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Old 02-28-2011, 11:06 PM
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Heads for a 400 sbc

okay guys! home stretch... Ive almost got my build done for a 400sbc thats going to be dropped in my 86 el camino, the bottom end is built and i have all the necessary bolt ons

all thats left is the heads, below i have the 3 heads i THINK are the heads i should be looking into(first ill tell you what im doing with the car!)

-This is a street strip car, mainly street. I plan on supercharging it next winter(under 10psi, probably around 6psi)

http://www.summitracing.com/parts/RHS-12052-01/

http://www.summitracing.com/parts/PAR-2169/

http://www.summitracing.com/parts/EDL-5089/


Im having such a tough time deciding on what heads to go with because ive never had a forced induction engine before, and i can find very little as to how to build your system(at least pertaining to heads) around forced induction... if you guys dont recommend any of these heads i would appreciate input on what to look for, for heads i would need


-thanks in advance!

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Old 02-28-2011, 11:20 PM
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All three of those heads are rather small for a 400 cube engine, I'd be looking at 200-215cc intake runners, even 220+ if you really want big power.

Forced inductionreally doesn't require anything different, except with some Turbo builds using a bigger exhaust port than Roots or Centrifugal supercharging or Naturally Aspirated. Supercharging really covers up any ills that too large a intake port head has on a Naturally Aspirated engine.

All three heads you linked have 64cc combustion chambers(small), are you going to be able to get the compression ratio correct for forced induction with them?? What piston do you have?? Forced induction will want no more than 8.5-1 compression in most cases.
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Old 02-28-2011, 11:48 PM
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nature of the beast

Quote:
Originally Posted by djohnson308
okay guys! home stretch... Ive almost got my build done for a 400sbc thats going to be dropped in my 86 el camino, the bottom end is built and i have all the necessary bolt ons

all thats left is the heads, below i have the 3 heads i THINK are the heads i should be looking into(first ill tell you what im doing with the car!)

-This is a street strip car, mainly street. I plan on supercharging it next winter(under 10psi, probably around 6psi)

http://www.summitracing.com/parts/RHS-12052-01/

http://www.summitracing.com/parts/PAR-2169/

http://www.summitracing.com/parts/EDL-5089/


Im having such a tough time deciding on what heads to go with because ive never had a forced induction engine before, and i can find very little as to how to build your system(at least pertaining to heads) around forced induction... if you guys dont recommend any of these heads i would appreciate input on what to look for, for heads i would need


-thanks in advance!
first a 400 small block is all by its self its a 2 year or so made engine & was mass produced carried into 74 it is internally & xternally balanced its heads call a siamees bore there are no collant passages between the cylinders plus there are small steam holes close to the center of the cylinders, do you understand volumetric efficiency a stock engine has low efficiency about 6.5 to 7.5 some raceing engines reach between 8 & 9 wich is still atmospheric pressure rushing in now with a turbo & or a blower it surpasses this to a point it forceses air fule mixture into intake making this inducted meaning depending on for most part lbs of boost the blower is set up to run its volumetric efficiency passes 1.000 to an induced state instead of a draw state with this factor in mind the valve spring pressure must be steped up to accomodate the boost pressure usually between 6 & 11 lbs of boost on a blower & then that depends on if its a 471, 671, or a 871 blower application do not run timing chain in this application gears only for longevity & then tell the manufacturer the intended use of their timing gears you need the best here did not mean to make input so big contact me if you want.
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Old 03-01-2011, 12:02 AM
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Quote:
Originally Posted by liquid launcher
first a 400 small block is all by its self its a 2 year or so made engine & was mass produced carried into 74 it is internally & xternally balanced its heads call a siamees bore there are no collant passages between the cylinders plus there are small steam holes close to the center of the cylinders, do you understand volumetric efficiency a stock engine has low efficiency about 6.5 to 7.5 some raceing engines reach between 8 & 9 wich is still atmospheric pressure rushing in now with a turbo & or a blower it surpasses this to a point it forceses air fule mixture into intake making this inducted meaning depending on for most part lbs of boost the blower is set up to run its volumetric efficiency passes 1.000 to an induced state instead of a draw state with this factor in mind the valve spring pressure must be steped up to accomodate the boost pressure usually between 6 & 11 lbs of boost on a blower & then that depends on if its a 471, 671, or a 871 blower application do not run timing chain in this application gears only for longevity & then tell the manufacturer the intended use of their timing gears you need the best here did not mean to make input so big contact me if you want.
just to add 64 cc chamber heads are small for cc when dealing with a blower usually a person calculates compression ratio & with a blower its usually 9 to one pistons a 74 cc chamber head due to the fact that you just may blow it up high compression does not mix with forced induction so ask people & or companies where you got your parts from to help you if they sell you a blower without some kind of setup requirements thats not correct thats would be like me letting you spend a couple thousand on an induction system but taking the instructions out of the box plus not warning you that this setup may fail if not correctly installed with other proper engine componenets atmospheric pressure fed is the other side of the fence compaired to induction from cranck there are pullies to decide on plus the splined shafts in the blower housing another its eather all aluminum or no aluminum meaning no cast block & aluminum heads xpecially with blower sorry for being long winded contact me if you want David.
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Old 03-01-2011, 05:11 AM
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liquid launcher: No offense, but can YOU even make sense of what you've typed? Nevermind the accuracy (or lack thereof) of the posts- I'm talking about using run-on sentences w/o any punctuation (periods, commas, etc.) is just too damned hard to read and understand.

