Speed Demon and Holley

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Speed Demon and Holley

Postby NixVegaGT » Tue Mar 25, 2008 9:01 am

And other Holley derivatives: I don't know anything about them. I have always stayed away from a Holley design because of what I see as an inherent flaw in mounting the fuel bowls sideways. I'm really having trouble rectifying that in my own mind. SO for the sake of keeping an open mind I will lay out my concerns and questions. I would really appreciate some differing opinions and real experience with them. I'm tired of reading articles about speed parts that seem biased toward the sponsor.

Fuel bowls on the side: they have GOT to leak! right? And splash fuel all over the engine when tuning, right? For cornering, is the center mount float better?

Square flange: Why make the secondaries the same size as the primaries. Wouldn't that impede low speed atomization? Is it better for some other reason than the spread bore? Are mechanical secondaries better than vac secondaries in a light car like ours?

Speed Demon: (this seems to be the best choice, from the Demon line for my application) Looks pretty. They say they have more adjustability than the Holley. They are actually comparably priced and sometime cheaper. Weird. The main body seems optimized for air flow and that is appealing to me - does it actually make a difference? It's got to, right?


OK so here's the reason I'm asking. I've got the rare opportunity to try a couple different things with my engine set up. I've built a Q-jet and I'm feeling pretty confident with my work on it. I made a bunch of modifications for better performance. It was a lot of fun. I only have one manifold that will fit the Q-jet and my engine. It's a single plane with a pretty large plenum. I also have a spare Edelbrock performer dual plane high rise with a square flange. I could try a few dyno runs to see what works best with my engine:

Q-jet with single plane
Holley (Speed Demon 575, or standard 600cfm) with single plane
Holley with Edelbrock intake.

Here's my cam specs:

Crower 50232 with an intake lift of 0.488", an exhaust lift of 0.490", Duration 276º, Duration at 0.05": intake 214 degrees, exhaust 218 degrees. Lobe separation angle: 112 degrees. (Aggressive street cam with a little idle distortion for my engine.)

The information below is for degreeing cam only.
Correct only at .050" tappet lift.

INTAKE Opens: -1.0 ATDC
Closes: 35.0 ABDC

EXHAUST Opens: 45.0 BBDC
Closes: -7.0 BTDC


Engine is a hybrid Buick/Rover stroker. 5.0L:
3.74" bore x 3.4" stroke
Rod ratio: 1.68 so it should have a torque curve characteristics similar to the Buick 350 if that helps. It's pretty close to a Chevy 350 (1.64) so similar piston speed at TDC. Make sense?
Long tube headers.

My last question is about aftermarket Holley manufacturers: Do they actually make a better product than the standard Holleys? How about listing a few so I can comparison shop. Thanks for the help.
- Nic '73 Vega GT "DogBoxx" Batwing LS1
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Postby Sirshredalot » Tue Mar 25, 2008 11:29 am

In all of my experience, What leaks the most on a holley is not the bowl gaskets but the bowl screw gaskets....an $8 set of mororso nylon gaskets will fix that.

As for the differences between demons and holleys...I have no conclusive evidence yet as I have just started to medel wit the demons but they DO seem like a high quality product...perhaps even more so than a holley.

THe Holley knock offs like proform and quickfuel are very high quality carbuertors...From what Ive seen the Holley HP series isnt too bad either....They seem to have better castings than the standard holleys as well as alot more features for tunability.

Yes the side float bowls do tend to leak when you take them off....but what I always do is either turn off the electric fuel pump....or unhook the mechanical fuel pump lines and crank the motor over with the pedal held to the floor to drain the bowls....then you dont have as much to spill.

In a light car with a decent starting line ratio I really perfer mechanical secondaries because they seem a little more responsive....vacuum secondaries are very good...dont get me wrong.....but the mechanical secondaries are what I would choose for a vega with a 5 speed and 3.23 gears or greater.

