BUILDING RELIABILITY INTO AN AUSTIN 7 ENGINE

Before building a reliable Austin Seven engine it is essential that you have some articles on other people’s experience and knowledge. Perhaps the best reference books are the Austin Seven Companion from the 750 MC and the Austin Seven Manual by Doug Woodrow and finally Austin Seven Specials by Bill Williams. The latter is the only place that tells you which way to assemble the conrods and pistons. There is a brilliant article in seven parts called Austin Seven Engine Rebuild which is on our DA7C website courtesy of Hereford A7C. There are many articles online, but these distil the essentials.
You need to be confident and have acquired some basic engineering skills and possess a good selection of the necessary tools. If the Austin is your first engine re-build then bear in mind that many years ago most of us have experienced a failure due to our own errors, because that is the way we learn for next time.

Checks and Measurements
a) Choose a crankcase that has a sound front bearing lip or have a new retaining ring fitted and stay away from 3-bearing engines.

b) If you are not fitting a Phoenix crank then source the best crank you can find and get it crack tested.

c) Ensure the crank and crankcase oilways are cleaned, scoured and pres-sure washed with white spirit or paraffin.

d) Ensure the conrods you have are straight and in good condition paying particular attention to little end bolt threads.

e) Check that big end bolts are either not necked or preferably buy quality new ones and use new Nyloc nuts and spring washers, not castellated nuts and split pins.

f) Always use new HT little end bolts and spring washers, not tab washers.

g) Make sure you have the correct combination of main bearings for your engine.

h) Always buy the best quality pistons and rings you can afford and be pre-pared to be meticulous about ring gaps.

i) Be prepared to use pressure fed liquid to prove the oil jet streams rela-tive to the crankshaft drillings.

j) Be meticulous about camshaft condition and end float and ensure front bush is locked by a threaded modified bolt.

k) Make sure your flywheel and ring gear are in good condition and gently lap it on the crank ensuring you tighten it to the same place with and without the key in position.

l) Face off all your tappet screws.

m) Torque up all critical nuts.

Modifications
a) Balance your conrods after any relief of the white metal.

b) Balance your pistons.

c) Tap a locking thread into the front camshaft bearing.

d) Check your head to block joint and re-surface if necessary.

e) Face your crankcase joint on plate glass and carefully countersink new crankcase studs and head studs to prevent pull up distortion

f) Research best current thinking on block to crankcase joints and if using any silicone, only use ThreeBond TB1215 Grey.

g) Ensure adequate side clearance on your re-metalled rods and very gently ease the outer edges of the white metal to allow for side pressure when the crank is flexing in the middle - see “Austin Seven Specials” Bill Williams page 55. I use a Stanley knife blade at right angles to the white metal but do not attempt this procedure unless you feel competent.

h) Don’t bolt your engine to the chassis. Use a combination of rubber mountings, bolts and valve springs to allow it to flex and not stress the crankcase.

So there we go, I am sure there are plenty of things I have forgotten and other members will have different ideas on some of my thoughts. It’s all good for discussion so let’s all hear your preferences. Letters to the editor.
Phil Whitter DA7C