Build suggestions for 340?
I'm looking for suggestions!
LD-340 intake
I have a Holley 650 vacuum secondary, that runs well on the current engine.
The engine is going in a '64 Barracuda with a 4-speed, and an 8 3/4 rear with 3.23 limited slip.
It will be mainly a street car,
I'll probably stick with a flat hydraulic cam,
I figure about 10:1 compression
- does that sound do-able?
I'd like to get to about 400 HP and a little more torque, but I DO want a broad torque curve.
Thanks for any advice!
The stock cam is not noticeably peaky, with adequate compression. The power curve is at the right place and the 114LSA is about right.
But it won't make 400hp. With open-chamber iron heads on pump gas;maybe 300 or a lil more.
If you think you really need 400hp, then IMO, you need to switch to alloy heads with small closed-chambers and jump the pressure up to say 190psi, using a solid-lifter cam of one size bigger at .050, after lashing; but on a 108 LSA. This will have the benefit of a much stronger more torquey bottom end, than the OEM camshaft :Nobody that I know, ever accused the factory340 of having a strong bottom end.
And over the top, the cam and 190psi, will more than satisfy;
Here is a comparison of what the bottom end might look like. First the 10/1 with the factory cam
Second is a custom solid lifter with one size bigger .050 spec after lashing, which is a full one to one and a half sizes smaller advertized.... after lashing.
Static compression ratio of 10:1.
Effective stroke is 2.57 inches.
Your dynamic compression ratio is 7.98:1 .
Your dynamic cranking pressure is
159.55 PSI.
V/P (Volume to Pressure Index) is
126
Static compression ratio of 10.7:1.
Effective stroke is 2.78 inches.
Your dynamic compression ratio is 9.13:1 .
Your dynamic cranking pressure is
190.61 PSI.
V/P (Volume to Pressure Index) is
163
160 psi is about all you can run with full-timing in the open-chamber iron heads, and that will take 91 or better gas.
The alloy heads will burn 89 or even 87 gas at full-timing.
The thing I want you to notice, is the V/P ratio
Notice that the number is
163 with the solid versus
126 with the factory cam. This is an
increase of 29.4%.
What does it mean?
Well, at low rpm
126 is a gonna feel a lil stronger,not much, than a 5.2 magnum , whereas
163 is like a 440Magnum of yesteryear.
read about VP here ;
V/P Index Calculation
VP in a nutshell ,is a measure of low rpm performance,
With a manual trans with starter gear of just....3.23 x2.66=8.59.......you don't have a TC that can nearly double this on the start-line, so this will be very important.
How low an rpm?
The break-even point might be around 3200;which you are gonna be married to, just about forever.
With 3.23s and 25" tires, let's say;
2200 is; 20mph in first/ 26 in second / and 36 in third.
If you don't have enough torque at those speeds to do what you want, then you will have to downshift or slip the clutch.Whereas the alloy headed combo , will always have torque like it is running in a 29.6% lower gear, or like 4.18s, compared to the engine with a 126VP and 3.23s
At the other end;
with a tad more Scr, and a ton more Dcr, and a truckload more pressure; plus the one size bigger cam, plus the tight-Q, and the better ports;
I'll guess, 40 more horsepower, could be doable, maybe more.
And finally, as to fuel-economy, cruising at
60=2600, when you get your timing figured out, you may be cruising at better than 318 specs.
This is a triple win.
IMO,
Case closed.
BTW; it is only new years day on Pope Gregory's Calendar. Ok so
Happy January First!
lol.