brngrhd

most of the reason for not running them on all out race cars is the limited RPM band (reads not low rpm) and restricted carb size. when your limited to a 390 cfm carb like a lot of the roundy rounds are EVERY single CFM counts and since it will have fine signal at higher RPM they don't need that good strong signal down low thats why when they come in the the pits they keep the RPM up while waiting to keep good clean plugs and good fuel metering.

stinkybutt

On the dyno I have watched the carb while doing a pull. It is amazing how much extra fuel flows thro the ann boosters. Like I said I've had to pull 6 jet #'s out to keep the motor from going pig rich. The down leg boosters are close because they are sitting down into the ventri.
Holley has had to step-up with the program because of the Holley clones. Holley always used straight leg boosters in the old days. All about cheaper/more profit. Remember also that Holley never had screw-in air bleeds except for high end dominators in the old days. Then along comes Barry Grant, Demon ,AED, Quick Fuel, Pro systems and of course PRO FORM(the cheap tunable carb). Holley was smart not wanting to give the home mech extra stuff to play with. With extra screws to play with more people want to "try" to tune. If you don't know why/where the fuel travels and what an engine needs/wants you are just guessing.
Another example is how Holley ships their vacuum secondary carbs with a tight spring plus a restrictor or ball in the passageway that applys vacuum to open the rear barrels. They also have a bleed-off hole that goes to the rear ventri, all these add up to a slow opening and also a never full throttle event. This is why most people go faster with a 750 dp than a vacuum sec. Take a 3310 750 vac carb add a 31 squirter,remove the check ball on the secondary diaphram,yellow spring and you will be amazed.
Again my wifes car ran identical ET/MPH using a 750 vac and a 750 mech carb. On the street the mech carb was more violent when you hit the throttle because it reved fast enough to need the extra pump shot of a double pumper. A bigger squirter and hollow screw and the 50cc pump would have helped the vacuum carb for full throttle slam, but when only needing a quick part throttle was a bit soggy. The mech secondary was also used to help at the track as to having more precise control when back peddling to try and get traction.
Notice the Pro-Form bodies as well as Holley HP series carbs have down-leg boosters and 4 corner idle and adjustable air bleeds.
The old style carbs we still use a drill and blanks or epoxy to tune.
We have been able to tune carbed cars to run pretty much like fuel injected ones.
Aleck

stinkybutt

This week I've been tuning a 1970 Olds 442. Car is a complete resto, powder coated frame, all correct tags,ink stamps even date coded spark plug wires. All #'s matching 4 speed, 455,ram air hood, buckets console. Looks like it was built last week. The owner wants to compete in the pure stock drags. The car comes to us for a tune and chassis tricks to run on bias ply tires. The stock 455 is rated by GM to have 370hp/510tq.at the flywheel.
First we install an O2 sensor then load the car to the dyno. Idle is good at 14.7A/F. Just tip the throttle to 1500rpm and 13.1 A/F. No load, just hold the throttle even so I know it's not pump shot. Now I get going in 4th gear 2,000rpm, then 2,500 then 3,000 etc until 4,000. Trying to see A/F at diferent cruise rpm with 3,800 pound load. This thing is getting to 12.3 A/F. just cruising. Now a few roll on's just to make sure no leaning out before the first full pull. Ok, the first full pull gets 240hp/370tq. Pig rich and big miss above 3,000 rpm. Hence the low hp. I noticed the alt light flashes some so I pull it off and find the reg is bad, so I now know the miss is from rich and low voltage to coil. Fix the alt and gain 60 ft/lbs@ 2,000 rpm and because the motor revs higher the hp jumps to 275 peak but the torque now carries further and gain 90 ft/lbs at 4150rpm. Not bad for only 2 full pulls and just fix the alt. Now to change the jetting meetering rods.
I pull the carb off and guess what? Someone has drilled the front butterflies to clean up the idle with a stock cam. Too funny. The jets are 78's. OK I now know why the A/F was nice at idle then instantly rich off idle. I epoxy the holes in the butterflies, change the front jets to 72. Next pull picks up a bunch in the bottem end as before the car was at 12.8 to 13.1 @2,000. I start the pull @ 2,000 so cruising is rich and loading the plugs then mash the gas get the pump shot and the engine goes 11.4. Now I'm 15.4 @ 2,000 so the car is more crisp at the start. I jet up to 74 front.
Are you ready for this?? I start the pull @ 2,000 rpm, instant 400 lbs/ft @ 2,000 rpm and carry over 400 to 4150 rpm. Peak torque goes to 431@ 2800. I tried dif timing and 30* total is what it likes best, also this car does not like to run richer than 13.9 at full throttle. I know you guys are into panick mode. This car will only see full throttle for short time periods and does not have a power adder. You have to learn to give an engine what it wants. Every car is dif. Still trying to fix the problem of the hp flatlines @ 308 from 3,500 to 4,500. I tried more/less fuel and timing. I had the distributer out and found a pertronix mounted in the wrong spot and only one screw holding it in. I also had to shim the endplay out. Had over 0.060". The car really has torque but the hp is down due to rpm problems. The miss is gone. I need to do a comp check and leak down. Engine has 1,000 miles. I put fresh plugs in after I got the A/F sorted. I'm leaning towards the cam and valvesprings as well as lifter preload are to be checked. This engine should rev to around 5,400 or so. I'm sure the hp will come around when I get the rpm up. The car has really improved BUT it's not right. A big change in how it climbs thru the gears simulating accellerating even part throttle, really crisp. Imagine 400 lbs/ft from 2,000 to 4,000.
I started this post to tell you guys about the boosters in a Q-jet. I seem to have gotten long winded. I need to open another reply. Aleck

