340 Max HP Potential with X/J heads?

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moparodbuster

moparodbuster

moparodbuster
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Does anyone have experience stroking a .40 over 340 with a 4.00 forged crankshaft, scat rods, 585 lift cam, Victor 340 intake, 11:1 Diamonds, worked 950 Holley, etc using ported J heads? What would be the HP limitation by using these?
Only asking because I have the chance to save over $1k by buying a pair of stock J's instead of using Eddy RPM's.
Thanks in advance.
 
moparodbuster said:
Does anyone have experience stroking a .40 over 340 with a 4.00 forged crankshaft, scat rods, 585 lift cam, Victor 340 intake, 11:1 Diamonds, worked 950 Holley, etc using ported J heads? What would be the HP limitation by using these?
Only asking because I have the chance to save over $1k by buying a pair of stock J's instead of using Eddy RPM's.
Thanks in advance.
Click to expand...

I do well with mine.
410cid
.040
10.1
Cranks 185psi on the gauge
Solid roller, mild at .575 104/108
I'm good for over 500 hp, and i very much enjoy driving it. In fact I fended off a 585 hp Audi in the rich part of Encinitas the other day. You gotta love the torque curve of a 4" small block, like light switch 500+ right now till 5500 or so then horsepower till 6800 and done 'with my dual plane still on there' lol
I havent put the ported victor on yet, just the matched LD340 that only does a measly 282 cfm 'yank yank' LOL
 
moparodbuster said:
Does anyone have experience stroking a .40 over 340 with a 4.00 forged crankshaft, scat rods, 585 lift cam, Victor 340 intake, 11:1 Diamonds, worked 950 Holley, etc using ported J heads? What would be the HP limitation by using these?
Only asking because I have the chance to save over $1k by buying a pair of stock J's instead of using Eddy RPM's.
Thanks in advance.
Click to expand...
Justin ( onewildandcrazyguy ) said he could get over 270 cfm (intake) from these heads.
If the adage is 2 horsepower potential per 1 cfm, then you are looking at over 500hp psycho camshaft potential from your 340 if the right camguy/machinist/builder god blesses your build.
Best wishes bud!
Don't die driving!
 
MOPAROFFICIAL said:
I do well with mine.
410cid
.040
10.1
Cranks 185psi on the gauge
Solid roller, mild at .575 104/108
I'm good for over 500 hp, and i very much enjoy driving it. In fact I fended off a 585 hp Audi in the rich part of Encinitas the other day. You gotta love the torque curve of a 4" small block, like light switch 500+ right now till 5500 or so then horsepower till 6800 and done 'with my dual plane still on there' lol
I havent put the ported victor on yet, just the matched LD340 that only does a measly 282 cfm 'yank yank' LOL
Click to expand...
Ok, is that with cast heads? Factory or ported? X or J?
 
Unless you're building a truck motor or the budget won't allow it why would anyone use "stock" heads on a performance stroker build? It's kinda like talking about sex versus having it.
 
moparodbuster said:
Ok, is that with cast heads? Factory or ported? X or J?
Click to expand...
915 J
11/32 stem
+.100
2.02/1.60
Healthily ported...roofs raised, press in bronze guides, guide bosses reshaped, intake windows widened to.030 thin@ the pushrod holes..etc Hardened seats- intake and exhaust, chambers worked some and opened to the bore.
 
justinp61 said:
Unless you're building a truck motor or the budget won't allow it why would anyone use "stock" heads on a performance stroker build? It's kinda like talking about sex versus having it.
Click to expand...
You must be the "talk about it" type.
I do it... and I do it looking bone stock.
If you dont get it, if not interested... then move to another thread about aluminum heads.
 
moparodbuster said:
Does anyone have experience stroking a .40 over 340 with a 4.00 forged crankshaft, scat rods, 585 lift cam, Victor 340 intake, 11:1 Diamonds, worked 950 Holley, etc using ported J heads? What would be the HP limitation by using these?
Only asking because I have the chance to save over $1k by buying a pair of stock J's instead of using Eddy RPM's.
Thanks in advance.
Click to expand...

