Cylinder Head Math

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Author Topic: Cylinder Head Math  (Read 1394 times)

Offline shaunp

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Re: Cylinder Head Math
« Reply #25 on: October 04, 2019, 07:15:07 AM »
A 427 will always have bottom end an mid range in Mustang  I reckon !

Offline barnett468

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Re: Cylinder Head Math
« Reply #26 on: October 04, 2019, 08:16:10 AM »
A 427 will always have bottom end an mid range in Mustang  I reckon !

I always wanted a 427 cougar. Saw s few for sale over the years snd just bsrely missed a deal on one sround 20 years ago. They are way to pricey now.

Offline shaunp

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Re: Cylinder Head Math
« Reply #27 on: October 04, 2019, 08:26:02 AM »
These big Dart Windsors are the way to go, if you want big numbers  you can build them up 450 cube, slap some Australian made CNC ported CHI 3V clevo heads on them and make 700+ hp on pump fuel. Run bottom 10's in an Aussie falcon or mustang and drive it to work on Monday with the AC on, fuel bill aside  :grin:

Offline barnett468

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Re: Cylinder Head Math
« Reply #28 on: October 04, 2019, 09:24:33 AM »
These big Dart Windsors are the way to go, if you want big numbers  you can build them up 450 cube, slap some Australian made CNC ported CHI 3V clevo heads on them and make 700+ hp on pump fuel. Run bottom 10's in an Aussie falcon or mustang and drive it to work on Monday with the AC on, fuel bill aside  :grin:

Your mileage may vary...  :lmao:

Offline barnett468

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Re: Cylinder Head Math
« Reply #29 on: October 04, 2019, 11:31:02 AM »
These big Dart Windsors are the way to go, if you want big numbers  you can build them up 450 cube...

The op started at a 408 and we're up to a 450 already.  :thumb:

Offline shaunp

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Re: Cylinder Head Math
« Reply #30 on: October 04, 2019, 01:21:33 PM »
and 700 hp

Online Dwayne

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Re: Cylinder Head Math
« Reply #31 on: October 04, 2019, 01:28:06 PM »
The op started at a 408 and we're up to a 450 already.  :thumb:

Only the 2nd page, lots more to go yet.

Offline barnett468

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Re: Cylinder Head Math
« Reply #32 on: October 04, 2019, 11:49:40 PM »
Only the 2nd page, lots more to go yet.

 :lmao:

Offline Macbain

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Re: Cylinder Head Math
« Reply #33 on: October 06, 2019, 08:52:37 PM »
Thanks for the informative replies gents, much appreciated.

I will stick with a Dart block, although it may be overkill, I like the advancements in tech and reassurance of a newly manufactured part.
The 4.125 bore did tickle my fancy for a while, as 427 is easily achievable. However I'm going to get the 4.030 bore, buying me more rebuilds in the future.

Reference the cylinder heads, please bare with me as I ask a few why questions.
Below is a brief summary of some heads at 0.600 lift, purely for comparison.

Assuming 408W has 708 cfm theoretical max VE.

Edelbrock E-CNC - 584 cfm (total) = 82% VE
AFR 195 - 616 cfm (total) = 87% VE
AFR 205 - 630 cfm (total) = 88% VE

Based on the AFR 205 heads recommendation, is the 'tipping point' for heads in the high 80's percentage volumetric efficiency wise?

If I were to use AFR 205 heads, but 'restrict' them with an Edelbrock Air Gap dual plane (for drivability), I could always easily swap in a Victor/Victor Jnr. later over a weekend, and compare drivability/bottom end. This was an interesting read: https://www.streetmusclemag.com/tech-stories/stroked-and-choked-inches-and-intakes/

I realise engine building is not all math, and experience coupled with trial/error are also large factors, but given I'm in no rush to build, I would like to explore the reasoning behind component choices.

Thanks again,

Steve


Offline GLENN 70

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Re: Cylinder Head Math
« Reply #34 on: October 06, 2019, 11:06:43 PM »
On a healthy 408 I would be going 205 heads and still the air gap intake for a street cruiser . For the top end power the victor intake .  195 heads and air gap work well but your limited if you want more go with those heads later .  Rodney's car that Shaun was talking about is a weapon really for what it is ,11.7 @117 mph . Does fall over at 6,150 rpm max  with that set up , been in it plenty of times and can feel it every time at just over the 6,000 rpm . Small heads for a 408 and just an edelbrock RPM intake . Pulls like a train but rev limited for sure .  Even the air gap with an open 1 inch spacer might work ok , still low end torque but a bit more top end .  PS if you can't get the power to the ground it's a waist of time anyway .  My 2017 goes nowear as it just frys the tyres anything under 80 /90 kph .
« Last Edit: October 06, 2019, 11:11:29 PM by GLENN 70 »

Offline barnett468

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Re: Cylinder Head Math
« Reply #35 on: October 07, 2019, 02:06:22 AM »
Thanks for the informative replies gents, much appreciated.

