I have stock Gen IV 454 & 781 Heads, Compression ???? - Page 2 - Hot Rod Forum : Hotrodders Bulletin Board
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  #16 (permalink)  
Old 12-01-2011, 08:48 PM
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Quote:
Originally Posted by wild_man84
Thanks again Techinspector1! I havent forgotten about this thread or post. Really been putting in the hours to be able to get off for Christmas. SOOO, I will get back to this post this afternoon and see what Ive learned..
Here is what I have for the SCR 9.75:1.. Im about to fall asleep sitting up. lol. its 920 my time and 315 comes early.. Im really excited about knowing this and learning it. I knew it wasn't a guessing game and solely experience. Dont tell me anything ill get back to this tomorrow..thanks again.

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  #17 (permalink)  
Old 12-02-2011, 03:32 AM
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This will help with the math.

http://www.wallaceracing.com/Calculators.htm

781's work great on a 454-468 but machine work and parts add up quick I have a bunch in the set I have.A small port works great up to a 496 A 540 or larger I would want rectangle port best out of the box head would be AFR 305's IMO

Last edited by winginit; 12-02-2011 at 03:42 AM.
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  #18 (permalink)  
Old 02-29-2012, 07:23 PM
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Finally everyone... I got off work early lol

I sent my heads to the machine shop yesterday. they wont get them till friday or monday. anyways, Id rather go ahead and spend the $$ now then wish I would of later. what all do you think I should get done?

http://www.steveschmidtracing.com/machine-shop

clean
surfaced
milled for cc's
cut for teflon seals
competition valve job
install valves and springs and spring heights
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  #19 (permalink)  
Old 02-29-2012, 08:24 PM
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for sure, go for the bigger size valves
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  #20 (permalink)  
Old 02-29-2012, 08:58 PM
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Copy. thanks

so..... 2.19"/1.88" valves it is... next question, any recommendations on type of valves I should buy. I want it to be able to handle 700hp/lbs.tq. its NOT a daily driver... not for drag racing but maybe street racing lol
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  #21 (permalink)  
Old 02-29-2012, 09:44 PM
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Quote:
Originally Posted by wild_man84
...not for drag racing but maybe street racing lol
You're gonna hear this eventually, so here goes: street racing is not condoned or glorified in any way and is verboten here at Hotrodders. Just so you know.

Making that kind of NA HP will be a lot easier- and no more expensive- using aftermarket heads, IMO.
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  #22 (permalink)  
Old 02-29-2012, 09:54 PM
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Well. My street racing would be something like getting on it after having dinner with the guys or something. Not really into painting a line snd running eachother like fast and furious.

Only heads id consider are tge afr 315's. They are 2800. I doubt ill spend 800 n the stock. Depending on valves. I already know the springs.
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  #23 (permalink)  
Old 02-29-2012, 10:36 PM
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Getting those numbers is not going to be easy- or cheap- unless you do all your own work and are a real good head porter. The flow needed for 700 HP/TQ doesn't come from just hogging the seats out for big valves...
If you have someone who can get you 350 cfm out of them for $800 including valves, well, what can I say.

http://speedtalk.com/forum/viewtopic.php?t=408
http://speedtalk.com/forum/viewtopic.php?t=13648
http://speedtalk.com/forum/viewtopic.php?t=13851
http://www.maliburacing.com/patrick_budd_article.htm
http://www.maliburacing.com/ovalvsrect.htm
http://speedtalk.com/forum/viewtopic.php?t=2610
http://www.j-performance.com/forum/p....php?f=10&t=97
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Old 03-01-2012, 09:03 AM
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Quote:
Originally Posted by cobalt327
Making that kind of NA HP will be a lot easier- and no more expensive- using aftermarket heads, IMO.
I agree 100%
Quote:
Originally Posted by matts37chev
i am no expert, and there are guys here that know way more than me on this subject, but........

i would check the math on the costs of doing those heads, parts and labor.
unless you are able to do some of the work yourself (porting/bowl blending for new larger valves)
also the cost of the springs and other pieces for the cam etc.

you might find it with be worth the couple extra bucks and just buy new heads
it all adds up quick
i'm building a set of 781's and if i was to do it over, i'd just sell them

you may be able to find a set that will work better with your flat top pistons
(smaller cc's)
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  #25 (permalink)  
Old 03-01-2012, 11:45 AM
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Quote:
Originally Posted by wild_man84
any recommendations on type of valves I should buy.
BOBCRMAN recommended +0.100" longer valves earlier. I'd pay attention if I were you, he knows what he' doing.
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  #26 (permalink)  
Old 03-01-2012, 02:25 PM
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Sorry, matts37chev- I didn't see the first page of the thread before responding. The comment about the heads was more to add something on-topic instead of just flakking the guy for the street racing comment.