stinkybutt

I tuned the car with the ram-air breather and hood shut. Man pretty tedious removing all that stuff for each change, plus removing the carb so as not to hurt the painted stock intake.I tried a pull with-out the ram-air lid and the hood open. This gives the 14x3 air filter better flow. HP fell 30 to 270 and the A/F went richer. I know you would think it might get more air and go lean. Not so. The A/F went from 13.9:1 to 13.4:1 and lost 30 hp. I tried more timing to offset the richer A/F just lost more power. I forgot to mention this car has full mandrel bent duals so the exhaust tho not perfect for hp it's legal for pure stock and better than factory.
In a couple weeks I have a 67 Ford Fairlane with a 427 dual 4 bbl 4 speed factory built car coming in. This car has never had plates. Always a drag car. Only mod is a cam and headers. We are putting the car back to stock for pure stock drags.
My old COPO Nova owns the record for small block 350/370hpLT1, non Yenko, one of two built. 12.37@112 on E70x14 bias ply Certified pure stock.
Jim Johnson has gon 11.50@122 in his L88 clone with F60x15 bias ply tires in pure stock. These guys use factory cams not cheater grinds, no headers etc. This is not the FAST clas.

Enough rambling I have an open house tomorrow at the shop. Check out the web sight www.chandlertechnologies.com. Web sight is older getting upgraded. But still a bit about us.

Aleck

3pedals

iTrader: (3)

pure stock is the most entertaining stuff there is in drag racing right now!!!! these guys get my respect!

cody161

iTrader: (18)

We most of the time steer street cars away from annular boosters becuase they do flow alot of fuel at low rpm's and cruising speed. A street car usually isn't happy with that much fuel at cruising speeds. Alot of our annular carbs go on blower motors or circle track cars. All of our QFX line up gets them becuase the carburetor is so big it needs as much fuel from the booster as it can get. We also modify our 1250, 1450, and alternative fuel models to have a stronger pull on them and eventually flow more fuel. Also adressing the bog a lot of LS guys have is from the cylinder heads. I know this seems weird, but think about it, these heads were designed to flow fuel from a fuel injector not a carburetor. So some of the fuel moves slowly and bam you have your lean bog. The annular carb will help this because it will have more fuel off idle and in the lower RPM's. Most of the time a down leg booster will work as good with some tuning unless it is larger 4500/4700 style carburetor.

speedtigger

iTrader: (16)

Thanx for that insight Cody. There is nothing like practical experience to help avoid a mistake. After reading that article, I really wanted to give a 750 annular a shot, but it sounds like I would have ended up with high street fuel consumption and fouled plugs.

Pop N Wood

iTrader: (1)

What do you guys recommend for a near stock or cam only LS swap?

Did QF ever think of building a line of carbs and marketing them directly toward LS motors? I know your stuff has enough tuning capability to make them run with just about anything, but if you read enough forum entries there seems to be a market for something that works better straight out of the box. Most guys don't have widebands so their tuning options are limited to jets and accel pumps. At least come out with a line of street carbs that get the idle circuits and air bleeds closer to what these motors need.

rojs234

iTrader: (5)

This is one of the most interesting conversations I've seen on the forum. I love this stuff. Some of the stuff in *stinkybutts * dyno work is familiar to me from years past but I'm happy to admit a lot of it is new, and I'm always happy to learn new things. Please keep bringing it AlecK, because I love it. Ron

cody161

iTrader: (18)

