1973 340, want more power.

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Richard McLaughlin said:
I really like the idea of the stroker moving the power band lower in the rpm range making it more street able. Makes sense to me anyway, maybe others have different opionions on it.
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Why do you want more power? Is the car slow as it is right now? I bet you might even be pleasantly surprised with a rear gear change. Figure out what your car has in it. Then worry about power.

I'll also ask this. Have you ever been in a 12 second street car? Have you driven one? If you haven't, hangout with some of the local car guys, see if anyone will give you a ride in their's. Everyone loves to think 12 seconds is slow. But to put it in perspective, a low 12's car, hits highway speed from standing still in 4 seconds or less.
 
Lustle said:
Why do you want more power? Is the car slow as it is right now? I bet you might even be pleasantly surprised with a rear gear change. Figure out what your car has in it. Then worry about power.

I'll also ask this. Have you ever been in a 12 second street car? Have you driven one? If you haven't, hangout with some of the local car guys, see if anyone will give you a ride in their's. Everyone loves to think 12 seconds is slow. But to put it in perspective, a low 12's car, hits highway speed from standing still in 4 seconds or less.
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I have not been in a 12 sec car. 420 hp like you said in a 3000lb car is more than enough.
I want more power simply because I want to have a car that when I tramp it it throws me back in the seat hard and seems extremely fast.
I like the current gears for highway driving. How can I find my exact gear ratio?
 
340's are a great choice. I was just throwing out the idea... saves downtime. 360 mags everywhere for 350 bucks. Build it while driving the 340. Swap in a Saturday afternoon.
 
Richard McLaughlin said:
I have not been in a 12 sec car. 420 hp like you said in a 3000lb car is more than enough.
I want more power simply because I want to have a car that when I tramp it it throws me back in the seat hard and seems extremely fast.
I like the current gears for highway driving. How can I find my exact gear ratio?
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So an all around street machine is basically what you are after. I will say this, if you get 400+, expect to start making suspension/chassis/tire changes. Or you will never put it to the ground. I run 245's on the back of my scamp, and can absolutely burn them at will in any gear. And thats with a snubber and SS springs. I will need to go cal-tracs and spring relocation or even mini tub if I want to really plant it.

The best way to find out gear ratio is to jack it up and put the transmission in neutral. Make a chalk mark on the drive shaft. Then spin the tire. Keep an eye on how many times the tire spins vs how many times the driveshaft spins. That gives you your ratio. EX: If you turn the tire once, and the driveshaft turns 4 times, you're in the 4.10 area. It will also help you tell if you have an open differential or not. If you turn one tire and the other turns the same way, or not at all, that's sure grip. If it turns the other way, open differential. If it is open, you'll have to block the one tire to figure out your ratio.

Your current gears might be great for highway driving. But a gear change will definitely help you get that neck snap you want. Common street gear is between 3.55 - 4.10. But once again, it's all in the whole combination. If you change rear gears, you should get a better converter. If you change cam you should change rear gears and compression. Etc etc etc. It all works together. The best thing you can do is figure out everything about your car. Know every last nut and bolt.
 
Richard McLaughlin said:
Thanks guys. I'll try and dyno my car asap.
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Don't worry about dynos and such. They only give you an idea of what your car is about. Drive it. Work on it. Take it apart. Figure out what it's got to it. Work on the engine. You'd be amazed how much horsepower is hidden in things like a basic tune up. Once you know your car, then figure out what you want to change.
 
Richard McLaughlin said:
Ok. What is involved in a "tune up" sorry for my ignorance
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Don't be sorry. If you're new to the car thing gotta learn somehow. It's basics. Plugs, maybe wires. Check timing. Carb is tuned for best vacuum or ideally you have it hooked up with an 02 sensor and make sure its pulling good numbers through the driving range. So maybe some jetting/carb changes. If it needs them. Check ignition/spark quality. Etc etc. Just the real basics of how the car runs. A proper tune on a poorly/bad tuned car can be with 10+ horsepower alone. Or more.
 
Richard McLaughlin said:
Ok. All of that has been done except the o2 sensor. That wouldn't be on. 73/74 correct?
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No. It's an aftermarket thing. You can get a bung, sensor, and gauge. Hook it all up and then you can always keep an eye on your 02 levels. So if you go to accelerate and get a part throttle bog. Or an off idle stumble. Or whatever else. You can see why. Maybe it's rich, maybe it's lean. Maybe it's something else. Just another tuning tool.
 
