Webers the right way!

[Ian Clark]

Hi Guys,

We'be been working away at the Webers for quite some time know. Nothing looks or sounds like them and they can be tuned, if you're patient and have good drugs LOL.

Anyways, most of the Weber V8 kits available today have the carbs arranged as per Cobra application with the fuel lines running the perimeter of the carbs. The original GT40 manifolds had the carbs arranged so the fuel line terminated up the middle. This also meant the throttles pulled together rather than opposed so there is no bellcrank in the middle of the manifold. Little things but...

Ray Mara asked me to modify his RaceTep setup with a vacuum chamber for the power brakes and vacuum advance on his CAV. Well one thing led to another and he ended up with the vacuum, one bank of carbs rotated, new throttle pull setup, heat shield and backfire plate, wow...

So this is how it turned out. The first one took a pile of hours, however if you'd like your existing setup modified or are considering a complete 48IDA setup for your car please give me a call, we can do the whole deal. Note this can be a forward, center or backward pull for the throttle cable.

Cheers

 

[Ian Clark]

Another pic...

 

[Ian Clark]

Another pic..

 

[Jac Mac]

Ian,
I hate to rain on your parade but what you have done creat's a situation where at any throttle position other than wide open one bank has the flow biased to the floor of the intake runner while the other bank favour's the roof or top of the runner. The people who made the manifold went to a lot of trouble to do it right.

Regards Jack

 

[Russ Noble]

Jack,

You're right of course but I like to think you're either hard on the loud pedal or hard on the brakes. Nothing in between matters /ubbthreads/images/graemlins/driving.gif /ubbthreads/images/graemlins/1poke.gif/ubbthreads/images/graemlins/bash.gif

Regards

 

[Jac Mac]

Russ,
I look forward to your first outing with some trepidation, I can think of a few corners that are going to stretch even your driving talent's using the above method. /ubbthreads/images/graemlins/icon_bs.gif Even my canadian friend has to modulate the throttle in some corner's.

( Im gonna have to learn how to post those g---- thing's so I can bash the s--- out of your he--, Im getting a thumper right now!!!) /ubbthreads/images/graemlins/smirk.gif

Regards Jack.

 

[Russ Noble]

[ QUOTE ]
Even my canadian friend has to modulate the throttle in some corner's.


[/ QUOTE ]

Yeah..... That's why he's gunna get beaten /ubbthreads/images/graemlins/beerchug.gif

But first I've got to spend more time building the car and less mucking around on this computer /ubbthreads/images/graemlins/banghead.gif

Seriously though you're right, (I hate saying that!!) you need good smooth response all the way through and it is better if all cylinders see the same flow and turbulence.

Regards

 

[Ian Clark]

Hi Jack,

I follow what you getting at. However it would require back to back dyno testing to see if this has any effect across the power band. Maybe this has more impact on EFI systems where the injector is firing into the port below the throttles...

Enthusiasts wanting as much visual authenticity as possible will appreciate the option of having the carbs oriented this way. The original FAV manifold on the 289-302 GT40s was this way. Good enough to win Le Mans, ought to get you to the Diary Queen Here's a pic of 1049, originally owned by Grady Davis, VP Gulf Oil Company 1966.

 

[Brian Magee]

Jack,
I have an original weber manifold on my car and haven't noticed anything unusual. I don't recall any of the drivers at Le Mans back in the sixties having any problems. If it was good enough for them, it's good enough for me. As Ian said I would like to see a back to back dyno test to see if there is a difference.

Brian.

 

[Jac Mac]

Hi Ian & Bryan, I know Russ is busy notching his chassis for the extra opposite lock tyre clearance he is going to need so I wont greet him!
Back to the discussion, any test to verify a difference would be best done with a full 8cyl EGT setup and check under part throttle load only- full throttle wont prove anything. If there is a gain to be made here it will be in fuel economy and driveability under road conditons at typical highway speeds.
The GT40 seem's to have it's webers all facing to one side as Ian has mounted his but the Cobra and Daytona Coupe cars have theirs mounted with them facing their respective cyl banks. I assume Shelby supplied the Cobra manifolds which raise's the Question -Did the GT40's prepped by Shelby have his manifolds. Brian I reckon the GT guys were just busy enough dealing with all the other problems sorting these cars without looking for problems of this sort. Thing's like keeping all 4 wheels on the ground and all the gear's in the transmission etc would be paramount. Which makes me wonder about your" If it was good enough for them, its good enough for me." If you copy someone that has done it wrong you seem to get slower, not faster. Would it not be better to look at something and say " yes I can improve on that"
To put it in a nutshell, you are asking one bank of cylinders to drink from the far side of the cup.

