what heads to use and why

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boilermaster

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what heads to use for a 408 street stroker.

if one HAD to use factory cylinder heads to be used on a 408 street stroker and cylinder head volume

did NOT have a role in determining compression ratio, what would be the best head to use.

1: 4v closed chamber  2.19int 1.71exh

2: early 4v open chamber 2.19 int 1.71 exh

3: late 4v open chamber (2.041 int. 1.65 exh

4: 2v open chamber

what choice do you think would flow the most and why ?

what choice do you think would deliver the most low end torque and why?

remember: cylinder head volume would NOT be considered in making compression ratio.

just doing a little fishing today

                                               Boilermaster

 
Here is a piece of info that may surprise you. If combustion chamber volume does not matter, I was really impressed with the later 4v open chamber heads on my first build. I think the smaller valves help with keeping up port velocity, and the smaller valves stabilize a little better. I would use the milodon mega flow valves, I think that's what they are called, they have a smaller stem in the port area to help increase flow. This combo gave me good torque without stroking the engine. Even with a 2.04 intake valve, it's still bigger than Chevy's famous 2.02 heads!!!!  But as always, the newer aluminum heads are probably still the best for street torque, I just love the old Iron stuff and think they are still amazing heads for their time!!

 
I would pick number 1, although better at higher rpms. Not on your list, a set of aussie closed chamber 2v heads for low end torque for a street application.

 
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Here is a piece of info that may surprise you. If combustion chamber volume does not matter, I was really impressed with the later 4v open chamber heads on my first build. I think the smaller valves help with keeping up port velocity, and the smaller valves stabilize a little better. I would use the milodon mega flow valves, I think that's what they are called, they have a smaller stem in the port area to help increase flow. This combo gave me good torque without stroking the engine. Even with a 2.04 intake valve, it's still bigger than Chevy's famous 2.02 heads!!!!  But as always, the newer aluminum heads are probably still the best for street torque, I just love the old Iron stuff and think they are still amazing heads for their time!!
I have been told that all other things being equal (compression ratio)

that the open chamber head outflows the closed chamber head because of valve shrouding.

As cubic inches are increased one will need increased cylinder head flow or power will fall off at a lower rpm.

would like to see a flow comparison of all the factory heads.

                                           Boilermaster

 
I would pick number 1, although better at higher rpms. Not on your list, a set of aussie closed chamber 2v heads for low end  torque for a street application.
rackerm,

you did not say why you would pick 4v cc.

So aussie small port, large valve over large port small valve (late open chamber )

Why ?

 
I would pick number 1, although better at higher rpms. Not on your list, a set of aussie closed chamber 2v heads for low end  torque for a street application.
rackerm,

you did not say why you would pick 4v cc.

So aussie small port, large valve over large port small valve (late open chamber )

Why ?
Boilermaster,

First I need to say I am a neophyte when it comes to this topic.  I love the closed chamber small 2v size ported Aussie heads and have them on my stock crank 351C 2v, along with an Edlebrock Performer and a 600 cfm 4300 A square bore carb.  From what I have read, closed chamber heads (2v Aussie or early 4v) with their smaller closed chambers are better quenching heads than their open chamber counter parts.

Given that you are building a 408 stroker, I am thinking the small valve, port and small chamber (56cc - 58cc) Aussie heads will not breath well enough to handle the swept volume required by your stroked motor especially at higher rpms. So I would opt for a set of early closed chamber 4v heads with their larger valves and free breathing ports. If it were not stroked or mildly stroked then the Aussie 302C 2v heads are my pick.

All that said, I have heard of Aussie 351C 4v closed chamber heads that have the same chamber and valve size as their early North American counter parts, but with slightly small ports. They may be another option, if you can find them.

Again, I am just a beginner so feel free to set me straight. I always appreciate expanding my knowledge by learning from the experts on the forum.

 
I would pick number 1, although better at higher rpms. Not on your list, a set of aussie closed chamber 2v heads for low end  torque for a street application.
rackerm,

you did not say why you would pick 4v cc.

So aussie small port, large valve over large port small valve (late open chamber )

Why ?
Boilermaster,

First I need to say I am a neophyte when it comes to this topic.  I love the closed chamber small 2v size ported Aussie heads and have them on my stock crank 351C 2v, along with an Edlebrock Performer and a 600 cfm 4300 A square bore carb.  From what I have read, closed chamber heads (2v Aussie or early 4v) with their smaller closed chambers are better quenching heads than their open chamber counter parts.

Given that you are building a 408 stroker, I am thinking the small valve, port and small chamber (56cc - 58cc) Aussie heads will not breath well enough to handle the swept volume required by your stroked motor especially at higher rpms. So I would opt for a set of early closed chamber 4v heads with their larger valves and free breathing ports. If it were not stroked or mildly stroked then the Aussie 302C 2v heads are my pick.

All that said, I have heard of Aussie 351C 4v closed chamber heads that have the same chamber and valve size as their early North American counter parts, but with slightly small ports. They may be another option, if you can find them.

