596 head performance mods

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Don't get me wrong undercut valves have there place and time. But by using a straight stem valves without the undercut is best in a mopar head. And it doesn't matter what the stem size is just make it a straight stem. Because if you have a 3/8 stem and it has a undercut then the undercut is 11/32, just as if it's a 11/32 stem the undercut is 5/16. But if you have both valves to look at you will notice that the radius or taper from the stem is greater on the straight stem verses the undercut style, this is what makes the difference.
Also too every fuel engine I've seen uses straight stem valves and most Pro Stock heads do too. Must be something to it or they wouldn't use them. I know someone will say well they have a blower to force the air by the valves, this is true but they don't spin the blowers very hard on a fuel engine. Something like 26 %. But the Pro Stock guys don't have blowers and they don't seem to be doing just to bad. But to this account they are using oxygenated fuels.
 
One guy says he can hear the difference 'sound wise on the bench', another says the difference is 5-6cfm, must be because the 340-360 heads have a deeper pocket=taller short turn then the chevro therfore more of the flow coming off the turn has to pass over the tapper/transition, which doesn't look like much but it is what it is.

I wondering if your removing a lot of material, drastically modifying the port, making a more straight shot if that still is an issue....
 
I dont think you need to worry about reaching 6500. Your heads will barely move enough to make power up there, and the cam is too small. I'd wager the engine will lose power like a turned off light switch over 5400.
 
moper said:
I dont think you need to worry about reaching 6500. Your heads will barely move enough to make power up there, and the cam is too small. I'd wager the engine will lose power like a turned off light switch over 5400.
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I'm not an expert by any means but I do know this is right on. Reason is no LA head, even a max ported head doesn't have near enough port volume to feed a 4" stroke engine up that high in the rpm band. At least that's my understanding of it.
 
I shift mine at 5350, probably 5500 when it actually shifts. 4" SB with 587 Iron heads.

Feels strong there but figure that I don't need to spin it anymore than that.

Tom
 
Stroker/cubic inch eats up cam duration like it's going out of style, so get a bigger cam like 288*+duration and .560 or so lift with like around 106-108cl

Heads not the limiting factor[completely that is]
 
TheCrusher said:
Stroker/cubic inch eats up cam duration like it's going out of style, so get a bigger cam like 288*+duration and .560 or so lift with like around 106-108cl

Heads not the limiting factor[completely that is]
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Since it looks like the heads are going to be the limiting factor, will these smaller heads choke the engine with that much cam?

I doubt these heads can handle that much lift in stock configuration.
 
I'm not sure why you feel you need to get additional lift by modifying teh valve arrangement. You can get beyond .650 at the valve without much fancy figuring. In stock port form, these heads will simply not move enough air. I am a fan of larger valves (Tom's heads have 2.05/1.65s 3/8 stem single pce stainless nail heads in them) and I'm not a fan of removing the guide boss or enlarging the bowl areas. Good porting will give great power and more importantly, also give efficiency. What will determine the capability of your heads are the overall job done, including the valve job, which is critical. You are adding a stroke longer than any factory big block. So you will need to feed it. If your heads don't flow huge at big lifts, you need to keep the valve open for a long time in the smaller lifts where they do flow. With a stock port, or one that has been mildly cleaned up but not much else, I would be looking for something in the .570 lift range and at least 260°@.050. That gives you lift at the valve of around .520 and good duration at .300-.450 lift, where the stock heads will flow. The stroke will eat up the duration, especially with a dual plane intake and smaller carb. Do you have power brakes?
 
Dave, Is this a case were a slower grind would work better ? In other words you want a cam with long duration at .580" lift instead of a short duration cam with .580"

Maybe something like the Mopar .590 solid which is around 275 @.050" ?
 
moper said:
I'm not sure why you feel you need to get additional lift by modifying teh valve arrangement. You can get beyond .650 at the valve without much fancy figuring. In stock port form, these heads will simply not move enough air. I am a fan of larger valves (Tom's heads have 2.05/1.65s 3/8 stem single pce stainless nail heads in them) and I'm not a fan of removing the guide boss or enlarging the bowl areas. Good porting will give great power and more importantly, also give efficiency. What will determine the capability of your heads are the overall job done, including the valve job, which is critical. You are adding a stroke longer than any factory big block. So you will need to feed it. If your heads don't flow huge at big lifts, you need to keep the valve open for a long time in the smaller lifts where they do flow. With a stock port, or one that has been mildly cleaned up but not much else, I would be looking for something in the .570 lift range and at least 260°@.050. That gives you lift at the valve of around .520 and good duration at .300-.450 lift, where the stock heads will flow. The stroke will eat up the duration, especially with a dual plane intake and smaller carb. Do you have power brakes?
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Yes I am running power brakes.

