Fitting Twin SUs, manifold first or all together?

[floormanager]

After my normal amount of swearing, dropping washers and turning nuts a fraction of a turn a time, I started to wonder whether I should put the manifold on first and build the carbs up on it, once the manifold is fitted. What do people do? Which way is best as I hate the job more than any other.
Paul

[Peter Laidler]

Can I suggest that you never, ever, not never put the carbs onto the manifold when the manifold is bolted on to the head. You WILL drop something small into the back of the carb(s) and it'll disappear. Assemble carbs and set-up primary adjustment on the bench. All free running spindles, needles not binding, nuts locked down with tabs.......? Now stuff tissue paper tightly into the rear and if engine in car, bolt to engine. Those of a more masochistic bent might have other ideas.

This also goes for Commando owners too.........

[floormanager]

Peter, I wish I'd you could have told me about stuffing paper down the back of the engine to catch things. The number of bits that fell, got caught up and lost. It took me 30 mins to get a manifold nut off the top of the remote gearbox! Pleased that I did it the "right way" pre-built on the manifold but I do hate the job. I wonder how back in the day the BL mechanics coped with having to do these routinely. Guess they had the best type of spanner to get at the second one in from the radiator grrrrrr.

[iain1967s]

The large thick washers are perfectly sized for disappearing down the gap between the subframe and the bulkhead, never to be seen again. Threading cotton through them and tying off to the carb dash pots can be a handy way of avoiding that.

Also don’t re-attach the three throttle springs to the heat shield crossbar until after you’ve tightened the manifold to head stud nuts. It’s much easier to get a short 1/4” drive ratchet onto the two center hard to reach manifold nuts that way.

You might also consider using the longer “special tuning” 51K1177 type nuts on the two center studs.

[Exminiman]

Use a “Floppy” https://www.amazon.co.uk/PIECE-FLEXI-HE ... 7586&psc=1

And make sure all nut have been run up and down studs a few times so can be wound on by fingers

[floormanager]

The large thick washers are perfectly sized for disappearing down the gap between the subframe and the bulkhead, never to be seen again. Threading cotton through them and tying off to the carb dash pots can be a handy way of avoiding that.

You might also consider using the longer “special tuning” 51K1177 type nuts on the two center studs.

Great idea with the cotton! I really wished I'd posted this last night. Might have saved me a few thousand swear words today

I have the larger nuts, they are the more straightforward ones. It's the alignment, washer and nut fitting that is so much hassle. I use forceps to hold the washers over the studs, then with a screwdriver push it onto the stud. Just hope it does not leak again after 180 miles like the last one started to do.

[iain1967s]

It's the alignment, washer and nut fitting that is so much hassle.

Which alignment method does your manifold use? There are three common types: Rings in the head/manifold, Flanges with semicircular cutouts for the studs, and straight flanges intended for roll pins / dowels.

[111Robin]

I have always removed and installed the carbs with the manifold in place, never had any issues and a lot less hassle. A short 9/16" open ended spanner is easy to get in to tighten the nuts, but then I have spindly wrists so may not be as easy for everyone. You run the risk of peeling chunks off the manifold gasket if you remove the manifold giving you a lot more work as a result.

[Daz1968]

I always bolt manifold to head first, mainly to make sure it’s properly seated along with exhaust manifold, then do as much assembly on carbs as I can and slide them on, I have a cut down open ended spanner for the nuts and tie it with a piece of string in case I drop it, although I never have, I find hs2’s easy to install but my h4’s were more awkward especially getting choke cable installed, easier with bonnet off though.

[Peter Laidler]

Great thread floormanager. I bet most of us have been taken back a few years thinking about it. Additionally, as I found while stripping and assembling the left and right side side hydro/brake/clutch parts while investigating the hydro system and to replace the broken rear engine stabiliser bracket (see tech article) I just stuffed an old quilt cover down the back of the engine bay. Being ham-fisted, that seemed to collect all the odds and ends that I seem to have dropped. I also learned at an early age, to tie string around small tools - if you'll excuse the phrase!. A good example is the little SU jet adjusting spanner.

I made a BIG mistake a year or so ago, caused by not accounting for everything that had fallen down the back of the engine. One of the fuel bowl screws didn't fall through when I dropped it. So being a dickhead, I just assumed that it'd fallen 'somewhere' and it'd fall out as and when. It had..... the little bastard fell through the small opening at the top of the gear change arm, just ahead of the remote housing. It jammed up the front fork of the rod in the remote housing. A salutory lesson to stuff the old sheet down the back of the engine bay now.

Have a great Sunday car tinkering

[floormanager]

It's the alignment, washer and nut fitting that is so much hassle.

Which alignment method does your manifold use? There are three common types: Rings in the head/manifold, Flanges with semicircular cutouts for the studs, and straight flanges intended for roll pins / dowels.

