Viewing Condensed info mobile device app

Full website is best viewed from PC
OR
select "Request Desktop"
from you mobile device's toolbar

Your basket is empty

Categories

Holley tuning for performance and the AussieSpeed intake manifolds.

This baseline tuning information goes for both Holley 2 barrel and 4 barrel carbs.

The signal strength at the base of the carbie with an AussieSpeed manifold is a lot stronger than most dyno tuners have experienced before. The main reason for this is that all the 6 cylinder manifolds that have come before us have not been flow bench developed for high flow and high air speed. This is a step by step guide to get the best base line from which to work from to then tweak your tune to get that tyre smokin’ power you desire.

This information is applicable for Holley 350 and 500 two barrel carbs, Holley 4 barrel vac secondaries and double pumper carburettors fitted to an AussisSpeed inlet manifold.

STEP 1 ~ Block off the power valve with a proper blank power valve from Holley, part# 26-36. Please note that this is the most important step. In most cases where people are experiencing tuning problems it will be the power valve adding too much enrichment. This will be highlighted by the fact that the fuel mixtures will look ok on the dyno sniffer sensor but you may be fouling a spark plug typically #6 and have an excessively wet floor on the intake manifold runners.

STEP 2 ~ If you are running a 4 barrel carbie disconnect the secondaries so that they do not open.

STEP 3 ~ Run the engine set the idle, and at idle set the accelerator pump shot so there is no stumble when you flick the throttle to half opening. The pump shot will differ from engine to engine depending on engine vacuum at idle, cam size, carby selection and more. The important thing for a start is that it is fairly crisp from idle with no load. That way it is not contributing to an oversupply of fuel.

STEP 4 ~ Now you are set to play around with the main metering jets in the primary fuel bowl without other factors skewing the results. If you are Dyno tuning the exhaust sniffer will tell you if you are too rich or too lean and you can play with jet sizes up or down to fatten up the torque curve.

If you are a home tuner or doing some track tuning you will have to decide to go up or down in jet size, take it for a drive and see if there is an improvement or a drop off in acceleration and power. When there is an improvement keep going that way until it drops off, then go back to where it was best. Always error on the rich side to prevent a lean condition, because a lean running engine can damage internal parts.

STEP 5 ~ 4 barrel carbs hook up the secondaries and do the same as in step 4 to set the secondary jets. Remembering that the rpm that secondaries come in at may need to be delayed [mech link on throttle shaft] and slowed down [stiffer spring for vac sec] for smaller capacity engines because most 4 barrels are sized for a 5 litre V8. Either way this is a trial and error thing. The secondary pump shot will need to be play with also and it may require experimenting with different throttle cam shapes available in a kit from Holley.

STEP 6 ~ Now you can size the power valve, it is a common thing that a lot of race engines running AussieSpeed manifolds do not require a power valve. All the power valve does is provide further enrichment of the fuel mixtures when the engine needs it. The engine may or may not need enrichment, it is not set in stone that a power valve has to be operational or a certain size.

The power valve works at wide open throttle when manifold vacuum is signal is low [remember it is low because the throttle blades are wide open ~ it is low below the carbie base and vacuum is high at the top of the carbie when the throttle is wide open.]

The power valve also operates at just off idle in that transition from the idle jets to the main metering jets when vacuum in the manifold dips. For example as you gently accelerate in a street driven engine the power valve provides some enrichment until the rpm increases and the main metering jets take over and manifold vacuum is high again. In a race engine when you stab the throttle at low rpm the manifold vacuum dips and an incorrect operating power valve of an incorrect size can provide an excessive fuel condition that will cause poor acceleration. This condition will be multiplied when feathering the throttle on low rpm corners, so it is imperative to get the power valve set right.

The power valve will open when the manifold vacuum is at or below it’s opening point. For example a 65 power valve will be open at 6.5 inches of mercury vacuum or lower. A 25 power valve will be open at 2.5 inches of mercury or lower.

If the power valve is open when the engine does not need it it will run like a pig, no matter what rpm it opens at. It is that simple.

If you find you are dropping power off at the top end of rpm then the power valve may need to be added back. Ideally if you can measure the vacuum at where the drop off in power is then that will be power valve size you should try.

As a rule of thumb the power valve should be no more than half of the vacuum figure at idle. For example a stock engine with have a good 15+ inches of mercury at idle so a 75 power valve would be your baseline to try. However a camy engine may only have 10 to 11 inches at idle so it will have to be a 55 or lower power valve. Remember in the summer on a hot day, atmospheric pressure changes and you can see a camy engine may only draw 8 to 9 inches of mercury at idle. This sort of engine can hold a 75 or 65 power valve open a bit or make it pulse at idle hence leading to it idle bad on a hot day.

Typically we have found that a 6 cylinder engine with an AussieSpeed intake manifold will require no power valve or a power valve in the 15, 25 or 35 range.

