~450hp from stock stroke 340?

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PROSTOCKTOM said:
I am getting to the party late, but there is no way I would use Keith Black pistons. You can get a much higher quality off the shelf piston with ICON and they have a lot of SBM options.

Tom
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I didn’t recommend KB pistons I just grabbed the very first post in the 11.20 area to show how easy 450 horsepower is to make. Unported Edelbrock heads too that flow 255-260cfm compared to 300
 
PROSTOCKTOM said:
I am getting to the party late, but there is no way I would use Keith Black pistons. You can get a much higher quality off the shelf piston with ICON and they have a lot of SBM options.

Tom
Click to expand...

Sure, but for a naturally aspirated street car, 450 hp build you don't need to spend more money on forged pistons.

And, they have a fraction of the options for SBM as the KB's do.

Don't get me wrong, I fully understand that forged pistons are more durable and usually a higher quality. I'm just saying if you're building an NA street car and not a drag race machine you don't need them at the 450 hp power level. I've got KB's in my 340, like anything if you do the machining and set the ring gaps correctly for a hypereutectic piston they're fine in the right application.
 
Streetable 340 making 450 hp… meh… I suppose I will post my combo in my 340 Duster.

10.5:1 flat top pistons
284/484 purple cam (241 duration at .050) hydraulic flat tappet.
Rebuilt X cylinder heads
1.5 Harland sharp rockers
LD340 intake
Edelbrock 750
3200 stall FTI converter
727 transmission
3.91 sure grip

I found a very detailed dyno simulator calculator online that took into account cylinder head flow, multiple cam specs, and dynamic compression and found all those specs thru this forum and calculated inputs on the low end. Final result for my engine was 390 horsepower.

Do I believe that number, sure, I believe it’s at least 350 hp and not quite 400 hp. But also this is fairly streetable. 72blunblu has specs just ever so slightly higher than mine and daily drives his duster. I don’t quite daily drive mine but I drive it between 30 degrees and 90 degrees outside as I please wherever I want.

Things to think about, I have 12 inches of vacuum, which is the low end for decent power disc brakes but acceptable. On the highway I turn 3600 rpm, tolerable to me because it’s in the power band of the engine’s cam specs. It has plenty of power to have fun, but not so rowdy that it’s impossible to idle thru town at 15 to 25 mph. Requires 93 octane pump gas to not detonate on shut down. Fuel mileage is 12 mpg out of the secondaries, 6 mph in the secondaries. And uphill gravel road is its enemy without proper planning to commit to a little momentum to not spin out trying to idle it up the gravel road.

While I agree 450 hp from a 340 is not impossible with todays cam grinds, cylinder head options, etc, I think it will put the car out of daily driver contention by requiring a little extra warm up time to get out of the grouchy cold engine mode and to remember to commit to throttle inputs etc when navigating stop and go traffic. Based on 72blunblu’s response I believe if not for the extra OD gears of the aftermarket transmission he fitted it would be a lot less enjoyable to daily. I don’t even daily mine and have thought about OD transmission options… but not worth the hassle for me. I am in top gear by 35 mph, after that rpm is speed lol.
 
My engine has some much lighter custom race-tec pistons and K1 rods which are also lighter. You have to get the rotating weight down to make the power. My camshaft is similar. 9.8:1 CR and Edelbrocks with a valve job and IIRC some minor blending. When it was dyno'd it had a 750 Annular DP and the air gap but I have multiport EFI and an Edelbrock Super Victor now.

To some people it might be a bit rowdy for the street with the carb, the multi-port EFI made it pretty tame though it still lopes a little at idle. Can easily drive up a hill at 1400 rpm in 6th gear. I get ~15 mpg most of the time now.
 
Desoto291hemi said:
When you say stock bottom end ,,,,do you also mean compression ?
The 340 is one of the best engines ever,,,,,very strong from the factory .
But,,,it was still basically a warm stock factory engine .

Chrysler should have went to 11 to 1 compression or better .
And the heads needed a little bit better ports .
The X heads were very good in my opinion,,,,but why didn’t they step up to more advanced ports,,,,more in line with the W2 heads .

The 340 had a great foundation and many excellent parts .
Very good block ,,with excellent main caps .
Excellent forged steel crank .
Excellent forged rods with floating pins .
Double roller chain .

If they had the budget to do it ?

Added 11 to 1 pistons .
A nice Solid cam,,,range of .490” lift or more .
Solid adjustable valve train .
And a better flowing Aluminum intake .
With a nice sized Holley carb .

Chrysler had most of this stuff available,,,they even used a few better parts to beef it a little anyway .

However,,,,,the budgets were not that flexible back then,,,and they were primarily pushing the big blocks for power in those days .

The 340 could stand toe to toe with any other brand small block,,,,,and usually best them .
At least in factory form .

