I'm currently putting together the HiPo 289 for my Cobra and I've come
to a question I'm going to have to decide the answer to within the next
week or so: Do I want to have oversized valves installed in the heads.
The reasons this has come up is because the machine shop currently has
my pistons and they will need to have the valve fly-cuts enlarged if I
decided on bigger valves. So the question is: Is it worth the extra
expense and how will this affect street driveability. I'm more
concerned here about overheating in heavy traffic. Most of my usage
will be street, but I'm not ruling out an occasional open track
session.
Here's the situation:
After market cam with essentially the same profile as the original Ford
HiPo
30 thousands over-bore TRW flat-top pistons
Probably after-market pointless distributor and electronic ignition
Street (thin core) brass cross-flow Cobra radiator, no oil cooler
Stock cam timing
The radiator worked fine for the original factory HiPo, but was
inadequate when I installed pop-up pistons and a hotter cam many years
back. I didn't like this setup anyway. I plan to have the radiator
rebuilt when I pull the current non HiPo engine out of the car. I'm
assuming it will need to be re-cored.
I have two sets of HiPo heads. One set is original and has never been
modified or worked on, including valve grinds. The second set already
has over-sized valves and some other modifications. I'm inclined not to
use these heads because I'm not too sure of their lineage. One of them
was welded by a former owner.
So the question really comes down to what to do, if anything, to the
original unmodified heads. This question will become even more
significant if it turns out new valves are needed anyway. So, will
larger valves and some head work to improve flow a bit put a
significantly larger demands on cooling? Fuel economy is not a big
issue, BTW.
Roland
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