I'm looking to budget build my 340. It's out of my 71 Duster but is a 73 block. It has J heads. Looking to get close to 400 hp without having to throw a ton of many into it. Looking for help and suggestions what others built theirs like. Thanks
340 Build help please.
- Thread starter Nkaiser81
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Ironracer
Gearhead
Mine's probably right around there the heads have oversized valves, but they're hogged out. It's a virgin bore but they're 10 and a half to one Pistons. I used the 484 purple shaft cam, a holley strip Dom, (its ported and matched to heads)and a 750 vac, patriot headers, good Springs, locks, and retainers on the valves and head, a large capacity pan and HV oil pump, feeding fully grooved Mains, Here's the Clincher the heads I'd had laying around for a long time when I bought the rest of them parts it was around 2010 things have gone up so much by now it's crazy.... maybe you can find some stuff at a swap meet or something
If you can do some home port clean up on the heads and intake, that would pay big dividends.
What is your intended use for the car? Any particular goals other than 400hp?
Edit! My bad… piston recommendations below.
Thanks @mgoblue9798
340 pistons and 360 pistons aren’t the same!
But the pistons, in at a zero deck height, .038 X 4.1 head gasket, RPM AG intake, 750 cfm carb, 1-3/4 headers into a 2-1/2 exhaust pipe. A cam with a LSA of 108, 236*’s at 050 or slightly greater with home ported heads or Edelbrock heads. Add a 1.6 rocker if lift is under .520.
Thanks @mgoblue9798
340 pistons and 360 pistons aren’t the same!
But the pistons, in at a zero deck height, .038 X 4.1 head gasket, RPM AG intake, 750 cfm carb, 1-3/4 headers into a 2-1/2 exhaust pipe. A cam with a LSA of 108, 236*’s at 050 or slightly greater with home ported heads or Edelbrock heads. Add a 1.6 rocker if lift is under .520.
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Ironracer
Gearhead
Sounds like the Hot ticket!
I guess you missed the 340 part. Gonna need different pistons but all the rest of the combo would make for a fun ride.
OMG! I so sorry, dead on correct. My bad. Hold on…
The 340 (LMAO- sigh) should use the KB replacement 340 slugs.
These KB’s should do the trick;
KB KB243.030 Keith Black KB Performance Pistons | Summit Racing
Or these Speed Pro skirt coated forged units Speed Pro L-2316F 30 Speed-Pro Forged Pistons | Summit Racing
The 340 (LMAO- sigh) should use the KB replacement 340 slugs.
These KB’s should do the trick;
KB KB243.030 Keith Black KB Performance Pistons | Summit Racing
Or these Speed Pro skirt coated forged units Speed Pro L-2316F 30 Speed-Pro Forged Pistons | Summit Racing
Hp basically comes down to heads, a set of stock 1.88 J can get 400+ hp with enough cam and cr, probably way more than you want to run. So you either can build with stock heads and run cam, cr etc.. You'll be happy with and it makes what it makes probably 350-380 hp or modify or aftermarket heads that make 400 hp with desired level of cam, cr.
Build a stock 68-71 short block. Add some ported and checked out Speedmaster heads. Lunati's version of the 268 cam, Air gap intake, 750 DP and Dougs headers.
The words "budget build" and "400 hp" don't seem to go together.
Your ears must have still been ringing from the flow bench work.
Ironracer
Gearhead
Not in these times
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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OP; don't get mad at me, but since you haven't told us why you want 400hp yet, I'm assuming it's NOT to go racing, so that sorta leaves it being a streeter. OOPs I missed it post 9 says "driver"
If that's true then it seems like most guys are quoting the 400hp number, which in a 340 may not come until pushing 6000 rpm. But what they really want is a smoking hot bottom end starting right off idle, or at least by the stall-rpm. Midrange is gonna be similar no matter how hot the street engine gets to be.
Now not to belabor the point, but 6000 rpm with 3.23s and a regular Torqueflite is about 61 mph, if not spinning. But if you are running street tires, they will be spinning at WOT for the entire duration, if the engine is assembled and tuned right. In fact, even 350 or 300 will do that. Maybe even less. So why spend a boatload of cash to get a 400hp@6000 rpm engine, versus a 350 at 5500, or a 300 at 5000..... all of which can smoke street tires, on the street, given a street rear gear and a streetable Convertor.?
400 hp is asking for 3.73s minimum and a stall as high as 3600
350 is around 3.55s and 3200
300 is around 3.23s and 2800
250 is whatever is already in the car, saving you another boatload of cash.
Point being;
what makes 400hp the magic number for you? and
what rear gear/trans/convertor are you thinking if running.
If that's true then it seems like most guys are quoting the 400hp number, which in a 340 may not come until pushing 6000 rpm. But what they really want is a smoking hot bottom end starting right off idle, or at least by the stall-rpm. Midrange is gonna be similar no matter how hot the street engine gets to be.
Now not to belabor the point, but 6000 rpm with 3.23s and a regular Torqueflite is about 61 mph, if not spinning. But if you are running street tires, they will be spinning at WOT for the entire duration, if the engine is assembled and tuned right. In fact, even 350 or 300 will do that. Maybe even less. So why spend a boatload of cash to get a 400hp@6000 rpm engine, versus a 350 at 5500, or a 300 at 5000..... all of which can smoke street tires, on the street, given a street rear gear and a streetable Convertor.?
400 hp is asking for 3.73s minimum and a stall as high as 3600
350 is around 3.55s and 3200
300 is around 3.23s and 2800
250 is whatever is already in the car, saving you another boatload of cash.
Point being;
what makes 400hp the magic number for you? and
what rear gear/trans/convertor are you thinking if running.
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Come on now. That's like saying B cups aren't any fun anymore. Got to know a lot more about the rest of the package before being able to make that call.
150 hp shot of nitrous, cheapest hp out there
On my car I'm detuning it with a smaller cam and china air gap, Richard Holdener dyno similar combo made 350 hp, right now it's a 380 hp crate 5.9l dyno ones shown to make 400-410hp, but I'm looking more for a cruiser daily driver type car, engine as is, is soft under 2500 rpm and got to drive in 2nd under 40 mph in town driving. I'd rather lose the 50+hp on top that I'll rarely use anyway.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I saw your 800ftlbs-blew-it-up video. I see where yur coming from.
Since I've never tried it, I can't miss it, and I'm real happy with about half of that.
I have an EXCELLENT set of head/ear gear. Sound canceling tech with a dial control to cut down on noise or let more sound in.Your ears must have still been ringing from the flow bench work.
Depends on how much torque is available. ;)
TT5.9mag
Two atmospheres are better than one
Ok you’re so right about that. We have a 250hp Miata road course car and it’s a hoot to drive. I should have said 3000lb 400hp car.
TT5.9mag
Two atmospheres are better than one
Not my video, but my daily driver does make 705hp to the tires and even that gets boring after a while. The answer is always more boost.
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