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Old 11-28-2012, 03:29 AM
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stuck on 400 heads

Ok guys im 19 and don't have to much experiance with engines but I am getting my hands wet right now with a sbc 400 it is stock with a little mild cam I have been told to run 350 heads on it but I don't want vortecs can sombody giveme some ideas I really only wanna use stock heads BC I don't have money for new ones im really just looking for a good set of heads that will work. Lookinf for casting #s any help will be appreciated

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Old 11-28-2012, 10:39 AM
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why are you changing the heads in the first place? A mild 400 is fun to drive.I hope you already have the easy bolts ons? good manifold,carb,headers,good exhaust,decent car,good suspension and tires?

What do you want to accomplish?
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Old 11-28-2012, 11:23 AM
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Be careful. With 64cc or 58cc heads, you could easily produce an 11:1 or higher static compression ratio, depending on piston crown configuration and piston deck height. Then you'd have to install a very aggressive cam to prevent detonation and you'd have no supporting components.
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Old 11-28-2012, 12:29 PM
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We bought as one lot number(a number of sets of heads) at auction a set of those aluminum Corvette 58cc heads.They almost don't have any chamber at all.It's like almost straight across.The OEM pistons for that are deep dish that I think where 18cc's.Those heads on a 400 would be crazy SCR's.And they don't port well given the thin castings they are.

Your best bet would to do the bolt on's as suggested and get a good three angle valve job with having the valve guides checked and new valve seals.
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Old 11-28-2012, 03:03 PM
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OK Smith, I'm gonna say this one last time and I'm outa here.....
ANYONE WHO TELLS YOU THAT YOU CAN BOLT 64cc OR 58cc HEADS ONTO YOUR MOTOR WITHOUT KNOWING THE PISTON CROWN CONFIGURATION OR PISTON DECK HEIGHT IS BEING TOTALLY IRRESPONSIBLE.
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Old 11-28-2012, 04:49 PM
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And don't forget to drill steam holes if you are going to use 350 or 305 heads.
http://www.crankshaftcoalition.com/w...ck_Chevy_heads
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Old 11-28-2012, 09:20 PM
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Quote:
Originally Posted by smith9300 View Post
Ok guys im 19 and don't have to much experiance with engines but I am getting my hands wet right now with a sbc 400 it is stock with a little mild cam I have been told to run 350 heads on it but I don't want vortecs can sombody giveme some ideas I really only wanna use stock heads BC I don't have money for new ones im really just looking for a good set of heads that will work. Lookinf for casting #s any help will be appreciated
The 400 SBC is going to be around 40 y/o by now, so "stock" might not be the way it was originally built, unless you know this engine's history.

The dished stock 400 pistons had a generous dish (the 400 often used a 24cc round dish piston stock), but by now there could be virtually anything in there for pistons. If the pistons are replacements for the original, you'll sometimes see a part number, or at least an oversize marking (like 30 or .030 for an 0.030" oversize, or similar). But unless the engine has been rebuilt there's a high chance the bores and pistons are worn.

If the original stock pistons are going to be reused, AND if the dish is 24cc, a 64cc chamber size will put the static compression ratio (SCR) at about 9.6:1 using a 0.040" quench. But the cam specs (intake closing point) and rod length needs to be used to find the dynamic compression ratio (DCR) to know if the combo will run on pump gas w/o detonating or not.

Which brings up the next point- you need to see if the rods are stock 400 rods (5.56" long) or if the engine was rebuilt using SBC 5.7" rods. Heck, you might get lucky and find a forged aftermarket crank and rods when you open it up, who knows?

But like has been said already- we need to know what it is you're trying to do along w/the specifics of the engine the way it sits (piston type, etc.).

Compression ratio calculators:
*Static compression ratio
*Dynamic compression calculator by Kelly
*Dynamic compression calculator by KB

Last edited by cobalt327; 11-28-2012 at 09:48 PM. Reason: Add links.
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Old 11-28-2012, 09:31 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
Don't be spooked by a small chamber head for your 400. Its likely it is a stock 400
with a stock dished 400 piston. This makes a 61-64cc head very usable on a 400.

See what you got available to work with. Then evaluate its suitability.

There are many good ways to skin this cat. A 58cc head is not necessarily the wrong head for you.
And can be modified.

Start by determining the pistons in your 400 ( flat top, dished) and what heads you got, can get, want to get.
and what your goals and budget are.
What fuel will you be using. Are you willing to use a good 92+ unleaded pump gas?

Again the 882 and 462624 heads are best avoided and not worth spending any money on.
If you are going to spend money fixing up a cylinder head find a better head to start with.
Don;t discount using a vortec head. Especially if there are good ones available (that are not cracked or fubared)
They make great budget power on 400's.
Quote:
Originally Posted by techinspector1 View Post
OK Smith, I'm gonna say this one last time and I'm outa here.....
ANYONE WHO TELLS YOU THAT YOU CAN BOLT 64cc OR 58cc HEADS ONTO YOUR MOTOR WITHOUT KNOWING THE PISTON CROWN CONFIGURATION OR PISTON DECK HEIGHT IS BEING TOTALLY IRRESPONSIBLE.
I'm with Richard on this one.F-Bird in terms of the 58CC heads you don't know what your talking about.It does sound like you haven't owned or used a pair of them.
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Old 11-28-2012, 09:53 PM
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After rereading my last post, I want to add (and repeat what others have said) that there's more to figuring the exact compression ratio than what I posted above- the deck height of the block needs to be known along w/the exact chamber size, gasket thickness and bore diameter and any overbore that may have been done. So like TI said- there's no way to know what the CR is going to be at this stage.

