Quoting mike sutton <mikanlin62@xxxxxxxxxx>:
> The 67 cylinder heads are the same valve sizes as the 68 heads , 2.14 intake
> and 1.74 exhaust but the 67 are a closed chamber style. Only the earlier big
> block engines used the 1.6 exhaust valves, though truck engines may be an
> exception to this but were not driving trucks here, were driving Imperials.
Mike, according to the literature I have, there were two heads in 67. The heads
for the HP 440s had valve sizes as you say. However, the "low output" heads (I
think they call them 915's) had the old size exhaust valves, 1.60" in diameter.
Now, my literature may be in error, who knows. But I think I have seen it in
more than one place.
> The closed chamber has a smaller volume than the open chamber - I dont
> recall the exact cc. offhand - so in a given engine the smaller chamber
> does increase the compression somewhat, but the valves are unshrouded by the
> open chamber on the later head and improves the breathing a bit - which in
> the case of a car the size and gearing of an Imperial is a somewhat moot
> point.
Not necessarily. If you have a tach in your car, you can utilize the upper rpm
breathing abilities of the 440 during WOT accelerations on 1st and 2nd. I
often hold second gear all the way to 4500 rpm on my LeBaron when I pass more
than one car on 2 lane highway (that's a bit over 90) and some times I hold
second on my sedan (even bigger cam) all the way to 5000 rpm (a bit over
100mph, about 110 indicated). The rate of acceleration is outstanding even by
modern standards. Of course, you can use this breathing abilities on 3rd gear
too! ;)
> As far as compression, dont be surprised if you were to do all the
> measurements and calculations and find your 10:1 engine is really 9.5 to 1.
> The factories back then tended to use a lot of published figures , as they
> say in the informercials " your results may vary"
I think I have heard that before. Intersting though that they published
compression ration 10.1:1. If they were so far off, why did they add that 0.1?
Who knows. This measurement is a bit tricky though, because the chamber
volumes need to be very carefully measured. They often use aceton for this
measurements because it has little surface tension and stays flat. If the
pistons stick up a bit, then the measurement is even trickier. Mike or others,
have you ever done that measurement on a stock 440?
D^2, 2x68
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