Tommy
Click to expand...
Don't forget about SBC LT 1
More than one Hp per cubic Inch
Just as stout or stouter
 
Wvbuzzmaster said:
Streetable 340 making 450 hp… meh… I suppose I will post my combo in my 340 Duster.

10.5:1 flat top pistons
284/484 purple cam (241 duration at .050) hydraulic flat tappet.
Rebuilt X cylinder heads
1.5 Harland sharp rockers
LD340 intake
Edelbrock 750
3200 stall FTI converter
727 transmission
3.91 sure grip

I found a very detailed dyno simulator calculator online that took into account cylinder head flow, multiple cam specs, and dynamic compression and found all those specs thru this forum and calculated inputs on the low end. Final result for my engine was 390 horsepower.

Do I believe that number, sure, I believe it’s at least 350 hp and not quite 400 hp. But also this is fairly streetable. 72blunblu has specs just ever so slightly higher than mine and daily drives his duster. I don’t quite daily drive mine but I drive it between 30 degrees and 90 degrees outside as I please wherever I want.

Things to think about, I have 12 inches of vacuum, which is the low end for decent power disc brakes but acceptable. On the highway I turn 3600 rpm, tolerable to me because it’s in the power band of the engine’s cam specs. It has plenty of power to have fun, but not so rowdy that it’s impossible to idle thru town at 15 to 25 mph. Requires 93 octane pump gas to not detonate on shut down. Fuel mileage is 12 mpg out of the secondaries, 6 mph in the secondaries. And uphill gravel road is its enemy without proper planning to commit to a little momentum to not spin out trying to idle it up the gravel road.

While I agree 450 hp from a 340 is not impossible with todays cam grinds, cylinder head options, etc, I think it will put the car out of daily driver contention by requiring a little extra warm up time to get out of the grouchy cold engine mode and to remember to commit to throttle inputs etc when navigating stop and go traffic. Based on 72blunblu’s response I believe if not for the extra OD gears of the aftermarket transmission he fitted it would be a lot less enjoyable to daily. I don’t even daily mine and have thought about OD transmission options… but not worth the hassle for me. I am in top gear by 35 mph, after that rpm is speed lol.
Click to expand...
What did you use for a head flow number? To the OP, I would not put a hydraulic roller in it. Solid, the maintenance is so overstated, check it once a year and you’re done. It’s like a physical for your engine. You choose a roller so you can snap the valve open to a useable lift quicker, but then saddle it with a lifter that will either pump up or more likely bleed down. Not a chance would I go hydr. Everything else is pretty serious performance orientated, then you tie your shoe laces together. I would suggest you search hydr roller lifter issues. I’m not saying you can’t get them to work, but you are going roller for a reason that is in direct conflict with a hydr lifter. Not to mention rollers REALLY don’t like bouncing when it does bleed down.
 
furrystump said:
What did you use for a head flow number? To the OP, I would not put a hydraulic roller in it. Solid, the maintenance is so overstated, check it once a year and you’re done. It’s like a physical for your engine. You choose a roller so you can snap the valve open to a useable lift quicker, but then saddle it with a lifter that will either pump up or more likely bleed down. Not a chance would I go hydr. Everything else is pretty serious performance orientated, then you tie your shoe laces together. I would suggest you search hydr roller lifter issues. I’m not saying you can’t get them to work, but you are going roller for a reason that is in direct conflict with a hydr lifter. Not to mention rollers REALLY don’t like bouncing when it does bleed down.
Click to expand...

Not sure who posted it or how long ago but a member on here posted flow numbers of various cylinder heads for various lift as he tested them on a flow meter and I used the flow number for X heads at around .400-.500 lift as I have .484 lift. It can be found with search function, that’s how I found it.

As for using hydraulic lifters in performance applications, it’s fine if you are running under .500 lift on single valve spring seat pressures. However, once you go double valve springs with those increased spring seat pressures I agree that you should use solid lifters. Also do expect more that 6000 RPM of performance out of said hydraulic lifters on single valve springs.

I had to redo top end of my 340 in car due to lifer issues, bent pushrods, and worn out factory rockers. I installed Crower hydraulic flat tappet lifters, Smith Brothers pushrods, and Harland Sharp adjustable roller rockers and shafts. I even mounted the brake booster on a 1” Hemi master cylinder offset bracket on the firewall to make it possible to easily remove driver side valve cover to check the adjustment, and reusable Moroso valve cover gaskets. Therefore if I were to do it again, I would go solid roller lifters and cam. But at the time I had additional car to rebuild to safe and reliable so throwing multiple grand at full engine rebuild didn’t make sense so I made a significant improvement and moved on.

Also the online calculator might say 390 hp but that is perfect conditions… and no shortcomings in the overall setup and tune, so I knock 30 hp off that for a more realistic number on my setup.
 
matt030305 said:
looking to get around 450 hp or possibly even more out of my stock stroke 340. This is mainly a street build so drivability is a must.
Click to expand...

This is the part that always get me with threads like this. You want 450 HP or more from a stoke stroke crankshaft, but it's street car, so drivability is a must.