Jack.

 

[Ian Clark]

Hi Jack,

It's probably best to have some hard data before poohooing a part. I suppose Harry Weslake got it wrong too when he did the now infamous heads for Dan Gurney. I your analogy an engine with Gurney Weslake heads would have a power imbalance from the left side of the block to to right. Tuning wouldn't be fun either and cylinder pressure differences would be hard on cranks and blocks.

As stated before, I can see where your coming from with this comment. It just seems more theoretical than actual especially with no documentation to say the carbs back to back works better than pulling together.

I'm not here to split hairs or defend somebody elses design. There are many many variables in induction system design and manufacture that effect performance and you may hit on one, then again maybe not. Only the dyno knows for sure and given how vocal the Webers are when not happy the point could be proven and quantified either way.

To each his own, we do the heat shield and vacuum to suit both carb layouts. That heat shield drops 50 degrees F off the back pair of carbs!

Cheers

 

[Keith]

Could someone possibly expand on this interesting technical difference in opinion for the benefit of those who's whole life has revolved around using the simple (but highly effective) Holley? /ubbthreads/images/graemlins/confused.gif

Thanks in advance /ubbthreads/images/graemlins/smile.gif

 

[Russ Noble]

Hi Ian,

You've lost me here!

[ QUOTE ]
I your analogy an engine with Gurney Weslake heads would have a power imbalance from the left side of the block to to right.

[/ QUOTE ]

I'm not that familiar with GW heads but each side will be the same won't it? Or do they have different heads for each side?

Regards

 

[Russ Noble]

Hi Brian,

[ QUOTE ]
I don't recall any of the drivers at Le Mans back in the sixties having any problems.

[/ QUOTE ]

There probably weren't any problems but how often were they on part throttle at Le Mans? Cylinder filling at part throttle is obviously going to differ from side to side. Ian is probably right in that this may be more a technical consideration than an actual practical usage consideration.

IMHO many people on this forum, and I'm speaking generally here, go totally overkill on solutions to problems or potential problems that may arise, and that's fair enough they want the best for their "baby". It does lead to interesting technical discussions and bench racing.

Some people prefer form over function, I will go for function over form any day. Generally speaking (and not limited to GT40's) I do not see why something that is theoretically flawed needs to be perpetuated just because it was original. All cars are a design compromise, for whatever reason, (cost, availability of parts, time, ease of manufacture, appearance etc etc.) why burden yourself with someone elses compromises if you don't have to? /ubbthreads/images/graemlins/twocents.gif Maybe that's just my Kiwi upbringing!

Regards

 

[Jac Mac]

Hi Fella's,
Ian you have me mystified as well in relation to the GW heads as I am looking at a photo of all 3 variants of the two valve head. then you post a pic of the GW equipped car with the carbs fitted in what IMHO is the correct manner. Since the valves run in the same sequence as the basic windsor head what change's?
Keith , if you have been around holleys for a long time (like me) you will no doubt remember instances where you have had to stagger jet them to make up for differences in flow and port design etc.(BBChevs for example) along with all the other variables. With the two basic designs of IDA manifold we have one which mounts the carbs so that the airflow pattern thru them is the same on each bank of cylinders, while the other bias's flow to the bottom of the intake runner on one bank and the upper of the intake runner on the other bank. This condition will exist to some degree at any part throttle position. This all came about as Ian in making a very tidy job of the airbox heat sheild assy for his car went to a lot of trouble to turn his carbs around on one side of the manifold in order to have an "original" GT40 look.
Like Russ I go for function over form, I guess thats just the old racer in me still trying to improve the breed.

Cheers Jack.

 

[JCoop]

I just want to comment quickly that throughout all this, Ian has been very careful to touch base with me with what he was doing. True, what started as a simple "...hook me up with a vacuum source, please?" project turned out to be a major undertaking; nontheless, I'm very pleased with the results and I'm appreciative of all the effort that went into it. He read his customer right, that I enjoy these cars as a work of art and take pleasure in what I consider visual artistry in a mechanical sense. Of course, I have yet to install and tune the kit but I'm optimistic; I have Oliver's DVD /ubbthreads/images/graemlins/laugh.gif
I'm new to this but regarding form over function, I'd be driving a Prius if I was a "function" kind of guy. What's the spirit of building and driving a replica anyway? Replication of both the visual and spiritual experience, right?

