scoop / air restriction ?

[Unchained]

I have been running a Mr. Gasket / Hilborn style scoop on my carbs since I put the engine together. No air filters, just the coarse mesh screen/foam that they come with.
Two different engine builders have informed me that the screen/foam is an air restriction for the flow that I need to feed air to the monster. I have two 850dp holleys, 8-71 Hampton blower, 540 ci Arias/Chevy engine. Has anyone else found the scoop/screen to be an air restriction?
This year I went from 23% blower OD to 38%
blower OD and am only getting 14.5 lbs.boost
at 6000rpm. I thought I would get a lot more boost with that much OD. I never concidered that the scoop screen could be an air restriction.

[DEL51]

Unchained,I think an 871 may be a little on the small side for a 540.I am going to test my scoop and my filter on the Dyno.

[DEL51]

I did not intend to have the sad face on the previous post.DEL51

[superdave013]

The scoop is not the restriciton, the carbs are. Put an Enedrle injector hat on that blower and @ 38% over you will get more than 14.5 pounds. When I ran carbs I never ran over 15% overdrive. Anymore made no more boost but it generates more heat. With the injector hat I was running 30% over. It would make 28-30 psi depending on how freash the blower was.
Put fuel injection on it and you will shit on the throttle response too.

[Unchained]

Thanks Dave, I always wanted to run an Enderle but was concerned about the drivability. The Enderle certainly has the ultimate bad ass look that no carbs can match.

[Infomaniac]

Unchained: This should start some discussion
At 6,000 engine RPM a typical 8-71 running 38% O.D. moves 2,721 CFM of air. At 23% O.D. 2,425 CFM of air. You should have enough carb to match this or the boost will be limited.
THIS IS CALCULATED USING STANDARD VOLUME NUMBERS IN THE MATH. This is a very good base line to select carbs with.
I am sure carbs flow more, the more vacuum you put under them. You can suck the power valves shut under conditions similar to yours. This is one reason some folks boost ref. their carbs. I choose to not run power valves on a blower.
Injection is great and I would be curious to know how much a bird flows vs a bug etc.
Hard starting when cold, fast idle and strange part throttle operation are all part of it.
If you go to twin doms. they are not the best for part throttle operation either.
I will have to send you the video of my 8 year old son on a tube behind the Cougar. The engine sounds terrible running 35 or 40 MPH down the lake. The butterflies are pretty much closed, only opened a few thousandths.
After I get where I am going the hat and blower are sweating like crazy. Just part of it when running injection. There are plenty of guys around here jet or v-drive, blown or not that run injection on their lake machines. Once you do it you will never go back.
Oh Yea: I ran the same scoop with just the screen when I had carbs. I did not use the filters either. I put some black foam filter element used in the Edelbrock Pro Flow triangle shaped breather sandwiched between the coarse screens. Never had a problem with restriction.
[This message has been edited by Infomaniac (edited November 30, 2001).]

[Unchained]

Info, After hearing about the drivability problems I really don't want injection. My boat is loud and impractical enough now but drivable enough to ski, tube, and cruise with. I won't give up the drivability so I need to do the best I can with carbs. I think that I want to go with a 14-71 blower, crank trigger ign, and two 1050 dominators.
You know, the typical boat performance plan. Throw more money at it until it does what you want.

[572Daytona]

How about one of the Holley 2000cfm injection units? http://www.holley.com/HiOctn/ProdLine/Products/Marine/FMS/FMSFI/MPI.html I've never used one but I remember a post by Duane Oberlander at Hi-Tech Performance http://www.hi-techperformance.com/ saying that he used on on his 572ci jet and was very pleased with it.

[1riverrat]

Ron's racing has an 8 port hat type af fuel injection and say that it has excellent
driveability but that is on tunnel they did not say anything about driveability on the blower. http://www.ronsracing.com/

[Blown509Liberator]

Unchained
I was talking with Dave from DNE about carb sizing on Blower motors. One thing he said was to check to see if your building vac just under the carbs. if you are then they are to small. This may be the place to start.
What HP are you making? I am making 850 and have a very good drivability with it. It starts easy and I have about 800-900 rpm idle
Runs well at ski/ tubbing speeds.
MikeW

[Unchained]

509Lib, I suspected the carbs were too small and took a vaccuum reading at the carb base.
I got just 1" of vaccuum at WOT/6000 rpm so I concluded that the power valves were open at WOT and the carbs were not too small even though the BDS chart says I need more carb.
Info was right that carbs will flow a lot more than they are rated at when you force a high vaccuum at the carb base. I ran hill climbs with a turbo honda dune buggy years
ago and ran a single motorcycle flat slide carb on a 1488 cc engine, It ran strong and I won hill climbs with it.
What HP am I making? Never enough, I am turning a AA impeller at 6000 rpm. The engine runs great, Has a killer sounding blower lope at idle. I feel I need to be making 25 lbs boost to make this motor run like it's built to.