The owner of the company is building a 6.0L LS Malibu right now that is going to be cam only. I'm sure we will do some testing with the and find out what it likes and I will get back with you on that. The car should be done in the near future.

tnewton

Thanks for the insight!!! I wanted to try the annular boosters but it doesn't sound worth it for my street car. Very helpful info, thanks!

stinkybutt

I plan on trying three styles of main bodies. They are the straight leg,down leg and annular booster. All are rated at 750cfm. I'll see what the diference is on the chassis dyno for peak and average #'s. I'll also be using a wide band to tune. First I'll get the flow #'s on the flow bench. I do know my wife's car picked up the 60' using an 830 annular holley main body vs the pro-form down leg 750. First i need to fix the V-P clearance on the motor. Seems the 0.040" head gaskets are not going to work on my dished 6.0. with LS3 heads and Comp XR281 installed with a 106 int lobe centre. I've got 0.060" and I know my wife loves to do her burnouts in drive up against the chip. Anyone got a cutter for 2.16" valves?
As for the annular boosters drawing too much fuel you just need to tune the carb better using air bleeds. Like I said i had to go down 6#s on main jet to get the same a/f as the down-leg booster. If memory serves me right I had to pick-up the high speed air bleeds as well. All we need to do is remember to give the motor what it wants. Liquid fuel will NOT burn. All about atomization. Ever look at the Holleys used by Ford in the 80's on the trucks and Mustang Gt's. They had annular boosters front and str on the rear. MMMMMMMM, I think they were after emisions, driveability and mileage.
Aleck

speedtigger

iTrader: (16)

I am very interested to see what comes of your test Aleck. I don't know if you will get much part throttle a/f ratio information in the test though. Especially with a drag car utilizing a 106 degree LSA. Either way, I am all ears.

team39763

iTrader: (3)

Aleck, I think there's a place that rents the cutter tool out. I know it's been posted here on tech before. I'll check my notes and post back if I find it.

cody161

iTrader: (18)

I've talked to two more people at work and both of those people have around 50 years of experience in spec'ing carbs and both of them said they would not reccomend one for the street. Both agreed that they would be too rich. I'm sure with enough testing and tuning and tinkering you could get the annular where you wanted it.

team39763

iTrader: (3)

So an annular carb may work better for a full race application?

rojs234

iTrader: (5)

To *stinkybutt *. Aleck, I don't have the cutter you need, but I can tell you the BEST and EASIEST place to get it. www.lindytools.com. Phone....1-800-823-2887. Guy named Dave there...nicest guy you ever talked to. He will do whatever size you want and get it to you in a couple days. He even has a rental deal if, like me you only need it for one engine. I bought one...you get the cutter and a guide rod and a collet? to set the depth of cut...$110.00 including shipping. Just sent it back for a partial refund. I can't remember what he said...around 50% i think. Tool worked great! I used it in a junk head but a good one is fine. IF anyone wants to see a pic of tool, go to search and put in flycutting tools. Ron

stinkybutt

The cam has a LSA of 112. I degreed it in with an intake centerline of 106. Most Comp Cams are speced to be installed with a 110 intake centerline.
Kelly's car is a daily driver with a 3.50 gear, heater wipers etc.


We can log all info on the dyno. I spend lots of time simulating part throttle roll ons. I'm amazed all the nay sayers here. I know our shop car went on Power Tour with twin turbo blow thru carb (annular boosters) and got over 20 mpg average. That was driving a weeeeee bit over the speed limit most the time. Gotta love those 6 speed trannys. I don't want to offend anyone on here, BUT look on the carb company web sights and oh ......look annular booster used in blow thru set-ups. MMMm... why not downleg? Yes I know they also have modified metering blocks, just saying..... .
Aleck

forcd ind

iTrader: (7)

i ran ann. boosters on my LS engine, but mainly because of the Procharger, i needed the fuel to really flow-one thing i ran across tuning it was off idle, the engine wanted fuel-with the Edelbrock intake runner design, prob a lot of fuel didnt get to the comb. chamber, sticking to the long runners, so untill the air flow got quicker, more fuel was needed-a FI LS engine has the fuel shot right at the head, rather than going down the runner
i used an agressive pump cam, i think a green one
at first i thought i had a bad coil, just in the way it would rev, then while rev. it, i also pushed down on the squirter, and the engine instantly sounded better, so that led me to work on the off idle fuel del-i did a lot of other tweaks to get it perfect, A/B's, etc, but the pump cam/squirters made the biggest diff

speedtigger

iTrader: (16)

I wondered about how a little bigger cam advanced some would run. What does the powerband look like on your 281 cam advanced to 106?