Weber Type 31 or 151 on a Sprint?

[Cadence]

Looks like the type 31 carbs on my ‘72 Sprint could use a full rebuild. It seems pretty expensive to have that done properly.

Therefore I’m considering switching to a brand new pair of 151’s which aren’t a lot more and possibly less overall if I then sell the 31’s.

What’s the collective wisdom on doing that?

Will the issue of originality bite me in the bum when it comes to selling the car?

Thanks

[SimonH]

Keep the originals to go with it if you’re doing the car based on what the next owner might think.
Getting them refurbished would be the best route if that’s a major concern to you.

[trw99]

I had the Dellortos on my Sprint rebuilt in 2023. The cost was a shade under £200 per carb.

Not sure how that compares to the cost of replacement Webers, but I am quite content with the way they have performed since then.

I specifically asked for them not to be over-cleaned or polished up; my car is very original and I wished to retain the patina, at least on the outside!

Tim

[rgh0]

I would have thought a 72 Sprint would have had Dellortos originally ?

[alanr]

Why spend money unnecessarily? I can't see what fitting 151's would achieve?
They are not as well made as the original Italian Webers were. The alloy castings seem not as nicely made on the Spanish 151's and IMHO overall I consider them inferior..
If the 31's are properly set up fitting 151's won't make it run any better.

My 31's run just fine on my late '71+2 S130.( Same engine as your Sprint)

My suggestion would be to stick with the 31's and either rebuild them yourself or get them rebuilt. Just wondering though what makes you think your present 31's need rebuilding? Are you sure they don't just need setting up properly?

Alan

[trw99]

[quote="rgh0"]I would have thought a 72 Sprint would have had Dellortos originally ?[/quote]

The spec changed from Webers to Dellortos around May 1972, Rohan.

I have a notion that Dellortos first appeared on the Europa in early 1972.

Tim

[JimE]

Tim. Domestic twin cam Europas were fitted with Dellortos from the outset in 1971. JimE

[tonyabacus]

Stick with your originals and rebuild them yourself.

Some people seem afraid to tackle this job but it is not so difficult except when setting up. However there are a couple of books out there which are quite detailed but easy to follow for this procedure. There is also a chap called Paul in Essex 07976 985477 who undertakes such work and has been building a good reputation, however the last time I spoke with him he had a short backlog due to demand, his contact follows,
https://weber-carbs.co.uk/


Kits for doing a rebuild cost around £90 depending on where you buy, there are some kits out there which are not good quality so buying from a reputable company pays dividends.
Tony

[Baggy2]

Paul at weber-carbs.co.uk mentioned in Tony's post rebuilt my carbs about 3 years ago and they've performed perfectly ever since - reasonable cost too

[Cadence]

Thanks everyone for the feedback. On the Dellorto question, my Sprint is a March ‘72 so perhaps one of the last to get 31’s.

Perhaps some history would help explain why I was considering new 151’s

I’ve had the car for two years now. It has Vegantune VJ5 cams and pulls strongly from 3,500 rpm. It’s always suffered from a hesitant progression below 3K, so I took it to a well known tuner in Hampshire that was recommended by happy customers on this group. My experience wasn’t great.

I was surprised that the tuner declared the car finished only a couple of hours after dropping it off . The result was an even stronger top end but the hesitant initial takeoff remained. Apparently no road test due to his inability to get in/out of a coupe. I wasn’t happy with the outcome so returned a few days later and he spent another 20 mins trying to improve the situation. It was better but still below par imo.

The car has always smelt of fuel after a run and I also asked the tuner to be look into this. No fix was found. Didn’t seem great value for £530 so I wouldn’t go back again

I then noticed that after a run, there was more than just fuel smell with petrol dripping from around the o-ring plate on the inlet tract joint nearest the radiator. Not convinced it’s the o-ring - just a low point where the fuel ends up.

I bought a genuine Weber float tool and discovered that both floats were out of spec and different to each other. Clearly they’d not been checked when the carbs were fettled. Pretty happy that they’re right now.

This correction didn’t stop the leak which doesn’t seem to manifest itself when running up to operating temperature in the drive but always happens after the car has been driven a couple of miles and higher revs used. It stops after 5-10 drips (obvs I don’t know if it’s leaking when driving)

Since then the I’ve done few miles waiting to get a new water pump fitted. Cooling is now sorted and this is the last big issue to fix.

A local Lotus expert thought it could be the pump valve ball and gave that a tap to reseat.
No change

I’ve ordered a new needle valve as a last ditch effort within my pay grade. I’m sure there’s other bits to explore but I’m no mechanic and carbs are a dark art for me.

The Sprint is just wonderful to drive but overheating and fuelling have meant that’s been a rare treat and I missed all but one of car events I planned to join this year

I’ve been quoted £500-600 to rebuild the 31’s. Buying a brand new pair of 151’s jetted for a Sprint are circa £850. In summary I’m hesitant to invest in 53 year old Webers and seeking a fast track to reliability and using the car.

I’ll certainly give Paul a call first to discuss his services

Thanks again

[NTG999]

I have some 151s from about 1990 (not sure if these are Italian or Spanish at this age.
I had them rebuilt by a 'professional' after being stood for a long time and I am struggling to get them setup. I have read on other threads that the internal drillings can become blocked and the lead bungs need removing and drilling is required as ultra sonic cleaning maybe doesn't clean it. So I'm in the same predicament.....

[alan.barker]

As i see it,
i like the Dellorto and you can use a "Carbtune" 4 collumn. This means you can measure the Vacuum on each cylinder without removing the Inlet Ducting. Spot on in 30mins maxi.

On 151 carbs they have the cross balance between the Chokes on each Carb very handy.

When refreshing Carbs the biggest problem is to remove Lead Bugs to clean out cross drillings. It's no good just changing a few Seals.

If i threw hundreds of £££££'s for someone to refresh i would like to know exactly what they do.
Alan

[Cadence]

I have some 151s from about 1990 (not sure if these are Italian or Spanish at this age.
I had them rebuilt by a 'professional' after being stood for a long time and I am struggling to get them setup. I have read on other threads that the internal drillings can become blocked and the lead bungs need removing and drilling is required as ultra sonic cleaning maybe doesn't clean it. So I'm in the same predicament.....

Perhaps we should swop

[Hawksfield]

Hi Cadence

I changed my 31s for 151s in 1991 never looked back, put the 31s on ebay and got 80% of new cost from QED.
The reason I took the plunge was the famous stumble from take off, I tried many things to alleviate the stumble, jets pump jets etc even butterfly plates and some with drillings. On reading John Passini I learnt of the common problems problems associated with these carburettors so took the plunge.
My 151s are Italian manufacture and have the take offs for my " carbtune " and bypass bleeds for better balance.
very pleased not bothered about about originality.

John

[richardcox_lotus]

Me too. I have long since fitted Spanish 151s - still have the 31s on a bench - and find them easy to balance and they seem to keep their tune. As said above, they support airflow balance across each choke, and have vacuum takeoffs so can easily see what’s going on.

Regards
Richard