That requires at least 1.32 HP per cubic inch, and while achieving that is possible, it's not going to have street manners. I suppose it's all relative to what you call street manners.

Build a 416" and you only need to make 1.08 HP per cubic inch.

Tom
 
I’m going to start this post out by saying myself personally I would never run a hydraulic roller cam. But some guys are doing so successfully and going fast doing so. My buddy’s son has an app 3200 pound duster and runs 6.60’s-6.70’s with his 408. He punishes this engine double entering and going lots of rounds winning lots of races. Not sure what his secret is but it can be done.
 
PROSTOCKTOM said:
This is the part that always get me with threads like this. You want 450 HP or more from a stoke stroke crankshaft, but it's street car, so drivability is a must.

That requires at least 1.32 HP per cubic inch, and while achieving that is possible, it's not going to have street manners. I suppose it's all relative to what you call street manners.

Build a 416" and you only need to make 1.08 HP per cubic inch.

Tom
Click to expand...


Exactly. The 500 HP 327 chevy from 1980 is still the king, even though a 500 HP anything back then was impressive. And very few of those were even 400 HP.

I can do 450 on 340 inches. In fact, I'm probably going to go over 500. And that's with some shitty parts.

Most guys wouldn't want to drive it because they will already have in their mind its too radical to be drivable.

@lead69 I think ran my engine through one of his engine programs and it was 540 HP or something.

I doubt it will get there. 500 is more than I originally started out shooting for. I want a nice, clean 11.60 car. At this point I probably overshot that ET by a little.
 
Gonna be tough to make 450 hp n/a without more compression ratio. I have an about 450 hp 340+.030, but I wouldn't call it streetable. Never dynoed, but the various calculators put it at somewhere between 430-465 hp. 12.2:1 forged pistons, .585/275°@.050 solid cam, 1.5 rockers, decently ported T/A heads w/ port matched single plane intake, highly modified 750 Holley DP carb, 1-7/8" headers, side kickout Moroso pan and crank scraper. Ran 11.0's at 120 in a '70 'Cuda. I built this in the early '80s, so better technology may make a bit more power, but CR is king.
 
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TheRacerDave said:
Gonna be tough to make 450 hp n/a without more compression ratio. I have an about 450 hp 340+.030, but I wouldn't call it streetable. Never dynoed, but the various calculators put it at somewhere between 430-465 hp. 12.2:1 forged pistons, .585/275°@.050 solid cam, 1.5 rockers, decently ported T/A heads w/ port matched single plane intake, highly modified 750 Holley DP carb, 1-7/8" headers, side kickout Moroso pan and crank scraper. Ran 11.0's at 120 in a '70 'Cuda. I built this in the 'early '80s, so better technology may make a bit more power, but CR is king.
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If that’s the case then that’s about where I’ll end up. Not 500. My build is pretty close to that.

BTW, do you remember the car weight and the elevation you ran at?
 
You can build hp with various ratios of basically duration to head flow, look at LS engines they build 450 hp with 218° cams, say OP hits his goal with his 230° cam as long he has decent gears and stall to go along with it shouldn't be fine.
 
TheRacerDave said:
but CR is king.
Click to expand...
No doubt higher CR is better but ultimately air flow is king, if your engine is less efficient just run more air through it, Air flow (fuel) basically equals hp effected by a somewhat narrow range of efficiency and of course air flow along with higher cr (efficiency) is even better.
 
340, 10ish :1, cleaned up eddies 270cfm, XS282 comp, victor, 750DP, tti's 450ish hp

Car ran 116-117 in garbage air and poor tune in Las Vegas at about 3200#

Biggest difference is the cam, XS is light on lift, more duration at .050 than the OP's cam plus solid vs HR.
 
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Newbomb Turk said:
Exactly. The 500 HP 327 chevy from 1980 is still the king, even though a 500 HP anything back then was impressive. And very few of those were even 400 HP.

I can do 450 on 340 inches. In fact, I'm probably going to go over 500. And that's with some shitty parts.

Most guys wouldn't want to drive it because they will already have in their mind its too radical to be drivable.

@lead69 I think ran my engine through one of his engine programs and it was 540 HP or something.

I doubt it will get there. 500 is more than I originally started out shooting for. I want a nice, clean 11.60 car. At this point I probably overshot that ET by a little.
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Don't forget you have a ported tunnel ram, two 750s and a dyno to tune it. If you only make 450 then you quit the pull early lol.
 
To the op I would set the compression around 10.5 and put a solid flat tappet cam in (something close to these two) and run it.

HUG STL4246AS-8
SB SLD FLAT TAPPET CAM 242/246 -108ºLSA

HUG STL4650AS-8
SB SLD FLAT TAPPET CAM 246/250 -108ºLSA
Even if it falls 15-20 short of your goal it won't matter on the street and you can always tune/tweak which you will need to do anyway, it would flat rip.
 
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