

The stupid thing is that this was a clean-sheet design, where they could easily have used a Holley-style diaphragm pump that's tried and proven. Demon is even owned by Holley, so that would be a no-brainer. But no, they re-hashed the Thermoquad pump that is clearly flawed in this instance. They used other Holley things like secondary jets, electric choke, squirters, etc so I dunno what they were thinking.

Another drama you may come across is the fitment to a standard Mopar manifold. The Thermoquad was a spread-bore pattern but this Street Demon, despite having uneven primary/secondary bores, uses a square-bore pattern. So you'll need to run a spread-to-square adaptor, which on some cars will give hood clearance issues.

To avoid these dramas, you could opt for a refurbed Holley spreadbore that would bolt straight in place of your Thermoquad.

Don't get me wrong, I love the Street Demon but they could've done a much better job, being a new design and all, they had the opportunity.

My 302 is very mild in the scheme of things. 204/214 cam, around 0.5" lift, 112 LSA. Tri-y headers, cats, 2.5" twins with x-pipe. Heads have been skimmed about 0.040 (estimated) from stock so that equates to about 10:1 comp. Ports were tidied up by me, just a bit of bowl and guide work is all, mostly inlets. 3-angle seats, stock valves. 115lbs springs on the seat, stock rockers for now.

Flywheel has been shaved by 1.5kg from stock. It buzzes to 6000 no probs since the heads went on, so I'm predicting (once back on the road) that it will have a bit more pep than before. I'm also running an MSD Programmable with a map sensor connected. All through a 6-cyl T5 box.

Hope this helps paint a picture of what kind of mild small block the Street Demon is suited to.

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Thank you Gerg.  My main concern was to make sure I'd selected the right size carb. Sounds like the Demon should meet my needs apart from that accelerator pump issue.  The carb fits on the spread bore Wiand twin plane without fouling the secondary butterfly and it looks like it fit under the bonnet but it'll be tight.  My cam has .454 lift and 110 LSA (Comp cam 268H)  It will run a DUI dizzy so the combo is a bit milder than yours.  It won't see much hard driving other than the occasional "squirt".   The car only weighs 1335kgs even with the V8, so the combo should work well.  318s were almost strangled with the 2 barrel carb and respond well to being able to breathe.  So thanks again this info is invaluable.

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