Also, with the stock rocker arrangement, will I be able to get that much lift?
Without using taller or wider springs, how can I still maintain good geometry and valve control?

I was planning on using a hydraulic roller.
 
Adam, yes, but I think the MP .590 is too much for a car with power brakes and iron heads. The compression needs to be up there to get the decent vacuum at idle, and iron has no quench or tumble, so it's not a good idea with iron and pump gas.

Mac, a hydraulic roller is a great compromise. Because you have power brakes, I'd drop down a little on the choice. something similar to this:

http://cranecams.com/?show=browsePa...-360 C.I.&partNumber=699631&partType=camshaft

Stock rocker arrangement can. Stock stamped steel rockers, I would think no. I'd suggest the sintered iron or stock 273 style. You'll need to get custom pushrods in any case because of the taller hydraulic roller. The aftermarket has a ton of springs that will work at the 1.65 stock installed height. They are a little wider diameter, but not by much. The reason we cut the spring seats and guides is to run the dual spring w/dampner springs. That Crane only uses 322lbs open springs. I think they are still doubles, and as such require the spring seats cut for the inner spring, and the guides trimmed for the positive type smaller teflon or viton valve seals.. But the factory height is fine.
 
Be carefull with those Crane Retrofit Hydraulic cams in a LA small block. The base circle was too big for me and exposed the lifter's oil groove at max lift. Another guy over on moparts had the same problem so it just wasn't my engine. I have a '71 340 block and he had a '73 340 block. You might be fine with the 360 block but look it over closely if you go that route.

The other guy I am talking about, he didn't check his during assembly and he had a lot of valve tapping and very poor oil pressure. And this was on a 416 that was running fine with a flat tappet; he only changed the cam.
 
Hey 340's, didn't you have a thread going on here about this?
And can you post up a link to the moparts thread?
 
fishy68 said:
I'm not an expert by any means but I do know this is right on. Reason is no LA head, even a max ported head doesn't have near enough port volume to feed a 4" stroke engine up that high in the rpm band. At least that's my understanding of it.
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Acurate or not, I don't know. Most of the reason in my eyes even before the head volume and flow comes into play is due to the 4 inch stroker making peak power almost allways before 6000 RPM's.

It's the long arm. Strokers make peak power alot lower in the RPM range than a stock stroke 340 (3.31) or the 360 (3.58) vs the 4.00 arm through.

Stroke differences;

____318/340
4.00 - 3.31 = .69

______360
4.00 - 3.58 = .42

360 vs 318/340
3.58 - 3.31 = .27

Just thinking out loud here today.
 
340, This is a block-to-block issue. If the tappet bores are spot faced as yours are, there may be issues. Whether they are hit or not is to me strictly luck of the draw, although i'd bet there is a certain factory/machining setup that did that. Also, that Crane was just an example for specs. I like Crane because they publish all the numbers that make a difference, so it's a good place to point things out.
Rumble, the power peak is entirely determined by cam profile and head. With enough port, the power peaks go right up. The problem is, even 270cfm (average ported Edelbrocks on a realistic bench) is barely enough to get peaks above 6K. So you really need some port to make the peaks higher. And remember by port, I mean everything from the carb baseplate to the back of the intake valve. I use percentages to show it.. A 4" crank is 21% longer than a 3.31. So it will need at least 21% more air, 21% more cam, 21% more carb, etc, to make power at the same peak rpm as the 340. The lower the increased percentage of air, the lower the rpm and level of the power peak, and the more drastic the drop off after peak power. In terms of cams, a 21% increase in duration at .050 from a streetable 220° is 266°. Very simple math really.
 
