8896 3 circuit rich down low

A couple weeks back I tried a friends new (last year) 8896 3 circuit against my old old 9375 two circuit. and it seemed real rich down low. Footbraking. It's box stock however Holley sent it. stumbled was slow 60 foot then Ok for a 10.52 128 lowed shooters from 37 to 31 helped stumble but same 60 and 330 for 10.53 @ 127 had a definite power increase at 6500 put my old 40 year old 9375 2 circuit on (unknown pressed in air bleeds but will be stock) 93 jets square with 25/28 shooters and went 10.52 @ 127 better 60 by .02 and 330 by .03 getting humid and slight tail we had was gone. another 10.52 all the same still had slight power increase you could feel at 6000 moved timing up 3 degrees went 10.47 @ 128 then miller time. next morning more humid 10.49 lowed jets to 92 square what the old girl came with and a 10.45 @ 128.83 good from hit. gained another .01 in 60.

So on that 8896 can you go up in intermediate air bleed size and down in high speed to get it leaner off the line and through low end but still get same high speed jetting. seemed fine and same as old tried and true 9375 after 6500 in first gear.

any thoughts would be appreciated .

Usually have to put a smaller intermediate jet in it rather than changing the air bleeds. The 3 circuit carbs I've worked on usually require at least 10 jet sizes taken out of the intermediate circuit.

You have some reading to do...

The 8896 sloppy calibration is what started me on the path to modifying carbs. The old style 9375 is the best of the 3 circuit calibrations, but even it can be improved on. And you can make adjustments to the 8896 to make it work OK, but a 2 circuit conversion and a booster change makes a world of difference.

http://www.motorsportsvillage.com/forum/viewtopic.php?f=6&t=3742

More reading on carbs here.
http://racingfuelsystems.myfunforum.org/viewforum.php?f=25

I`ve indulged in these readings for several years now and the info is crazy good and makes my head hurt but I have proven that the info given works...............no snake oil bs just flat out works.

I had the same issue with my old 8896 until I sent it to Thumperdart. It would kill plugs in no time at idle & cruise. So I had him modify and install some new 2 circuit metering blocks and 12 hole boosters along with the other modifications he does and could not be happier with what I received back from him.

The plug on the right is before. It was brand new and had less than 2 minutes on it

On the left is the after Thumper Carbs rework. New plugs with some street miles and idling. Out of the box with no adjustments

Seat of the pants performance is noticeably improved

I have one identical to this from Thump....my results were the same. Sad thing,,,my block cracked first time to the track after installing it. Putting new motor together now. Probably be Fall before I get to try it some more.

One very easy trick to try is to take the intermediate air bleeds out and see how it runs. Holley left them out on at least one version of the 3 circuit 4500 so there is some history behind that thought.

It would be helpful if you had a wideband when you try stuff like this but even without a wideband you should be able to tell if you're on the right path by how the engine sounds.

A set of billet metering blocks is probably your best investment if you want to dial the carb in yourself. Otherwise you can send the carb in and get it sorted out for you.

Removing the int. bleed is a band-aid at best and I have two 2-circuit conversions on 8-second street/strip cars that will never go 3 again.......no need to.

Thanks Guys not my carb guy just wanted me to try it so I think I'll report back and let him decide what to do. he said he had idle and drive ability issues on his street Barracuda with a hemi. can see why a 2 circuit carb would have made more sense.
Thanks again

The 8896 dominator on the Camaro was a pig when we first started w/ it. Removing the int. air bleed definitely helped a lot. Ended up getting a set of billet blocks from Quick Fuel, still 3 circuit, and leaned out the int. circuit. It made a big difference and is a lot better now, but still needs improving.

Yep, that is a fairly typical sequence for tuning a Holley 3 circuit. First remove the intermediate air bleeds, then buy billet metering blocks, then switch to a 2 circuit!

For a street car a person can also put power valves in both primary and secondary just to lean out the main circuit some more. If you have the billet metering blocks then the next trick to try is to make the PVCR larger and the main jets smaller to try and get the cruise AF lean.

The intermediate circuit can be very difficult to get right in a street car since the throttle position will heavily influence how much fuel gets pulled out of the dump tubes. Worst case is when you're driving down the freeway and the throttle blades are pointed right at the dump tubes and the intake vacuum is just sucking fuel out of the bowls.

The intermediate circuit was designed for NASCAR use so no surprise that it doesn't work very well in other uses.

