2.0 Head Tuning
Manta Engine Tuning
2.0 Head Tuning
I bought a second-hand but unused and "as new" 1.9 Ascona
CiH cylinder head a few years ago and it's still sitting in my garage
since I went all V8
Manta powered. With the new cylinder head I also got some photocopies
from an old car magazine of some Manta head tuning articles. There's
a lot of talk, testing and speculation but I managed to glean some
items of info from the pages that I thought you might find useful...
The article mainly goes into the cfm (cubic feet per minute) of
airflow and ways of improving horsepower for road-going vehicles
with bigger valves and trick cams.
The valve guide boss on the injection head is smaller than
on the GM carb head - 10mm on the inlet side.
Standard valve sizes are 42/37 (inlet/exhaust) but can go up
to 45/40 for a road-going car.
Manta cylinder heads can be (apparently) prone to split across
the seats (inlet to exhaust) and a wider valve (46mm+) will
only accentuate this on a high-mileage road car.
Standard Flow on an injection head is virtually identical to
the carb head - 85 cfm on the inlet at 400 thou lift
A well-flowed head can achieve over 100 cfm on the inlet at
400 thou lift (30/45/60º cut seats, removing most of the
valve guide boss.)
Beware - over-shortening the valve guide bosses can
lead to rapid valve wear.
Often, by using bigger inlet valves (Carlton 2.2) and leaving
the exhaust valves as standard will suffice. The standard Manta
exhaust valves are very efficient anyway (flowing 75-82% of
the inlet) and bigger exhaust valves are purported to only add