Build suggestions for 340?

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Jim64

Jim64

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Hi Folks! I pulled my '69 340 last weekend; it was previously built in about '89.

I'm looking for suggestions! Here are the basics...
I want to use the stock block, crank, rods, and heads. (I have 'J' heads with 2.02 valves.) I have an old LD-340 intake I want to use. (I do have a splash shield that fits in the valley under the intake.) I do have the MP windage tray, and the MP bigger oil pump. (I also have the high pressure spring...not sure if I should keep that.)

I have a holley 650 vacuum secondary, that runs well on the current engine. Long term I might want to go with a TBI system, like FiTech, Sniper, etc. Long-tube Hooker headers.

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, as I like driving it! I will probably take it to a track once in a while, but that's not a primary goal.

There are a LOT of cam options out there! I'll probably stick with a flat hydraulic cam, and will keep the stock rockers if I can.

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.

The pic is a 'before' pic.
20200718_200549 (Large).jpg

Thanks for any advice!
 
I would build a stock 69 340 short block. Use the Lunati 268 VooDoo cam. Have the heads professionally ported. Then put it together.
 
What RRR said. Used that cam in my friends 340 built to 69 specs with a 73 intake and TQ and 69 manifolds. In his 69 cuda 3.55 and 3 speed od trans. Thing pulls hard.
 
I’m running this cam in my 340. It has stock rotating assembly with J heads like yours. Running Air Gap intake and 750 Holley carbrator. Engine made 438 hp on dyno at machine shop.
F31ABFEA-54F9-4729-80EB-1E5C70DC299D.png
 
i got 425 hp out of a basic stockish 1970 340 cam had 513 lift with 1.6 rockers mahle pistons air gap intake stock heads with some mild porting 10.3 compression 190 cyl pressure 670 holley elec choke ran well and was reliable as could be . electric fuel pump helped start up on cold mornings
You should have no problem reaching your goal .
Good luck
EDIT HERE IS 1ST RUN ON DYNO BEFPORE SETTING UP 377TQ 414 HP
FIRST RUN 340 STOCK.jpg
FIRST RUN 340 STOCK.jpg
 
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No one actually cares what a stock 48 year old motor can do. Punch it out as big as it can go. Jack the compression up. And wing that baby up to 7200 Rpm. Then show them what a 340 BLOCK can do. :poke:
 
Choosing a cam is like buying a pair of shoes, you need something that fits you and your car. There is a number of people here on FABO that know quite a lot more than myself. I did a search for info on a cam a while back and due to my application. I fallowed the advice I received and called Racer Brown. He suggested and I purchased from him a cam that looks mild but due to my tire size 26" and rear ratio of 3:00 should work. I also called Hughes, Comp, and Lunati and they all told me that I needed a custom grind, Racer Brown just made the most sense. His cam for my car is an eh20, with In lift .450, Ex .450, duration @ 50, In 220 Ex 220, centerline In 107 Ex 113 and lobe separation of 110. My motor is a 372ci with Eddy heads and a LD3430 with 10.8 compression. For a trans I am using a 833 with a 3.09 first gear. Unfortunately, I can't tell you how it runs since I just put the motor in the car yesterday. Hope this helps.
 
RustyRatRod said:
I would build a stock 69 340 short block. Use the Lunati 268 VooDoo cam. Have the heads professionally ported. Then put it together.
Click to expand...

Thanks for all the input so far!
Rusty - I could not figure out exactly which cam you were referring to - below is a 'table' of Lunati cams in the range I'm considering. Is your choice one of these?

Below that is a list of COMP cams, with the suggestion from "D" as the third row.
-Jim

BRAND SERIES DURATION AT .05 ADVERTIZED DURATION LIFT LSA RPM Range
Lunati
Voodoo 10200700 208/213 253/258 .454/.454 112/108 idle-5000
Voodoo 10200701 213/220 256/262 .454/.475 112/108 1000-5500
Voodoo 10200702 220/226 262/268 .475/.494 112/108 1400-5800
Voodoo 10200703 226/234 268/276 .494/.513 110/106 1800-6200
Voodoo 10200704 234/242 276/284 .513/.533 110/106 2200-6400
Voodoo 10200705 242/252 284/292 .533/.552 110/106 2500-6600
COMP
Xtreme Energy 20-223-3 224/230 268/280 .477/.480 110/110 1600-5800
Xtreme Energy 20-224-4 230/236 276/286 .488/.491 110/110 1800-6000
Xtreme Energy HI-LIFT 20-227-4 231/237 275/287 .525/.525 110/110 2000-6000
Xtreme Energy 20-225-4 240/246 284/296 .507/.510 110/110 2300-6500
Xtreme Energy 20-226-4 250/256 294/306 .519/.524 110/110 3000-7000
Xtreme Energy HI-LIFT 20-228-4 241/247 285/297 .545/.545 106/106 2500-6500
Xtreme Energy HI-LIFT 20-229-4 251/257 295/304 .564/.564 110/110 3000-6800
 
If you have the money, go to a roller cam, set it up with some beehive springs, try to lighten up the rotating assembly as much as possible.