Stock or ported?
Layman’s math, cfm X2 for aggressive builds but not the maximum obtainable.
 
moparodbuster said:
Does anyone have experience stroking a .40 over 340 with a 4.00 forged crankshaft, scat rods, 585 lift cam, Victor 340 intake, 11:1 Diamonds, worked 950 Holley, etc using ported J heads? What would be the HP limitation by using these?
Only asking because I have the chance to save over $1k by buying a pair of stock J's instead of using Eddy RPM's.
Thanks in advance.
Click to expand...


It isnt hard or easy to make a set of j heads support 550 hp, just patience and the right cam. Its math, put $600 - $1000 into heads that cost next to nothing -build around them-
Or 1600 rpm heads , porting extra.

If cheap head flows the same as higher priced head.... you did good.
Save weight by going to a manual steer box, aluminum master cylinder, small alternator, aluminum radiator, chuck the clutch fan n go electric or light flex etc...
 
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greymouser7 said:
Justin ( onewildandcrazyguy ) said he could get over 270 cfm (intake) from these heads.
If the adage is 2 horsepower potential per 1 cfm, then you are looking at over 500hp psycho camshaft potential from your 340 if the right camguy/machinist/builder god blesses your build.
Best wishes bud!
Don't die driving!
Click to expand...

Who da hell is that guy and what does he know? LOL
 
MOPAROFFICIAL said:
You must be the "talk about it" type.
I do it... and I do it looking bone stock.
If you dont get it, if not interested... then move to another thread about aluminum heads.
Click to expand...

No, I'm the go fast type and dont care that my engine doesn't look stock. This engine is going to have a .575 lift cam, Victor intake, a Holley carb and most likely headers so it's not going to fool anyone into thinking it's stock. I could understand if it was a FAST type build.

My advice to the OP is to call some good head guys and pick their brains, they'll give him the pros and cons of both types heads.

Is this a street or race deal? If it's a street deal with iron heads and 11.0-1 what gas is the OP planning on running?

And I'll move along when I'm ready.
 
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Here's a dyno sheet from my 340/416 stroker with mildly-ported J heads and 10:1 compression, .547 lift cam. Don't have it in the car yet but I'm guessing it should be a pretty fun street car with 3.73 gears.

Dyno Pull # 10.jpg

IMG_20180722_161837657_HDR.jpg
 
MobileCustoms said:
Here's a dyno sheet from my 340/416 stroker with mildly-ported J heads and 10:1 compression, .547 lift cam. Don't have it in the car yet but I'm guessing it should be a pretty fun street car with 3.73 gears.

View attachment 1715239742
View attachment 1715239743
Click to expand...
That's awesome for "mildly ported J's"! What exactly was done to them, do you have the post-porting specs? Combustion chamber cc's, Intake valves, etc?
 
MOPAROFFICIAL said:
You must be the "talk about it" type.
I do it... and I do it looking bone stock.
If you dont get it, if not interested... then move to another thread about aluminum heads.
Click to expand...

Justin knows what he is doing, is a long time racer, his stuff runs excellent, and he is a very valued poster.
He is 100% correct. Putting a tiny iron head on a 4 inch arm motor is like wearing a life jacket in ankle deep water.
Even a well done eddie head is WAY to small to support a long armed 420 inch motor. I had such a motor and it was weezing at 1100-1200 foot mark.
For that matter, even a W2/5 head is marginal for a 420 inch motor. Even they were designed long before the advent of 4+ inch cranks. Been there done that too with a 422 W5 deal thats been 140 mph at 3200 on leafs.
Your barking way up the wrong tree here. Justin knows exactly what he is talking about and is 100% on the mark.
Can you do it. Yes. Is it a tractor. Absolutely
 
moparodbuster said:
That's awesome for "mildly ported J's"! What exactly was done to them, do you have the post-porting specs? Combustion chamber cc's, Intake valves, etc?
Click to expand...