[Dimarco Kid]

My motor is a Kuhl 490 Chevy with a 6-71 (driven to the hilt) with two inline 1050's. 11lbs of boost. The person that originally had Mike Kuhl build the motor said he tried an 8-71 Teflon stripped and it would suck the carbs dry. It runs a Mallory 250gph pump and he said you couldn't crank enough flow from it. IF this is true, wouldn't an 8-71 still build me more power because of slower blower speeds for the same amount of boost? Less heat, right? Also, do you "blower pros" think that my carbs and pump COULD handle a bigger 8-71? You guys have some good advice and we all appreciate it.
D Kid

[Blown509Liberator]

GMC root blowers where designed as air movers not blowers on diesels. When bolted to a Gas motor it gave a boost affect but with that came heat. A 6 71 was designed for a 6 cyl. with 71 ci per cyl diesel motor and 8 71 is for 8 cly with 71 ci per cly diesel motor so on and so on. With that in mind an 8 71 will move more air than a 6 71. To make 10 psi with a 6 71 will need to be turning faster than an 8 71 to make the same PSI of boost. Slower speed = less heat. So if the 8 71 was sucking the carbs dry I think you have a carb problem. I am running 2 Mallory 140 Marine pumps One on each tank with 3/8 fuel line to a Y block ½ Line from the Block to a Payton PSI regulator then to the carbs I don’t have a flow or psi problem

[Unchained]

On the GM/Detroit Diesel engines the governor is at 2300 rpm and the blower is gear driven 1:1.
The diesels that these blowers came from are all 2 cycles. Detroits Diesels have their own unique sound. From the truckers that I have talked to they view the Detroits as being an econo unit, not at all the longevity / durability of a Cummins or Cat deisel.
On a gas engine the redline can be 6000 or more. Then add the blower overdrive of 38% in my case the blower is turning 8280 rpm.
For a fuel pump I am just running a P.O.S.
Holley blue pump but it maintains 5.5 lbs at WOT.

[Dimarco Kid]

One thing I am running is a -10 inlet "split" hard line system to each carb from that one -10. That might be something to address when looking for more fuel maybe?
D Kid

[058]

Unchained, The blowers on Detroits are driven at 1.90 to 1 or 2 to 1 [depending on the "71"] on the diesel applications if my feeble old memory is correct. Do you know the orig. application of Roots blowers? And when did they use them for that purpose? Just a bit of trivia.

[Unchained]

058, Some roots blowers were to pressurize the cabin in an airplane. That one madman back in the 70's put one of those aircraft cabin blowers on a bike and set a record on an old Vincent motorcycle engine. Sorry if I was inaccurate about the diesel drive ratio. I saw one of those dissassembled years ago and it looked like 1:1 to me but that was many brain cells ago.

[superdave013]

That madman was Max Kelley and he did it in the late 50's and early 60's. He did set all the records. He ran Vincents and Triumphs. Here are some pic's of he twin engine Triumph from '59. I am good friends with his son.
Nice safty gear back then hu.
http://wsphotofews.excite.com/005/s8/Rm/YF/mH98873.jpg
http://wsphotofews.excite.com/008/54/Su/zd/mA73333.jpg
http://wsphotofews.excite.com/018/ak/1n/XH/mz73670.jpg

[Infomaniac]

058: I believe they were first used to ventilate mine shafts?
Do not know when or how big they were.

[Blown509Liberator]

Ever see one of them Detroit have a oil leak at the base of the blower. I watch one at a Tech school where the Students muffed up the seal then fired it up and it just started to scream. I though a 3" hard back text book on the air inlet and it nearly suck it in. Thank god it shut it down.

[058]

Infomaniac, You are right, Invented by a guy named Root in the early 1800s for pumping air into mineshafts and purging deadly gases out. The dead bodies must have been stacking up slowing production down.

[Infomaniac]

058: Cool, must be why they call the Roots blowers.
Question for you. What was the first use of nitrous oxide in internal combustion engines? Also who and when?

[Unchained]

I think nitrous was used in some airplanes in WWII to give them a boost when carrying a large load of bombs or when they needed to climb at high altitude.

[058]

Used by the Germans in WW2 for high altitude power on fighter aircraft, about the same time the Brits found out about it also and used it for the same purpose, guess it evened the playing field. We also used it during the war and our guys came home with the idea about using it on racecars....and as they say "....the rest is history" Next question, Who used Hydrazine and for what? What was the outcome of its use in the 60s?
[This message has been edited by 058 (edited December 08, 2001).]

[Infomaniac]

I do not know for sure about the Hydrazine question. The other two questions I had filed away in my head. An educated guess is that was used as a propellent in a rocket engine of some type. Maybe drag machine? They eventually out lawed them.

[058]

You guys are good. Was used for rocket propellent as far back as WW2. Germans used it in the U2 rockets if my feeble old memory is correct again. It was also used as fuel for drag cars in the mid 60s, it was banned by NHRA because of its unstable nature...it had a nasty habit of exploding unexpectedly. Sure made some great power though. Want another question? Eddie Hill ran a unique dragster in the early 60s, what was its power and what made the car unique?
[This message has been edited by 058 (edited December 08, 2001).]

[mcollinstn]

cheez
since you are all on a roll, I hate to break in to the flow, but, King Eddie ran a double-motored quad-blown Pontiac 428-based rail.
"Too cool is was, myeeah...", says Yoda

[058]

Yeah....and what was the unique feature of this car? [other than it was a twin engine]

[PE857]

4 wheel drive?!?

[Unchained]

1riverrat, I e-mailed rons racing about the fuel inj. He e-mailed me back that unless you're running alcohol stick with carbs.

[058]

Eddie Hill's car had a unique chassis. The front of the chassis bolted to the front of the engines and the back half bolted to the rear of the engines. The engines were part of the chassis.

[wsm9808]

I was thinking Hills dragster was a tandom twin engine. And the engines were Pontiac???

[058]

They were indeed Pontiacs. mounted side by side at about a 45 deg angle to each other. I don't remember if this was the same car that had 4 slicks mounted similar to a tandem mount truck tires. You ask "How else would they be mounted?" Someone ran a car that ran 4 slicks on two rear axles about the same time Eddie ran his twin. Some strange shit back then.

[fryzll]

Tommy Ivo was probably one of the pioneers of the multi-engine stuff. Evidently this car would come off the line and when it unloaded the front end it would go up in smoke, go figure http://free.***boat.net/ubb/biggrin.gif www.nhra.com/museum/features/feature2.html (http://www.nhra.com/museum/features/feature2.html)