At 10:12 PM 7/10/2002 -0700, you wrote:
>I think we've had a failure to communicate here. It's the exhaust valve
>sizes that I quoted as smaller. If there is a difference in intake ports, I
>have not noticed it.
Actually, I thought that these two conversions went together (ie, when the
intake ports were enlarged, the exhaust valves were also changed at the
same time). However, you and Mike both say that your 67 heads are measured
similar to the 66. What might be happening here is that Chrysler came up
with the new head design in the 67 model year (explaining the automotive
press reports), but there were several old 915 heads left over. Also,
(based on 67 road test of a GTX) it appears that the HP engines got
priority to the new head design, and the regular 440s got all the old heads
till they ran out of 915's. This is just a speculation on my part, but I
think it explains the conflict of information.
As for off-line response, here is an interesting note. Both my 68's have
cam upgrades. The LeBaron seems to have an equivalent to an HP cam (strong
low end, but it peaks a bit higher than standard at about 3300-3500 rpm)
but the sedan has an even bigger cam and a CH4B Ederblock manifold (peaks
about 4000-4200 rpm). My 68 Sedan has a lot less torque than the LeBaron
in the 2000-3500 range, but it also has quite a bit better off-line
response than the LeBaron! Confusing? When wet for example, I can get
both tires loose with the sedan (has limited slip) but with the LeBaron,
you can barely get one tire loose (regular differential). This is done
without revving the engine with brakes on, just hit the gas. My guess is
that the LeBaron would soon catch up due to its better torque, and then the
Sedan might pull away again due to its considerably stronger upper end!
I think the explanation may be in the carburetors, but it gets confusing
there too. Both have spread bores. The LeBaron has an unusual Rochester
(with fairly small primaries) and the sedan has a "standard" (a bit bigger
primaries) Carter. It is likely that the accelerator pump on the LeBaron
is not properly set, and causes the lag. Also, there is a spacer to et the
Rochester to fit, and may be the spacer kills the low end. Also, the two
cars have different torque converters. The LeBaron has a lock up converter
from the late seventies, which seems to be slipping a bit more. So, the
LeBaron should have had the edge during the initial take off, but it doesn't!
The difference in displacement between the 413 and the 440 is due entirely
>to a bore change, they are both 3.75" stroke engines, thus the low speed
>torque is probably not much affected by the displacement change as it would
>be if it were due to a longer stroke in the larger engine.
Dick, very often people claim that a longer stroke will give you more off
line torque. I am not sure if this is directly true. A longer stroke
engine will usually have smaller intake ports and valves than a short
stroke engine of similar displacement, and that might give you good low end
response, but its not the longer stroke that provides directly this
"advantage". So, a 66 440 with the same intake manifold and ports as the
413 should have a stronger off line response almost proportional to the
displacement difference...
D^2
Back to the Home of the Forward Look Network