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340 question.......

Posted By: Russ H.

340 question....... - 02/11/13 10:10 PM

Is an honest 400 HP obtainable without stroking a 340 using these parameters. A 69 block with nominal boring, X heads, stock 68 HP exhaust manifolds and a hydraulic roller cam. Intake and carb as needed.

Thank you,

Russ
Posted By: Streetwize

Re: 340 question....... - 02/11/13 11:12 PM

Yes, easlily with good porting and the right cam. The shortblock would also benefit (not required to hit 400 but it makes it a bunch easier on all things) from a lighter bobweight via aftermarket pistons, pins and rods.

When you think about it, 400 hp is only 50 horsepower from each 44-ish cube cylinder.

360's do get there a little eaiser. (less RPM)
Posted By: Southern Wolf

Re: 340 question....... - 02/11/13 11:44 PM

Streetwize I see you are from Weddington thats not far from me. Want to tune my 340?
Posted By: Sublime70

Re: 340 question....... - 02/12/13 12:40 AM

Check out the numbers on the last page;
http://www.moparmusclemagazine.com/techa...ance_mill_dyno/
Posted By: RobX4406

Re: 340 question....... - 02/12/13 04:43 AM

Quote:

Check out the numbers on the last page;
http://www.moparmusclemagazine.com/techa...ance_mill_dyno/




I got a bridge in Brooklyn for sale...

Build that and see what it runs for MPH in the 1/4... you'll be sorely disappointed.

That's a 340ish hp build, BTDT many times.
Posted By: Streetwize

Re: 340 question....... - 02/12/13 03:20 PM

Aar,

PM me and we'll talk.

The question was can you make a 400 hp 340 with a stock stroke and OEM heads and manifolds. The answer is Yes.

X or j heads can be ported to flow at least 260-270 CFM with a fair amount (and a 2.055 or 2.08 and a thinner/lighter stem valve is a big help) but not a TON of port work and with very good mid lift flows which are the key to torque. A performer RPM and ported heads on a lighter bob weight shortblock will be a very stout package, even at Only 340 cubes. Bullet makes some awesome hydraulic roller lobes, the key to 340's is (more than any other Mopar IMO) is you gotta synch the cam and converter and give it some gear to work with.
Posted By: Russ H.

Re: 340 question....... - 02/12/13 06:40 PM

Thanks to all who replied. My intention is to run this engine in my 68 Barracuda coupe. I am not going to be racing this car but still want it to have impressive power/torque and decent street manners. I want to run stock exhaust manifolds because I already have them and a complete 2 1/2" TTI system. Also to avoid the fitting problems associated with headers and 4 speed cars (clutch linkage).

In my original post, I forgot to mention, the car is a 4 speed and with 391 SG gears.

Russ
Posted By: Russ H.

Re: 340 question....... - 02/12/13 06:43 PM

Quote:

Aar,

PM me and we'll talk.

The question was can you make a 400 hp 340 with a stock stroke and OEM heads and manifolds. The answer is Yes.

X or j heads can be ported to flow at least 260-270 CFM with a fair amount (and a 2.055 or 2.08 and a thinner/lighter stem valve is a big help) but not a TON of port work and with very good mid lift flows which are the key to torque. A performer RPM and ported heads on a lighter bob weight shortblock will be a very stout package, even at Only 340 cubes. Bullet makes some awesome hydraulic roller lobes, the key to 340's is (more than any other Mopar IMO) is you gotta synch the cam and converter and give it some gear to work with.




WIZE,

Do you have a specific roller cam in mind considering a 4 speed car with 391 SG?

Russ
Posted By: autoxcuda

Re: 340 question....... - 02/12/13 06:47 PM

Quote:

Quote:

Aar,

PM me and we'll talk.

The question was can you make a 400 hp 340 with a stock stroke and OEM heads and manifolds. The answer is Yes.

X or j heads can be ported to flow at least 260-270 CFM with a fair amount (and a 2.055 or 2.08 and a thinner/lighter stem valve is a big help) but not a TON of port work and with very good mid lift flows which are the key to torque. A performer RPM and ported heads on a lighter bob weight shortblock will be a very stout package, even at Only 340 cubes. Bullet makes some awesome hydraulic roller lobes, the key to 340's is (more than any other Mopar IMO) is you gotta synch the cam and converter and give it some gear to work with.




WIZE,

Do you have a specific roller cam in mind considering a 4 speed car with 391 SG?

Russ




What do you consider "decent street manners" that you would be happy living with are?
Posted By: RobX4406

Re: 340 question....... - 02/12/13 07:01 PM

Don't use that article as a guideline was the point of my post. It's not going to make it.

You can build one and it can be somewhat mild at idle especially with a hyd roller. Clean up the bowls/ports, LD/rpm/Air Gap, headers and a HR cam in the 235 at .050, .525-.550 lift and you should be in the neighborhood.