My 72 340 Scamp went into the 12's with the following
10.5 comp pistons
Stock 2.02 X heads
490 lift hydro Comp Cam
Torker single plain intake
780 DP Carb
Hooker comp headers
recurved dist
Crane Hi 6 Box
3.91 gears

Engine made 344HP
 
Here's my 2 cents worth. This engine was built over 30 years ago when my father was still the original owner before I bought the car. Std bore 340 with factory 10.5 pistols. Stock x heads with port matching and milled to bump compression. Cam is a Ramcharger solid lifter 500" lift, 300 duration, although these days there are much better choices but it does sound VERY wicked and is streetable with the 4 speed. H.v oil pump and Carter street fuel pump. Milodon 8 at oil pan and Heddman husler hedders. 40 yr old Holley 780 carb that STILL works great. Stock valve covers hide the 273 adjustable rockers and still has the stock air cleaner. Molar electonic ignition. Nothing exotic or highbuck. With 4.56 gear and dragradials, bone stock suspension with pinion snubber, this 3200 lb dart drives to the strip, runs 12.20s with mufflers all day, then drives home, after a stop for ice cream.lol. Forgot to add it has an oldWeiand Xterminator intake. This motor is shited at 7000rpm, although it's missed a few gears and seen the north side of 7500. Point is, in a a body with a 4 speed or a GOOD converter, DONT skimp on the converter! A decent set of gears and tires, itdoesnt take a stroker kit, alluminu heaads, or exotic pieces to build a 340 to go deep in the 12s and still live a long trouble free life!
 
You have some options for making the car quicker before you start upgrading the engine for power. First off I bet if it's a factory 340 car it has a 727 automatic which will never break but sucks a lot of power compared to a 904. I'd recommend a higher-stall torque converter but since you need to pull the trans (or engine) to put that in I'd look at a 904 or 999 trans. Then gears, my bet is you have 2.76, 2.94 or 3.23s, 340s like to rev more so they definitely need some lower gears in the rear end. You said a tune-up has been done, do you happen to know the timing specs (initial and total @ what RPM)?

Beyond that I think the only upgrade worth your time would be an aftermarket intake manifold and bigger carb which might give you 20-30 HP. If you do a compression test and the engine is healthy you might be able to put a better 'modern' higher-lift cam and valve springs in it without losing too much low-end but at that point you will need to have the converter and gears to match or it will be a turd. Beyond that the engine should just be pulled and rebuilt IMO, or swapped with something else like a 360/5.9L Magnum as 340s have a lot of restoration value but for making power they have no advantage over a 360.
 
I have to disagree with MOPE a good bit working backwards on his list and say that the 340 has the HP advantage without a doubt. Not the torque. (IMO at least.)
2nd, pulling the 727 for a 904 is a pricey thing that includes driveshaft work.

IMHO, the following parts would be a better bet.
Open air cleaner
750 Holley/800AVS Thunder
RPM intake
RPM heads with some minor work done
(This over stock heads with a bowl porting and 2.02's.)
1-3/4 header - 2-1/2 exhaust
3.91 gears

My only two concerns are where the pistons sit in the hole and the cam to be used. These two areas as I read the read are a bit grey to me due to your goals. One feeds the other and to properly answer the question i need more clearity.

Just as an example, Edelbrock claims 417 hp with there set up which includes there cam, which I am not exactly a fan of. Add some duration for a street stripper. 10*'s ought to do it. (Hyd. cam)
To copy cat a build is not a shameful thing, but give accolades to the original builder.
Just food for thought.
 
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rumblefish360 said:
I have to disagree with MOPE a good bit working backwards on his list and say that the 340 has the HP advantage without a doubt. Not the torque. (IMO at least.)
2nd, pulling the 727 for a 904 is a pricey thing that includes driveshaft work.

IMHO, the following parts would be a better bet.
Open air cleaner
750 Holley/800AVS Thunder
RPM intake
RPM heads with some minor work done
(This over stock heads with a bowl porting and 2.02's.)
1-3/4 header - 2-1/2 exhaust
3.91 gears

My only two concerns are where the pistons sit in the hole and the cam to be used. These two areas as I read the read are a bit grey to me due to your goals. One feeds the other and to properly answer the question i need more clearity.
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True I guess I was just thinking out loud; I'm personally peeved by inefficiency so those are the first places I tend to look on these old cars. Totally forgot about the driveshaft needing to be longer, duh. I still wouldn't really recommend doing anything regarding the heads without knowing for sure the condition of the bottom end and how much actual compression you have. Correct me if I'm wrong Rumble but wouldn't a set of RPM heads after being gone through and assembled with good parts be like $2000? I think it would be worth a shot to do a cam and intake swap first and see how it runs with the rest of the stock engine parts, just to save a bit of money in case that gives you enough of the kind of power you were looking for.

