I have a 69 Dart with a 340. I want to add a new cam with a lot of lope. Can I do this without much additional work to the engine, just adding the cam, rockers ect. It's pretty much street driven only. Suggestions? Does the motor need to come out to do this?
So you want a lopey idle?
>If you have a goodly amount of cylinder pressure, You may actually be able to install a real cam, and do what everybody else does, namely, install a higher stall convertor, to eliminate any soft bottom that may come with the cam. But a real cam, will need real springs. The springs that so many are talking about, are just there to keep the rocker gear from losing control at high rpm. The factory springs are easily good to 5500 on the stock cam.
On the Whiplash cam; advertised at .480/.516 lift, 213/ 226@050/109; your stock springs might be Ok to the same.
The point is, that if you have 3.23 gears, first gear with 26" tires, is gonna hit 48mph at 5500, and 5000=44, so, if you don't go there, the stockers might be fine for your application; you can always change springs later.
>As to not having power with retarded timing, I just gotta say this;
If you have a goodly amount of cylinder pressure, in my experience, even down to 5 degrees Idle-timing, with a manual trans even, that is not an issue. The trick is to run a 318 type 2-stage timing curve, that brings a lot of timing to the table, early on, then slows it down, when it needs to. And this works together with a higher stall, which the 340 could use anyway, and will absolutely need with a whiplash-type cam. That's the only way this is gonna work; with 3.23s anyway.
So, that's what the guys are saying without actually saying it, just alluding to "a tune".
>The bigger the cam, (bigger meaning a later-closing intake, the more cylinder pressure is given away at low rpm.
But a Whiplash-type of cam, is different; and in an already hi-compression engine, it may increase the low-rpm pressure into the detonation zone at WOT.
But as the rpms climb, Dynamic pressure at WOT, normalizes, and the midrange comes back. Then at some higher rpm, the power starts to come in again; and it may exceed, the power of the 340 cam. To overcome this monkey-business, the usual plan is to just eliminate the low-rpm with a higher stall, and/or ramp up the ignition timing to suit.
>Bigger rear gears are often used to make the car quicker thru the gears, and to use up more of the Second-gear powerband by 60/65 mph, and, in the case of the Whiplash, to reduce the engine load to help it stay out of detonation.
It's really no different than the regular plan, with a regular performance cam, except that, the early 340s had more pressure in the first place, so they would have special needs down low, to stay out of detonation.
The take-away is that you gotta budget for the whole plan, and that the cam is just the cheapest part of it. Unless, you just never nail the gas-pedal, I guess......... yeah right with a 340 car, lol.
So to recap;
Most times that a rowdy cam is installed, the additional costs are;
Stage-1
assumes that you have headers, a free-flowing exhaust, and a tachometer
Stage-2
new cam kit includes; cam/lifters/springs, adjustable rockers, a convertor, and somebody to tune the ignition and carb.
Stage-3
performance rear gears, and maybe a slight re-tune.
Stage-4
about this time the trans will give up, so you need somebody to rebuild it BEFORE it blows up, and wrecks your new convertor. and there's no better time to install a shift kit. and while the driveshaft is down, install some new U-joints.
Stage -5
By this time, the cooling system is acting up, and the fuel-system is revealing it's weakness, so more money.
Stage-6
Now that the car is a ripper, you come to find out that the brakes are crap, and the 55 yearold suspension and steering, aren't cutting it anymore. and of course the tires already gave up months ago.
So then, as you can see, everything just snowballs, and in a hurry. and it all started with wanting a lopey idle....... which is never a goal for most of us, rather, it is something that just comes to us as a result of the quest for power, which only comes with rpm, and the cam unlocks rpm, at the expense of the idle, and often/usually, the low-rpm performance suffers.
Money, money, money. Make sure you are aware of this, and have coin at the ready.
BTW
Typically, a 213/226/109 cam is a hi-torque fun small street cam. It is smaller than stock (which IIRC was 228/235/114), but in a high-compression 340, cylinder pressure will start higher and build higher sooner; which automatically means the need for a higher stall, and special ignition timing needs, to keep it out of detonation. Don't think that you can get away without changing the convertor. That's why I listed it in Stage-2 together with the cam. This problem can be mitigated with alloy heads, that tend to run at higher pressures than "normal", without detonation. For example, my alloy headed 367 has run on 87E10 for decades at 180psi, (or more) and at one time, ran as high as 195, still on 87E10. More money ................. but goes like hell. well worth the extra cost..
I gotta say that if I still had a 340 car, I would be gung-ho to try this, cuz I think I could get some great hi-way fuel-economy out of that Whiplash...... especially with a 5-speed manual.
IMHO,
If you have a hi-compression iron-headed 340 engine, and you take out the factory cam, with it's already late Ica of 64*; to replace that cam with something that closes the intake-valve sooner, you are just looking for trouble. IMO, the best solution is alloy heads. and a still better solution is flat-top pistons at zero-deck.
But, that factory 340 cam, because it has such a late-closing intake, and already has a modest 44* of overlap, running with iron logs....... will quickly get lopey as the idle-rpm is reduced, to allow more time for reversion to happen in the intake, and for EGR to back-up thru the overlap period. Take away a bit of Idle-timing, and badaboom! there's your lope.