With regards to mechanical secondary carbs there are single and double pump carbs....youll be hard pressed to find a 600cfm mechanical secondary single pump carb....so go with the double pumper.
Dont listen when people tell you youll fuel wash out your engine with a double pump carb...theyre just more tunable to be able to further tailor the fuel delivery curve.

Center hung floats are really the only ones that come with double pumpers but I have seen some conversions....I dont know why...
But I would imagine the center hung float would be best for the corners...youd get the best response...might even wanna increase the springs pressure under the float and up the fuel pressure...for a road coarse.

As far as a design goes my favorite by far hands down is the edelbrock/carter design. Its so easy to change jets and pumps that you never loose a single drop of fuel.
But as with every upside there is a down side....Ive never been able to tune them as well as a holley for a very radical cam...
I can never seem to be able to get enough pump shot out of an edelbrock....

But for a motor as mild as yours Nick (dont be offended...itll run)
I really think that any of the listed options would be more than adequate for your needs as well as provide some room for growth....
Id go with a 600cfm carb.....with the single plane Id recommend a double pumper.
Holley/Demon/QFT/Proform....I dont think youll notice a difference between them...other than the cool factor....some look cooler than others.

God bless
-Shred
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Postby NixVegaGT » Tue Mar 25, 2008 12:51 pm

Thanks Wes. You rock. I forgot to mention my CR is 11.8:1 in case that helps anyone.
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Postby mldeolde » Tue Mar 25, 2008 10:29 pm

MY NOVA ENGINE- THO MODIFIED I HAVE THE SAME TRIED AND TRUE PERFORMER MANIFOLD, 480/280 COMP CAM. 650 DP HOLLEY, PORTED 202/160 IRON HEADS, STAINLESS STEEL TRI -Y HEADERS AND APPROX 10.5 TO 1 COMP... GOOD FOR 400 + HP AND STILL HAS AMAZING LOW END AND MID RANGE FOR A SMALL 355 CU IN MOTOR. THE INTAKE AND THE HEADERS ARE KEY HERE BUT I THINK THE PORTING ALSO IS A CONTRIBUTING FACTOR IN ALLOWING THE ENGINE TO STILL HAVE GOOD TOP END POWER IN A SET UP REALLY DESIGNED MID RANGE POWER FOR THOSE 3.08 FWY FLYER GEARS THAT WE HAVE IN THIS CAR. NOT A DRAG RACER FOR SURE BUT DECEPTIVELY FAST NONE THE LESS.
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Postby BillPappy » Wed Mar 26, 2008 7:12 am

Yea nice Wes. Sweet. I know Holley,demon and edelbrock/carter carbs . Not sure about the QFT/Proform.
I agree with Wes.
my experience.
With the secondaries the same size as the primaries I found you can run 3 to 5 deg. higher base timing.( Sorry don't mean to open up a new can of worms.Some are glued to there timing light) Still easy starting. with faster throttle response. need to readjust total timing.
Leaks, screw gaskets ,Excel pump, Single line carbs, the long tube that runs to the back bowl
can leak. When taking off float bowls. Cut off 3in bottom of oil jug. set under bowl. Pull bolt.
Let drain into jug. No mess no worry.
Holley/demon rocks when it comes to performance.
edelbrock/carter carbs They work good. get good MPG. I got one on my work truck.
It's hard for an old street racer to stay on the safe side of stupid

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Postby 73astregt » Wed Mar 26, 2008 8:39 pm

