Ok lets see just how far I can throw a 750 Holley.

[SactoJim]

Originally Posted by Dice

I have a speed shop and after 30 years of wrenching, I can't say that one brand of carbs is better than the other. They both have their quirks and can have problems if they aren't set up properly or get some debris in them. Here's the annoying problems I've experience with Edelbrocks: If the fuel pressure is slightly higher than stock, they flood over or run super-rich. Next, they're very sensitive to engine heat and if you don't have a good insulator between the intake and carb, they run erratic when hot. Finally, if you let your car sit for a few days, the gas magically disappears from the bowls and you have to crank them until the fuel bowls fill up again before they'll start. I prefer Holleys.

Funny you say that about hard starts after a few days of sitting......mine does exactly that....if it sits for a week, I have to crank on it a bit before it fires. Other than that, it works very well.

[67chevemall]

Sold the 1406 and bought the 670 Street Avenger! Awsome carb.

[Wrenchbender Ret]

I didn't realize the thing had a blower. I've never worked with one that has.

[caminokid]

Originally Posted by 68Stepbed

What's the brand of carb got to do with fan blades coming off?

If it hadnt been the 400th time tuning the stupid Holley...I wouldnt have been under hood again when the blade came off.

See my point now?

Holleys are out and out junk.

[prostreetC-10]

There is no doubt that edlebrocks are for the "I don't know anything about carbs" guys.....for the most part. They are good out of the box and designed so "herby" can't really mess with them. When it's time for big power, you will run a Holley. Go to your local race track. Edelbrocks are on the trucks that tow the drag cars that all have Holleys!!! end of story!!!

[smoked68]

Guys, thanks a ton for all the input. As SactoJim stated I do have a small SC on the 350. I have some work done to the eng and a good set of heads. I had a 650 Eddie on the truck, brand new outta the box with elect. choke. It was really sweet untill I stomped it the first time. No Goooo. Not enuff carb for the app. I had the Holley sitting on the shelf and ordinarily it would be too much carb but not with the SC. The Eddie would not build the Boost, the Holley on the other hand builds the 6lbs of boost which is the pulley I am running. Hopefully Santa will drop the 8-10 lb pulley down the chimney. I am going to work on the Holley next week and save my pennies for the 800 that was mentioned because we have almost the same setup. Thanks one and all for your ideas I will try most next week while I'm off work. Thanks and everyone have a safe and happy CHRISTmas. Mike

[68Stepbed]

Originally Posted by caminokid

If it hadnt been the 400th time tuning the stupid Holley...I wouldnt have been under hood again when the blade came off.

See my point now?

Holleys are out and out junk.

That's kind of what I had figured after I posted. It's funny how everyone has different issues with different stuff. I was exactly the opposite with the Edelbrocks. I was constantly under the hood fiddling the darn things. After installing the Holley, the only thing I did to it was try to make it go faster. As far as everyday driveability, it was great.

Something else I like about a Holley carb, Every, and I do mean EVERY time I start my truck, all I have to do is bump the ignition key and the engine fires right up. If it's been sitting a while, I tap the gas once and it fires right up without a hitch. Every Edelbrock I've ever had, I had to turn the engine over a few times to get it to start. It was always worse when when the engine was hot. I don't know what causes it, but it always got on my nerves.

I will say this though, the only good Edelbrock carb I ever had was a 500cfm manual choke on a stock 350 in a 66 Chevy truck I used to have. That thing ran great! I'll never go bigger than 500cfm on stock engines anymore.

[special-K]

I can appreciate opinions.Here`s mine:I`ll take a Holley over an Edelbrock any day.I buy carbs from carburator companies and manifolds from manifold companies.That`s my preference based on my experience.I`ve used both,obviously alot more Holleys since Edelbrock only started selling carbs in more recent years.I`ve had less problems with Holleys.Holley makes so many carbs you really can`t compare the as a whole.Some Holleys I`ll never buy (600).But,I haven`t had an Edelbrock I was impressed with.But,I won`t tell someone else how to feel.

[corn]

3310 Holley on go fast stuff & Carter AFB comp on daily driver stuff for me. I like all Edelbrock products but not their carbs...

[kookykrispy]

smoked 68, I am putting together a 6-71 setup for my GTO, so I have done alot of studying up on how to set up carbs for the blower. I like both edelbrock/carter and holleys. Edelbrocks seem to work better 'out of the box' when first bolted onto the average engine for some reason... and for that reason they are considered more 'trouble free'. That being said, the edelbrock does not have the 'tuneability' that I like about the holley. I am by no means anything close to a Holley expert, and I do not have my books here with me... so I am going off memory here. I will try to help, but I encourage you to learn and research as much as you can about your carb. If you learn to tune it, and dial it in, I think you will love it and it will perform great!