In some instances we have found the power valve orifices are too big for the six cylinder engines even when you get the power valve coming in at the right vacuum and we have seen or felt the power drop off [becomes too rich]. Now on some of the Barry Grant carburetor metering blocks they have adjustable power valves but we have not experimented with them yet but would be worth looking at. We have had alot of success in restricting the power valve orifice [power valve jet is the hole in the metering block] by using a short, bent, piece of different gauge mig wire that will sit in the orifice of the metering block and restrict it's volume. You make it fit so that when the power valve is screwed in the wire can never fall out of the orifice / hole in the metering block. It has proven to be a cheap and very successful tuning method to leaning out the power valve enrichment charge of fuel, there are some pictures on the AussieSpeed website and it is explained in more detail, follow the link below.

SUMMARY
In summary if you find this does not help you achieve a base line to work from then contact us. If your dyno tuner is dismissing this information and is not tuning by blocking off the power valve and just keeps ranting on then the only solution is to find another tuner. Something to keep in mind is that just becasue that shop has a dyno does not necessarily mean they know how to use it, or tune your application. I have worked with allot of tradesmen over the years and somethings you just don't let some of them to get anywhere near it, your problem is working out who those guys are. Getting your engine dialed in can be one of the most rewarding experiences for us car nuts, even if it the solution hides itself from us for a while, so keep at it and don't give up.

Further information is also provided on the AussieSpeed web site click on the logo

AussieSpeed carbie tuning for 500 Holley's, Holley 350 and Holley Avenger carburettors

Carburetor tuning for an AussieSpeed manifold

There are no products to display

Want to know more

Follow our workshop projects, new products, news and events on Facebook.

Kustom Bitz news

EV conversion 1955 MG ZA Magnette by Kustom Bitz

by kustombitz on 04 Jul 2024

Kustom Bitz is doing an EV conversion on this 1955 MG ZA Magnette. The job is a complete restoration and driveline conversion, it doen't look much at the moment but we have been pulling it apart to completely strip the paint for a full rotiserie restoration on the body. The sills need replacing and the rear guards need some rust repairs but apart from that the body is mint. You can follow the restoration on https://www.facebook.com/MGEVMagnette We will be installing an air cooled Hyper9 AC motor and controller with two LFP battery packs, one in the boot and one in the front engine bay. The electric motor will sit in the gearbox tunnel with a Torque Trends USA Long tail housing reduction box, with integral park lock, like an auto trans has. The base EV technology that is going into this car has been around since the 1990s and I have been selecting, repairing and working on IGBT drive technolgy in the automation industry since that time, so combining my restoration skills and EV technology make sense to me. Intended as a city run around it should be a pretty stout combination as the Hyper9 puts out a similar torque to a stock 289 Windsor but from zero rpm all the way up. Rated at approx 200hp. The body is light weight at just on 1080kg stock, weight gets pulled out, engine and gear box [all cast iron], and the batteries is similar in weight so ends up around the same once finished.

8:71 Supercharger install on 454ci powered '55 Chevy

by kustombitz on 30 May 2022

You would think a supercharger kit install would be pretty simple .... well no, is the short answer. A wise man once told me a 'kit' is not a solution. And having worked on a few of these set ups now these words keep ringing in my head and I remember this old man who at the time I didn't think was that wise at all .... now I am older and I see. In this install I had to port match the heads to the intake as there was a substantial lip into the head port because of the large intake manifold ports. If not corrected would have led to fuel puddling and fouled plugs and drivability problems that would have been hard to diagnose once assembled. Also the distributor hole at the back of the manifold was off centre and way too big for a standard chevy dizzy and any aftermarket dizzy too. So I had to make a boss to take up the slack and provide a stable boss for the dizzy clamp to work properly. To add to the woes, the engine assembler failed to pick up that it was a tall deck block and required a longer oil pump drive shaft .... that was hard to diagnose when a new engine loses oil pressure for no reason. I got there in the end with modded accelerator links, better fuel line route, boost referenced carburettors and a proper harmonic balancer for a blower application. The install was challenging on this one but the end result was a sweet running engine with monster amounts of torque to hall this heavy full size sedan around the hills .... and cool looks of course.

41 Willys Coupe Gasser Chassis

by kustombitz on 30 May 2022

41 Willy Coupe chassis fabricated to original dimensions yet extra strength provided in the depth of the chassis and via tubular centre X member and many tubular cross members to take the weight and torque of a big block Ford drive line. This chassis will have an original steel body fitted to it and the owner wants the whole car to resemble an early 60s drag car, right down to the rear radius rods that look like ladder bars, however it has to have nice street manners and pass ASRF construction guidelines for safe street rod engineering. Now many may argue a leaf sprung front end and rear end is not the best handling street car and I would agree, but there are always trade offs for the look you want and the right combination of parts installed with the correct geometry can still yield a very nice driver with a really cool look. When driven responsibly this 41 Willys will provide hours of enjoyment for the owner cruising around. Chassis by Kustom Bitz [our custom designed rails], Engine Ford Hemi V8, T400 auto, 9" diff installed on leaf springs with diff housing floaters designed by Kustom Bitz for street use [so we have flexibility and suspension give], Super Bell front I beam with disc brakes cleverly mounted to parallel leaf springs without any mods to I beam and not relying on welded parts. See our section on Hot Rod Chassis construction for more images of our various Willys Coupe chassis that Kustom Bitz has built.

