John Maddison's Blog...

Correct Carb sizing for your motor

John Maddison — Sun, 01 Jul 2007 22:35:00 +0000

I have a 406 cu with pretty much all the goodies,the aluminum heads could take a little more porting,11.5 compression 1.6 roller rockers with a Victor junior single plane manifold which I shift at 7500-8000 and I have run the same old 800 spreadbore double pumper for ages.The carb gives me decent mileage( small primaries) and when I stomp on it ,it pulls like like there’s no end.The equation above works out right at 792 cfm with 90% VE.I have thought about changing to a square bore carb on many occassions,but I know that I will suffer in the gas mileage.I believe for the street the spreadbore is hard to beat. (I don’t want to start another argument though!)

Clunk in Jaguar rear end

John Maddison — Sun, 01 Jul 2007 22:34:42 +0000

The jag rear end is susceptable to the outer fulcrum rods wearing, which gives the hub a little play and hence a clunk. Also it can cause a shudder when pulling off and make the car pull one way when accelerating and the other when braking.You need to check all the universals as well which can also cause “clunking”.I use a hypoid 90w and a limited slip additive (if you have an LSD” .Sometimes the big center nut on the axle will also come slightly loose (even with the pin) and may require a little shimming to get no play. Don’t just tighten these!
www.slitherclothing.com

Optimum wheel alignment for Cobra’s

John Maddison — Fri, 29 Jun 2007 05:19:35 +0000

Because a Cobra is a short wheelbase car and funny things in the handling department start to happen when the track(width) starts approaching the wheelbase, Imagine driving a square car? With my setup I was always in the top 3 on road race courses in South Africa Cobra Club meetings.(Pissed a lot of guys off)

Well because of this I have found that 1.5 degrees of negative camber on each wheel ,front and back,and 1.5 degrees toe in on each wheel will make the car handle just right. Now of course we need to dial in some castor ,that makes the car self center ,so also I like about 2 degrees of castor on the front wheels. Obviously if you are running a “live” axle at the rear you have no rear adjustments other than to make sure that the triangulation is right ,which of course is important on all cars.If the triangulation is out the car will go down the road like a crab (you know).

Watch here for Question and answer sessions with Carroll Shelby himself (if I can get it right,I’m working on it)

Jaguar rear end wheel hop…

John Maddison — Fri, 29 Jun 2007 04:58:35 +0000

The Jaguar rear end’s are prone to slight wheel hop. I reversed the lower control arms and installed heim jointed track rods extending rearward to the chassis.This gives a little final tweek for toe in.

How to calculate correct carb size…

John Maddison — Fri, 29 Jun 2007 04:55:47 +0000

Here’s a formula for working out the correct size of carb for your motor:

395cu/2 =197.5
6000rpm/1728=3.47
197.5 x 3.47 =685 cfm assuming 100% efficiency,but take it you did a good job on cams head exhaust etc we will use 80%

685 x 0.8 =548 cfm

Just substitute your engine size in cu” and your redline max revs in the above formula.
So if your carb is jetted and set right a 600 cfm will be perfect.Here’s a link for you to find the correct carb size for your motor.

Good luck.

PS. It does not help to overcarb your motor!

Welcome to my Blog!!

John Maddison — Fri, 29 Jun 2007 04:53:46 +0000

Well, after months of planning and designing we have finally launched our Carroll Shelby line at www.slitherclothing.com. The concept began with my “lifelong” love of the Carroll Shelby Cobra. Being a Cobra owner myself, I was never able to find the right clothing or caps to match the pride I have for my car. So, I decided to make them…..

Slither Clothing is an Licensed Carroll Shelby retailer and all Shelby merchandise is sold under license from Carroll Shelby Licensing, Inc.

I know all you other Shelby owners know what I am talking about and I hope you guys check it out…it’s for you!