 

[Russ Noble]

[ QUOTE ]
regarding form over function, I'd be driving a Prius if I was a "function" kind of guy. What's the spirit of building and driving a replica anyway? Replication of both the visual and spiritual experience, right?


[/ QUOTE ]

I drive a twenty year old Rangerover which I have had for years coz it is reliable and does everything I need a car to do! That sort of says it all!!

A GT40 was a race car, race cars in their day are in a constant state of development and improvement.In the case of my GT40 which I am building from scratch I am trying to combine what I consider the best features of all the different GT40's and technology of the time in one sort of generic build rather than replicate one actual car. Very few people drive a true replica, most including mine are lookalikes which have major mechanical and structural differences to the originals. Some come closer to original than others but very few are true replicas. However there's nothing wrong with trying to get them as close to "original" as possible, but for my part function always before form.

Someone else may want to put the latest suspension and modern running gear hidden beneath an original style body. Someone else with a genuine car would most likely want to preserve it exactly as it was at a particular point in it's racing career. Personally I wouldn't want an original car for many reasons.

There are as many different GT40's out there as there are owners and we all build our cars to suit our individual requirements. Your car will be most suited to your requirements and preferences in the same way that mine will be for me.

In the meantime it is interesting to consider the technical side of changes and improvements that many innovative members make to their cars. In the time that I have been on this forum I have learnt heaps, found different ways of doing things and also found that some things that I had contemplated were not really viable options.

I'm sure your carb setup will be fine and Ian will have done a great job, but theoretically......
Theoretically, who gives a damn so long as they work.

Good luck with your CAV and keep us posted.

Regards

 

[JCoop]

Thanks Russ,

No argument from me. I'm with you in that regard. I guess the farthest one would go would be the fuel injection rail that kinda "looks like" a Weber stack line but offer the reliability and modern technology of fuel injection. Not my cup of tea, however, and too much money.

I completed a concours restoration on a 1967 Austin Mini Cooper S a few years ago, and I overbored it .40 over, installed a slightly lumpy street cam, high-lift roller rockers, and a hidden Pertronix optical ignition inside the stock distributor. She also has 2.5" rampipes inside a stock airbox with K&N filters in them. She wins most all the concours British car show events she attends for originality and accuracy; but occasionally, I've stuck a set of Hoosier slicks on her and kicked arse in the Autocross circuit.

US Customs has my box right now. I just got a message from Fedex and they say it's awaiting release. They must think it's an Al Queda package with some fancy detonating circuits coming to the US. I may have to wait the weekend before installing.

Cheers! /ubbthreads/images/graemlins/beerchug.gif

 

[Ian Clark]

Hi Jack, Russ

Thanks for the input. Keeps the grey matter moving. I was mistaken about the GW heads carb orientaion, should've looked at the big picture instead of the thumbnail I'm sure that someday if a dyno test comparison is done we'll hear about and share the knowledge.

As noted the GT40s are built to personal taste and how much new tech gets utilized is a matter of choice.

Things like paddle shift, abs, traction control, launch control, cruise control, variable assist power steering and on and on each make todays cars easier to drive and live with. Put them on a GT40 and what turns one guys crank might make another cringe...

At the end of the day nothing beats these beasts for driving excitement and crowd pleasing visual impact. Plus the GT40 Forum remains an excellent resource for enthusiasts everywhere.

Cheers

 

[JCoop]

Install Update

Removal of the old induction system and installation of the Weber setup was pretty straightforward. We used 2 sets of gaskets as Ian suggested, to get better port matching. The complete setup looks awesome complete with the anti-reversion plates; but alas, the rear window glass gets in the way by about an inch and a half. Oh well, I guess they'll have to stay off until I can undertake another upgrade project (as Bob Childress has done) to lower the motor and nudge it forward a bit.
A couple of snags...I had to refabricate the fuel feed line back to the CAV-designed -6AN size hose. It had been modified to use a larger hose to feed the Holley. And, when hooking up the throttle cable, we only get half throttle at full throw. This is yet to be resolved, perhaps by flipping the existing throttle actuator lever on the manifold to increase the ratio, or fiddle with the cable hookup at the pedal. We're tackling that today. Pics coming.

I can't wait to fire her up!