You might at least try breaking the post down into 'chunks' of some sort (aka "paragraphs") to help make it understandable if you cannot or will not use punctuation.

Thanks.
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Old 03-01-2011, 06:39 AM
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Quote:
Originally Posted by cobalt327
liquid launcher: No offense, but can YOU even make sense of what you've typed? Nevermind the accuracy (or lack thereof) of the posts- I'm talking about using run-on sentences w/o any punctuation (periods, commas, etc.) is just too damned hard to read and understand.

You might at least try breaking the post down into 'chunks' of some sort (aka "paragraphs") to help make it understandable if you cannot or will not use punctuation.

Thanks.
It's a good thing that it is difficult to understand. There will be fewer people actually following the ill-advice and misinformation that way.
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Old 03-01-2011, 07:17 AM
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my skull....

Im not one for beating deceased horses, but I can't even read that, let alone agree or disagree with the advice.

To the OP; 400s require some special care, and any 400 core needs to be checked to make sure its in good shape, especially with your goals in mind. You may find that its a better idea (cubic dollars wise) to source an aftermarket block if you want to get serious. I distinctly remember a 400 4bolt crankshaft leaving the party in epic fashion, and he had a half fill of hardblok.
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Old 03-01-2011, 07:31 AM
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If you want to supercharge this engine later on, how much are you willing to either give up now, or change later? Because the cam and compression ratio will have different requirements between the two, unless you're willing to put up w/a tame set-up for now in anticipation of a blower later on.

Or if you get into making good power NA, the CR will be too high so the pistons will need to be swapped out, along w/(possibly) the cam, come time for the forced induction set-up.
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Old 03-01-2011, 09:15 AM
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Thanks everyone

i appreciate all the help, ill try to answer as many as possible!

My pistons are at the garage but im almost possitive they are -16cc and with 64cc heads ill have 9.5 compression, again i dont know as much as i would like to so sorry for any ignorance.... since im looking into aluminum heads and a low psi supercharger i thought 9.5c would be okay since aluminum will run higher compression on pump gas...

and a few people made comments on my intake runner size, this also confuses me... I completely see were your coming from when telling me a bigger intake runner is better, but does that matter with a supercharger? i assumed(making an *** out of you and me) that whether i have 185 or 210 intake runners the psi is still going to be 6... i may be thinking to much about it
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Old 03-01-2011, 09:34 AM
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the idea of a supercharger is to increase air flow hence the reasoning to increase the intake volume size to 200+. check into afr heads too
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Old 03-01-2011, 09:38 AM
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Quote:
Originally Posted by djohnson308
i appreciate all the help, ill try to answer as many as possible!

My pistons are at the garage but im almost possitive they are -16cc and with 64cc heads ill have 9.5 compression, again i dont know as much as i would like to so sorry for any ignorance.... since im looking into aluminum heads and a low psi supercharger i thought 9.5c would be okay since aluminum will run higher compression on pump gas...

and a few people made comments on my intake runner size, this also confuses me... I completely see were your coming from when telling me a bigger intake runner is better, but does that matter with a supercharger? i assumed(making an *** out of you and me) that whether i have 185 or 210 intake runners the psi is still going to be 6... i may be thinking to much about it
As long as the boost is kept low, along w/hopefully a boost retard box for the ignition and of course premium fuel, the 9.5 CR won't necessarily be a deal killer- but dam near. But it WILL severly limit the boost you can run. As you can see w/the chart below, 8-8-1/2:1 CR would be much better.

You have a valid point in regards to the port volume w/forced induction- to a point. Remember that the port has to be able to flow enough w/o "backing up", so to speak. This is where the port flow cannot increase even though the boost is still rising. If the intake ports are causing the restriction, power will not increase unless the ports are made less restrictive.

Also w/forced induction, the velocity that's often lost in a NA engine if the ports are too large, isn't lost to the same degree w/forced induction. That allows a certain amount of what might be excessive port volume (if NA) to be used w/o penalty w/forced induction.

Even NA, the ports could be larger than 185cc, anyway. I believe ericnova72 gave you the 'correct' port volumes above.

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Old 03-01-2011, 11:33 AM
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Quote:
Originally Posted by ericnova72
All three of those heads are rather small for a 400 cube engine, I'd be looking at 200-215cc intake runners, even 220+ if you really want big power.
Without even getting into compression, this is your answer for port volume.
The 215s are a nice fit for the 400.
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Old 03-01-2011, 02:12 PM
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[QUOTE=cobalt327]If you want to supercharge this engine later on, how much are you willing to either give up now, or change later? Because the cam and compression ratio will have different requirements between the two, unless you're willing to put up w/a tame set-up for now in anticipation of a blower later on.

Or if you get into making good power NA, the CR will be too high so the pistons will need to be swapped out, along w/(possibly) the cam, come time for the forced induction set-up.[/QUOTE


I was hoping to build the engine around it for a bolt on type application
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Old 03-01-2011, 02:32 PM
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Quote:
Originally Posted by djohnson308
I was hoping to build the engine around it for a bolt on type application
Then you need to do a juggling act between adaquate NA power now and keeping the CR low enough for adding boost, PLUS choosing a cam that will serve both masters.

You got your work cut out, I think.
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Old 03-01-2011, 02:35 PM
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Haha I think you right... hence all my confusion
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