I'm using a standard Mk2 manifold, with the locating rings. However, my original engine, the head had been 'worked' so the locating rings would no longer sit in the head, so I sort of had to measure to get the manifold in the right place. The new engine, I can use the locating rings, although I do not like them much. I would like to get my original 'worked' head and manifold pinned when I have the valve seals replaced.
Paul

[floormanager]

I made a BIG mistake a year or so ago, caused by not accounting for everything that had fallen down the back of the engine. One of the fuel bowl screws didn't fall through when I dropped it. So being a dickhead, I just assumed that it'd fallen 'somewhere' and it'd fall out as and when. It had..... the little bastard fell through the small opening at the top of the gear change arm, just ahead of the remote housing. It jammed up the front fork of the rod in the remote housing. A salutory lesson to stuff the old sheet down the back of the engine bay now.

Have a great Sunday car tinkering

Funny you should say that, a manifold nut dropped and disappeared. I was convinced it was sitting in the remote opening. I was worried it might jam the linkage but I think I've shaken it loose now. Fancy leaving a small hole there -what were they thinking?

[agricola]

The key is having the mounting studs well prepared. Firstly I shorten them to accommodate the thickness of a normal nut plus a washer and about 4 or 5 mm. I make sure they have a decent lead then run a 5/16 die down them to make sure the threads are free running, make sure nuts are A1 also. The inner studs I use minispares extra long brass nuts,and washer . Grease can help holding washers.
https://www.minispares.com/product/classic/51K1177.aspx
and tighten with a 1/4 drive socket with a UJ and extensions to suit, finish with a spanner. The outer I use flanged Knuts (integral washers) which are 3/8 af and tighten with a ratchet ring. You need to be at a comfortable height, I used to do it on a car trailer where I stood on floor and car elevated, car ramps not as good as engine is leaning backwards encouraging nuts washers to fall off. I now have a ramp. Peter's point about using a cloth is Stirling. With this technique I put the manifold carbs in fully assembled. Hope this helps

[Simon776]

I find it depends on which inlet manifold you are fitting and also the size of hands/fingers.

For myself, with relatively small hands, the 12A 661 has enough room around it to fit easily enough with the carbs attached. The AEG 573 with its bigger, square carb mounting flanges that seem to get in the way of every stud to some extent is just damned awkward with or without the carbs on it, even with the flanges trimmed to match the carb body shape.

I echo the comments about stud preparation being helpful.

[Polarsilver]

Tape over the open Hole positioned on top of the remote adaptor (if car has a remote gearchange ) Tape stops falling washers etc entering the remote adaptor.. Then with nice free running manifold stud threads use "Copper Slip" this will be a big advantage when you come to remove the Carb /manifold setup.

[Herbert]

I always put the whole inlet and carbs on in one go.

Put the manifold gasket on,

Put the inner 4 washers and bolts on but only turn them in one turn each. By the way all these 4 nuts are the longer ones, not the short stubby ones.

Put the retaining rings on the cylinder head, not the manifold. Put the long socket and extension on one of the inner nuts.

Take the elbows off the carbs and slide the whole caboodle till the aligning rings are located on the manifold.

Now slowly tighten the bolts ( Center ones first) till the carb and manifold stay in place.

Now do up the outer two nuts.

I use a long 1/2" socket with a 5" extension to do the inner two nuts, a ring spanner on the outer ones.

Then put the elbows back, and its done.

SIMPLES !

[whitewithblackroof]

When I tried to remove the assembly complete i seem to remember I had trouble getting enough clearance for the heatshield to get past the bulkhead so took the carbs off the manifold in the end and installed the same way. I have a technique now but anything dropped will usually end up in the remote housing hole

[Alex]

It depends entirely on the manifold you're using.
Some will go on whole, some need assembling on the car.

Setting up linkages and ensuring the carbs are level off the car is always bestest, but sometimes it's just physically not possible...

[Exminiman]

When I tried to remove the assembly complete i seem to remember I had trouble getting enough clearance for the heatshield to get past the bulkhead so took the carbs off the manifold in the end and installed the same way. I have a technique now but anything dropped will usually end up in the remote housing hole

Bit of a punt, but could it be an inline manifold causing an issue ? - might make it harder to remove carbs ? - think midget is 20 degrees and mini is 30 degrees ?

[Peter1071]

Tape over the open Hole positioned on top of the remote adaptor (if car has a remote gearchange ) Tape stops falling washers etc entering the remote adaptor.. Then with nice free running manifold stud threads use "Copper Slip" this will be a big advantage when you come to remove the Carb /manifold setup.

I've recently rebuilt my H4s and on re-fitting as a fully assembled unit, dropped the last manifold nut down the back. Three times. First time, neatly into the remote housing, jammed. Only solution was to remove sump guard and remote. Second time, same thing but had thought to leave sump guard and remote off of course. Third time, despite being the long brass nut, it managed to jam itself neatly inside a drive shaft coupling which then had to be dismantled to remove it. It's all back together now and I can see the funny side but at the time the thought that got me through was that at least it hadn't fallen into the engine.