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 Post subject: Help on afr 227 porting.
 Post Posted: Mon Jul 18, 2011 10:57 am 
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Hello to all,
I am hoping someone will be willing to share their experience in porting on the AFR227 CNC heads. #1068. I am happy to email you if I am asking too much to be posted. I understand how business is tough at the moment. Any help is much appreciated.

Basic engine specs
434 cu SBC
Super victor
Dominator
2.1 intake and 2.83 throat 90.5%
Jesel 1.8 ratio .550 offset rockers
Peak HP looking at 6800-7000rpm plus 300shot of nos.
solid roller 275/285 @ .050 with .720 lift int and exh.

I have welded the pushrod slots and opened the pushrod wall out around 0.060 so far. Airspeed through the pinch area is 320 on this side and 285 on the straight side.
Airspeed over the SSR was in the early 400fps so I have widened the SSR around .070 on the pushrod side and .020 on the straight side. Now we have 344fps on each side and 390 in the middle. The CSA at the flange is near 2.9sq"(1.34 x 2.20 less corner radius). I am looking to go around 3sq".

Currently I have 316cfm @ .700 but did have 321 before I widened the port( I am aiming to get to 330-340 odd cfm). If I put a 5/16 ball in front of the SSR it picks up to 327 cfm. I assume it is re-attaching the air to the SSR. I am looking at laying SSR back next but would like the input from guys that have been there before.

How wide are you guys going on the pushrod side and are you raising the roof and how much?
When you work out throat area as say 90% are you then adding the area of the valve stem or is this considered in the 90% rule? I have seen mixed opinions on this one.

Looking forward to your reply's.

Craig.

PS As I have just joined this forum, I copied this from a post i have on ST. Hope that was ok. I just need some solid advice as it has been a while since the grinders were out.


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 Post Posted: Mon Jul 18, 2011 12:39 pm 
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My best 23dg stuff sometimes was a little "ugly." I ported several sets of Dart Iron Eagles that made over 800hp but the flow numbers were never that great and the low lift numbers were REAL bad. To get 3sq inches through the PR I had to raise them up a mile. The short turn was always too fast. I believe its just too much of a turn to make "pretty." And when I opened the PR area it would cause problems down stream and kill the low and mid lift flow, but they still made power with the correct cam.

With a high hp 23dg head, I believe the size of the port is more important than all else.

Oh and make the throat bigger. ;-)

Denis


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 Post Posted: Mon Jul 18, 2011 2:13 pm 
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I think laying back the SSR next is the right approach. Move the highest point back in the port for a longer radius SSR. Floor speeds around 390 have worked good for me and been right there on the best heads I've seen. Finding the best shape for the SSR is the trick. I like to use a valve cut just smaller than the throat to use as a reference as I move up and down the throat area.

I like to leave the throat small as I think it is the most important velocity in the head. It should be peaking close to your target rpm with what you have now if not over that rpm.

To help the NOS, you need to make the exhaust throat bigger than normal probably ~90-91%.

What are your goals?

Rick


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 Post Posted: Mon Jul 18, 2011 4:58 pm 
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Hi Rick and Denis,

thanks for your replys
I want to make around 750-800hp aspirated then add the nos.
The plan was to have the following sizes.

3sq" tapering to throat at 2.85-2.9sq" (but needing to slow the SSR if I gain more cfm)
Intake entry 3.8-4sq" depending what I can get it to.

What I would like to know if possible is;

Would you go wider or higher at the intake flange to go to 3sq"? (i have easy another .100 to use on pushrod wall with 3/8 pushrod with the .550 offset rocker)
What method is best to slow the SSR if I get it too fast again?
What shape should the floor be approaching SSR and corner radius?
How far before SSR should I start to make the port wider to slow down before turning?
Should the seats have a radius up to the .060 and pulled back a little on the short side?
Do you take any material beside the valve guide boss and the roof over the SSR to help slow the air? and gain CSA
How wide should I have gone over the SSR on the sides of the bowl?
I read somewhere where chad said the needs to grab more of the bowl, what does that mean?

Now I bet your thinking you should of left this post alone hey??

Thanks again for your input it is much needed and appreciated. Anything you have to add I am all ears. I wish to learn as much as you guys are willing to give.

Thanks Craig.


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 Post Posted: Mon Jul 18, 2011 7:36 pm 
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I'd like to hear Denis' answers too but here is what I think. It is really hard to put some of this into words.