I will stick with a Dart block, although it may be overkill, I like the advancements in tech and reassurance of a newly manufactured part.
The 4.125 bore did tickle my fancy for a while, as 427 is easily achievable. However I'm going to get the 4.030 bore, buying me more rebuilds in the future.

Reference the cylinder heads, please bare with me as I ask a few why questions.
Below is a brief summary of some heads at 0.600 lift, purely for comparison.

Assuming 408W has 708 cfm theoretical max VE.

Edelbrock E-CNC - 584 cfm (total) = 82% VE
AFR 195 - 616 cfm (total) = 87% VE
AFR 205 - 630 cfm (total) = 88% VE

Based on the AFR 205 heads recommendation, is the 'tipping point' for heads in the high 80's percentage volumetric efficiency wise?

If I were to use AFR 205 heads, but 'restrict' them with an Edelbrock Air Gap dual plane (for drivability), I could always easily swap in a Victor/Victor Jnr. later over a weekend, and compare drivability/bottom end. This was an interesting read: https://www.streetmusclemag.com/tech-stories/stroked-and-choked-inches-and-intakes/

I realise engine building is not all math, and experience coupled with trial/error are also large factors, but given I'm in no rush to build, I would like to explore the reasoning behind component choices.

Thanks again,

Steve

Your approach is very logical and well thought out, but unfortunately some of it is a little hampered by the available info etc.


FLOW NUMBERS

Flow numbers are most useful when comparing numbers between the same mfg and/or where the numbers come from the same source. You can have a head flowed by 3 different shops and come up with 3 different numbers. Same thing with dyno testing an engine.

In addition to actual flow, the air speed is very important, an engine with high flow but low air speed will run like crap in the low and mid range compared to an engine with less flow and higher air speed. The 69 vs the 70 boss 302 engines are one mild example of this.

Also, it's important to compare flow numbers at .200 lift as well, and not just the "alleged" max flow numbers.


VOLUMETRIC EFFICIENCY.

Increasing compression increases volumetric efficiency but it may not tell you this in your book.


CYLINDER BORE SIZE

You will likely never have to rebuild this engine because it should easily go a minimum of 50,000 miles with your type of use, and the 4.125 block can be bored to 4.165, and the bore can be increased in size by as little as .005" each time you bore it if you use custom pistons, so you could theoretically bore a 4.125 block EIGHT MORE TIMES,  :thumb: therefore, in this case you are really worrying about a problem that doesn't exist....unless you live to be around 874 years old.  :lmao: 


VALVE SHROUDING

The bigger the bore, the farther away the edges of the valves will be from the cylinder walls. This increased distance will increase flow some because it won't be as obstructed by the cylinder wall.


AIR GAP VS VICTOR INTAKE & INTAKE PORTING

The air gap intake is arguably the best intake ever made for the majority of street builds, but it is not ideal for big displacement engines that are making even moderate power if they rev very far, so unfortunately one size does not fit all. This is not to say that the air gap is a horrible choice for your build, and it will work great...up to a point.

You can put an open plenum intake on a nearly box stock 302 engine and it will drive perfectly if it does not have a huge cam. I know this because I have had several. This is not ideal either but the point is that it won't run like crap at low rpm just because it is an open plenum.

If you build a 427 and use the moderate cam I posted and a victor open plenum intake, it will pull like a freight train right off idle with no low end "drivability" issues whatsoever, and it will rev to at least 6000 rpm, at which point most average (non racer) people would be very afraid.

All this being said, it is obviously not a huge cost or huge amount of labor to buy and change just the intake, so I would say that if you want to try an air gap to start with, because it definitely isn't a "mistake" per se, plus, if a victor intake would cause hood clearance issues, you could just get the air gap ported if you need clearance.

The 289/302 version of the air gap is different than the 351 version and the 351 version benefits more from proper porting than the 289/302 version does and a properly ported 351 version will flow just as much as a non ported victor senior. You can also think of a ported intake as cnc machined heads. They are not perfect s cast, and can benefit from cleaning up the flaws etc.

Chevy intake comparisons from Dr J.

    RPM Air-Gap    Victor Jr.    Super Victor
     Cast Ported Cast Ported Cast   Ported
Runner
1    214    288    241    295    300    345
2    224    308    243    302    293    351
3    221    312    241    286    276    341
4    208    282    243    301    271    357
5    218    304    250    305    277    352
6    213    288    230    287    277    341
7    210    286    246    300    290    355
8    220    306    235    299    295    346


INTAKE SPACERS

As glenn mentioned, they can definitely increase power, and can do this on many intakes, but there are a few different designs to choose from.


