Any recommendations for building a '73 340?

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Shane65

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Hey guys,

So I finally took the plunge.. I'm gonna swap out the 273 in my 65 barracuda with a 340..

This is my first build so I have a lot of questions..

With the '73 being the smog friendly version of the 340, I know I'll have to do a little more work to it than the earlier 340's.

I'm wanting to get to about the 400+ hp mark / 350 to the wheels.. I want to keep it steetable.. fast and fun but still dependable..

I have the 587 heads, trying to figure out if I should keep them or sell them and buy x heads. Ive read mixed opinions ion the 587's... Seems some people prefer to keep the valves stock size 1.88 but use the sst mopar valves.. vs going with 2.02 intake valves.. Thoughts?

I'll probably run the eddy air gap intake, keep the stock crank, and bump the compression up a little, just not sure which pistons and cam to run..?

Also should not sure if I should run stock 340 exhaust manifolds or spring for some headers.. Not sure the best route for power and fit in a 65 barracuda..

I guess I should also mention my budget is between 2-3 grand... So, is there a tried and true formula for building a later 340 to a steetable 400 hp
 
Everything is more expensive for the 340. A 318 or 360 would be cheaper to hit your HP range. I believe the K member will need swapped for the 340, but I'm not an expert.

Also, will your tranny and rear handle the extra HP/TQ?
 
bkbond12 said:
Everything is more expensive for the 340. A 318 or 360 would be cheaper to hit your HP range. I believe the K member will need swapped for the 340, but I'm not an expert.

Also, will your tranny and rear handle the extra HP/TQ?
Click to expand...

I've done a little bit of reading on the subject, I believe the 340 bolts right in with a some modification to the passenger side mount... I have the 4 speed a833, and a 8 3/4 rear on the way...

I came across a 340 for a good price, and like the idea of a hi revving v8... Keeping it for sure.
 
Shane65 said:
Hey guys,

So I finally took the plunge.. I'm gonna swap out the 273 in my 65 barracuda with a 340..

This is my first build so I have a lot of questions..

With the '73 being the smog friendly version of the 340, I know I'll have to do a little more work to it than the earlier 340's.

I'm wanting to get to about the 400+ hp mark / 350 to the wheels.. I want to keep it steetable.. fast and fun but still dependable..

I have the 587 heads, trying to figure out if I should keep them or sell them and buy x heads. Ive read mixed opinions ion the 587's... Seems some people prefer to keep the valves stock size 1.88 but use the sst mopar valves.. vs going with 2.02 intake valves.. Thoughts?

I'll probably run the eddy air gap intake, keep the stock crank, and bump the compression up a little, just not sure which pistons and cam to run..?

Also should not sure if I should run stock 340 exhaust manifolds or spring for some headers.. Not sure the best route for power and fit in a 65 barracuda..

I guess I should also mention my budget is between 2-3 grand... So, is there a tried and true formula for building a later 340 to a steetable 400 hp
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400 hp out. of a 340 is n prblem. At that hp level it is 100% streetable , drive mine daily no problem .
 
jerry6 said:
400 hp out. of a 340 is n prblem. At that hp level it is 100% streetable , drive mine daily no problem .
Click to expand...

Mind shedding any light on your build? Did you run the 587 heads or swap to the earlier ones?
 
Shane65 said:
I've done a little bit of reading on the subject, I believe the 340 bolts right in with a some modification to the passenger side mount... I have the 4 speed a833, and a 8 3/4 rear on the way...

I came across a 340 for a good price, and like the idea of a hi revving v8... Keeping it for sure.
Click to expand...

Driver side mount is different than 273/318
73 340 was external balance. Build it with internal balance to keep your neutral balance flywheel setup.
 
mderoy340 said:
Driver side mount is different than 273/318
73 340 was external balance. Build it with internal balance to keep your neutral balance flywheel setup.
Click to expand...

That's another thing I wanted to ask about...

So in order to build it as an internal balanced engine. I just need an earlier forged crank right?

Any issues with that?
 
You can run the earlier stock crank and appropriate vibration damper and you are all set if you already have a neutral balanced flywheel. You can also use the older neutral balance vibration damper and try to internally balance the current crank. If you ahve to add mallory metal it will get more costly.
 