RCEcraig wrote:
Would you go wider or higher at the intake flange to go to 3sq"? (i have easy another .100 to use on pushrod wall with 3/8 pushrod with the .550 offset rocker)
From where you are I'd go up if your intake can also go higher. In the past I would have said wider, but after seeing how well some Vortecs (tall & narrow) work I have changed my opinion some there.
RCEcraig wrote:
What method is best to slow the SSR if I get it too fast again?
Lay back and lower the SSR and move the peak of it closer to entrance.
RCEcraig wrote:
What shape should the floor be approaching SSR and corner radius?
fairly flat small radii in floor corners.
RCEcraig wrote:
How far before SSR should I start to make the port wider to slow down before turning?
It's a gradual thing from the pushrod.
RCEcraig wrote:
Should the seats have a radius up to the .060 and pulled back a little on the short side?
A lot of seat combo's don't like radiuses and some do. I've used a really small half-round file to shape the SSR side of that last angle into the port.
RCEcraig wrote:
Do you take any material beside the valve guide boss and the roof over the SSR to help slow the air? and gain CSAHow wide should I have gone over the SSR on the sides of the bowl?
I like a tail after the guide and wouldn't take any from that area. Take it from the sides of the guide, but not beside the guide in the roof unless the whole roof has been raised a lot and you still need the size.
RCEcraig wrote:
I read somewhere where chad said the needs to grab more of the bowl, what does that mean?

???

I think Denis has had more experience with the big ci sbc's than me.
IMO you will have a hard time keeping the rpm of peak hp <7000 rpm and making 750-800hp with a 23ยบ head. It is more likely going to be at least 7500.

Rick


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 Post Posted: Mon Jul 18, 2011 7:42 pm 
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One other thing. If somebody over on ST recommends a 2.30" intake valve you should ignore him.

Rick


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 Post Posted: Mon Jul 18, 2011 9:29 pm 
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On a SSR what confusses me is if you lower the floor hieght and lay it back further, does the air stay on the short side or go accross the back of the valve to the other side of the port(long side of bowl) given the hieght of the SSR on a this style of head.

I widened the SSR before your replys and gained 3-4cfm back from .300-.550 seems to have fixed a low at the convergent point (if that is the correct way of saying it)

Do you have a picture of what the SSR corner radii should look like. I will try and post a pic of what I have done tonight for you to see.

The chamber I not sure if I can do anything with it. The valve has .180-.200 clearance when lifter .250. I had the seats done at 45 deg with a 35 top cut which blended into the chamber from the 35 deg top cut to the 90 deg wall with a .280 radius in order to get some kind of presure recovery. Hollowing out the chamber I think will only hurt presure recovery and I don't think it is restrictive as some might think. If Chad reads this I'd like his thoughts also.

As for RPM I know you are dead right on where it needs to be to make the power but then we are lift limited. The camshaft is what we have to use(clearance issue with rods) and that is why I got the 1.8 rocker ratio. Still only gives us about .710 lift where we probably need about .780-800 for 7500rpm.

Craig


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 Post Posted: Tue Jul 19, 2011 8:22 am 
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Examples of a few of my motors,all with the same 4150carb:
1)406,2.73@PR,285IN lobe,2.125valve,92.4%throat,762hp@7350--.830lift,1.7rockers very solid motor.
2)406,3.00@PR,280IN lobe,2.140valve,91.8%throat,806hp@7750--.860lift,1.75rockers and motor was a beast!
3)406,3.05@PR,280IN lobe,2.140valve,91.8%throat,832hp@8100--.912lift,1.9rockers and was a dog!
The 3rd motor had more area at the short turn but I believe the lift curve was wrong and I ended up with a motor that wouldnt recover on the shift in the heavy truck it was in. It never ETed as good as motor number 2. Later I moved classes and made motor number 3 a 422cid and used it in a liter truck with a glide instead of a turbo 350 and it did really good.

I never lowered the floor at the short turn, just lay it back a mile and just touch the peak. It will be a little peaky if your heads are anything like the Dart iron heads i had to use.

The trend has gone to a larger throat with the 23dg stuff on big motors. It worked for me but Im not saying its the only way. Might take a totally different combo with a "normal" throat.

Remember I said 23dg heads are "ugly?" I flowed my heads with no intake valve and they lost 15cfm @ .800 lift.

Denis


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 Post Posted: Tue Jul 19, 2011 9:44 am 
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Denis,

When you lay back the short turn, what does the transition to the throat look like. I am worried about the air being able to turn at the lowest part of SSR into the seat area.