I believe the chambers were 57cc. 2.02, Manley valves (intake), Racetec Dished Pistons, Molnar Crank & Rods, Erson Hydraulic Roller Cam (547 [email protected]) , Comp Solid Lifters and Comp Roller Rockers 1.5 ratio...
I don't think I have any good photos of the heads after they were finished.

Pistons.jpg
29257589_10211807111070147_8780757619191898471_n.jpg
29244365_10211807111230151_2169665949955062099_n.jpg
 
It's easy to see from my dyno sheet that my build would peter out in a 1/4 mile run with the heads I have, so that is something to keep in mind if you plan to race it at all vs strictly street driven. It might do pretty decent at an 1/8 mile track and I will probably do that, for fun. I will also probably upgrade to some better heads eventually... who doesn't want better head??? LOL
 
MobileCustoms said:
It's easy to see from my dyno sheet that my build would peter out in a 1/4 mile run with the heads I have, so that is something to keep in mind if you plan to race it at all vs strictly street driven. It might do pretty decent at an 1/8 mile track and I will probably do that, for fun. I will also probably upgrade to some better heads eventually... who doesn't want better head??? LOL
Click to expand...


Measure your Port volume next time. People don't realize you can just make that port a hell of a lot bigger and even flowing the same will RPM higher. One of the reasons why my production head 4 inch motor will RPM higher than others with production heads is because I got the port volume to 186cc.... that's in the neighborhood of W2's. I'm a nerd about having

To anyone using production iron on a 408-410 CID small block... just open them up. You can do this without touching the short turn if you havent the shaping skill. Raise the roof, knock the link down some, open the pinch, work the straight side wall, shorten the guide 'height and length... lightly blend that all to the bowl.
Part of the reason the rpm head flows more, is mostly due to it being a larger port...the turn is not a gem by any means. Think.
 
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B3422w5 said:
Justin knows what he is doing, is a long time racer, his stuff runs excellent, and he is a very valued poster.
He is 100% correct. Putting a tiny iron head on a 4 inch arm motor is like wearing a life jacket in ankle deep water.
Even a well done eddie head is WAY to small to support a long armed 420 inch motor. I had such a motor and it was weezing at 1100-1200 foot mark.
For that matter, even a W2/5 head is marginal for a 420 inch motor. Even they were designed long before the advent of 4+ inch cranks. Been there done that too with a 422 W5 deal thats been 140 mph at 3200 on leafs.
Your barking way up the wrong tree here. Justin knows exactly what he is talking about and is 100% on the mark.
Can you do it. Yes. Is it a tractor. Absolutely
Click to expand...
As someone once said, it’s hard to get enough head.. on a sbm stroker. This was stated for the smaller 4.00 arm and a 4.03 - 4.07 bore engine never mind the increased stroke to 4.15, 4.18 or 4.25. Upper W heads can get what you need when we’ll ported.

But tht is also a racing venue.

The W2-5 was out when the MP stroker cranks were in, but! They (MP) limited the stroke to 3.79 and told you to use a race block with a big bore for more cubes.
 
I will let you know how it turns out. I am accumulating parts for my winter time project. la318-->390 J head unported with a XE275HL HFT Cam SCR yet to be determined based on actual CC size but estimate with 70CC Chamber will be 10.6:1. As @justinp61 said tho... Just a street motor in a truck...
 
stumblinhorse said:
I will let you know how it turns out. I am accumulating parts for my winter time project. la318-->390 J head unported with a XE275HL HFT Cam SCR yet to be determined based on actual CC size but estimate with 70CC Chamber will be 10.6:1. As @justinp61 said tho... Just a street motor in a truck...
Click to expand...
I will be interested to follow your build. I wouldn't mind a 390 myself. I have a mid 80's roller cam block that would be a great start.
 
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