I agree Andy. I tried to talk the owner into doing the 2 circuit conversion, but he went ahead and bought the 3 circuit blocks from QF. Hey, I just drive and wrench on the car...he pays for it, lol. It is a race only car though, so it's not critical we get it razor sharp. It runs great at WOT, goes up on the transbrake real nice, and idles clean. The tuning we've done has made it a lot cleaner, but it could definitely be better.

Monte offered a good tip. A 3 circuit is a tuning tool, to get the car on the converter. For part throttle, transitory use, not so good. I struggled with one leaving at 3,000. The 2 circuit 1050 I use now, is clean as can be. AND, not to sound like a broken record, those 8896 metering blocks, with the idle feed tube in them, suck. Has this been changed yet?

There are rare instances where a the intermediate circuit can be useful, but most will never need it. The intermediate circuit was designed specifically for an IR manifold, and can be useful on a 4 or 6 cylinder comp engine where plenum pulsing is high enough to disrupt low RPM and part throttle booster signal. On an occasion it can be helpful on an under carb stop, if the engine is large enough to force the stop blades to close too far, but it takes less fuel than most 3 circuit carbs come with to do the trick in those few cases. As far as using it to come up on the converter, if you use a decent booster it's never an issue.

I originally used 3 circuit carbs and struggled with them so I switched to 2 circuit. But now I find myself going ahead and buying 3 circuit carbs for certain applications with the knowledge that I can always just lean out the intermediate circuit. It can be leaned out all the way to zero if a person wants to so I guess I don't see much harm in having a 3 circuit carb. It is just another option that may or may not be needed for the specific application.

Of course, this all assumes that the carb has billet blocks in it and that the person tuning the engine has a wideband or some other means to see what is going on.

One other point is that the intermediate circuit doesn't have any emulsion and it doesn't flow out of a booster. So it is fairly raw fuel that is being pulled out of the dump tubes. Some fuels (high RVP) might work better than others in that situation. I've never seen any sort of tech writeup on the subject but I think it is probably important. I'm sure someone has high speed video of the fuel coming out of the dump tubes. I've never seen a video myself but I'm sure that the engineers at Holley or BLP have looked at this stuff.

Thanks again guys nice to get get good info from old wise ones?? :-)

Everything about making any carb work well is in getting a relatively homogeneous mix and equal distribution. When you do you can run a larger carb, use less fuel, and run less timing, all while making more power. Booster selection is for me the most important factor in accomplishing this. When you design the booster correctly for the carb emulsion becomes insignificant other than correcting the fuel curve, and an intermediate circuit only hurts this by dumping a load of fuel out of a tube. Methanol is an exception, with a larger style Dominator the intermediate can be used to ensure sufficient fuel as the main circuit passages can be restrictive. However on these I move the discharge tube, makes the intermediate more of an auxiliary main.

Just thinking on this could you not block the intermediate jets and just jet up the mains??

Thanks again In advance.

Maybe you can but maybe you can't. All depends if the main circuit is designed to handle all the fuel that the engine needs or not. Before you tried that you would want to pull the carb apart and measure the main passages to see if it can handle the larger jets.

Thanks Andy buddy say play with it a bit sooooo! LOL!

Was the new carb. a HP version or a original pre HP carb? I like and have used a bunch of the original non HP 9375 on foot brake cars, they work good, last a long time Not so on the other early carbs, same thing on the later 9375 HP I bought several years ago, it needed tuning before running good

The 9375 (no dash) is old as dirt with pressed in air bleeds works awesome all the time the 8896 i'm trying for a friend is 1 year old hp I think pig rich down low great after 6500 1st gear for rest of the quarter. going to crack it apart next week and look in there. play with it a bit.
It would not work worth [censored] on his 410 Cubic inch de stroked hemi for a street car.

Good luck Let us know your results I think I had one of those carbs. for a while, I sold it before fixing it The old stock # 9375 rock

Took new 574 to chassis dyno with my old 9375 pressed in air bleeds it was great AF till 6500 then leans out up two jet sizes that help AF past 6500 but then it lost hp and TQ.

Then dyno computer kept freezing so was done

94 octane 12.5 to 1

That`s because the jetting controls the overall fuel available and the bleeds control the timing/curve of the fuel. Rich low lean up top is what we`ve gotten used to over the years but it doesn`t have to be that way anymore.......

what about trying a 30cc accelerator pump instead of 50cc?

Not sure you can put a 30cc on a dommy?