You can use a 273, 318, or 340 forged crank. No need to swap K frame. Just need drivers side 340 mount LOL!! Get it balanced to your new bob weight anyways. 400 hp out of a 340 is easy. Mine current 340 dynoed 398 HP and it nothing real radical. 10:1 compression mildly ported 2:02 J heads, stock 340 forged crank and rods, LD340 intake, Holley 750 carb Comp XE284H cam .507/.510 lift I run 3:55s and drive the car all day city or country. Great street manors
 
Build a stone stock short block. They had forged pistons and full floating connecting rods from the factory. They were a touch under 9:1 compression. Perfect for the street. Pump gas friendly. Go with the 2.02 valves. If this was something that I was doing and wanted your power level, I would not waste time with iron heads. I would choose an aluminum aftermarket head, have it prepped and ported to match the power I was looking for.

The Air Gap intake is a great choice coupled with a good set of headers. TTI and Dougs are two good choices. Most any of the modern camshafts will get you where you want to be power wise very easily. Something in the .550 lift range and around 240 or so duration @ .050 ground on a 108 LSA will get the job done. Some may say that's a little big, but instead of advancing it the recommended 4*, since you will have under 9:1, go 6* or even 8* advanced. Yes, with aluminum heads you can run more compression, but since it's a street motor, why? 1 point oc compression equals about 3% more power. Not worth having to run premium or having to worry about detonation in the hot summer months sitting in traffic at idle when the temp creeps up.

All of this of course is my opinion.
 
i agree with rusty on the heads but if you want to run factory iron heads run the 308's
 
gonna throw my opinion in here and throw a twist on the whole thing....I know you already have this 340 however, changing cranks and a bunch of machine work may warrant buying a stroker instead and choosing a little bit higher than stock compression ratio, no replacement for displacement....by the time you weigh in the cost of machine work, pistons and possibly another crank as you indicated, you are very near the cost of a stroker kit and considerably increasing displacement . a mild cam and minor head work would get you near 400hp and keep you within your budget. they are mostly ready to assemble when you get them, look around... here is just one company, http://www.campbellenterprises.com/...opar-340-360-magnum-stroker-kit.htm#340street
 
you want a high revving V8 and are ditching a 273? 73 340 was a cast crank, weird balancer, weighted convertor...I'd take the advice and build it to a neutral balance mill. Then you can use neutral balanced rotating parts, flywheel and balancer. Youll need to machine the crank for a manual pilot bearing/bushing or use the 273 manual crank and balance job.
 
barnfindcuda said:
gonna throw my opinion in here and throw a twist on the whole thing....I know you already have this 340 however, changing cranks and a bunch of machine work may warrant buying a stroker instead and choosing a little bit higher than stock compression ratio, no replacement for displacement....by the time you weigh in the cost of machine work, pistons and possibly another crank as you indicated, you are very near the cost of a stroker kit and considerably increasing displacement . a mild cam and minor head work would get you near 400hp and keep you within your budget. they are mostly ready to assemble when you get them, look around... here is just one company, http://www.campbellenterprises.com/...opar-340-360-magnum-stroker-kit.htm#340street
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Haha.. Damn. You make a good point sir.. And definitely threw a wrench on the whole thing...
So I guess I'm faced with one of two options: do the stroker and keep the head mild, or go mild on the bottom end and do aluminum heads etc... Anyone have first hand experience with a 340 stroker?
 
pishta said:
you want a high revving V8 and are ditching a 273? 73 340 was a cast crank, weird balancer, weighted convertor...I'd take the advice and build it to a neutral balance mill. Then you can use neutral balanced rotating parts, flywheel and balancer. Youll need to machine the crank for a manual pilot bearing/bushing or use the 273 manual crank and balance job.
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Well trust me, I was pretty set on keeping the 273 because of it's revving capabilities, but for the money to hp ratio, the 340 just seemed to make more sense...
 
2-3 K budget.
You just ate 1/3 of that up with good headers and intake if you buy new.
I would put some Keith Black 243 pistons in it. Balance the stock bottom end.
Re-do the heads you have, and buy a McLeod flywheel that takes the bolt on weight.
Match it up with a cam and valve springs of your choice and you will have a nice strong street friendly pump gas motor.
You should end up around 3K with careful shopping.

The KB 243's with stock x-heads put me right at 9.1 compression in a 72 340.
 