Again, I am just a beginner so feel free to set me straight. I always appreciate expanding my knowledge by learning from the experts on the forum.

Racerm,

The aussie head with it's smaller ports , large valves and small combustion chamber does quite well and it would appear that you make a good point.

When we take a look at AFTERMARKET heads for the Cleveland, AFD and EDELBROCK use a 2.060'' intake valve with large ports and some have 72 cc chambers.

Did they learn this from the factory D3ZE heads ?

On the other hand some make great power with the 2v ports.

in the case of a Cleveland stroker for the street the increased displacement would effectively

lower the rev range required to make power.

So what is the difference if we choke off the incoming air at the port or the valve ?

this is why I am trying to find some flow data on the D3ZE heads.

much easier to increase the valve size of a small valve head than to reduce it on a large valve head.

Boilermaster
 
Closed chamber 4V, due to the flow and quench. You'll need the big valves to provide the air for that size of pump.

The increased torque will be more a product of stroke, which should be very noticeable, and cam selection.

I've started on mine, too, to stroke it and am sticking with the 4V CC heads. I have no lack of torque now, with them at 351 cubic inches, 280-ish cam, and 3.73 rear end.

 
Closed chamber 4V, due to the flow and quench. You'll need the big valves to provide the air for that size of pump.

The increased torque will be more a product of stroke, which should be very noticeable, and cam selection.

I've started on mine, too, to stroke it and am sticking with the 4V CC heads. I have no lack of torque now, with them at 351 cubic inches, 280-ish cam, and 3.73 rear end.

Don,

I respectfully have to disagree,

Did you do a compression calculation on a 408 C stroker ?

I come up with almost 12.2 static comp ratio with 63 cc heads zero deck height and .040''head gasket.

so if one were to use a combo like that, what would be your desired compression ratio ?

would not a dished piston defeat the quench ?

I have had two different, well respected stroker builders tell me that the open chambered heads will outflow closed chambered heads in a stroker (port size and valve size being the same)

they both state that the closed heads limit flow because of valve shrouding.

Boilermaster
 
Closed chamber 4V, due to the flow and quench. You'll need the big valves to provide the air for that size of pump.

The increased torque will be more a product of stroke, which should be very noticeable, and cam selection.

I've started on mine, too, to stroke it and am sticking with the 4V CC heads. I have no lack of torque now, with them at 351 cubic inches, 280-ish cam, and 3.73 rear end.

Don,

I respectfully have to disagree,

Did you do a compression calculation on a 408 C stroker ?

I come up with almost 12.2 static comp ratio with 63 cc heads zero deck height and .040''head gasket.

so if one were to use a combo like that, what would be your desired compression ratio ?

would not a dished piston defeat the quench ?

I have had two different, well respected stroker builders tell me that the open chambered heads will outflow closed chambered heads in a stroker (port size and valve size being the same)

they both state that the closed heads limit flow because of valve shrouding.

Boilermaster
Did a little research on the Aussie 351C 4v CC heads (not the Aussie 302C 2v heads) and the specs are 64-67cc, Valve size 2.19 Intake and 1.71 Exhaust, Port Size 2.02 x 1.65 Intake and 2.00 x 1.38 Exh. That tells me these heads have D1ZE Boss closed chamber and valve size, but with 2v size ports. Of all the choices here, to me that seems to be the best street combination. Where am I going wrong in my thinking here?

 
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would like to see a flow comparison of all the factory heads.

                                           Boilermaster
Hi

I googled that question as I remember SEEING this file before .  You may have found also BUT I FIGURE it is good to put with this thread for all  http://www.strokerengine.com/clevflo.html

Not sure where you are in MI , but you are welcome to stop by the museum in Brighton - can provide Cleveland stuff IF YOU need to build up BEFORE pulling your motor (and making your car undriveable - WHICH IT IS RIGHT NOW WITH THIS SNOW !   LOL

Mark

P.S.  I get back from the auctions in AZ in Feb and the next thing on the plate is Autorama.

 
would like to see a flow comparison of all the factory heads.

                                           Boilermaster
Hi

I googled that question as I remember SEEING this file before .  You may have found also BUT I FIGURE it is good to put with this thread for all  http://www.strokerengine.com/clevflo.html

Not sure where you are in MI , but you are welcome to stop by the museum in Brighton - can provide Cleveland stuff IF YOU need to build up BEFORE pulling your motor (and making your car undriveable - WHICH IT IS RIGHT NOW WITH THIS SNOW !   LOL

Mark

P.S.  I get back from the auctions in AZ in Feb and the next thing on the plate is Autorama.

SVO2SCJ,

You Sir absolutely rock.

exactly what I was looking for, please give me a few seconds to review the data.

thanks,  Boilermaster
 
Great information on that link.

Did someone figured out what information is in the lift column? The first line is the measured flow, but what are the other lines?

Sent from my SAMSUNG-SM-G930A using Tapatalk

 
been reading up some today and,

George Pence himself states that ( There is no power advantage in using quench chambers over open chambered heads, both chambers have the same thermal efficiency and both chambers are equally resistant to detonation.)

