<VV> best timing setting for a 140/4 with a 280 cam?
tony.underwood at cox.net
Sun Jul 4 10:43:58 EDT 2010
At 09:10 AM 7/4/2010, Ray R. \(aka Grymm\) wrote:
>Played with my timing yesterday. This engine has the rear cover
>(turbo?) with the riveted timing plate that goes up to 21 or 24 or so..
Should go to 24.
>It's a 140 with most of the "step" machined out of the heads,
This means there's gonna be an increase in compression that could
give argument to running premium fuel always. Or else.
>forged rods and pistons, and a 280 Isky cam. I can advance the
>timing all the way to the last mark (looks like 24 but I read the
>plate should only go up to 20? Maybe its a custom riveted on
>plate?) and not get any pinging.
You might not notice pinging at lower speeds even with high
compression if the camshaft has considerable overlap that will cause
less cylinder filling at lower rpm. It's at higher rpm under a full
throttle load that you get into trouble... if the engine has a
camshaft that has a bit of a rougher idle it usually means you won't
have much trouble with pinging until the engine is really working
hard... so do NOT get all overboard with ignition timing. You don't
want pinging to happen at higher rpm. It will jackhammer the seats
loose in seconds. ...if it doesn't bend a rod or jam up a piston first.
>This is a street car but I'm looking for max power without totally
>killing my gas mileage etc. as I put a lot of miles on it. Where do
>you think I should set my timing considering the 280 Cam and the
>fact that the car is a driver for best performance?
You might need to consider recurving the distributor for best overall
performance. Some quicker springs/weights might help lower end
performance... to compensate for the lessened bottom end torque,
although the 280 cam isn't THAT bad on low end.
You might wanna ask Warren. He has a lot of experience with 280
cams... I've only had one car with a 280 Isky (it's actually a
regrind of an 891 cam done to 280 specs) and my own experiences don't
include extensive research in how to extract the maximum from the
engine. I just ran it while playing with settings now and again to
find out what worked.
The 280 DOES work pretty well on the street though... :) and it adds
a little bit of lope the engine that lets people know it's not a
bread & butter car. And, it has a pretty decent midrange pull. I
know, people will say it's not a dual profile cam and there's better
stuff out there these days but... ;)
>PS- this car also has an ignitor2 and flamethrower coil
If the ignition is working properly, spark won't be an issue. Where
and when it sparks will be. ;)
As far as initial timing goes, AND the curve in the distributor, you
might wanna remember the old hotrodder's adage for a modified engine:
"Once you change something, all bets are off. Just run what it likes."
By the way: a 280 cam in a 'Vair engine REALLY likes headers.
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