well boys my opinion is this, a holley or a demon might be a good race carb but for the street for cruising i went with the edelbrock. why?you ask because my bro had a holley on his camaro and every week he was twisting screws to keep it in tune and it was a new carb. 2 i bought a demon when i first put my car on the road it was a 650 road demon and i could turn the screws any where i wanted it did nothing drove the car from scarborough to pickering and burnt 24.00 worth of gas round trip, that isnt far believe me. the shop i bought the demon from said you gotta bring it to us no one that buys a demon and installs it them selves can tune it properly, well ive played with carbs for years and never had one act like this i sais so ill tell you what ill bring it to you you make my car run right ill pay you if not you get nothing ok he says bring it i take it and leave it for the day i go back guess what they put a new one on cant tune it. so now i drive away with the car it feels real good snappy throttle everythings great. my bro comes over for a visit i take him out for a run to show him how it works hit the street crack the throttle and were flying great! im happy shes running super get two stop lights up the road and its stumbeling dont wanna run turn around and head back get home and it barely wants to run shut it off open the hood and pull the breather look down the carb and the secondaries are pissing fuel like the jolly green giant and his twin are taking a leak in my carb now im really going ballistic my brand new motor is reading 2 1/2 inches above full on the dipstick it just flooded the hell out of my motor. i called the guy back and told him what he could do with his demon carbs had him order me in a 650 thunder series edelbrock and now the car runs sweet flick the key shes running drive it up north on the weekend and go to the wifes parents by camp borden(army base) about a 2 hour run paid 1.22 a litre of gas there for the return trip and only burned 22.00 bucks worth of gas all the way back to the city THATS A HUGE DIFFERENCE and i mean huge ! any of the members here that are in ontario can vouch for the difference in kms. demon maybe for racing but if you want to make it between gas stations get the edelbrock! set it and forget it!
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Postby BillPappy » Wed Mar 26, 2008 10:52 pm

Im Not being mean.
You got trash in your gas. Only thing I know of
that will flood a Holly/ Demon after the needles
are set. unless you getting boil over. Hot Gas.
Anything like fine rust will go strait thu a fuel filter Will make a holley flood even mess with the idle screws
A edelbrock can suck down
A golf ball in never miss a beat.
It's hard for an old street racer to stay on the safe side of stupid

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Postby 73astregt » Thu Mar 27, 2008 12:01 pm

on the second demon i agree that it was maybe trash from the gas tank(rust)that caused the flooding or maybe some filings from manufacturing of the carb or the dual inlet fuel line but by that point i was soo pissed with it i didnt want anything to do with a demon friggin thing set me back near 800.00 for the carb alone all i wanted was my car to run the way its supposed to. the first demon was just totally untunable i set it up as per the instructions trying to get the transfer slots to the size they wanted and nothing worked turning the idle screws in or out made no change the carb was one of the newer ones with the idle ease screw in the bottom of the breather bolt hole you could turn that one in or out and no change at all only way to adjust the idle was with the screw on the linkage and that buggered up the transfer slot settings. the carb they gave me was a mechanical secondary and my car is an automatic wich should have a vacume secondary carb they also had me running no vacume advance wich drove my temps up to the point that i couldent drive for 10 mins with out the temp spiking. after this was all done with i found the h body club and found out a few things like drilling holes in the throttle plates for more air at idle but the demon was long gone by then. the edelbrock i went with is the 650 thunder series avs and it works great i havent had to touch it since i put it on and thats the way i like it no hassles. for the track if and when i run the car i think id go with a holley 750 double pumper to gain some horses. they told me i was loosing about 50 hp going from the demon to the edelbrock i think thats bull a few horse fine but 50 horse naaa.. not gonna miss it on the street anyways probably hook better with less horse in a light car like mine with street tires.
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Postby Sirshredalot » Thu Mar 27, 2008 12:28 pm

Holleys are very particular about getting junk in the needle and seat....by that I mean they like to do it...Ive seen many people replace a whole carb with a new one...when a tap on top of the float bowl would have fixed it.

Edelbrocks have a special place in my heart....theyre bulletproof...get great gas mileage and decent enough power....easy to tune and clean looking carbs.
For a FAST car though....Id choose a holley everytime.

Wow Nick, over 11:1 compression?...with a wide LSA?...youre asking for trouble on pump gas....are you still going with E85?...I would with that compression ratio and cam.
Speaking of which:

Get yourself the cheapest 600/650 double pumper you can find....Convert the metering blocks to alcohol blocks and jet it DOWN from the normal alcohol jets.
Get some 50cc accelerator pumps and have fun.