MILLING THE CENTER DIVIDER IN AN INTAKE

Milling the center divider down around 20 mm or more in a dual plenum intake can sometimes improve overall performance, but this is another topic, and results can vary for each particular  build, but this info may not be in your book either.


This is a stock 396 hp block. The valve relief is factory.



.



« Last Edit: October 07, 2019, 04:42:35 PM by barnett468 »

Offline GLENN 70

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Re: Cylinder Head Math
« Reply #36 on: October 07, 2019, 10:35:32 AM »
With all this don't forget about hood clearance .

Offline barnett468

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Re: Cylinder Head Math
« Reply #37 on: October 07, 2019, 11:56:33 AM »
With all this don't forget about hood clearance .

Hood clearance is not a problem.  :lmao:


Offline GLENN 70

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Re: Cylinder Head Math
« Reply #38 on: October 07, 2019, 12:10:07 PM »
I have seen on some tests when using the victor Jr. Intake they then have to fit a 1 inch four hole spacer on top to get some of the torque back . Then yes you will need to cut a hole in the hood .

Offline barnett468

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Re: Cylinder Head Math
« Reply #39 on: October 07, 2019, 01:11:04 PM »
I have seen on some tests when using the victor Jr. Intake they then have to fit a 1 inch four hole spacer on top to get some of the torque back . Then yes you will need to cut a hole in the hood .

A spacer helps on a lot of intakes, but I was suggesting a victor senior, and just failed to specify that, so a spacer would be less important on that intake for his app.
« Last Edit: October 07, 2019, 01:14:51 PM by barnett468 »

Offline barnett468

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Re: Cylinder Head Math
« Reply #40 on: October 07, 2019, 01:22:31 PM »
ok, how about a 434 with a ported air gap intake. done, ship it.

Offline Macbain

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Re: Cylinder Head Math
« Reply #41 on: October 07, 2019, 09:47:52 PM »
This thread shows how much useful information is out there, you just need to ask. What a great forum. Thanks a bunch Barnett468.

The argument for the 4.125 block is strong with that much rebuild-ability, if even needed. Why not go 427?

Reference intakes, I had not even thought about porting. A ported Air-Gap is best of both worlds. Dual plane, but can get a decent flow up top. 

So my latest parts list has the Dart 4.125 bore, AFR 205 heads and the Edelbrock Performer Air-Gap (ported).

Good video here:

https://www.youtube.com/watch?time_continue=587&v=i2DvnoHWagk

I have a standard length '67 Shelby style hood in a box. A little Googling leads me to believe this will all fit in my '68 FB. It may need a drop base air filter.   

Thank you again for the very detailed responses. I'll continue my research, particularly the cam mentioned.
« Last Edit: October 07, 2019, 10:04:59 PM by Macbain »

Offline barnett468

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Re: Cylinder Head Math
« Reply #42 on: October 08, 2019, 01:07:07 AM »
Xlnt choice on the 437 lol

no need to thank me  glenn and shaunp know just as much as i do and more,  i guarantee it, but i think they just don't like to type lol. Both of them have a ton of racing experience and shaunp has built some insane engines. Just ask him about his jaguar.

As far as the cam i posted goes,  it really is a superb cam, and in my.opinion it is a great choice for your intended use as i interpret it, but as shaunp mentioned, it is a little on the small side as far as duration goes, but ts really hard to guestimate exactly what someone wants just by reading their comments. Its much easier to take them for a ride in a car that has a built engine and see what they do and do not like about it. As car as cam science hoes  please don't even try to understand it because you will just get a headache. I know a moderate amount about cam science, which us just enough to make decent guesses on which cams.might be a good choice for certain apps, but i also learned from first hand experience and other engine builders, so i combine the two knowledge bases when picking a cam.

Shaunp has used way more different cams than probably anyone on this site, and he and glenn will have good suggestions. The main difference is usually that at least shaunp tends to like bigger cams than i do cuz he is a tyre burner  :grin:, and i am a little more sedate (old)  :lmao:.

