Overhead Carb Video

[R.Brown]

Hey gang,

Submitting for your viewing pleasure, LOL... An overhead view with some unique lighting to help visualize the fuel pattern. Hope ya like it!

https://www.youtube.com/watch?v=exVHXLTzlfY

cheers!

RB

[Carnut1]

That is a good carb, a bad carb looks like pouring fuel with a funnel.

[MadBill]

Cool vid, but is the engine going rich up top? It looks like fuel starts coming out of the shooters in the last few seconds of the pull.

[R.Brown]

Hi Bill,

I had not looked at that aspect very close, so I just reviewed it. In my opinion, that is a very low amount of fuel being added.

As a comparison for you, I grabbed an old video that was on my website and uploaded to youtube just now.. it is a 4412 showing a similar view:

https://youtu.be/qMLnqWy-_BY

From my testing, most Holley carburetors will have some amount of pullover or siphoning out the shooters as the RPM goes up. If desired, this can be virtually eliminated with various techniques, but on larger 4 barrel (not a 390)... the fuel contribution is quite low. I will frequently replace the shooters with blank ones and make a pull to quantify this volume of additional fuel.

As a worst case scenario, on a 350 7448/ 80787 carburetor, the shooter (in stock calibration form) contributes .2 A/F ratio at 4000 RPM, and .5 A/F ratio @ 6500 on a 375 HP limited late model engine.

Cheers!

Ryan

[MadBill]

I had no idea the phenomenon was so widespread! Love to see a vid of that 4412 fitted with an anti-pullover shooter, just to verify that they work.

Seems like the enrichment fuel would be unpredictable re timing, quantity (dependent on shooter size?) and distribution (having a similar effect to booster distribution tabs/notches?)

Of course it's possible that dyno-specific vibrations are a factor, but in both cases it seemed to be closely RPM-dependent.

For the minor price difference it would seem to me that all Holleys should be factory-equipped with the anit-pullover hardware.

[DaveMcLain]

Don't most places that require the 604 crate engine also require a carburetor with a straight style booster?

[hondo383]

Nice vid! Do you have LEDs in the carb spacer for lighting?

[R.Brown]

I had no idea the phenomenon was so widespread! Love to see a vid of that 4412 fitted with an anti-pullover shooter, just to verify that they work. snip...

In my testing the anti pullover shooters work very well for reducing, even eliminating any MEASURABLE amount of fuel added. So I don't think vibration on a V8 is a contribution factor.... 4 cyl and 6 cyl is another story. The anti-pullover shooters are not however legal in some oval classes, and I'm not entirely saying that SOME pullover is a bad thing. Again, it all depends on what your application/calibration is.

rb

[R.Brown]

Don't most places that require the 604 crate engine also require a carburetor with a straight style booster?

With pavement racing that is still fairly accurate... but most dirt classes are open rules.
rb

[R.Brown]

Nice vid! Do you have LEDs in the carb spacer for lighting?

yes sir... I have gone thru many, many variations over all the years of videoing in the dyno room. I just recently opened up a box with all the tripod attachments, wiring adapters, old spotlights, etc... LOL. Was a blast from the past.

The 4bbl video is about 3 years old and was the first video I had made with LED in the plenum. Huge improvement in what you can see!

rb

[R.Brown]

That is a good carb, a bad carb looks like pouring fuel with a funnel.

I was happy with the way that carb ran, but when you see a stop motion picture out of any booster it is surprising how the fuel looks like jelly, lol.

rb

[In-Tech]

I had no idea the phenomenon was so widespread! Love to see a vid of that 4412 fitted with an anti-pullover shooter, just to verify that they work. snip...

In my testing the anti pullover shooters work very well for reducing, even eliminating any MEASURABLE amount of fuel added. So I don't think vibration on a V8 is a contribution factor.... 4 cyl and 6 cyl is another story. The anti-pullover shooters are not however legal in some oval classes, and I'm not entirely saying that SOME pullover is a bad thing. Again, it all depends on what your application/calibration is.

rb

It's amazing how bad it gets on the 4 cylinders. I use a spring under the screw to push on the piston.

[pamotorman]

drill a .015 anti siphon hole thru opening #1.

[tsanchez]

Wouldnt that then fill the cavity with air making a hesitation next tip in?

[pamotorman]

Wouldnt that then fill the cavity with air making a hesitation next tip in?

no the check valve in the metering body keeps the cavity full