Lagonda Rapiers

5 minute(s) of a 484 minute read

Happy Luna New Year.

1-31-2017

Hello All

I am still waiting impatiently for the pistons but to fill in a day or two I have decided to do something about the balance pipe on the inlet manifold. This has been bugging me for years and years so there is not time like the present but not tonight it is past my bedtime already.

Bj

Hello Ben

Your wish is my command.

To speed the process up a bit I will copy the relevant part of an email to Mike Pilgrim one of the technical gurus of the Rapier Register.

While I am (still) waiting for the new pistons to be made I have been filling in time correcting a problem that had been worrying me for the past 30 odd years. The previous balance pipe on the inlet manifolds was almost completely ineffective because it was made using 1/4" pipe. Too small to be of any real beneficial use.

In the interim I have proceeded with my modification of my existing Barker manifolds. This has involved drilling out the original David Seath 1/4 inch balance pipe off-takes enlarging then to  accept the 9/16” OD / 7/16” ID steel pipe from my (useful) scrap box. I then took a length of 1” OD steel tube also from the USB and drilled matching 5/8” holes  1 1/4” from each end. Not having any welch plugs of a suitable size in stock I found two large (mudguard) washers with 1/4 “ holes in my "only slightly used washer bin".These I welded over each end of the 1” pipe filling in the 1/4” hole at the same time. Placing the 9/16 pipe in the holes drilled in the Barker manifolds I could trace the shape of the inside of the manifolds onto the 9/16” pipe at each end. I then cut this into two equal lengths and ground one end  of each to match the inside of the manifolds. I could then weld these into the 1” pipe which I then cut in half. Finally I could then fix these into the Barkers, Fixing steel into aluminium I used a high temperature-high strength two pack epoxy cement. I have yet to obtain a length of 1”ID petrol resistant rubber hose. I also have to clean up the inside of the manifolds with a ball shaped grinder and some fine emery paper. Initially I will place a 1” OD 1/2” ID washer in the rubber connector. As I am still waiting for the new pistons for KG’s motor I am unable to report on the final result.  Due to the close proximity of the cylinder head (cam box) this balance pipe must go on the underside of the manifolds when in situ. While it goes against the recommendations of Phillip H Smith it is something I will have to live with. Life  as I have found during the past 80 years is full of compromises. It will give the next owner of KG something to think/worry about, whoever and whenever that may be. It has been running with the David Seath arrangement hanging underneath the carbs for a very great number of years.For those not familiar with his work, Phillip H Smith,FIMechE MSAE is the author of several books on the design and fabrication of both inlet and exhaust systems and is considered by many people to be "THE" authority on this often vexed subject. In his book, Scientific Design of Exhaust & Intake Systems, he suggests that the balance pipe should be placed on the upper side of an inlet manifold. N.B.  Phillip, H Smith devotes just two pages out of 275 to the subject of "balance pipes". I should add that the "Barker" inlet manifolds were originally designed and made by then Rapier Register member David BarkerThey have been for years the "go to" inlet manifold, they are designed to take 1 1/2" SU carburettors in lieu of the original 1 1/4" carbs and enhance the all round performance of even otherwise standard Lagonda Rapiers. Being made as two matching inlet stubs the do not have any balance pipe. Many people still run them without this however in view of my recent experience I have considered the fitting of a balance pipe worthwhile.Bj