To properly tune a holley, you must learn and understand each system within the carb, and know how to tune it for optimal performance on your particular engine combo... the idle circuit, the power circuit, and then the secondary system, (depending on what holley you have) all need to be dialed in for the carb to work properly. The holley is a modular carburetor, infinitely tunable and adjustable, so that is why it is a favorite of racers... and for that same reason it is a bane of those who do not understand how it works or how to tune it.

I think on a blower application, the Holley is the way to go because it is easy to tune and modify to work with the blower. Also, running a blower increases the airflow requirement for your engine... because the blower is stuffing all that air into the engine, much more than naturally aspirated engine would injest. I would say your small blower on a 350 engine would need at least 750 cfm, at a minimum.

The blower engine will require more fuel at idle, and also at all other engine speeds. Try turning up the idle fuel mixture with the holley and see if you can get it to idle that way. Also, you will want to increase the main jets... keep checking your plugs as test drive it and you go up in jet sizes. You want to err on the side of being rich, better to be too rich than too lean on a blown engine. A lean condition under boost can potentially cause serious engine damage. The best way to tune is with back to back runs at a dragstrip, so you can use the timeslips to know if performance is actually improving or not.

One thing I found in my research is that on a roots-type blower, where the carb is above the supercharger, the carb should be modified so that the power valve is "referenced" to the manifold vacuum, below the supercharger. The power valve in a holley is designed to work with a normally aspirated engine. The power valve opens at a set amount of vacuum (or lack of). It gets the vacuum signal through a small hole that is on the base of the carb, so it 'reads' the engine's vacuum signal below the throttle butterfly plates. On a normal engine, with no blower, when the engine is at idle, and there is a high vacuum condition in the engine... the power valve is closed while there is high vacuum. When you open the throttle, the vacuum signal drops as the butterflies open and the engine, the power valves opens in the low vacuum condition, and adds fuel, richening the mixture. You can tune this by swapping out power valves that open at different points of vacuum.

The blower is constantly sucking air... and there is always a vacuum atop the supercharger, even at wide open throttle, so the power valve on an unmodified Holley will always 'sense' a high vacuum condition, and the power valve will never open, creating a lean condition.

"boost referencing" refers to plugging up the factory vacuum sensing hole in the base of the carb and then drilling into the side of the vacuum circuit feeding the power valve. You put a small tube in this hole, and then you can run a vacuum line down to the manifold below the blower. With this mod, when the blower starts to build boost, the power valve will sense the lack of vacuum, and will open, adding the needed fuel.

the blower FAQ tech section of the Holley website http://www.holley.com/TechService/FA...ategory=Blowertouches on this a bit also:

QUESTION Do I need to run a blower calibrated carb with a supercharger?
ANSWER A lot is going to depend on what the setup is and what you are going to do with it. If it is strictly a race setup with no street use then usually you can get away with a standard carb with the power valves plugged and the carb jetted up to compensate. This does not work well on an application that will get mostly street time. For those applications we do offer out of the box Holley carbs with Manifold Referenced Power Valves which will work correctly on the blower. These carbs will allow the use of the power valves which will give better idle quality and street driveability with a blower.
QUESTION What is a Manifold Referenced Power Valve?
ANSWER Nothing will kill a blower or Nitrous engine quicker that a lean condition. You want plenty of fuel available for the engine to use .There is a thing you need to know about the power valves on a roots style blower engine. The power valve is installed to keep the engine from loading up and running rich at an idle. On a normally aspirated engine the engine vacuum at idle will hold the power valve closed. When you step on the gas the throttle plates open and the engine vacuum drops as you accelerate. When the vacuum drops below the rating of the power valve , it snaps open and richens up the main system. On a blower with the carb mounted above the rotors there is constant vacuum all the time even under wide open throttle. The power valve will never open and you will have a lean condition. To remedy this there is a modification you can have done that is called manifold referencing the power valve. You plug the vacuum feed hole in the baseplate for the power valve. Then you drill a hole in the side of the main body into the hollowed out vacuum chamber for the power valve. You then insert a vacuum nipple in this hole. You will run a vacuum line to the lower intake manifold from the new vacuum nipple. Now you will have vacuum on the power valve at an idle, and when you hit the gas as the boost builds, it will force the power valve to open and richen up the main system. This can be done by most carb modifiers or even yourself. We offer quite a few different size blower carbs with this already done. Consult you local Holley dealer or our Techline for the correct application.

Here is a good step by step article with pictures (on a Ford website, but it still applies) about how to add "boost referencing" your holley:

http://www.fordmuscle.com/forums/tec...d-engines.html




A couple questions related to the blower... what heads are you running? Do you know your compression ratio? And what cam are you using?