In any event, wild man- check out this build to get an idea of what kind of flow (CNC ported AFR Magnum 315's w/2.25" x 1.88" valves milled to 110 cc chamber volume, being fed by a Vic Jr.) and how much cam duration (254/260 @ 0.050") is needed to make 738 HP/666 TQ based on a Gen. VI 502 short-block (GMPP p/n 24502619)- an engine w/a lot larger bore diameter and a 4" stroke (giving less piston speed) than an engine based on a BBC 427 TD.

If you lower the power expectations by at least a hundred or so, things will become much more "doable", IMO.
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Old 03-01-2012, 02:44 PM
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Quote:
Originally Posted by cobalt327
Sorry, matts37chev- I didn't see the first page of the thread before responding. The comment about the heads was more to add something on-topic instead of just flakking the guy for the street racing comment.

In any event, wild man- check out this build to get an idea of what kind of flow (CNC ported AFR Magnum 315's w/2.25" x 1.88" valves milled to 110 cc chamber volume, being fed by a Vic Jr.) and how much cam duration (254/260 @ 0.050") is needed to make 738 HP/666 TQ based on a Gen. VI 502 short-block (GMPP p/n 24502619)- an engine w/a lot larger bore diameter and a 4" stroke (giving less piston speed) than an engine based on a BBC 427 TD.

If you lower the power expectations by at least a hundred or so, things will become much more "doable", IMO.
you dont need to be sorry, i'm just glad i'm not the only one thinking this way
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  #28 (permalink)  
Old 03-01-2012, 02:44 PM
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http://www.airflowresearch.com/artic...le076/A-P1.htm

This is where i began my search a few years back. Thats really more of a conversation I'd rather have when the time comes. Dont want to put the cart in front of the horse. And yes, i will be talking it over needing help from the guys here. For now though...


Should I go for the bigger valves . Not the 2.19/1.88 bigger. Nows the time to get the head work done. If i should go bigger then what size? Alao what other valve wkrk should I get. Basically, what work should I have done to put these heads at full potential for what im using it for. Not dragging.
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  #29 (permalink)  
Old 03-01-2012, 02:51 PM
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Quote:
Originally Posted by cobalt327
In any event, wild man- check out this build to get an idea of what kind of flow (CNC ported AFR Magnum 315's w/2.25" x 1.88" valves milled to 110 cc chamber volume, being fed by a Vic Jr.) and how much cam duration (254�/260� @ 0.050") is needed to make 738 HP/666 TQ based on a Gen. VI 502 short-block (GMPP p/n 24502619)- an engine w/a lot larger bore diameter and a 4" stroke (giving less piston speed) than an engine based on a BBC 427 TD.

If you lower the power expectations by at least a hundred or so, things will become much more "doable", IMO.

Wow Cobalt, thanks for posting that Article, I have been searching for builds like that, as I am building a 540 w/AFR 315's (with a Gen VI Block)-my Cam is close to those figures, so this gives me more material to day dream about-

sorry to hi-jack this Thread-

To the OP, I am waiting for the Heads from AFR now (ordered about 5 weeks ago), and used 2.25" valves and PAC Springs-I started out building a 496 for the street, bought some Edelbrock Heads (290cc w/2.19") and realized I wanted more-those Heads you have can build power though-I have a friend who gets big power out of them, and goes 2.25"-

http://www.vortecproperformance.com/...binations.html

Last edited by 35WINDOW; 03-01-2012 at 03:00 PM.
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  #30 (permalink)  
Old 03-01-2012, 03:29 PM
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Honestly, it doesn't have to hit 700. But the closest i can get to that. The better. Im going to do what the guy earlier in this post recommended . Stroke and. 30 over.
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