Amazon: Swopping a Zenith 36VN to a Weber 34 - Any views?

[fishyboy]

Hi all,
Given the rather leaky nature of the Zenith 36VN on my 1966 131 (https://www.volvoforums.org.uk/showthread.php?t=336115 and https://www.volvoforums.org.uk/showthread.php?t=312839) I am thinking about replacing it with a Weber 34 (https://www.skandix.de/en/spare-part...4-kit/1022670/), which seems to be a straight swap for the B18A engine.

Only minor modification is required to the rubber seal with the Volvo air filter and the actual filter (https://www.skandix.de/en/documents/...er-34/3000188/).

Has anyone any experience of making this swap. I found only one reference on the forum (Willsapples - https://www.volvoforums.org.uk/showthread.php?t=334485) but was rather hoping other users might have made this swap.

One question I have is that the Weber 34 has a 34mm throat size (where it joins the manifold) whereas the VN36VN is 36mm. Presumably this difference of 2mm should not cause any issues.

Phil

[Rustinmotion]

Originally Posted by fishyboy

Hi all,
Given the rather leaky nature of the Zenith 36VN on my 1966 131 (https://www.volvoforums.org.uk/showthread.php?t=336115 and https://www.volvoforums.org.uk/showthread.php?t=312839) I am thinking about replacing it with a Weber 34 (https://www.skandix.de/en/spare-part...4-kit/1022670/), which seems to be a straight swap for the B18A engine.

Only minor modification is required to the rubber seal with the Volvo air filter and the actual filter (https://www.skandix.de/en/documents/...er-34/3000188/).

Has anyone any experience of making this swap. I found only one reference on the forum (Willsapples - https://www.volvoforums.org.uk/showthread.php?t=334485) but was rather hoping other users might have made this swap.

One question I have is that the Weber 34 has a 34mm throat size (where it joins the manifold) whereas the VN36VN is 36mm. Presumably this difference of 2mm should not cause any issues.

Phil

Are you sticking to a single barrel for originality or to save money? I’d go for the progressive twin barrel 32/36 but you need a new manifold

[fishyboy]

Hi rustinmotion,
I'm trying to find a compromise between originality and safety, making changes that can be easily reversed by any new owner. The two previous owner car has only done only 17,000 miles from new, still in its original paint and underseal, original fuses, never welded, all original trim etc etc. When I got the car it still had the original plug leads, distributor cap and air filter.
Phil

[grumpydad]

Hi
I dont understand you could get a second hand inlet manifold and SU for less
and it would be much easer to tune

I did that swap on a austin A35 used stuff from a morris minor
it made a great diffrence

[Willsapples]

Hi Phil,
On my 121 it was a straight swap. Just had to file a small semicircular shape in the side of the airfilter where it slides over the carb air intake. It's described on the SKANDIX website where the carb is displayed. My 121 is an automatic so it's important that the engine doesn't stall and ticks over reliably which the Weber has done for 10,000 miles now. I did a roadtrip to Sweden back in June this year which included a lot of motorway driving. It kept up with traffic without a problem.
I see you are in Andover. I'm in north Hampshire so could meet up with you.
I haven't been very active on the forum so can't pm messages but you can Whatsapp me on 07910 962222
Cheers,
Will

[Derek UK]

The Dutch company BCCP does a Weber 34ICH conversion. It may also be the one that Scandix sells. The 34ICH comes in three choke sizes, 25mm,27mm and 29mm. The 29mm is supplied for 2.2l Land Rovers and is a common conversion and available from various sellers in the UK. The 27mm is used on the 1.5l Saab96 V4. 25mm has been used on 1.2l Vauxhall Corsa.
Take up Will's offer. The conversion isn't cheap but is correctly jetted and a simple conversion.

[Rustinmotion]

The progressive twin barrel correctly jetted with manifold is around £700 plus vat so not cheap but other than re fitting the existing air filter is plug and play
I have run cars with Webber DCOE for over 30 years and a car with twin SU for two years and my own personal experience is the SU is much more finicky to get just right
Seems like the requirement is to stay as close to original as possible so a single barrel carb is what’s required here

[Derek UK]

Both the BCCP and the Scandix kit use the single barrel/choke 34ICH. Don't know what twin choke kit you are looking at.
If you want to stay "Volvo" the best conversion is to the later single Stromberg angled carb. as fitted to the last B18A and B20A. This uses the one piece inlet and twin downpipe manifold and does give you up to 5bhp more. Yes it will need at least a new front exhaust section but with a bit of luck will still cost less that the Weber carb conversion. You will also need a new airfilter but as this single carb set-up is often taken off to fit twin SU's there might be one with it.

[Rustinmotion]

Originally Posted by Derek UK

Both the BCCP and the Scandix kit use the single barrel/choke 34ICH. Don't know what twin choke kit you are looking at.
If you want to stay "Volvo" the best conversion is to the later single Stromberg angled carb. as fitted to the last B18A and B20A. This uses the one piece inlet and twin downpipe manifold and does give you up to 5bhp more. Yes it will need at least a new front exhaust section but with a bit of luck will still cost less that the Weber carb conversion. You will also need a new airfilter but as this single carb set-up is often taken off to fit twin SU's there might be one with it.

It’s the Volvo b18 kit on classic carburettors, what I like about progressive twin barrel carbs are they have a small initial choke that gives good response to small airflow then the bigger one opens when the need for more air is required
Single barrel are always a compromise that’s why SU variable choke works so well if I could get the damned things to run properly

[Derek UK]

The single Stromberg works surprisingly well on a twin carb engine even if it does still have the C cam. Only loses a bit at the top end and that is an area of the rev band that most don't use much anyway. A friend in Holland had a very sound F.I. B20 from a 144 which he used as a "donkey" engine and it got swapped into what ever car needed one. It used the single Stromberg. Having been thrashed across the Dutch countryside in a late Amazon fitted with it in order to catch the Hook to Harwich ferry, I certainly didn't find it lacking. We were in the 90's all the way!
Yes a progressive twin choke is fine but does need correct jetting and a suitable cam plus a reasonable CR. £700 for the kit? A pair of properly reconditioned SU's would be much less and good for up to about 150bhp.