I'd use the 587 heads with the 1.88 intake valves. I'd only run the 2.02 intakes if the 1.88's are sunk too far in the head, the exhaust seats are already hard by 1973. Pocket port them yourself, just clean up the sharp edges under the valve. Use the crank from the 273 with pistons to get you to around 9.0 to one. Stock 273 Commando and 340 pistons are all cast. Use the 340 rods and have them reconditioned with good rod bolts and length equalized. Have the rotating assy balanced, and bore and hone the block with torque plates. Use good rings, see the thread on gapless rings. It is simpler to use the good Viton valve seals with single springs, which will limit lift and hp, but will last longer on a street engine. You will have plenty of power with a good 340 and 4 speed. On an early A body there are tricks and expense to running a 10.5 or 10.95 clutch. Check out Passon Performance or Brewers Performance. Have to agree with RRR about headers and Pishta about the pilot bushing in the crankshaft. I doubt you will need to stroke a 340, if you want a stroker just get a 360, and say goodbye to a high rpm screamer. If done right, your biggest problem will be getting traction.
 
I missed the 2-3 grand budget part. Change hobbies. Tiddly Winks is much cheaper. I know that was smartass, but consider this.

GOOD QUALITY machine work to get a good foundation to build with is going to take HALF your budget very quickly. POOF. GONE. Not even having bought any parts. Then comes headers that will fit well. Consider another thousand, POOF. GONE. Then, whichever way you go with heads is a lot of money. Your HP goal won't be met with unported heads, IMO. That's why I recommended aluminum heads. By the time you get the iron heads RIGHT in terms of guide, seat, valve and port work, there's the cost for aluminum heads. It's also my opinion skipping 2.02 valves at this power level is ludicrous. See where I'm goin here? I think you need to back up and punt with your budget plan, or back up and punt with your power output plan. Otherwise your outcome will not be what you want.
 
RustyRatRod said:
I missed the 2-3 grand budget part. Change hobbies. Tiddly Winks is much cheaper. I know that was smartass, but consider this.

GOOD QUALITY machine work to get a good foundation to build with is going to take HALF your budget very quickly. POOF. GONE. Not even having bought any parts. Then comes headers that will fit well. Consider another thousand, POOF. GONE. Then, whichever way you go with heads is a lot of money. Your HP goal won't be met with unported heads, IMO. That's why I recommended aluminum heads. By the time you get the iron heads RIGHT in terms of guide, seat, valve and port work, there's the cost for aluminum heads. It's also my opinion skipping 2.02 valves at this power level is ludicrous. See where I'm goin here? I think you need to back up and punt with your budget plan, or back up and punt with your power output plan. Otherwise your outcome will not be what you want.
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You're right, tiddly winks it is... :D

I know its going to cost more than 2-3 to get it complete and in my car running, but I guess I was hoping to have just that much in the motor. Block, pistons, crank, heads, machine work

Then headers and intake manifold together for no more than 1000

other misc bits probably another 1000
 
Shane65 said:
You're right, tiddly winks it is... :D

I know its going to cost more than 2-3 to get it complete and in my car running, but I guess I was hoping to have just that much in the motor. Block, pistons, crank, heads, machine work

Then headers and intake manifold together for no more than 1000

other misc bits probably another 1000
Click to expand...

Ain't happenin. You have only two choices for GOOD headers that FIT and don't hang low. Dougs and TTI. Though Dougs are a little cheaper, they are around 800. The TTI will be around 1000. If you backed off maybe to a 350 HP goal, you could run exhaust manifolds and the 340 intake and save some money, although not as glamorous.
 
just build it stock...with a good tune you will be pleasantly surprised in the performance.
 
Wait until Autozone has a 20% coupon. I was able to get a pair of new D453 ceramic coated Doug's headers for $475 shipping to my door back in January. They also had free shipping on orders over $100.
 
RustyRatRod said:
Ain't happenin. You have only two choices for GOOD headers that FIT and don't hang low. Dougs and TTI. Though Dougs are a little cheaper, they are around 800. The TTI will be around 1000. If you backed off maybe to a 350 HP goal, you could run exhaust manifolds and the 340 intake and save some money, although not as glamorous.
Click to expand...

Spitfires no bueno?

If i go over a little I'll just have to pull out the plastic and make monthlies. I'm just trying not to get into the 6-10k range. 5k total or below, I think i'll be alright.


mopowers said:
Wait until Autozone has a 20% coupon. I was able to get a pair of new D453 ceramic coated Doug's headers for $475 shipping to my door back in January. They also had free shipping on orders over $100.
Click to expand...

That's a good idea.
 
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