340 for Cruising and Fun 1/4 mile Passes
That's in the plan before proceeding. Bore measurements conveyed to me on the phone ranged from 4.071 to 4.075.
Just so you know;
When I built my 367, the machine shop refused to install my KB107s at the KB recommended skirt clearance of .0015>.0020.
I got the block back measuring .0035skirt clearance.
Ok fine, I said, you guys build race motors so, it is what it is now.
I gapped the rings to KB ringfactor of .0065, which was .026
That first summer, I had nothing but hot-running issues .
I didn't dare drive it in traffic.
Coming off the hiway, pulling in for gas, when I would shut it off, the engine would lock up, and it could be 15>20 minutes before the starter could crank it back to life.
I tried all the usual things; HO-starter, Hi-Flo-waterpump, rodded out the rad, Big steel fan. etcetera.
So when winter came, as I would for the next five winters, I installed a 318/auto; she was my DD. Winter was for freshening the 367.
So then;
I pulled the 367 apart, sent the block out for a lil more skirt clearance. It came back at .0040 skirt clearance.
Next I opened up the top ring gap to .0080 factor, which was .032, and second went in at "a lil less".
Next spring, when I installed it, she was a completely different engine. I took off that big bastard steel fan, and installed a Thermostatic clutched slightly smaller steel fan, and a 195 Hi-flo. Engine now warms up very fast, and she runs at 207*F exactly. No more hot-running.
With a 223/230/110 Hughes hi-lift cam and 1.6 arms, she popped off a
106@12.9 on 245/60-14s, spinning for a long, loooong way, on the only run it ever made.
I was expecting piston slap, and on cold mornings, I think I hear it; but, by the time I have backed out of the car port and idled past my neighbors homes, it's all quiet under the hood.
The question is;
Which change made the difference? was it the skirt clearance? or the gap-increase? Cuz those were the only changes I made that winter. Well, besides catching and fixing a wrist-pin bushing migrating sideways.
Answer;
IDK, but since there was no damage to the skirts of any kind, I suspect it was just the top-ring gap. A few years later,
that 223 cam dropped lobes, and I took the opportunity to up -am,
to a 230/237/110, which promptly ripped off an Eighth-mile of
93mph@7.92 , spinning 325/50-15 BFG-Drag Radials a long way. Some say still hazing the tires thru the traps; yes I know, crappy old airport runway. This engine now has over 100,000 miles on it, a lot of them pretty hard.
The First point is this;
If you install Hyper-Eutectics (mine were at 028>032Q), I wouldn't be afraid of a lil extra gap nor skirt.
The Second point is;
Those alloy heads nearly broke me to buy, but as it turns out, they paid for themselves in just a couple/few years, in fuel savings alone. That 223 cam was a real fuel-sipper on the hiway, and since I live in the country, it's all hiway to anywhere I want to go.
The Third point is;
I'll never go back to a low-pressure engine.
I will make a lotta sacrifices to be able to run at least 185 with a 4-speed, closer to 200 with an auto. The difference is that with a manual trans it's a little harder to drive really slow at a really low rpm. With the current 230* cam, I have to retard the Idle timing down to 5*advance, in order to tame her, for parading with 3.55s, at sub 4mph.
BTW-1
that 223* cam got me into the 30s mpg, with a dedicated carb, a manual-trans, and geared at 75=1840rpm in overdrive; and, with alloy heads, Tight-Q, running 195psi, she's always burned nothing but 87E10.
This combo has evolved over the years so, those days are gone.
and yes!, I really miss that 223* cam.
BTW-2
I'm 72 now, and so, if I was to build a hotrod today, It would likely have a Mopar overdrive automatic, 3.73/3.91s, and stall around 2800/3200, for 65=2200 in Lock-up.
At that point, I wouldn't really care what engine is under the hood...... but;
since I have this early 340 short block, and
some old closed-chamber 318 heads, and
this Offenhauser Dual-Port taking up shelfspace, and
a selection of spreadbore to feed it.........
Ima thinking to connect it all together with a really small Solid lifter cam, and
I'd paint it turquoise, cuz turquoise looks pretty.
Like I said, just so you know.
Happy HotRodding.