I'm coming from the angle of someone who is new to the whole classic Mopar thing and wants to try learning and doing things himself. Doing upgrades in stages I think is more "educational" lol. But whatever, it's the OP's choice not mine :)
 
OK so I need your help. Since your already talking about the 340. I have a 67 Barracuda fastback that weighs 3140 without me and 3300 with me in it. It has a 68 340.
340 .030 over TRW forged shaved to flat tops 10.5.1 comp.
X heads with some cleaning and port work
Lunati voodoo 284/292 533/552 hyd cam
RPM airgap intake
750 holley vacuum sec.
70 340 sixpack exhaust manifolds with no heat risers.
2.5 in.exh. with magna flow mufflers dumped in front of the rearend.
727 auto. with converter that stalls to about 2300 rpm.
8.75 suregrip with 3.91 gears and 275 60 15 tires(28 in. tall).
rev-n-nator ign.
This combo is horrible off the line and I am sure the cam is the problem running the gear, tire size, and stall that I have.
This is my best run
r/t... .228
60'... 2.193
330... 5.195
1/8... 8.946
mph... 81.40
1000... 11.55
E/T... 13.767
MPH... 101.35
Looking for suggestions on cam choices staying with a hyd. because it sees a lot of cruising time. Comp XE274H cam? maybe.
Makes power and torque at a lower rpm to get it out of the whole and still good up to 6200 rpm. Any help would be appreciated. It would not even spin off the line going around the burn off box straight to the starting line. The voodoo cam really needs a true 4.10 gear and 3500 stall to make it perform well. My fault live and learn, but it does sound really good.
 
dusterman71 said:
OK so I need your help. Since your already talking about the 340. I have a 67 Barracuda fastback that weighs 3140 without me and 3300 with me in it. It has a 68 340.
340 .030 over TRW forged shaved to flat tops 10.5.1 comp.
X heads with some cleaning and port work
Lunati voodoo 284/292 533/552 hyd cam
RPM airgap intake
750 holley vacuum sec.
70 340 sixpack exhaust manifolds with no heat risers.
2.5 in.exh. with magna flow mufflers dumped in front of the rearend.
727 auto. with converter that stalls to about 2300 rpm.
8.75 suregrip with 3.91 gears and 275 60 15 tires(28 in. tall).
rev-n-nator ign.
This combo is horrible off the line and I am sure the cam is the problem running the gear, tire size, and stall that I have.
This is my best run
r/t... .228
60'... 2.193
330... 5.195
1/8... 8.946
mph... 81.40
1000... 11.55
E/T... 13.767
MPH... 101.35
Looking for suggestions on cam choices staying with a hyd. because it sees a lot of cruising time. Comp XE274H cam? maybe.
Makes power and torque at a lower rpm to get it out of the whole and still good up to 6200 rpm. Any help would be appreciated. It would not even spin off the line going around the burn off box straight to the starting line. The voodoo cam really needs a true 4.10 gear and 3500 stall to make it perform well. My fault live and learn, but it does sound really good.
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The biggest thing I see is your exhaust. You are pissing away a bunch of power through exhaust manifolds.

Your combo should produce 106-108 MPH which should put you in the mid 12's. There is nothing wrong with the cam either. Wouldn't have been my first choice but changing the cam would be picking the pepper out of the fly poop
 
Exhaust manifolds, more than likely, are not hurting your off-line performance. I would look elsewhere for the problem.

I'm not a fan of tall rear tires.
 
1968FormulaS340 said:
Exhaust manifolds, more than likely, are not hurting your off-line performance. I would look elsewhere for the problem.

I'm not a fan of tall rear tires.
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I was referring to what was posted in post 44. The MPH in that post is slow.

I have no idea why you would think piss poor exhaust won't kill 60 foot times.
 
I have ran a quicker 60' and higher trap speed with a 340, through stock manifolds, but that doesn't really matter in this conversation.

If I were to make a list of things that could be causing his car to be soft off the line, stock exhaust manifold would be towards the bottom.

I do agree that the manifolds could easily be hurting him down track.
 
MOPEkid, whatever brother, what ever.
Everybody has a complaint on price and parts. What ever... what ever.....
 
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