~450hp from stock stroke 340?

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matt030305

matt030305

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Hey all, I’m starting my 340 build and I’m 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.

Stock bottom end 72 340 (Keith black pistons), trick flow heads (Specs for them), 1.6 harland sharp roller rockers, Edelbrock air gap intake, 750 double pumper and hydraulic roller cam from Hughes (still undecided if I should go for this cam) cam card is under post.

I plan on putting in a TCI 3000-3500 stall converter in my 727TF and 3.91 posi. (High gear because I plan on swapping in a 5 speed to make it more fun to drive)

how does my setup sound for that goal? Am I overestimating or underestimating my potential power from this build? I would appreciate some feedback, thanks FABO!

IMG_7757.jpeg
 
I want to stick with a hydraulic roller to make it more streetable. From what I’ve read up on, people have made 440-470 hp with a hyd roller cam of similar specs.
 
Just throw a 150 shot on that combo your good
As stated more cam and carb to get there
Maybe 410 420 with that setup
 
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
 
Why is 450 the goal and how will you know if you meet it? Will the engine be dyno'd? Whether or not you get there is beside the point for me. It should be a kickass combo regardless.
 
The 380hp crate engine makes 400 hp with similar cam and stock magnum heads, don't sound like 450 hp with Trick Flow is that much of s stretch. What's the cr gonna be ?

Here's a 450 hp stock short block 5.9l with edelbrock heads and similar cam.

https://www.motortrend.com/articles/hrdp-0804-small-block-mopar-engine/
Test NotesBase:Production Mopar 5.9 Magnum long-block with passenger-car oil pan, MSD distributor, Mopar M1 Magnum dual-plane intake, 750 Speed Demon carb, 1-inch open carb spacer, 13/4-inch Hooker Super Comp Headers, LA-series engine timing cover

Modified:Add: Comp XFI hydraulic roller cam lobes 3016/3037, Comp pushrods Comp aluminum rockers, Edelbrock Performer RPM Heads, Mopar M1 single-plane intake

230/236-degree duration at 0.050 Comp custom grind on a 110-degree lobe separation, using Comp's XFI hydraulic roller lobes No. 3016 and No. 3037 on the intake and exhaust,

Dyno ResultsMopar Magnum 360SuperFlow 901 engine dynoSTP correction factorTested at Westech Performance Group

RPMBase TQMod TQBase HPMod HP
3,00039837.31228212
3,200410373250227
3,400419390271253
3,600424402290276
3,800420408304295
4,000412412314314
4,200396420316336
4,400381431319361
4,600362432317378
4,800346434317397
5,000328434312413
5,200298433295429
5,400274426282438
5,600-417-444
5,800-406-448
6,000-361-412
 
mopowers said:
Why is 450 the goal and how will you know if you meet it? Will the engine be dyno'd? Whether or not you get there is beside the point for me. It should be a kickass combo regardless.
Click to expand...
First time building an engine, will probably get it dynoed at some point. I’m using very basic preliminaries (my butt dyno). It will be a very dramatic change to what I have now.

Stock small valve J heads, ld340 intake, 670 street avenger, slightly bigger cam than stock.
 
273 said:
The 380hp crate engine makes 400 hp with similar cam and stock magnum heads, don't sound like 450 hp with Trick Flow is that much of s stretch. What's the cr gonna be ?

Here's a 450 hp stock short block 5.9l with edelbrock heads and similar cam.

https://www.motortrend.com/articles/hrdp-0804-small-block-mopar-engine/
Test NotesBase:Production Mopar 5.9 Magnum long-block with passenger-car oil pan, MSD distributor, Mopar M1 Magnum dual-plane intake, 750 Speed Demon carb, 1-inch open carb spacer, 13/4-inch Hooker Super Comp Headers, LA-series engine timing cover

Modified:Add: Comp XFI hydraulic roller cam lobes 3016/3037, Comp pushrods Comp aluminum rockers, Edelbrock Performer RPM Heads, Mopar M1 single-plane intake

230/236-degree duration at 0.050 Comp custom grind on a 110-degree lobe separation, using Comp's XFI hydraulic roller lobes No. 3016 and No. 3037 on the intake and exhaust,

Dyno ResultsMopar Magnum 360SuperFlow 901 engine dynoSTP correction factorTested at Westech Performance Group

RPMBase TQMod TQBase HPMod HP
3,00039837.31228212
3,200410373250227
3,400419390271253
3,600424402290276
3,800420408304295
4,000412412314314
4,200396420316336
4,400381431319361
4,600362432317378
4,800346434317397
5,000328434312413
5,200298433295429
5,400274426282438
5,600-417-444
5,800-406-448
6,000-361-412
Click to expand...