[caminokid]

Originally Posted by 68Stepbed

That's kind of what I had figured after I posted. It's funny how everyone has different issues with different stuff. I was exactly the opposite with the Edelbrocks. I was constantly under the hood fiddling the darn things. After installing the Holley, the only thing I did to it was try to make it go faster. As far as everyday driveability, it was great.

Something else I like about a Holley carb, Every, and I do mean EVERY time I start my truck, all I have to do is bump the ignition key and the engine fires right up. If it's been sitting a while, I tap the gas once and it fires right up without a hitch. Every Edelbrock I've ever had, I had to turn the engine over a few times to get it to start. It was always worse when when the engine was hot. I don't know what causes it, but it always got on my nerves.

I will say this though, the only good Edelbrock carb I ever had was a 500cfm manual choke on a stock 350 in a 66 Chevy truck I used to have. That thing ran great! I'll never go bigger than 500cfm on stock engines anymore.

I have been using the 1405 Edelbrocks for a long time. I think that is 600 cfm. Never have had a problem. Out of the box onto the motor.

Some people are better with certain things...I am not good with Holleys.

[grancuda]

Have any of you guys tried the new AVS carbs? They are great for performance and daily driving and very easily tuneable. I ran one daily for 6 months and the car ran in the low 12s with a small block and some 3.91:1 gears.

I think I can throw my monojet further than you can throw your Holley.

[red69ss]

I have been having the same problem with the 750 I have on my chevelle I live in sc too and with the temps going up and down I've had to adjust it a few times (is this a symptom of a blown power valve?) I like the holleys because they seem to be easier to work on although harder to tune ..... the 600 holley I put un my truck has been trouble free so far

[smoked68]

Ok guys, I have a set of the Double Hump heads worked on with 202 valves. The cam is an Engle 501 lift, I dont remember the duration but it is wide. 223/230 something I think. (Hey its been a year and my brain is fried, at best, on good days). Anyway, 4 bolt 350 bored over and forged internals. It makes pretty good power, and the advice from SactoJim and Kookykrispy makes since that I will check into. A lot of you guys said power valve, well after reading up and listening to the advice here I think you were all correct. Therefore I will either replace and correct the one I have or go with the 800 Sactojim recomended. Thanks again to all and merry CHRISTmas...Mike

[smoked68]

Oh red69SS, I live in Rock Hill...So we both have the same weather. Crappy, this week. 73 deg. when I left out this a.m. Truck ran great, 50's and probably foggy again tonight equals..a lot of action at stop lights. Gas-brake-clutch gas-brake, irratated, hand brake, then light changes and I off the hand brake then usually spinning pretty hard till it grabs. The Leo's love to follow me down the road.

[shortbed70]

Go demon and dont get a flex fan they are a good way to vent your hood after a new paintjob or bodywork or worse when your over the top of it. I've run edelbrocks,3310 holleys and now a demon and the speed demon are AWSOME simply said they have the throttle response of the 3310 but after doing some research and setting mine it starts and idles all day in cold days and wet days and hot days.

[Arad68]

Originally Posted by shortbed70

Go demon and dont get a flex fan they are a good way to vent your hood after a new paintjob or bodywork or worse when your over the top of it. I've run edelbrocks,3310 holleys and now a demon and the speed demon are AWSOME simply said they have the throttle response of the 3310 but after doing some research and setting mine it starts and idles all day in cold days and wet days and hot days.

I have a 750 Speed Demon on my '68. Best carb ever. It always works well, even in the searing heat of Nevada.

[kookykrispy]

Originally Posted by smoked68

Ok guys, I have a set of the Double Hump heads worked on with 202 valves. The cam is an Engle 501 lift, I dont remember the duration but it is wide. 223/230 something I think. (Hey its been a year and my brain is fried, at best, on good days). Anyway, 4 bolt 350 bored over and forged internals. It makes pretty good power, and the advice from SactoJim and Kookykrispy makes since that I will check into. A lot of you guys said power valve, well after reading up and listening to the advice here I think you were all correct. Therefore I will either replace and correct the one I have or go with the 800 Sactojim recomended. Thanks again to all and merry CHRISTmas...Mike

Hmmm... ok, sounds like you may have more problems with your supercharged engine combo than just the carb. From what you've described, you would have a great street motor... if it was naturally aspirated. In my opinion, your current combo is far from ideal for supercharger use. Those camel hump heads are small chamber and will produce alot of compression on a flat top 350, probably close to 10:1 or more. Too much for a blower on pump gas anyways. Ideally, you want 8:1 or 8.5:1 compression to run boost and still be OK on pump gas without detonation. If you're going to keep that blower on your engine, consider swapping to some large combustion chamber heads to drop a point or two out of that compression ratio.