I gotcha there moper. Very good post. Now, from the view I was thinking of, all things being equal except stroke. Nothing more, nothing less. The talk on this subject could go on for a good bit.
 
Top fuelers are undersquare, more stroke than bore and they can rev.

I see where you're coming from Rob and what you say was true years ago before we had the heads and metallurgy that we have now and this is why:

Oversquare engines (larger bore than stroke)

Advantages:

1. More room for larger valves and less valve shrouding. This isn't the problem that it used to be as good, high flowing heads can be had for relatively low prices.
2. Lower piston speeds allow higher revs without stressing the rods. This has become less of a problem as high quality H beam rods have become readily availible.
3. A longer rod can be run reducing side loading, this has also been resolved with readily availible stroker pistons with a higher pin placement. This can cause problems though when the pin gets up into ring lands to compensate for really big strokes.
4. Less friction due to lower skirt loads and reduced piston speeds.
5. Less rotatating mass to get moving.

Disadvantages:

1. Larger bores for a given displacement can add to the tendency for an engine to detonate. The larger piston top area means that the flame front has to travel further to ignite the same volume of compressed air and fuel.
2. Larger bores have a greater tendency to distort under high pressure causing a loss of combustion pressure.
3. Less crank throw means less torque. The piston and rod have less leverage to turn the crank.

All of the above can be reversed in the case of strokers. I hope this sheds some light on the subject and many of the disadvantages of either can be compensated for in a myriad of ways. I may well have missed a few points and I'm sure we can find someone here who can add to this.
 
I have a 3.58 scat crank in my 72 340(372) with X heads,slight p and p with a xe284h cam.Max hp452 at 5700.shifting at 5500,idles fine and I,m happy with the build.Good info. here for my next 360 stroker.:read2:
 
ramcharger said:
Top fuelers are undersquare, more stroke than bore and they can rev.

I see where you're coming from Rob and what you say was true years ago before we had the heads and metallurgy that we have now and this is why:

Oversquare engines (larger bore than stroke)

Advantages:

1. More room for larger valves and less valve shrouding. This isn't the problem that it used to be as good, high flowing heads can be had for relatively low prices.
2. Lower piston speeds allow higher revs without stressing the rods. This has become less of a problem as high quality H beam rods have become readily availible.
3. A longer rod can be run reducing side loading, this has also been resolved with readily availible stroker pistons with a higher pin placement. This can cause problems though when the pin gets up into ring lands to compensate for really big strokes.
4. Less friction due to lower skirt loads and reduced piston speeds.
5. Less rotatating mass to get moving.

Disadvantages:

1. Larger bores for a given displacement can add to the tendency for an engine to detonate. The larger piston top area means that the flame front has to travel further to ignite the same volume of compressed air and fuel.
2. Larger bores have a greater tendency to distort under high pressure causing a loss of combustion pressure.
3. Less crank throw means less torque. The piston and rod have less leverage to turn the crank.

All of the above can be reversed in the case of strokers. I hope this sheds some light on the subject and many of the disadvantages of either can be compensated for in a myriad of ways. I may well have missed a few points and I'm sure we can find someone here who can add to this.
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Another advantage is greater volumetric efficiency. If your using a big power adder though it makes more sense to go undersquare so you can get the best of both worlds. Thats why top fuelers do it.
 
Thanks ramcharger. My train of thought was on the street guy level. Not a race car level or street car with expensive parts. I see where you and moper are coming from.

I figure if the average street guy takes a 340/360 block and adds a 4 inch arm. The route most people will go is cast crank and more likely Hyperu. pistons on aftermarket rods like Eagles or scats. What ever style there pocket allows. (H or I beam) There cam shaft, a general HP grind, example like a off the shelf Comp grind or Lubati. Matching valve train parts. Typical heders and intake carb combo.

While these typical builds are just damn dandy for the street or even light racing, there both, in general, the same as most typical builds of regular displacement engines. 340/360 non stroked.

The real limit on RPM on any engine is the cubis dollors of one wallet. Since 99% of us have a average street guy budget, parts and mods will limit the RPM we can get from any combo. Of course build perameters, IE; what we want out of the engine, will also limit what the engine does.