Mr. Pence goes on to say that low rpm turbulence improves torque a small degree @ lower rpm with the closed chamber as well as easier to reach ones desired compression ratio with flat top pistons with less machine work.

                    Boilermaster

 
None of the 2V port size, as cast, heads will support a high performance 408C. The intake port hits a wall at about .400 lift. Any of the 4V heads can be used to make good power with a 408C. There is some truth in valve shrouding discussion for the OC heads. However, some shrouding remains even in the OC heads. I prefer CC for two fundamental reasons, squish does matter at high rpm. Squish moves the mixture away from the cylinder wall into a smaller volume that is closer to the ignition source. This matters because, fundamentally, the speed of flame propagation is constant but the time available to complete the combustion decreases as RPM increases. So the smaller the volume, or distance, the flame has to travel the higher the probability of near complete combustion and resulting power. The second reason is financial. It is more likely that you can get most of your money back from the sale of CC heads than OC heads.

   The biggest factors as to which 4V head works better, it depends on the quality of the valve and the quality of the valve job. In other words find the right performance/racing machine shop. If you want to fight detonation don't leave the piston down the bore more than .010 at TDC and use the best gas you realistically can. I shoot for zero deck on all performance builds. Even on stock/budget rebuilds I'll hold deck to .015 or less. If it ends up out of the bore a few thousandths it is not a problem because you still have the head gasket thickness to prevent the piston from contacting the head and different compressed thickness gaskets are available.

   Good luck with the build.  Chuck

 
Interesting thread as I'm not far off getting heads sorted for my 406 stroker

I think it depends what you are after and your budget restraints not just the many different opinions of what works best

As I'm on a tight budget I'm sticking with my 302C Aussie heads with dished pistons and chambers opened up slightly for about 10.5:1 comp

Not building a high revving engine I will probably go with getting my heads done by an Aussie company who use the 302C heads successfully on their stroker engines for the 450-500 hp range which is my target

Great link posted on the flow rates of various heads but this one wasn't on it which has flow figures etc -

https://www.pavtek.com.au/index.php/ford-heads/340-clev-2v-cast-iron-competition-ported-cylinder-heads-192cc

If I was after something to gain more torque and HP I wouldn't hesitate with CHI 3V alloy heads as my personal favorite but factory 4V should work well although getting harder to find these days and by the time you rework them you may as well pay a bit extra for alloys

 
None of the 2V port size, as cast, heads will support a high performance 408C. The intake port hits a wall at about .400 lift. Any of the 4V heads can be used to make good power with a 408C. There is some truth in valve shrouding discussion for the OC heads. However, some shrouding remains even in the OC heads. I prefer CC for two fundamental reasons, squish does matter at high rpm. Squish moves the mixture away from the cylinder wall into a smaller volume that is closer to the ignition source. This matters because, fundamentally, the speed of flame propagation is constant but the time available to complete the combustion decreases as RPM increases. So the smaller the volume, or distance, the flame has to travel the higher the probability of near complete combustion and resulting power. The second reason is financial. It is more likely that you can get most of your money back from the sale of CC heads than OC heads.

   The biggest factors as to which 4V head works better, it depends on the quality of the valve and the quality of the valve job. In other words find the right performance/racing machine shop. If you want to fight detonation don't leave the piston down the bore more than .010 at TDC and use the best gas you realistically can. I shoot for zero deck on all performance builds. Even on stock/budget rebuilds I'll hold deck to .015 or less. If it ends up out of the bore a few thousandths it is not a problem because you still have the head gasket thickness to prevent the piston from contacting the head and different compressed thickness gaskets are available.

   Good luck with the build.  Chuck

C9ZX,

I understood quite well from the link that SVO2SCJ posted that the 2v port will not support the air flow requirements for a 408 C stroker, and that the 4v closed chamber iron head will.

In looking at what you like to see for deck clearance with a closed chambered head, that would tell me that one would have to use a reverse dome piston of around 14 cc to achieve a 10.5 /1  compression ratio with 4.030'' bore and a a .040'' head gasket ?

If I am correct in that assumption, does that size of a reverse dome still promote squish ?

and would that squish be better than an open chamber head with a smaller reverse dome ?

Still wanting to figure out if the D3ZE with the smaller valves would support a 408 C without extensive modifications.

Boilermaster
 
It would indeed require a reverse dome or dished piston. The shape of the dish plays a role in retaining some of the squish benefits. The Mahle piston dish resembles a bowl with curved sides and a flat bottom. The lip of the bowl is about .375 wide and pushes the mixture up and the curved sides pushes the mixture towards the center preserving some squish benefits. The part number is

930252430 . I couldn't find a picture, perhaps you can.Sory about the font size. It went to that after I pasted the part number.




My machine shop did a number of small valve 4V heads for dirt track cars with 2.08 intake valves and they made good power. I think the small valve 4V heads will support a 408C if properly prepared.  Chuck

 
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