I have a 227/231 duration at 0.050, .530/.530 lift, 110 LSA hydraulic roller with edelbrock heads and 9.8:1 compression. K1 rods, beehive springs, crane gold roller rockers, its an excellent street engine and it dyno'd at 470hp/455 lb-ft and makes 400+ lb-ft from 2900-6100 rpm. Been together for 7.5 years. I changed it to EFI and it feels stronger yet.
 
For a streeter,
IMO;
Since it is going into in a lightweight-A, with log-exhaust, and 3.23 gears;I would treat it as a big-bore 318..
With 3.23' and a 4-speed, first gear will be a tireburner no matter what cam you put into it. That means Second gear is gonna be where all the action is.
With 25" tires, 3000rpm is 36mph and 6000 is 72mph
You need to decide where you want the bulk of your power to be, then chose a cam to put it there, and finally, adjust your cylinder pressure, with static-compression ratio, to make best use of the chosen cam.
The iron open-chamber heads will limit your cylinder pressure.
400hp requires a bigger cam, which drives the operating rpm up.
Just remember, that 400hp is not likely to arrive until close to 6000 rpm/72mph in second gear, and 400hp will spin any street tires you can fit in the factory tubs, all the way thru second gear. Is that what you want?
I'd settle for 380/400ftlbs at 36 mph, and all-done by 60mph/5000 rpm with 3.23s..........but that might just be me,lol.

Oh sorry, the "before pic" shows headers, that will not change my discourse
 
Dblackmt said:
I’m running this cam in my 340. It has stock rotating assembly with J heads like yours. Running Air Gap intake and 750 Holley carbrator. Engine made 438 hp on dyno at machine shop. View attachment 1715660534
Click to expand...
I think that is the XE275HL cam? I have one of them sitting on the shelf. What kind of work have your heads had? I’d be pretty happy with that hp number from my nearly identical combination.
 
I think you may want to figure out what you're going to do with your heads first or at least along with all the other decisions you will be making. As much as I love ironheads I ran ported X's for 30 years it is getting harder and more expensive to have good machine work done. If your heads have been done fairly recently and don't need a complete rebuild then I would go for it. but my finding was by the time I had quality work done keep your( fingers crossed), and quality parts installed I still had a 50-year-old head that weighed close to twice as much. And without any port work produced approximately 15% less power maybe more.
 
gzig5 said:
I think that is the XE275HL cam? I have one of them sitting on the shelf. What kind of work have your heads had? I’d be pretty happy with that hp number from my nearly identical combination.
Click to expand...

Opened them up to 2.05 from 2.02. Block has been bored .30 over. The rotating assembly is pretty well stock. 10.8 compression. It really likes the 96-98 octane fuel. Has good street manors too. I didn’t go with aluminum heads, cause I wanted to keep it as period correct as possible.
 
Dblackmt said:
Opened them up to 2.05 from 2.02. Block has been bored .30 over. The rotating assembly is pretty well stock. 10.8 compression. It really likes the 96-98 octane fuel. Has good street manors too. I didn’t go with aluminum heads, cause I wanted to keep it as period correct as possible.
Click to expand...
totally understood! How did you achieve 10.8 compression even with the factory dome style piston I found true compression to always hang right around 10 to 1 with a 75cc chamber. I guess you milled them quite a bit?
 
Several years ago I bought an all original 73 340 Duster. The motor and transmission were tired so I rebuilt both. I had 2.02" valves installed in the heads, did a little clean up work, blended the bowls and port matched the heads and intake. The bores were good so I used a set of early 340 higher compression pistons that I had on hand. For the cam I used a MP 280/.474 hydraulic. It had the original intake, exhaust manifolds and factory convert with 3.55 gears. I was surprised how hard it ran, the cam had a little thump and was about the limit for a stock converter.
 
Thanks for all of your input so far, and Happy New Year!
 
Jim64 said:
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!
Click to expand...

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.
 
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AJ, typical high compression 340’s typically dyno’d over 300 hp. Adding a 750 carb, headers, well ports heads (2/02-1/60) w/a cam like a Comp or Lunati 268 has brought the goods of 400+ hp home.

The heads we had ported flowed in the 250/255 range.
Similar to the Edelbrock head flow curve.

Later we added more aggressive ramp (& lift) cam of approximately the same advertised duration which added 30 hp. The quicker valve lifting action with a bit more duration @.200 it was still a nice street camshaft.
 
AJ/FormS said:
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.
....
BTW; it is only new years day on Pope Gregory's Calendar. Ok so
Happy January First!
lol.
Click to expand...
Thanks for all the detailed information - now I need to go learn about VP!
-Jim
 
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