WEBER conversion on my BT7

[Jim_Newman]

I've kinda been waiting for a Weber thread to pop up.

When I bought my BN7 15 years ago, it was a vintage racer and equipped with 3 45DCOE Webers. As I have tried to civilize the car for street driving, I have managed over the years to get the Webers working just fine over the full range of engine speeds. However two, possibly related, problems remain and any advice would be appreciated.

1. At highway speeds, an occasional cough will eminate from under the hood. I think this is may be due to an accumulation of fuel in the inlet manifold that ignites and blows back through the carb.
2. When, after a run, I park the beast in my garage, I have to leave the door open for a few hours in hopes of dissipating the smell of gasoline which will otherwise accumulate. I've checked the usuual sources of possible leaks to no avail. I suspect it is unburnt gas sitting in the carbs/manifold that evaporates when the engine is turned off.

Any thoughts out there as to how I might correct this/these?

As always, any help or advice is appreciated.

 

[Randy Forbes]

I had three Solexes on my Bristol 400, which is basically a pre war 328 BMW engine. It was a b---y nightmare to jet them correctly and took me about six months of utter misery. Getting the engine out was bad enough and the rebuild had cost me $20,000, so I was anxious not to hole a piston or whatever and have to do it again.

SUs are simple and work extremely well, only at peak revs to the Webers have any advantage, so apart from pose value, they probably don't make a lot of sense on a Healey engine.

Actually, to me anyway, the real advantage of the Webers is having an accelerator pump, as my setup gives me instantaneous throttle response and quickly builds RPMs (lightened flywheel is helping here too). Constant Depression carbs (plenty of joke material there...) just by their nature take longer to react to change. Of course there's the argument that an engine (regardless of induction type or brand) can only respond so fast.

And before anyone even says it, I learned to <span style="font-style: italic">squeeze </span>the throttle (NOT MASH) a very long time ago__no need to expose any engine to excessive bore-washing with liquid fuel!

The Webers have been on my car so long (26+ yrs) that they look right at home to me.

 

[AJAX50]

Webers can handle a Healey engine with a higher overlap cam better than SU's. Also with good manifolds there is a pretty direct straight port and choke tube for each cylinder. The benefit of a long inlet tract without the problems of interference in the inlet manifold should not be underestimated. On a right hand drive car it is possible to use the works pattern manifold which are long (need to cut away the inner web)and straight. Once properly set up on a modified engine they are better than SU's in every respect, except fuel economy!

 

[Hurricane]

Hi,
do all three carbs have the same number of progression holes? If not, you can't even start to sort your setup out. Find a weber guru is my thought.

 

[DerekJ]

Every time the word Weber crops up it seems to induce a feeling of fear and panic. I was probably the same until I had actually had them fitted to my car. That was nearly 5 years ago and they have never been touched since. Once set up they are totally reliable.

The basic starting set up for Weber’s on a 3000 engine is well known. They are usually 45 DCOE s with 36 mm chokes. Other jets and valves are:

aux Venturi 4.5
main jet 145
air corrector 155
emulsion tubes f16
idle jet 55f8
needle valve 200
pump jet 45
pump spill 40

There are many types of Weber’s and lots of valves and jets but you don’t need to worry about them or go out and buy them all. Take the car to a rolling road that knows about Weber’s, they will have a stock of parts and one or two may need to be changed. My idle jets were changed from f8 to f6.

As mentioned above, you need to have 3 matching types of Webers as different models have different progression circuits, which is a fancy name for a few small holes. Some earlier models only had 2 holes, my DCOE 9s have 3 but the versions sold by DWR and others now have 4 holes and I recommend these. The progression circuit has always been an issue with Weber’s but they are designed for power so you don’t want to be lingering in the progression circuit anyway, as soon as the throttles are open the progression is irrelevant.

You are going to be overfuelled if you just have the regular cam but I’m sure they can be made to run with it. You must go to a rolling road, it makes no sense to try to set them up in any other way. Those skills are too time consuming and have long since gone. Once they are set do NOT touch them and you will enjoy trouble free motoring. People like to fiddle with SUs! The rolling road will (or should) do the timing at the same time.

Good luck and go for it.

 

[dougie]

I'm happy to stay with my triple 2" SU HD8's at 265 hp and 245 torque of streetable performance.

 

[Legal Bill]

Hurricane, this thread is six and a half years old. I'm guessing the original poster has already dealt with this problem.