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  #1  
Old 02-25-2006, 05:38 PM
73blueduster 73blueduster is offline
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Arrow 340 build up

I am currently restoring a 1973 duster, with a 340 from 1968. It is goin to be a street driver on pump gas and i want the horse power to be 400 or close to that(maybe more). I was wondering if anybody knew a website that has complete ground up 340 engine builds so I can save myself the trouble of figuring out the right engine combinations.

Your feedback is appreciated!!!
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  #2  
Old 02-25-2006, 10:12 PM
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rumblefish360 rumblefish360 is offline
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Do you have any parts for it now. Otherwise, 400 is an easy build.
Rather than give you a parts list, I'll generlize.

From the top down;

Open air cleaner. I really like the K&N set up with extreme lid
750 cfm carb.
RPm intake
For stock heads, port them w/2.02-1.60 valves
Street headers into 2-1/2 inch pipe exhaust with an "X" pipe in there, mufflers your choice but I would recomend Dyno Max ultra flows to handle the chore.
Your comp. ratio should be about 9.5-1. MAX
And the all important cam.
A comp cams Magnum line, 280* duration will get you there no problem.

Last edited by rumblefish360; 02-25-2006 at 10:25 PM..
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  #3  
Old 02-26-2006, 12:07 AM
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pishta pishta is offline
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Rumble, not really an easy build according to how these guys rated their mill, oh yeah, this is gross HP on a stand! Ill go a little farther and give him 16 builds all with dyno numbers and modifications. This is all stock running gear with exception of the cam, ignition (not really an issue until 5500 RPM) intake and headers, no head work. This was done on a bone stock '68 340, already had the 2.02 heads and compression. Has cam design really evolved since this 1969 write-up?

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  #4  
Old 02-26-2006, 12:22 AM
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rumblefish360 rumblefish360 is offline
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Quote:
Has cam design really evolved since this 1969 write-up?
Oh yea, oh yea, LOL, oh yea. Big changes. ha ha ha ha. Oh yea.
Being that he has a 68, not a 73 340, he needs to port his heads and install better cam. and bigger carb with headers.
But I really do not like to simplify such things to this degree.
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  #5  
Old 02-26-2006, 05:41 AM
73blueduster 73blueduster is offline
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The engine is .30 over and it has the X heads 2.02/1.60. Thats it for now
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  #6  
Old 02-26-2006, 05:52 AM
Dart 65 Dart 65 is offline
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Does it matter that his 340 has the cast crank versus the forged piece? Is 400 horses possible without breaking it?
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  #7  
Old 02-26-2006, 07:07 AM
dusterdood dusterdood is offline
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Didn't they make 400 horse with a 318 and modern magnum heads in a magazine?
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  #8  
Old 02-26-2006, 07:22 AM
sanborn sanborn is offline
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Thinking back, 450HP from a 340" engine in 1970 was a potent engine. I don't know if cam technology has evolved that much---but cylinder head and valve train technology certainly has.

"X" heads were good in their day! But, that also was before flow benches. Cylinder head mods are much better today than the "hit or miss" of yesterday. Although the "X" heads have limits. W2s are much better but that is another story.

Back in the 60s, the "hottest" cam for a race small block GM was the Chet Herbert 280 roller---with a gross valve lift of about .480". We couldn't keep the valve train together above 7400-7500. Kept punching holes in the rockers. I remember when we installed a Thomas shaft rocker system on the SB---with (gasp) 1.6 rockers. We picked up about 3-4MPH in the traps. And RPM went up to about 7800. And those Thomas rockers were crude compared to today. Suddenly, the Herbert 280 was obsolete for racing. It would be considered a mild street cam today.

Yes, better cylinder head work and more lift will yield better HP! But, you won't get that with stock components.
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  #9  
Old 02-26-2006, 11:57 AM
Dart 65 Dart 65 is offline
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Quote:
Originally Posted by dusterdood
Didn't they make 400 horse with a 318 and modern magnum heads in a magazine?
Yeah, that was in Mopar Muscle. I just can't get excited about building a 318, though.
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  #10  
Old 02-26-2006, 01:27 PM
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Quote:
Originally Posted by Dart 65
Does it matter that his 340 has the cast crank versus the forged piece? Is 400 horses possible without breaking it?
From post #1,
Quote:
I am currently restoring a 1973 duster, with a 340 from 1968.
And yes, cast cranks can handle alot of power. 600 is the accepted ceiling , but I'd stop around 550 as a max power output on a cast crank. It would be better IMO to just spend the money on a fordged part for 550 and better Hp engines. (At least the way I treat them.)

dusterdood, Yep.

sanborn; I'd say the cams made in the late '60's and todays cams are alot different. Yeasteryears race cams are todays street cams. If that ain't big.....
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  #11  
Old 02-26-2006, 02:06 PM
party340 party340 is offline
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I have a 67 dart with a 340 that I THINK has around 400 hp. The car has gone 12.70's at 112 mph with street tires, muflers, full interior, and no fiberglass parts. I just bought some slicks and hope to be in the high 11's this weekend weather permitting. Anyway, this car is very streetable (except for the loud exaust which I've never been pulled over for.) Heres my combo.