The cam you have may not be suitable for blower use either. It might be a great cam for a higher compression street/strip engine, but not anywhere close to what you want to run when using a supercharger. You said it has a pretty rowdy idle, which makes me suspect it has alot of valve overlap. If you can figure out what cam you have in there, see if you can find the specs and see what the LSA (lobe spearation angle) is. Too tight an LSA with lots of duration will create alot valve overlap... (where both intake and exhaust valves are open at the same time) and then your blower is basically going to be blowing most of the intake charge right out the exhaust before the exhaust valve closes. Blowers work best with an LSA of about 114, and most 'blower' cams out there are cut on a 114 with relatively short duration to minimize valve overlap.


Good luck and keep us posted!

[smoked68]

Hey thanks for that, I am looking at the Edlebrock alum heads. Whats your take on those or best fit for my app? I am all ears, I learned a long time ago that my dad was right. I dont know everything, but now, I am willing to listen. Thanks, Mike.

[phipp13]

hey smoked 68, please pm me and let me know how you make out and i'll do the same. i;m running almost the same setup but mines a 383 CID 72 cc dart 2.02/1.60.200cc runners 110cc dished pistons B&M 144 blower 750 holley mech secondaries msd etc etc. imho if its a daily driver i try to use a good quadrojet, hard to rebuild right but, when the're right you can put then on and forget about them. MY hot rods get holley carbs. holleys are like Dating a stripper.... high maintenance, fun to play with and, well worth the ride! phipp

[kookykrispy]

Originally Posted by smoked68

Hey thanks for that, I am looking at the Edlebrock alum heads. Whats your take on those or best fit for my app? I am all ears, I learned a long time ago that my dad was right. I dont know everything, but now, I am willing to listen. Thanks, Mike.

You need to tailor your engine combo for the supercharger... and luckily you can do this without spending a whole lot of money. I'm gonna tell you how to do it on the cheap. First of all, you're going to need some 76cc heads to get your engine into that 8:1- 8.5:1 ideal compression ratio area for blower use. (I'm assuming you have typical 4 valve relief flat top pistons... you mentioned the internals are forged which is necessary for blower use)

Aluminum heads are nice because they will help to cool the chambers and make it less prone to detonation... this means you can crank the boost up a bit more and give some more timing... (your blower engine is going to like alot of timing). If you have the extra money, go for it, but its not necessary at all. You can get fine results with a set of big chamber factory iron castings, and you certainly don't NEED fancy aluminum heads to run a supercharger.

I would look for a deal on a set of large valve 76cc chamber heads that have been rebuilt, or get 'em rebuilt... don't need anything fancy, but stainless valves would be nice because the valves are gonna see more heat than on a regular engine. Chevy produced tons of these heads so they are plentiful and cheap. Make sure they have the large 2.02/1.6 valves because the blower is gonna be doing some heavy breathing. Also make sure to use some quality valvesprings.

Go to the Mortec website to ID the casting numbers to know what you're getting when shopping for heads: http://www.mortec.com/castnum.htm

Next, you'll need to run a cam that is suitable for a blower. Something on a 114 LSA and I would run a split profile that favors the exhaust side. A blower produces alot of heat so you want to do everything you can optimize exhaust. You need full length headers and at least 2.5" dual exhaust with low-restriction mufflers. I suggest the K1105 cam from Summitracing:

http://store.summitracing.com/partde...5&autoview=sku

Duration at 050 inch Lift: 224 int./234 exh.
Advertised Duration: 282 int./292 exh.
Valve Lift with Factory Rocker Arm Ratio: 0.465 int./0.488 exh. lift
Lobe Separation (degrees): 114
Basic Operating RPM Range: 2,200-5,700


I think this looks like a good street blower cam... even better would be to swap to 1.6 ratio rockers for a little more valve lift. I ran this same grind in my Ponitac 400 naturally aspirated and loved it... I plan to use it in my new 455 I'm building for use with the 6-71. at $89.95 for cam and lifters you can't beat it.

If you want to stick with Engle, they make a blower grind too, Part number: 1005-H, gring number TCS-5 and I'm sure it too would be a great cam.

[smoked68]

All I can say is THAAANNNKKK Yooouuu!!!
I really appreciate the info and will put it to good use. I will flie this under "More things I did not know". Thanks a ton...Mike ( Between the truck and the Bike I'll never have any money! But lots of fun...

[AllenKarber]

Maybe this carb tossing should be an event in the Gearhead Olympics!

[kookykrispy]

Originally Posted by AllenKarber

Maybe this carb tossing should be an event in the Gearhead Olympics!

Along with the bare engine block carry, muncie 4-speed bench press, and of course, the truck pushing events!