'67 Toyota Crown Ute - another air ride bagged project

by kustombitz on 01 Apr 2021

The Toyota Crown ute is progressing along, the body is fitting the modified original chassis and this is how it will look when it's dropped ... I think it has the right stance ... The framing you can see is holding the upper body together as the floor and lower sections are rusted away and have been cut out, then to be completely refabbed by us. The frame allows us to lift the body on and off as we please during this stage.

1940 Ford Coupe chassis BBC 454 L80E 9" and air ride

by kustombitz on 01 Apr 2021

Kustom Bitz just completed a 35-41 chassis, stepped up at the rear and a reversed centre X member allow this chassis to sit 40mm off the deck. It runs a Rod Tech IFS, big block chevy and L80E auto, a 9 inch diff with floating hubs, all on modified original rails. Kustom Bitz has developed our own boxing plates that suit the original rails near on perfectly. Original Ford rails are curved from front to back there are no straight sections, so to get something that fits right we had to jig the chassis up and map them out. This is what we do, when it just needs to be done right to make it a well engineered car. This allowed us to make a nice transistion for a high step at the rear. We have designed in 6 inches of travel at the back, so this car can have a normal, almost stock ride height then dumped to the max when parked.

LS Engine swap and custom air bag IFS

by kustombitz on 19 Feb 2020

'67 Toyota Crown ute chassis build is going well. Got the LS engine and 6 speed manual box in place and we can use all the orginal serpentine pulleys, brackets etc. The narrow wheel track on the Toyota called for a tailored solution when it came to the front end. These old Toyotas dont have service parts available any more so the front end had to be changed, so that made a brake upgrade alot easier too. We run R6 air bags from Air Ride sitting at a ride height of 6" for the air bag so got plenty of air volume in them for a good ride quality and a full length travel shock absorber so we get proper rebound tuning, along with a power steering rack. So at the sill [belly of the car] we get a 5" ride hieght with a 4 inch drop, this thing will look great.

Double shear brackets - rear coil overs Hot Rod Chassis

by kustombitz on 30 May 2019

Recently in Victoria some engineers have called for the upper and lower mounts for the rear coil over shockers to be a double shear bracket. The thoery is that the bolt has too much twisting force on it and it will break. Well thats why on Hot Rods we use a 5/8" grade 8 bolt in a single shear bracket application to over engineer it so it does not break. A typical OEM application uses a 1/2" bolt in a double shear bracket. However to please the engineer we have thought out a simple plate kit that can be welded in on the upper mounts as you see here to satisfy their requirements and should fit into most applications without too much effort or rework. We have a lower mount bracket nutted out as well.

Diff bump stops custom made

by kustombitz on 08 Mar 2019

So many hot rod shops don't install proper bump stops. In this instance we had to rebuild the shocker mounts on the diff as the rear end was bottoming out on the shocker travel becasue it had no properly designed bump stops in place. So the shock absorber mounting bracket was absorbing every bump when the suspension bottomed out, easy to see why both mounts broke. While we were repairing the diff I made a simple yet effective progressive bump stop that is held in place via the U bolts that hold the diff to the leaf springs. It turned out a very successful set up. This is yet another example how Kustom Bitz can sort out problems on your custom car or hot rod, its what we do.

Torana A9X custom made rear pan hard bar 9" Diff

by kustombitz on 08 Mar 2019

Back in the day Group C racing one of the tricks to get the Holden Torana to handle nice and be more predictable in corners was to fit a rear pan hard bar to give much better diff locating than the OEM triangulated 4 bars offered. However the body, subframe and floor pan at the rear is no where near strong enoungh to concentrate the loads of pan hard bar in any one spot, so it has to be carefully planned and constructed, especially so in a street car like this that we cannot put a full roll cage in. You see in a race car I can place the roll cage in a position to pick up such loads placed on the pan hard bar brackets, but in this situaton we couldn't. The picture above is with the unit installed, keep in mind the car was just a shell so no weight was in it and the rear is sitting high. Once the full wieght of the car is on, it will sit fairly level. It retains the original triangulated 4 bars however we run PU bushes in the bottom arms and ordinary rubber in the top arms. So the lower arms and pan hard bar do the locating and the top arms have some give so they don't bind with the pan hard bar.

Ecommerce Software by Ashop