Tripple Webbers

[TR6Dave]

I have tripple Webers (DCOE 40 151's) fitted to my 1973 TR6, the car was bought back from the US in approx 1992, I did not fit the Webers.

 

The problem I have is a very bad hesitation, and spitting back, when the throttle is pushed hard under 2000 RPM, over 2000 RPM is fine, and the car pulls like a train.

 

The second problem is that after going out on a run, on stopping, a strong smell of petrol is present, after running my hand under the K&N air filters, neat petrol is evident leaking out of the end of the carbs, on all three.

 

I have fitted a variable fuel pressure regulator, thinking that fuel pressure was the problem, but have run it at various levels, all under 5psi, with no success, new needle valves have also been fitted, the plastic floats have been adjusted to 12mm from the gasket, with the floats resting on the ball of the needle valve. The travel of the floats is 6.5mm.

 

Has anybody who has tripple Webbers fitted to a 6, had this problem? do you know the jet sizes fitted to Webbers on a 6?

 

Trearing my hair out, would be grateful for any help.

 

Dave

[Guest Wyn]

I have a TR5 on triple 40s and had a not too disimilar problem. The car kept missing when loaded at low revs e.g. to overtake, or going up a hill. Tried everything, thought it was electrical, changed the leads, distributor cap, thought then there was some form of fuel starvation. Decided to find a reputable rolling road and the problem was solved in 10 minutes. It was running too rich and the plugs fouled on low revs. Most of the time it runs between 2000 and 3000 rpm with overdrive and the mixture was too rich for such low revs. As a bonus, I increased torque by 20% and bhp by the same amount, now runs like a dream. Maybe worth a try, a rolling road can find things where you could be using a process of elimination for ages.

 

Good luck,  Wyn

[lee]

Probably no use to you but you never know.

 

I had the exact same problem with webers on my Manx Beach Buggy (No laughing at the back)

 

Same as Dave, onto a rolling road.

 

Turned out there was too much fuel pressure so it was flooding on tick over or low revs. But fuel starvation higher up the rev range. So turned the pressure down and increased the size of the main jets....Perfection

 

Hope it helps

[Tom Fremont]

I've got triple 40s on a TR250 with P.I. cam and head, and I also have drips of fuel which normally occur upon shutting it off. This with MISAB rubber gaskets between the carbs and manifold ( this is where mine leak, not at the filter end ). It seems to be due to fuel pooling in the manifold - I have had mixed success revving the motor to 3000 rpm just before switching it off. Though I was originally quite worried about it setting the engine bay ablaze, I was reassured that it is very unlikely. My Webers have been on for 11 years and ~70,000 miles. Having said that, I do carry a charged fire extinguisher since the beginning

 

Concerning the jets: below 3000 rpm the idle jet is what governs, so here are some reference points: stock U.S. cam etc. 50F11, P.I. cam 60F11, or going a little leaner 55F8, 60F2, or 60F4 if you can find them; I settled on these but can't get any more for the next car I'm doing. Main jets range from 115 to 130 for most TR6s, and emulsion tubes can be F11, F2, F16 or, as I'm currently using, F7. I use blocked pump bypass valve, 40 or 45 pump jets, and 30mm chokes. For a stock engine without gas flowed head you may have to use 28mm chokes; this will improve " progression " behaviour, i.e. accel up to 3000 rpm. The 40DCOE151s have some adjustment features not found on earlier carbs which may enable 30mm chokes; I don't know for sure.

 

Nirvana is achievable with Webers but requires some perseverance. Once you've got them right they don't move, so hang in there. Books by Haynes and Passini are highly recommended; Passini in particular makes for entertaining reading too.   ::

[jemgee]

Hi Tom

 

and I thought the PI system was a black art!

[Guest Frans C.]

Hello Dave

I'm new to the list, and i'm a TR Register of Belgium member for some years now.

When I did my restoration,i had 2 newly rebuild HS6 SU with the same symptoms.The solution for me was to retard the ignition a lot.The gas in the cilinder ignite when the inlet valve was still open and and the flames shoot trough the carb's with a big bang.Not so healty for the carb's.

Hope this helps.

 

Frans C.

[Tom Fremont]

Hi Tom

 

and I thought the PI system was a black art!

That is certainly the prevailing perception!

 

To be fair to Eduardo, however, we should compare an already engineered application of Webers to the Lucas P.I. application - how user friendly are they after launch? The tough part about Webers is the calibration. As others will confirm, thereafter they're a snooze.

 

I'm very pleased to see from prices on classics that Weber conversions don't detract from values. I would nonetheless bet that quite a lot of them aren't calibrated optimally, so expect to do some fiddling after acquiring one of these. ::

[TR6Dave]

Thanks to all who answered my questions, off to find out these jet sizes.

 

Dave

[david ferry]

Hello Dave

I'm new to the list, and i'm a TR Register of Belgium member for some years now.

When I did my restoration,i had 2 newly rebuild HS6 SU with the same symptoms.The solution for me was to retard the ignition a lot.The gas in the cilinder ignite when the inlet valve was still open and and the flames shoot trough the carb's with a big bang.Not so healty for the carb's.

Hope this helps.

 

Frans C.

Frans

 

Change the colour of the font you use.

 

It is almost invisible

 

David

[JohnC]

Hello Dave

I'm new to the list, and i'm a TR Register of Belgium member for some years now.

When I did my restoration,i had 2 newly rebuild HS6 SU with the same symptoms.The solution for me was to retard the ignition a lot.The gas in the cilinder ignite when the inlet valve was still open and and the flames shoot trough the carb's with a big bang.Not so healty for the carb's.

Hope this helps.

 

Frans C.

Frans,

Now that I can read your post (thanks David), I'm intrigued... My cam data sheet shows the inlet valve closing at 79deg ABC, which is well before any concieveable spark event. Is it possible your cam is very retarded, leaving the inlet valve open much too late? What power output are you getting?

Cheers,

John

[jean]

Wrong David, this is secret ink, you will have to pass an appropriate developer over the screen to read the text

Jean

[Guest Frans C.]

Hello John;you were right and I was wrong;one can't get the distributor this faulty by turning;but the story about the flames came trough the carb were right.

 

Hope the color is OK now.

 

Frans

[Harbottle]

Hello Dave

I'm new to the list, and i'm a TR Register of Belgium member for some years now.

When I did my restoration,i had 2 newly rebuild HS6 SU with the same symptoms.The solution for me was to retard the ignition a lot.The gas in the cilinder ignite when the inlet valve was still open and and the flames shoot trough the carb's with a big bang.Not so healty for the carb's.

Hope this helps.

 

Frans C.

Frans

 

Change the colour of the font you use.

 

It is almost invisible

 

David

Font? thats something that gets you wet in church isn't it.

And theres me looking for where the ribbon goes on this computer.