Some things to research on cams if you want is gross lift, advertised duration, and lsa,  Another thing is duration at .200 lift. This measurement helps determine ramp angle or valve opening speed. In general (but not always) a can that has a faster valve opening will make a bit more power than a cam that opens a valve more slowly if all other aspects of the cam remain about the same. Howards cans often have more duration at .200 lift than most other cams including the voodoo series from lunati and the voodoo cams are probably the most popular cams and i have used many of them, its just that howards does not have a bazillion dollars for advertising like lunati does do many people  especially people outside the us have not heard of them, but many racers that are in the know here use howards cams. In short,  i for one think uou really need at leadt .600 lift gor your app and that even a little more would be better. I ust .600 lift on some 347 engines, and a 437 obviously has 100 more cubes. A cams leffective lift can be inncreased with higher ratio rocker arms. A 110 lsa is by far the most common for most any type of strert build  112 is the second most common but it makes for a slightle milder udle and a slighty sifter, wider, power band. Most production cars have at least 114 lsa and many have 116 so they idle smooth and will pass emission testing etc.
« Last Edit: October 08, 2019, 01:30:31 AM by barnett468 »

Offline barnett468

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Re: Cylinder Head Math
« Reply #43 on: October 08, 2019, 01:24:33 AM »
COMPRESSION

This will probably be one of the most difficult choices to make, and since you are not going to drag race this on a regular basis, and are mostly going to be cruising it, I would err on the side of caution and be a bit conservative. shaunp has more experience with this type of 427 than I do so I would make the compression whatever he suggests. The cam will also determine how much compression you need, but in general, the "bigger" the cam, the more static (uncorrected) compression an engine needs, because big cams lower the static compression.

My best guestimate for your app is that somewhere around 9.5 would be a reasonable bet.


PISTON MATERIAL

There are 2 main types of material that pistons are made out of. One is 2618 aluminum and the other is 4032 aluminum. It's a bit complicated to explain, but in short, I prefer 4032 aluminum for most non power adder applications because they can have less cylinder to piston clearance. The 2618 material is less brittle or more "flexible" than 4032 and therefore more resistant to shattering, but this is only a concern in apps where nitrous or a blower or supercharger etc is used.


PISTON DOME SHAPE

This is a science unto itself that I know very little about, but some think that using a dished piston with a small combustion chamber is better than using a piston with a flat top or raised dome and a large combustion chamber when the compression is the same on both. I don't have much input on this.



.
« Last Edit: October 08, 2019, 01:27:17 AM by barnett468 »

Offline barnett468

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Re: Cylinder Head Math
« Reply #44 on: October 08, 2019, 01:39:06 AM »
DART BLOCK PROBLEMS

You may or may not run into a couple minor issues with the dart block but they are easy to fix.

https://hotrodenginetech.com/a-735hp-438ci-small-block-ford-bullet/

1. "The Dart billet rear main cap pushed the Milodon oil pan too far back, so the cap was pulled and clearance ground on both sides near the main bolts. You can also see the tacky non-hardening sealer used to hold the RMS in place. It's messy, but it works."

FIPG sealer may also be able to be used to hold the rear seal in but shaunp will know.




2. "Dart blocks do not include a cam retainer plate or bolts. The oil galley plugs typically stick out too far for the plate to seat properly so you have two choices; tap the pipe threads deeper, or mill the plate's back-side to clear, as Petralia did."

« Last Edit: October 08, 2019, 01:52:59 AM by barnett468 »

Offline shaunp

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Re: Cylinder Head Math
« Reply #45 on: October 09, 2019, 09:32:10 AM »
Thanks for the informative replies gents, much appreciated.

I will stick with a Dart block, although it may be overkill, I like the advancements in tech and reassurance of a newly manufactured part.
The 4.125 bore did tickle my fancy for a while, as 427 is easily achievable. However I'm going to get the 4.030 bore, buying me more rebuilds in the future.

Reference the cylinder heads, please bare with me as I ask a few why questions.
Below is a brief summary of some heads at 0.600 lift, purely for comparison.

Assuming 408W has 708 cfm theoretical max VE.


Edelbrock E-CNC - 584 cfm (total) = 82% VE
AFR 195 - 616 cfm (total) = 87% VE
AFR 205 - 630 cfm (total) = 88% VE

Based on the AFR 205 heads recommendation, is the 'tipping point' for heads in the high 80's percentage volumetric efficiency wise?

If I were to use AFR 205 heads, but 'restrict' them with an Edelbrock Air Gap dual plane (for drivability), I could always easily swap in a Victor/Victor Jnr. later over a weekend, and compare drivability/bottom end. This was an interesting read: https://www.streetmusclemag.com/tech-stories/stroked-and-choked-inches-and-intakes/

I realise engine building is not all math, and experience coupled with trial/error are also large factors, but given I'm in no rush to build, I would like to explore the reasoning behind component choices.

Thanks again,

Steve

Steve even at 427 you have a min of another 080 to over bore which is twice what you have in a stock block.  You will never wear the first bore out with the build you are planing,  Just buy the 4.125 bore block and they just hone to size. You will never bore it again unless you have a catastrophic failure which you will never have with spec you are looking at. Guys bore these blocks to to 450 cube and make 600-700hp no worries. 

 

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