Kb pistons with total seal rings. Blueprined 10.3 to one. Runs fine on 93 ocatne. Polished the piston tops by wetsanding them. Started with 220 grit and worked my way up to 600 grit.

eagle h beam rods

stock cast crank

318 flywheel ( KB piston and eagle rod have almost the same weight as a stock 318 rod and piston combination, hence internal balancing) No mallory was needen with the balancing job.

360 heads with 2.02 and 1.60 valves. Heads were home ported by yours truely with a dremel tool and flex shaft. Intake port volume endend up at 170 cc. Also polished the chambers to prevent detonation.

Ultradyne 242 @ .050 cam with .548 lift solid advanced 6 degrees to a 104 intake centerline with Lunati springs and 273 rockers. Ran the cam straight up and lost 3 tenths. The ultradyne cam is now a Lunati grind.

Eledbrock RPM air gap intake with 750 holly vac. sec. with 76 primary jets and 50 cc pump. Seconday has no spring. This car needs a DP.

Flowtech 1 5/8 headers with 3 inch collectors with full duel 3 inch exaust and 40 series flowmaster with turndowns. (very loud and nasty!)

Reworked mopar dist. with 35 degrees advance at 2300 rpm and 17 at idle.

Car is a 4 speed car with 3.91 gears.

One other note, when the valves are loose the motor does ping at low rpm's in high gear which tells me that if I would have went one cam size smaller, the engine would detonate. (loose valves makes the cam seem smaller).

If you know how to port heads, this is the cheap way to go. If not, get a set of after market heads like the eddies.
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  #12  
Old 02-26-2006, 03:23 PM
73blueduster 73blueduster is offline
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Thanks guys!
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  #13  
Old 02-26-2006, 07:35 PM
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pishta pishta is offline
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Quote:
Originally Posted by party340
I have a 67 dart with a 340 that I THINK has around 400 hp. The car has gone 12.70's at 112 mph with street tires, muflers, full interior, and no fiberglass parts.
Looks to be about 388 gross (speed method) or 342 (ET method)
assuming 3000 lb car. I bet with some 4.56's your times would be better but so would your gas bill!
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  #14  
Old 02-27-2006, 01:20 AM
sanborn sanborn is offline
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Rumble, I know you don't think I am that old---but I was talking about the early 60s. I remember the 50s too; but that was the flathead days and I didn't know anything about cams anyway.

BTW, still have that Herbert roller is a 265 sitting in the corner of the shop.
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  #15  
Old 02-27-2006, 01:21 PM
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rumblefish360 rumblefish360 is offline
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Quote:
Originally Posted by sanborn
Rumble, I know you don't think I am that old ---
BTW, still have that Herbert roller is a 265 sitting in the corner of the shop.
I may not know your number, but I know your smart enuff to put collage kids to shame in your game. Also since I know fellas that are +60 and have, gone back to school for degrees, body build and one I know just recieved his black belt, I would never handicap a fella or joke to hard on his age. I might just get, Out smarted, squezzed inbetween a couple of muscles (LOL) or judo chopped and thrown across the room at a moments notice.
I just think cams have gotten alot better. Valve trains are light years of what was.

And on that cam, Have no dout, I'm sure it was and still will be a killer performer.
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  #16  
Old 02-28-2006, 12:08 AM
sanborn sanborn is offline
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Rumble, thank you for the compliment(I Think!).

BTW, my only concern with belts is if I can buckle mine---and see my toes without bending over.
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  #17  
Old 02-28-2006, 12:08 AM
sanborn sanborn is offline
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Rumble, thank you for the compliment(I Think!).

BTW, my only concern with belts is if I can buckle mine---and see my toes without bending over.
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  #18  
Old 01-17-2012, 09:59 PM
mopar.dude.ps mopar.dude.ps is offline
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I would also recommend a HEI distrubator that I found off ebay for 54.00. It uses an external coil which gives you plenty of firewall clearance. I replaced my MSD ignition system with it. I couldn't be happier. It not only performs well but is easy to hook up. Well worth the money. I also went with the edelbrock performer RPM package. I am hoping to be pushing over 400 after I get the RPM heads and my headers.
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  #19  
Old 01-17-2012, 10:01 PM
mopar.dude.ps mopar.dude.ps is offline
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My question would be, would stroking it out to a 408 really make much difference? Would I have to use a different intake and heads?
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Old 01-17-2012, 11:04 PM
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Dude, that post was from 2006! lol
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Old 01-20-2012, 07:38 AM
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340_GTS 340_GTS is offline
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Quote:
Originally Posted by mopar.dude.ps View Post
My question would be, would stroking it out to a 408 really make much difference? Would I have to use a different intake and heads?
Well, 68 cu. in. is a whole bunch. Probably worth at least 60-80 horsepower over a smilarly built 340 cube motor. Of course it is "worth it", if you want a lot of horsepower!
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