Yup, that’s why I think I will be able to get there with this combo. Definitely am thinking about getting bigger cam than what I initially suggested, I think 750 Holley (whether that be a DP or street demon) carb with a couple of adjustments should be able to handle whatever cam I plan to throw at it.
 
matt030305 said:
Yup, that’s why I think I will be able to get there with this combo. Definitely am thinking about getting bigger cam than what I initially suggested, I think 750 Holley (whether that be a DP or street demon) carb with a couple of adjustments should be able to handle whatever cam I plan to throw at it.
Click to expand...
Bigger cam definitely get you 450 + hp, the one you pick probably get you 450 hp maybe come up a little short especially if cr is a little wanting.
 
How big of a cam are you willing to tolerate in a street car? Everyone has a different threshold. In my opinion, drive-ability should come first for a street car. As such, I always err on the smaller side when it comes to a cam and I've never been disappointed. It's always a give and take.
 
Here go read this:

CamKing’s 355 boat motor cam

My 355" SBC boat engine
It's 10:1 with ported 492 heads, Performer RPM, and Holley 600.

RPM---TQ--BHP
3200--436--266
3400--443--287
3600--445--305
3800--444--321
4000--443--337
4200--440--352
4400--440--368
4600--441--386
4800--441--403
5000--432--411
5200--422--418
5400--412--423
5600--400--426

The cam is 216/220, on a 112 LSA, and 108 ICL

Its more than doable with that cam and carb in my opinion. Its only 1.32 HP per cube. Whether or not the OP has the ability to screw it together and make it work is another discussion all together.
 
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A friend of mine put ported Eddy magnum heads on a stock stroke 340. Compression is 10.8:1. Don’t remember the cam but it did 435 hp on the dyno.
 
The 340 in my Duster was built with the intent of it being between 430-450hp. I haven't had it on the dyno, just a street street car that I daily drive most of the year. Based on power/weight in other stuff I've driven and somewhat similar builds I've seen dyno'd I would wager it's probably more like 420 hp, but that's just a somewhat educated guess. Dyno's are kinda funny anyway, some are definitely more generous than others.

It's a '68 340 with .060" over KB hypereutectic pistons, 9.8:1 compression. Stock 340 rods, resized w/ ARP bolts, OE forged crank, .020"/.020". It has 308 heads, "stage II" ported, 2.02/1.60 valves, that flow 264cfm @.500" and have 65cc chambers. I run Crane ductile adjustable rockers, 1.5 with a Lunati 60404 flat tappet hydraulic cam/lifters/springs, lift .513"/.533", duration 234/242 @ .050" . Also has a Milodon road race pan and pickup, stock windage tray, new main bolts with windage provisions, mellings high volume oil pump w/ milodon pickup, Edelbrock AirGap RPM and a Holley 750 Ultra double pumper

Camcard
Lunati60404camcard.png


Flow bench test on the heads, intake side only
Screenshot 2024-09-20 at 4.48.34 PM.png


The part I would caution against is going nuts with the engine build to get to a number. If you're concerned about drivability for a street car I don't know that you'll want to do a whole lot more than what I've got, although that will depend on how you're using the car. For a fair weather weekend car only it's great, no issues. For a daily driver that gets stuck in traffic, has to operate in both freezing and 100°+ weather, and has a 60+ mile one way commute I can say it can be a bit much sometimes. Don't get me wrong, I love driving it which is why I drive it all the time. But the car/engine is definitely a lot happier being driven like I "stole it" than it is being lugged along in traffic. And it is not subtle when being driven like it wants to be, it definitely draws attention like that.

The 3.91 gears should be ok with a 5 speed, I know I ran an 833 behind mine for awhile with 3.55's and that was not enough gear for the cam but I was a bit limited because I was also doing freeway driving and needed to be able to maintain a good 75mph long term with how fast the freeways move around here. I run a T56 magnum now with 4.30's and that's a lot easier to start from a stop than the 3.55's were.

I would not suggest increasing the compression all that much from where I'm at, I pulled timing back to be at 34° all in mechanical (I still run vacuum advance too) because all I can get easily is 91 octane so with "summer gas" and high air temps (100°+) I was starting to get some detonation running around in the valley close to sea level. And if it's gonna be a street car you're not gonna want to be running race fuel or additives all the time.

One of these days I should dyno it so giving out my build info is more helpful, but it's more than enough fun for a street car and more than enough power to get you in trouble.
 
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matt030305 said:
I want to stick with a hydraulic roller to make it more streetable. From what I’ve read up on, people have made 440-470 hp with a hyd roller cam of similar specs.
Click to expand...
Maybe on the internet.
 
matt030305 said:
I want to stick with a hydraulic roller to make it more streetable. From what I’ve read up on, people have made 440-470 hp with a hyd roller cam of similar specs.
Click to expand...
I don't know what the hangup is with some of you fellers about mechanical camshafts. There's nothing "less streetable" about them. You're reading the dead wrong things and listening to the wrong people. It's your build though. Just remember, you asked for advice. I'm not as confident as some of these guys your combo will make the power you're looking for. I guess maybe bench racin it might. I just don't see it.
 
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