Last edited by cobalt327; 11-28-2012 at 10:01 PM.
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Old 11-28-2012, 09:56 PM
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never seen tech post with so many caps? thanks for doing that,lol.and the post
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Old 11-29-2012, 12:54 AM
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I certainly didn't say I didn't recognize the vett head potential. We resold the set we bought to a guy who has the OEM short block and deep dished pistons to go with the heads. While we had them,we sonic checked the runners and did in fact find all of those to be thin wall castings.You see you have to be careful about what you read vs what it really is.I am very sure about that.

Now porting.RHS during a R & D research found after all the yrs of porting they have done professionally,and their best guys,couldn't port match any better than 25% and that it was very labor intensive.Now these guys I know and they have the best of the best flow benches anyone could have. BTW-you got a flow bench at all??. You need that. They constructed the CNC programs for 5 axis porting.It produced port matches that are within 5% and cut down the labor time to 8 hrs. The shape is as important as the sizing.You really need a good understanding of air flow dynamics. But one of the things RHS said was more important than the size of the ports is the cross section of the port.They added in there are many "rated" ports out there that plainly just don't flow as advertized.I know for a fact the production Vortecs stock are about 165cc intake runners and your damm lucky if you can get them to open up to 170cc's before running into water and what's more the rough intake runners is what makes Vortec's suspend the air/fuel mixture.Smooth port them and you destroy the Vortec effect.What you can do to the production Vortecs is to clean up the exhaust port to help them out.You see there is a reason behind the 180cc and 200cc Vortecs.Here again I am very sure about this.

So unless you can match the experience level of the yrs RHS was hand porting and have a very good flow bench to check each port,you can not match their performance level of port matching 25%. You are alot less than that. If you can come up with a $250,000 CNC machine and then do a study for a number of yrs for the programing,you "might" get close to correct porting.Sorry man,but that is the plain simple truth. But these day and age,hand porting is caveman tech.

Yeah-doesn't that suck? A old guy who isn't stuck in back-in-the-day way of doing things.Die grinder madness.OMG!!

Last edited by 1Gary; 11-29-2012 at 01:21 AM.
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Old 11-29-2012, 01:13 AM
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To the O/P.What happened to the 400's was GM never intended them to be a performance engine.In fact during the early days of the 400's was during the early days of emissions.GM had a hell of a hard time to get the 400's to even pass those early testings.So most of the OEM steam hole heads for performance are the worst of the worst.

So I suggest you start out with a conservative approach with bolt on's first that you can reuse as more money becomes available.Work on getting a very sound foundation that doesn't have any issues like burning oil,leaks,good compression,no knocks and good oil pressure.Go out and enjoy that with the understanding of it's limits.Once you have a feel for that,then you can post what you have and where you want to go.We can help you out more at that point.Wrap your thinking about hot rodding at the best case it costs thousands and not hundreds when it is all said and done,and done the right way the first time.
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Old 11-30-2012, 12:27 AM
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2 old school rules on SBC heads:

1. A flat-top piston is better than having to run a dish piston. So pick the chamber volume that will allow you to run a flat-top. ( domed is also good for race motors on race fuel )

2. Always better to squeeze a 2.02 intake valve in there. 2.02 > 1.94

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Old 11-30-2012, 12:36 AM
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Quote:
Originally Posted by 1Gary View Post
Now porting.RHS during a R & D research found after all the yrs of porting they have done professionally,and their best guys,couldn't port match any better than 25% and that it was very labor intensive.Now these guys I know and they have the best of the best flow benches anyone could have. BTW-you got a flow bench at all??. You need that. They constructed the CNC programs for 5 axis porting.It produced port matches that are within 5% and cut down the labor time to 8 hrs. The shape is as important as the sizing.You really need a good understanding of air flow dynamics. But one of the things RHS said was more important than the size of the ports is the cross section of the port.They added in there are many "rated" ports out there that plainly just don't flow as advertized.I know for a fact the production Vortecs stock are about 165cc intake runners and your damm lucky if you can get them to open up to 170cc's before running into water and what's more the rough intake runners is what makes Vortec's suspend the air/fuel mixture.Smooth port them and you destroy the Vortec effect.What you can do to the production Vortecs is to clean up the exhaust port to help them out.You see there is a reason behind the 180cc and 200cc Vortecs.Here again I am very sure about this.
You are correct. "Port profile" is very important, which is why aftermarket race heads have very different castings over stock heads. "Port location" and "profile" along with larger valves are why aftermarket race heads make more power. Also the valve pocket areas play a role.
In every serious race head you will ever see, the port locations are raised.
Some of them are radically relocated.
You will never achieve this with stock heads.
Intake runners should always be rough. Minimizes seperation.
Chamber and exhaust side can be polished smooth if desired. Usually doesn't result in any power gains, but can help minimize carbon deposits.
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Old 12-01-2012, 11:57 AM
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Hey guys sorry for not sayin anything but I just picked up a set of vortec heads and it is an all stock 400
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