God bless
-Shred
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Postby NixVegaGT » Thu Mar 27, 2008 6:28 pm

BillPappy wrote:A edelbrock can suck down
A golf ball in never miss a beat.


LOL!


Shred, Yeah I was planning on E85. Also since the engine is all aluminum it runs safer at higher compressions. I ran my dynamic compression based on my cam specs and came up with about 10.5:1. Do you think I should be more aggressive with the cam? I was concerned about having enough compression for E85. I'm going to risk the Qjet components to see how long they last bathed in E85.

These CR numbers are based on my theoretical math so far. Those may (will likely) change when I measure the actual assembly.


[quote="Shred"]Get yourself the cheapest 600/650 double pumper you can find....Convert the metering blocks to alcohol blocks and jet it DOWN from the normal alcohol jets.
Get some 50cc accelerator pumps and have fun.
quote]

Great advice. Thanks Bro. Thanks to everybody for weighing in. Edelbrock said they were going to make an E85 carb but info on it pretty much disappeared. Anybody know anything about that?
- Nic '73 Vega GT "DogBoxx" Batwing LS1
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Postby mldeolde » Thu Mar 27, 2008 7:19 pm

yes nicks aluminum engines heads will allow for way more compression or way lower octane fuel before encountering detonation or other problems related to hot spots in the heads............
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Postby 73astregt » Thu Mar 27, 2008 8:45 pm

hey nick if you are going with the e85 fuel have you thought to check the availibility of it in newfoundland? you said you wanted to run the targa there. if not available what are the regs for transporting fuel across the border? you might be in kimchee there!
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Postby NixVegaGT » Fri Mar 28, 2008 4:29 pm

Yeah… Good point Fred. YIKES. Hmmmmm. Ok. Well I guess I might have to tune a carb for high-octane fuel too. DAMN. good point, Fred.

There's the second reference to Kimchee. LOL! Thanks for reading my CarDomain page, dude.

OK the other issue is that at a theoretical 11.8:1 compression is still a bit low to optimize for E85. It could be I end up with 10.8:1 when I assemble the engine or something like that. We'll see. I am a year off from being ready to race in NF so maybe you guys will be importing E85 by then! LOL.


Hey check out this hot 600 holley I found on ebay:

Image
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Postby 73astregt » Fri Mar 28, 2008 7:02 pm

ya nick im yhinking specialty fuels like e85 are going to be a hard find in n.f. i could be wrong tho. as to high test i think 92 octane is the best you can get here in ontario i think you can get higher ratings where you are right? i know that i have to run the 92 oct in my car and the compression ratio is about 9.7 to1 my engine builder says. other thing is that for an organized race they might bring in race gas i know they have it here at the local roundy round tracks but for a road race? also yhe price of fuel is higher down east than here and i know i paid 1.22 a litre for high test here last summer and im thinking it might be higher this year! holy crap! 1.22 per litre,4.5 litres per gallon shit thats about 5.50 a gallon when i was 14 i was buying 5 gallons for 4.75 , ouch!
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Postby SWT Racing » Mon Mar 31, 2008 9:23 pm

If you want to go with a Holley style carburetor, I would suggest sticking with a genuine Holley, and not one of the knock offs. The bowls will not leak if you use the Moroso bowl screw gaskets as suggested. I pressurize my carb with 17 psi of boost via twin turbos, and have never had a leak. I personally know of people running over 30 psi through them without leaks. You can buy used, but be sure to use genuine Holley parts on it when doing the rebuild.

As a side note, you will have to alter the fuel curve in the carb and open up some passages to get the correct AFR with E85 if you are putting down some decent power. You will need to burn approximately 1.5 times as much fuel as gasoline to make the same power, so the carburetor will need to be calibrated to provide more fuel. You will need to jet it up, open up the power valve channel restrictions, and increase the size of the idle feed restrictions at the very least. . .depending upon your power levels. Also, because you need to burn more fuel, you may need a larger fuel pump to keep up with the demand of the engine. One other thing to keep in mind is that the E85 blend may change depending upon the time of year.
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