What flow figures do you end up with ugly or not on those motors you mentioned.

Craig


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 Post Posted: Tue Jul 19, 2011 10:37 am 
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RCEcraig wrote:
Denis,

When you lay back the short turn, what does the transition to the throat look like. I am worried about the air being able to turn at the lowest part of SSR into the seat area.

What flow figures do you end up with ugly or not on those motors you mentioned.

Craig


Craig,
The transition to the throat is touchy but above .650 lift or so it wont make that turn anyway! =; I did see that you wont be using much lift but I believe you should make your heads flow as stable as possible to atleast .800 lift. I used aprox a 65dg bottom cut under the seat, then a 90 straight aprox .100 long then the short turn. You will have to play with the blending between angles but they wont need much, if any.

All of my Dart 23dg heads flowed between 330 and 337 @.800 on my conservative bench. I always made sure the flow did not drop off at high lift. I was able to keep them flowing to 1" when I started using higher lift cams. If I remember correctly: 345cfm @ 1.0 lift. Again my bench was un corrected and very conservative.

IMO 23dg heads on a big motor (or high hp motor) require all sorts of things that real race heads dont need. More intake duration and the cam a little retarded never hurt my mid range and it picked up the top end.

Read some of what shrinker wrote about droplet size and fuel actually being used by an engine. The air in a 23 motor doesnt take the turn very well so the fuel REALLY wont make the turn!

Denis


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 Post Posted: Tue Jul 19, 2011 11:07 am 
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viewtopic.php?f=6&t=8245

It doesnt look like this applies to head porting but somewhere in those pages shrinker talks about the short turn going turbulant and what it does to the fuel. Now IMO the 23dg head is so bad that it will undo all the good things the carb did. So the tune is out the window and everything must be tweaked for best hp. Shrinker is way smarter than me and sometimes I have a hard time understanding all he writes about. I just thought that thread is worth reading.

Im not saying that you should give up on making a "sound" port but the rules have to be stretched some. Especially when you have a 4 inch stroke and a "bad" rod ratio. All just my opinion and there might be a better way so Ill stop going on about it. =;

Denis


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 Post Posted: Wed Jul 20, 2011 9:50 am 
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Location: NW MO.
Personaly I think the 750-800 HP goal at 6800-7000 rpm NA is a little on the optimistic side.
Look at 2009 Engine masters when they were pulled to 7000 rpm and solid rollers with no lift limit were allowed. The second place engine was a 435 ci gm ls7 and made 713 at 6300. So some more cam compression and targeting 6900 could? get 750, but these aren't do it your self hobby engine builders. So to get a true 750 HP out of 434 ci with a 23* head at 6800-7000 rpm would put you in very good company.

As far as what to do to the heads? I didn't see a car combo/starting line rpm (stall speed)/ max rpm your willing to rev it past peak hp for et/ street driving, is et with nos more important than NA, etc.
If the goal is just 340 cfm, make the ports big. If the goal is power in my operating rpm, then some of the things above need decided first before grinding on the head.

Just my opinion, and it has known to be different than others!

_________________
Slow racing is better than no racing!

Randy


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 Post Posted: Thu Jul 21, 2011 10:12 am 
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randy355 wrote:
Personaly I think the 750-800 HP goal at 6800-7000 rpm NA is a little on the optimistic side.
Look at 2009 Engine masters when they were pulled to 7000 rpm and solid rollers with no lift limit were allowed. The second place engine was a 435 ci gm ls7 and made 713 at 6300. So some more cam compression and targeting 6900 could? get 750, but these aren't do it your self hobby engine builders. So to get a true 750 HP out of 434 ci with a 23* head at 6800-7000 rpm would put you in very good company.

As far as what to do to the heads? I didn't see a car combo/starting line rpm (stall speed)/ max rpm your willing to rev it past peak hp for et/ street driving, is et with nos more important than NA, etc.
If the goal is just 340 cfm, make the ports big. If the goal is power in my operating rpm, then some of the things above need decided first before grinding on the head.

Just my opinion, and it has known to be different than others!

G'day Randy,

Personally I like to think we do stand with very good company and definitely not your home hobby builder(said respectfully). Like you said 800hp is I admit to far a stretch but close to 750 should be ok. It would have definately been cheaper to buy the AFR245 than to bring these up to spec, but we do these things to challenge ourselves. I will give some feedback in the next few days on our progress.

Craig.


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