Holley 950 Carburetor | Free Flow Improvements with Results | Flow Bench
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- Опубліковано 20 жов 2024
- I take the carburetor off my stroker big block engine to modify it and do back to back flow bench test comparisons. These mods anyone can do at home and you do not need a flow bench to test. 1 CFM = 1.44 Hp. I keep it quick and simple in the process I go about making changes and show you actual data. All the CFM measurements were taken off of a Super Flow 600.
Throttle shaft contouring
Tapered spacer modification
Correcting over center - if you can see that its over center, it is over center!
Tapered Spacer Alignment
Booster clean-up
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This is awesome. Total attention to detail does add up to significant gains.
Very good. I’m going to watch the air cleaner vid.
Very nice video with all the attention to details and close up photos. I have a pair of Holley 950HP cfm carbs that have the smaller size 1.375" venturi. I sent one of the carbs to the people at BLP in Florida about a month ago for a Annular Discharge Mini Down-leg Booster swap from the stock/factory regular booster design.... they did a Before and After flow bench test...Before it actually flowed 1011cfm....and after the Annular Discharge mods it made 1052. No other mods were performed. These carbs already perform well on my pair of BBC 565cid Marine engines... they idle super sweet and smooth @700rpm in Neutral with great drivability and yet super responsive signal/throttle-response at mid-range/part throttle---just awesom. I just wanted to send them to BLP to see where they are at CFM wise and add the Annular Discharge for better fuel atomization/distribution---so I did not want to mess with them too much when they were already performing great in stock factory form.
Very good numbers. I think the next thing I need to do are the annular boosters. Seems to work ok on e85 with the downleg step booster. It went farther than i thought it would go. The annulars i believe will break up the stream and control drop size better. If everything goes well il be doing a bunch of track testing this season. This is on a 489 setup.
If you could drill and tap the center around the air cleaner stud for air bleeds and use new undrilled butterflies that would yield the best booster signal. Not that there is anything wrong with drilling for idle control. There's just another place to do it. I felt like there was more signal with the cam I ran. Good work though.
How much do all these changes effect air fuel ratio. I tend to look at air fuel ratio at 1700 rpms. Just before any fuel starts being pulled from the primary boosters. Change idle feed restrictions to get it close to 12.7 at fixed throttle. Then i drop 200 rpms and chart the air fuel ratio drop 200 more all the way back to idle. If the fuel curve is off i look at the idle air bleeds. Then verify i nice flat af ratio from 700 to 1700 . Then i look at af ratio at 3700 to 4000rpms. This lets me know where to go with the primary main jets. Then look at the fuel curve between 2500 and 4000. Look at the high speed air bleeds to adjust the curve.
With idle feed restrictions and primary mains set. I make some almost WOT runs. But not dropping the manifold vacuum enough to open the power valve or put a power valve plug. This sets your secondary jets. While a accelerating from 4500 to 6500. I look at the secondary fuel curve to see if i need to do the secondary high speed air bleeds. With the secondaries jetting set. Now into true WOT to see which way to go on the power valve restrictions.
With at least the idle and primary jetting set. A few fast blips of the throttle will let you know which way to go with the primary pump discharge nozzle. If it blows your ear drums and burns your eyebrows off. Go up a size.
Verify af ratios with a spirited test drive. Be totally amazed that you can smoke the rear tires no matter how you feather the throttle.
I like your method. Unfortunately i only have 4 inches of vac at idle to play with and part throttle spirited loads arent accepted. The car cruises well without any changes. I cant give you a complete answer on full throttle condition due to having an electrical problem (between 55 and 6000 the car hits what seems to be a limiter but its not) The car 60ft its best this year so far and gets to the 330 pretty quick. On gasoline i was getting between 12-14 mpg on sick summer dragndrive. I didnt notice a big change in fuel requirements but i suspect that going up 1 or 2 sizes might be normal.
I'm curious to see how your mods affect the jetting.
I have heard 1 or 2 sizes typically. Cleaning up the boosters will help aid with fueling. We will see if this is true... Im curious too.