Dommie 99 correct manifold assembly sequence

It needs a "Tufnol" spacer between the carb and the manifold, with a gasket each side of it to keep it airtight.  The manifold bolts to the 4 studs on the head using standard gaskets.

I have a 1959 '99' - still in pieces!

The 1960 onwards single carb Dommies  had  2 seperate special tufnol insulators  between the manifold and the cylinder head and an O ring between  Monoblock and manifold. No paper gaskets. This was to stop fuel vapourising in the carb. Unfortunately it also stopped heat transfer in freezing conditions  which can be a bind , heat needed to stop fuel freezing around the main jet.An electric heating element in the air cleaner box  is on my  gadget  list !!. Never had a wideline so don't know what they had.

1949-56 M7 had  insulators always on the head/manifold joint

Only on early flat no oring carbs did they have gaskets on carb/manifold joint.

All oring carbs went on the bare manifold, no gasket no insulator.

I think the tufnol spacers are on the RGM cat item t2241    with 11/2" centers studs. Sounds like you may have the wrong length studs . Don't know what the threads are but normally whit into head and cycle for the long slim nuts  ,unless they are in the wrong wayround!. RGM long studs ref 18380  ,but they don't appear to list the correct  long cycle nuts to go with them , they show t2220  which appears wrong..

The 1.5 spacing is for pre 60 head R12/136

1.625 is for the 88SS/136 head normally 61&62

All of the manifolds below use isolators at the head

I think Peters  troubles are the long studs and long nuts that hold the manifold to the head?. Not long enough to allow the fitting of the 3mm tufnol spacers?. I can't spot the  reduced hex nuts ,but Norville may have them ,but their catalogue is not illustrated . One day I will learn how to post foto's !.

My 1959 Dommie Parts List (with 1960 Supplementary Parts List) shows part number T2241 (2 required). These are listed as ‘distance piece for manifold’. When I Googled the part number, the photo that comes up shows a phenolic spacer. I bought two from RGM - they are about 3.5mm thick.

Regards

Tony 

Hi Peter. I will go out into my sub zero  garage and  look at it all .   May take some time to work up to it !!!.

BRRRRRRR !!  Studs appear to be only 3/16 or 1/4"" dia  so its likely that they only go in  about 5/16"   , with small sleeve nuts holding it all together.   After all this palaver you  now owe it to us to get this right!!    My garage is so cold and damp  the condensation drips on you,  Working on a cure but not easy , First I have to dig a french drain .(start at the bottom).

Robert:  On this cold day and also considering that it is the morning after the New Years celebrations, you definitely will be in need of some Scottish anti-freeze that comes in a brown one liter bottle.

Have a great New Year!!!

Mike

manifold 1.06-1.12" tall

stud length  range 2.07-2.12"- 2 more threads length would be nicer

head end 10 threads

outer end 11 threads

insulator 3 mm

nut .218" tall reduced hex (.340") 1/4 CEI

I believe a tissue paper thin plain washer goes under the nut.

5/16hex - .3125"  seems wrong?

I show 3/16 BS wrench size(.3375")  for the nut. Also some nuts are a bit taller.

Attached is a photo of an original Payen gasket kit for all twins up to 1958 for Models 7. 77, 88 and 99 (1956) I opened today for use on my Model 7.

It clearly shows the two heat resisting washers which are fitted between the head and the aluminium manifold and the paper gasket which is fitted between the manifold and the carb 

Sometime in the late 1950's  the Amal 376 came with an O ring reccess in the flange.  Better able to cope with the bow that often developed .