3.58 stroke x 340 main (rods/pistons?)
to continue post 14; You said;
Objective: Hot Street driver/cruiser
Thinking about a rebuild to up compression in a '73 340. Hmm.
Also, this hypothetical "fun" having wouldn't be from racing other cars. The fun for this car would be personal enjoyment driving. This is for corner ripping, down shifting, fast acceleration, and twisty roads.
Knowing what I now know;
and for your application, as detailed above;
Firstly; If you want to row gears, I'm sorry, but yur gonna need a much smaller engine and at least a 5 speed. So;
If I was gonna upgrade as you are thinking about doing, to go with a 4-speed, then, here would be my plan;
1) I'd get rid of that 114Lsa pressure busting cam.
2) I would install alloy heads pretty much just so I could run 190 or so psi cylinder pressure.
3) I would analyze at what roadspeed you are doing most of your driving, then gear the car to cover that window. Yur likely gonna find Second gear is gonna cover it.
4) From that information, I would cam it for torque at the bottom of the speed window, and spring it to keep the valve train together at the top of the window. and I would install whatever cam I need, on a 108 or tighter LSA.
5) and then I would build the Scr, up to whatever it takes to get close to at least 190psi.
What I mean is this,
my car has 3.55s, and in 1.92 Second gear;
3000 rpm in is 35mph, and 6000 is 70. So that is my window/that's where all my hot-dogging occurs.
so I stuck a lil cam in it ; 270/276/110 (223/230 @050), at 11.3 Scr.
This cam made gobs of torque at 3000 (in a 367 mind you), and peak power was around 5100, so the springs held it together (actually to 7200, or more) and so, I rarely need to up/down shift. And those 3.55s still got me 65@2870rpm.
Your manual shifter costs you time to shift. By gearing it right, using just one gear, you never lose that time.
Ok I get it, in competition, you want to keep the engine on the cam and if that takes a shift, or two, that is just how it goes; staying on the cam, trumps the time to shift.
But not for a country-road ripper. On gravel, you're gonna have your hands full just trying to keep it on the road.
As for the Factory 340 cam here's what the factory 114LSA cam looks like in at 110, to your engine; Followed by same cam on 108, in at 106.
268 intake-116 compression-103 power-276 exhaust-Ica of 64*-44* overlap
268 intake-120 compression-112 power-276 exhaust-Ica of 60*-56* overlap
Notice 120* of compression, versus 116. That by itself is worth about 8 or more psi
Notice 56* overlap versus 44*, that will put more hp on the table over the peak.
Notice 112* of power extraction, versus 104*. 340s with stock cams suck gas principally because of that short power extraction cycle. Those extra 8* are a game changer.
But, in your case, I wouldn't use either of those cams.
I would likely choose
Firstly; a SOLID-lifter cam, that has a faster rate-of-lift than what the hydro has,
Secondly; has more lift, and
Thirdly ............... something that works in your window of operation, and
Fourthly; never mind about the actual power numbers. Yur almost never gonna be at 5000, and never for any length of time, so then there is no good reason to sacrifice the bottom of the torque curve for a few power numbers on top that are nothing mostly just bragging rights.
I mean, IMO, lol.
To that end, here's a cam possibility, measured at zero lash, which could have the very same 050 numbers as the factory cam;
262 intake-124 compression-118 power-270 exhaust-Ica of 56*-54*overlap.
Notice 4* more compression, and 6* more power with a loss of only 2* overlap.
Again, more pressure, and more mpgs, with what could be the same 050 numbers.
In an 8/1 engine, the Wallace predicts a 10psi pressure rise. over the stocker. Not much, and not enough to be able to keep those 8/1 pistons, but it's a start.
For chits and giggles here's the hi-torque hydro cam I once ran. In at 106*
270 intake-119 compression-108 power-276 exhaust-Ica of 61*- 53* overlap
This made over 190 psi @11.3Scr, at my elevation of 930 feet. and it pulled fantastic mpgs in double-overdrive geared for 65=1650rpm.
This cam was 223/230@050. Engine was happy with 87E10 full time. It was a crazy-much fun combo. That cam would happily pull every starter gear I tried.
And it would easily roast 245s thru two gears and more. Even 275s burned a good part of Second gear.
Do you need 190 psi?
No that's just overkill, When that 270cam dropped lobes, I installed the next bigger cam, and dropped the compression down to 11/1 and the new pressure is just around 180psi, which is still plenty of fun.............. but as you know, I got a 3.58 stroke, which I'm not supposed to mention, lol.
At 180 psi, she is easier to drive real slow. I just retard the timing to 5* and idle along at a tic under 4mph. She runs much smoother. That 270 cam would idle at 3.5mph.