The last feature on the “Georgia Peach” was in late April of 2017, so an update on progress of the rebuild is in order. The engine, transmission, and overdrive were removed for a complete rebuild in mid-April, and all three were dissembled and all of the pieces where cleaned up for an inspection. At that point, the search for needed replacement parts began.
Since the 1800cc B18 engine is now over forty-nine years old, most of the stock of quality original OEM and aftermarket parts has dried up, although after a prolonged search here in the US, in the UK, and Europe all of the needed parts have been sourced. The largest issue was finding pistons that could withstand the increased horsepower and added heat produced by the boost from the vintage Judson supercharger.
- The original engine before being dissembled for cleaning, inspection and measurement for rebuilding. The lead photo in the post shows a 1967 to ’68 Vermont license plate with a unique number found for the 1968 Volvo 122s project car.
In the end, after not being able to find any high-quality Mahle (German) OEM pistons, CP-Carello located in Irvine, California was chosen to make a set of forged lightweight aluminum pistons and supply modern narrow wrist pins, and state-of-the-art treated steel low friction piston rings for the engine. The Company was the only piston maker found in the US that had forged piston blanks of the correct length needed, and is regarded as one of the best in the business and also manufactures the famed Carrello forged steel and aluminum connecting rods.
- The CP-Carrilo Volvo B18 forged aluminum pistons, and wrist pins are finely CNC machined inside and out and will be able to withstand the higher combustion pressure and resulting heat due to the use of the Judson supercharger.
An earlier cast iron B18B ohv rocker arm and push rod actuated cylinder head is being used with a lower 8.7:1 compression ratio that better suits the use of a supercharger and will help to control spark knock with boost pressures of up to 7 psi. The original 1968 head has a 10.0:1 compression ratio that is actually to high to use with today’s premium pump gasoline without octane boosters.
This head is being slightly modified to take advantage of some of the Volvo cylinder head advancements made up until the last ones were manufactured in 1975 before the change to a SOHC head for 1976. To increase flow through the intake and exhaust ports new conversion valve guides for later B20 valves were machined here in the shop from cast iron. The later (1969 to ’75) valves have smaller .312-inch (5/16″) diameter stems; the earlier stems measure .343-inch (11/32″). The new intake valve guides are shorter and have tapered instead of blunt ends on the bottom end of the guide where it projects into the intake valve port. Both changes will increase air flow into the engine. The top of the new valve guides also were machined to use later B20 valve guide seals.
- New and original valves and valve guides side-by side, exhaust on the left, intakes on the right. The heads of both new valves will later have a second angle machined where the 45-degree angle face meets the swirl polished head to improve airflow.
After the valve guides were finished, attention turned to the new B20 intake and exhaust valves. The image below shows how the valve stem thickens were it meets the head; in the interest of better airflow flow this area was machined smooth (see the changes in the photo above) on the lathe and then swirl polished. This form of polishing promotes a twisting motion of the incoming air and fuel as it enters the combustion chamber and cylinder, resulting in a better mixture of both which increases engine power.
The heads of the 42 MM B20 intake valve heads were machined down to 41 MM in diameter that is larger than the original 40MM B18 valves; the valve seat, combustion chamber and port will be opened up to accommodate this change. The exhaust valves on both the early and later engines are 35 MM (1.375″) in diameter and the only the changes here will be some very minor porting of the valve seat area.
- Standard B20 intake valve before being modified, they have hard chromed stems that prevent wear and are compatible with the cast iron guides that were finished off with a very smooth honed interior bore.
Photos below show machining operations on the new valve guides, and a 1975 Volvo B20 cylinder head being used as a model for valve, guide, seat and port improvements. When we return more of the engine rebuild will be covered.
Thanks go out to Swedish VP Autoparts US branch for many of the parts being used on this project. For advice on modern Volvo 122s aftermarket and performance parts Cameron Lovre of Swedish Relics and Eric and Ian at Hi Performance Auto Service for original parts, advice, and vintage Volvo Competition Services factory racing parts.
View the first six parts of this feature covering The Old Motor Volvo 122s.
- After being cut and machined to length the valve guide bores are drilled and the reamed in the lathe followed a smooth final finish by honing – the image below shows the top of a guide being machined to accommodate modern valve stem seals to keep excess oil out of the air and fuel mixture. The bottom image shows a similar valve guide precision finished here on a Sunnen honing machine.
- 1975 B20 fuel injected cylinder head used as a model for valve, guide, and seat improvements for the earlier B18b head.