Vintage Austin Services
Engineering services for pre war Austin Sevens
Engineering services for pre war Austin Sevens
Vintage Austin Services
1930 Saloon
Re-bore your engine for peak efficiency
We can re-bore your cylinder block without having to remove studs and accessories. Liners can be fitted if necessary.
Examine the Cylinders.
When you examine the cylinder bores you will find a ridge at the top of each bore. This is caused by the fact that the top piston ring does not sweep right to the top of the cylinder and a fair indication of the amount of wear can be gained by examining this ridge.
Check the Gap.
To check more accurately remove the rings from the piston that has been working in that bore and fit it into the cylinder, the right way up and the right way round. Using feeler gauges inserted between the piston and the cylinder wall, determine the clearance between the piston and the cylinder at the bottom, middle and top of the bore (avoiding the unworn ridge at the top). The normal clearance for split pistons is about 0.0015 inch. Up to about 0.0045 inch is probably acceptable, possibly with new piston rings, whereas a gap approaching 0.010 inch indicates a re-bore is needed.
It’s also worth inserting a piston ring into the top of the bore, above the wear ridge, level with the top of the block. Check the gap in the piston ring. It should be between 0.005 and 0.006 inch. Using the piston to keep the ring square in the bore, push the ring down the bore so that it is below the ridge and recheck the gap. An increase in gap of more than 0.003 inch indicated that a re-bore will be necessary.
To check more accurately remove the rings from the piston that has been working in that bore and fit it into the cylinder, the right way up and the right way round. Using feeler gauges inserted between the piston and the cylinder wall, determine the clearance between the piston and the cylinder at the bottom, middle and top of the bore (avoiding the unworn ridge at the top). The normal clearance for split pistons is about 0.0015 inch. Up to about 0.0045 inch is probably acceptable, possibly with new piston rings, whereas a gap approaching 0.010 inch indicates a re-
It’s also worth inserting a piston ring into the top of the bore, above the wear ridge, level with the top of the block. Check the gap in the piston ring. It should be between 0.005 and 0.006 inch. Using the piston to keep the ring square in the bore, push the ring down the bore so that it is below the ridge and recheck the gap. An increase in gap of more than 0.003 inch indicated that a re-
Other things to check.
While the block is off inspect all the tappet screws and if they are recessed grind them flat on an emery wheel.
Head tightening sequence
Tighten each nut a little at a time until all are tight.
Tighten each nut a little at a time until all are tight.
The Austin Seven Engine showing rubber engine mounts and side draft carburetor introduced in 1932.
Spark Plugs.
Early cars were fitted with 18 mm spark plugs, whereas later cars were fitted with higher compression cylinder heads and 14 mm plugs. The correct gap is between 0.022” and 0.025”. Softer plugs run hotter and can temporarily relieve the problems of plug oiling experienced on worn engines.
Early cars were fitted with 18 mm spark plugs, whereas later cars were fitted with higher compression cylinder heads and 14 mm plugs. The correct gap is between 0.022” and 0.025”. Softer plugs run hotter and can temporarily relieve the problems of plug oiling experienced on worn engines.
Check for recessed tappets and grind flat.
6
4
9
11
7
1
3
14
8
12
2
13
5
10