How many of us are willing to invest the time and dollors into a 4 inch stroker engine to rev to 7500 rpm? On a street machine.
On a comparo, 340, 360 and 408 engine, all built the same, (Generally speaking, lets not get silly here, just in general) with the same parts and cam, which on is reving higher and which one is makeing there peak HP earliest in the RPM band.

Whats the limit of these engines? Certainly no one will spin there 408 to 7500 with a cam, lets just say at a @.050 duration of 230.

A ported LA head can and will move enuff air for a lower RPM stroker. Now where this head peters out is cause for debate but science to show. To many permeters to have just one quick answer.

(This talk is getting interesting and fun. Maybe a new thread on this?)

OK, I'm shuttin up on this. I've went on enuff.
 
From what I have read if you plan to rev your 4" stroke small block about 5,000 RPM you should go with a forged piston due to the excessive piston speeds those engines have. The book How to Build Big Inch Small Block Mopars discusses this topic about piston speed and the need for forged.
 
Now that I'm "revved up" on coffee, lets continue this discussion, lol!

macdiesel said:
Another advantage is greater volumetric efficiency. If your using a big power adder though it makes more sense to go undersquare so you can get the best of both worlds. Thats why top fuelers do it.
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Well, the higher piston speed in a stroker equates to higher intake charge velocity which in turn can, when combined with the right head, port configuration and cam selection equals some great VE figures. IMHO, the only VE advantage that an oversquare engine has is room for big valves and ports.

I agree that forced induction does compensate for the lack of valve size availible in a smaller bore but we have now have some great heads to choose from in the Mopar world.

rumblefish360 said:
Thanks ramcharger. My train of thought was on the street guy level. Not a race car level or street car with expensive parts. I see where you and moper are coming from.

Yep, I'm delving into theory here. What can and could be done. It would not be neccessarily be cheap either.

I figure if the average street guy takes a 340/360 block and adds a 4 inch arm. The route most people will go is cast crank and more likely Hyperu. pistons on aftermarket rods like Eagles or scats. What ever style there pocket allows. (H or I beam) There cam shaft, a general HP grind, example like a off the shelf Comp grind or Lubati. Matching valve train parts. Typical heders and intake carb combo.

While these typical builds are just damn dandy for the street or even light racing, there both, in general, the same as most typical builds of regular displacement engines. 340/360 non stroked.

These builds are great for the street as they produce power right where we need it and then we don't have to use 5000 rpm stall converters and scream around the city at 6500 rpm, lol!

The real limit on RPM on any engine is the cubis dollors of one wallet. Since 99% of us have a average street guy budget, parts and mods will limit the RPM we can get from any combo. Of course build perameters, IE; what we want out of the engine, will also limit what the engine does.

Agreed 100%!

How many of us are willing to invest the time and dollors into a 4 inch stroker engine to rev to 7500 rpm? On a street machine.
On a comparo, 340, 360 and 408 engine, all built the same, (Generally speaking, lets not get silly here, just in general) with the same parts and cam, which on is reving higher and which one is makeing there peak HP earliest in the RPM band.

Given LA heads and any given cam, a 340/360 will definitely show a HP and torque peak higher in the rpm range, no doubt. Spinning a stroker with a cast crank and I-beams past 5500 would be ill advised IMHO. A 7500 rpm engine on the street would be a bear to drive and not much fun at all anyway regardless of cash outlay.

Whats the limit of these engines? Certainly no one will spin there 408 to 7500 with a cam, lets just say at a @.050 duration of 230.

With a duration of 230 I would think that 5400-5500 would be the upper limit, no point of revving it any higher.

A ported LA head can and will move enuff air for a lower RPM stroker. Now where this head peters out is cause for debate but science to show. To many permeters to have just one quick answer.

You just said the key word, "Low Rpm Stroker". Yes it will. It's all about the combo though. No point in adding a cam with 260 dur @ .050 with .650 lift if the heads stall at .500 lift. A person would then end up with a crappy idling engine with reduced torque where the heads would work and no where near the gain in the upper rpm range where it should come alive.

(This talk is getting interesting and fun. Maybe a new thread on this?)

OK, I'm shuttin up on this. I've went on enuff.
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