High All,

Has anyone tried to run Velocity Stacks with HS8 Carbs and the standard air filter?

The standard S1 has nothing but a square edge at the carb, which is horrific from a flow point of view!

Woz

 

I’ve bought some 35mm velocity stacks. When they arrive I’ll give them a trial and report back.

 

Interesting. Being 35mm they should fit inside the air cleaner housing as long as no filter is installed- is that correct? In my view the biggest impediment to engine performance in the twin carb XJ6 is the manifold. It is nowhere near as good as that on the triple carb E type or Mk 10 setup

 

Dont know about a measurable or noticeable performance effect, but jeez they would look good

 

I’ve always thought there was little point upgrading to Tripple SUs unless supporting/complimenting mods have been carried out, such as head porting etc.

Webers only if racing, due to shocking economy!

It would be interesting to get some flow figures for the std manifold!

 

The introduction to this post has some historic comparisons of the two carb, three carb and three carb Weber manifolds on a 4.2 engine. The actual mod was done on an 1968 XKE S1.5 engine, (and was from 2 ZS to 3 ZS on 420 manifold). but you could see similar results on later 4.2s. You are right, the two carb manifold is the restrictive element.

I also looked at 25-35 mm V. stacks for inside the factory snorkel flange, but in the end, went with 3 K&N filters with internal blended contours, which allowed intake runners of any desired length.

XKE 4.2 S1-S2 Dual Stromberg vs Triple Carburetion

 

David, That is a great post on Jaguar carburettors that you referred to. Very interesting to me.

My experience of Weber carbs dates back to the late '70s when I fitted my series 2 roadster with 3 x 45DCOE on a Warneford manifold. This car really had some go with this setup. Perhaps only a few more bhp up top, but the throttle response and acceleration was improved greatly. As has been said, the mpg was not too good. I used to drive pretty quick back then and was getting around 18mpg out of the triple SU setup ( Australian delivered car, same as UK), but only 12 to 13mpg with the Webers. But the extra enjoyment was wonderful!
Pictures below, just scans of the old photos. Lucky to be in colour - back then I was still doing a lot of B&W photography

 

Sure do look good!!!

Way back a few, I messed with a derelict 65 Corvair. It was not a Corsa, but Corsa stuff was fitted, sorta. Included the turbo!!! Included in fixing the PO's misdeeds, was adding a Webber. Same as described here. Man, that flat six would run. But, needed 5th. Well, the PO used a 3. I had to pull the engine to put in a 4 speed... Corvairs are odd beasts but sure a lot of fun...

Carl

 

Yes, the Weber's do look like they were made for the the Jaguar engine. When I looked at this, there were more stories about needing a proper shop to tune Weber's than their fuel economy.
I am curious what you did about the S2 ignition when installing the Weber's. In US, S2s had a lot of emissions compromises on ignition curves and additional differences for octane numbers between US and UK at that time. I went back 1967 UK distributor spec.

Rgds
David

 

Well, the 35 mm Velocity Stacks won’t fit with the air filter in the air box. Options are:

1. Keep the air box, but remove the OEM filter and replace it with a different filter on the air box intake (sock type filter?)

2. Remove the air box completely and run two separate filters such as K&N or foam sock type.

3. Find shorter Velocity Stacks.

Each has their own merits. No air box would mean louder induction noise, but I’d quite like that.

Woz.

 

Made no changes to the distributor. The Australian E Types were identical to UK models at the time. Mine was the standard import with an S engine meaning 8:1 compression. Prior to the Weber installation I had my English mechanics build up the engine. I wanted 9:1 pistons but they advised against it as they said it needed the equivalent of UK 5 star petrol to run properly and this was not available in Australia.

Woznaldo, if you are determined to see this through, I would use the standard air cleaner housing and fit each velocity stack with an oiled foam type air filter as fitted to MX motorcycles. Should be plenty of room to fit a good sized filter once the paper element is removed.

 

the length of the velocity stack is directly proportional to the response of the engine. long stacks vs short stacks with enhance or degrade the different ranges of the engine. I am not familiar with Jag intake mods, but on racing Alfas, short stacks are normally used for more low RPM response. They can mess up air flow at higher RPMs. good thing to find out before you choose. where are you going to get the enhancement??

 

I hadn’t heard that the length affects response? My understanding was that longer was normally better for torque and shorter better for top end power?

My aim is just to improve on the square edges at the entrance of each carb, so anything will be an improvement over that!

 

Yes, that is my understanding as well. Make sure you post a pic when you fit these stacks