If the heads are left in factory port configuration, it's harder to get there.
Posted By: Streetwize

Re: 340 question....... - 02/12/13 07:19 PM

AutoX,

For an A body with at least 3.91-4.30 gears with a 3200-3400 stall 9.5" vert and a HR cam in the 232-236 @.050 range on a 110 split in no later than 106. Performer RPM or AG intake is your best bet and a tweaked downleg 650-700dp. A 10.5:1 340 with at least 255 cfm of intake port will get you right at 400 hp in a very streetable low 6000 power range. That's plenty of airflow potential for that 400 hp range.

Bullet lobe HR12 is 234@.050 and 155@.200 and .565 lift with a 1.6 rocker, I'd look at that one really close in a single pattern for what you want. Bullet HR's work really nice and rev QUICK.

Heads are really key, the old iron can be pretty darn good if you know where to whittle.
Posted By: RobX4406

Re: 340 question....... - 02/12/13 07:49 PM

Quote:

AutoX,

For an A body with at least 3.91-4.30 gears with a 3200-3400 stall 9.5" vert and a HR cam in the 236 @.050 range on a 110 split in no later than 106. Performer RPM or AG intake is your best bet and a tweaked downleg 650-700dp. A 10.5:1 340 with at least 255 cfm of intake port will get you right at 400 hp in a very streetable low 6000 power range. That's plenty of airflow potential for that 400 hp range.

Heads are really key, the old iron can be pretty darn good if you know where to whittle.




Yep, not too far off from each others recipe!
Posted By: autoxcuda

Re: 340 question....... - 02/12/13 07:52 PM

Quote:

AutoX,

For an A body with at least 3.91-4.30 gears with a 3200-3400 stall 9.5" vert and a HR cam in the 236 @.050 range on a 110 split in no later than 106. Performer RPM or AG intake is your best bet and a tweaked downleg 650-700dp. A 10.5:1 340 with at least 255 cfm of intake port will get you right at 400 hp in a very streetable low 6000 power range. That's plenty of airflow potential for that 400 hp range.

Heads are really key, the old iron can be pretty darn good if you know where to whittle.




I'm sure that is streetable and you can drive it on the street. No doubt.

But what I was getting at is that some people don't like a rumpity loud cam, like a low idle speed, enough vacuum for power brakes, etc.

Each person has a different threshhold or expectation for that. IMHO, that many times is more of a constraint than the parts you can put in it.
Posted By: Streetwize

Re: 340 question....... - 02/12/13 08:01 PM

AutoX,

I agree but the intake closing event with a good HR lobe combined with a smallish (but adequate) carb Venturi and a VERY good dual plane, you will be streetable. )Acceptable manifold vacuum in gear no lugging in the 35-45 range in high gear, that's my definition of streetable. The RIGHT cam can lope at idle and be Plenty streetable too, IMHO.

I would venture to be a little milder you could knock the cam down ~ 4-6 degrees @ .050 and go to a 2800 stall 10" vert with 3.55 gears and still be right in the 400 range and that much more streetable....if I built it anyway

A blueprinted 340 can make about 310-315hp, especially if you use the '68 only manual cam profile advanced 4 degrees. And that's with a too small carb and an undersized intake manifold cross section. Back in the day the old LD340 and a 68-69 440 AVS of a New Yorker and a distributor spring tweak was a Huge step up on a 340, maybe 35-40 hp with no other mods...except you needed new valve springs if it was an old long block.

The old Ultradyne 231/239 @.050 hydraulic is a beast in an otherwise stock 340 stick A body car with good valve springs.
Posted By: Sublime70

Re: 340 question....... - 02/13/13 12:33 AM

Umm.. the OP asked if you could get 400HP out of a 340. The answer is yes, where do you come off saying that he wouldn't be happy that wasn't the question.
Posted By: Streetwize

Re: 340 question....... - 02/13/13 01:12 AM

Russ,

I'd look at that H12 bullet lobe I mention above, single pattern on 110 in at 106. The key with manifolds is you #1 need Velocity so don't go too big on the duration and #2 you really can't get very much in the way of upper RPM scavenging so the better the intake tract works on its own, the better the motor is gonna pull up high. The RPM intake can do pretty well with filling that short stroke motor. More duration will kill torque, less will limit the RPM you need above the mid range.

Opinions always vary though
Posted By: RobX4406

Re: 340 question....... - 02/13/13 01:31 AM

Quote:

Umm.. the OP asked if you could get 400HP out of a 340. The answer is yes, where do you come off saying that he wouldn't be happy that wasn't the question.




And the build YOU referenced from that article won't get close. Just pointing that out. Build that engine expecting that power output (390+) and you'll be unhappy

I posted what I'd use and mods to make it get there... how about you?

Have fun in here.
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