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The flowbench operates at 10"...I multiply the flow results by 1.67 to get 28" for comparison. The inlet was radiused...and there was a pipe on the exhaust. So...these heads were just that bad, I guess. The heads were stock valve, with apparently some crappy valve job work done on them before. No port work had been done.
Using only carbide cutters, I opened up the intake opening, opened up the pushrod pinch, removed as much casting as I could get to, and pocket ported and bowl blended the best that I could do. Same for the exhaust except I did not touch the exit area, just removed casting, pocket ported some, and tried to blend it and remove the sharp edge on the short side. This was the 1st time I have ever truely looked at a set of heads, much less ported any.
Having said that, here are the results on the same flow bench at the same lifts with the stock valves, and then some stock type Stainless Steel Replacement valves:
Side by side comparison
Intake
Lift_______CFM
0.097...52......49....54
0.194...101....100...108
0.291...145....146...158
0.388...167....183...189
0.485...179....200...206
0.582...185....200...203
I think I have done well so far. Heads are cut for 2.02/1.6 valves now. Just need valve job, blend again, polish exhaust, and 80 grit the intake side, and I will be done. I have the Manley RaceFLo Valves to top it off. I will flow test again when I'm finished.
Cutting for the valves cost me $125.
let me know what you think. At least I didn't butcher them. I have seen where others lose flow at the bottom, and gain at the top. I didn't seem to lose much, if any, at the bottom, and gained some on the top. I hope the blending, bigger valves, valve job, and Manley valves will help considerably.
Here are some other stock flow numbers from other posts for comparison sake:
Corvette Aluminum # 113
Lift/Intake/Exhaust
.100 62 49
.200 116 98
.300 161 130
.400 185 152
.500 195 159
Although your bench does not give exactly the same results as mine,or others (looks like a 10cfm+/- difference)
The perecentage in gain in your numbers makes sence
for what you've done. The gain shown is all that matters.
looks like you can take it further and raise and straighten the intake port roof and common wall. The guide can be cut down
some, thined and streamlined. the area right between the guide and common wall in the roof of the port right near the bowl responds to being opened up. The pushrod pinch can be opened up.
The port opening at the flange does not need to be made huge but can be squared up and the roof raised a little.
work the roof from the port opening all the way back to the bowl.
You can use a felpro 1205 gasket as a guide for a street job.
This will get the flow benefit out of going to 2.02's
Same on the exhaust side. TheGuide boss in the bottom of the bowl is a major flow loss now. You need to slim and streamline the guide boss and carve flow paths on either side of it.
The roof again can be raised some. The port opening can be opened some especially the roof area. But again huge will only get you gasket sealing problems. I use a 1/5/8" round header
gasket as a guide, but i don't make the port opening round.
The floor of both the intake and exhaust port just need to be cleaned up.
.looks like you can take it further and raise and straighten the intake port roof and common wall.
Already did...but will look into raising the roof some more.
The guide can be cut down
some, thined and streamlined.
Hmmm. I did this area pretty basic. How much can I "cut down" from stock. I didn't cut it down any.
the area right between the guide and common wall in the roof of the port right near the bowl responds to being opened up. The pushrod pinch can be opened up.
Did this area to the max I think. Won't touch this anymore except to 80 grit the finish.
The port opening at the flange does not need to be made huge but can be squared up and the roof raised a little.
work the roof from the port opening all the way back to the bowl.
You can use a felpro 1205 gasket as a guide for a street job.
This will get the flow benefit out of going to 2.02's
I will take a second look at the roof. Otherwise, I was told by shop I may have some sealing problems in one or two areas where I may have opened up a little much. The "common" wall was a little thin on one area. I matched up to some FelPro gaskets that were just stock versions I got at Advanced Auto Parts in a gasket kit. I went too far in most cases...but wanted to be sure that my intake manifold exit was smaller than my intake port entry. I think I'm ok, but won't open further.
Same on the exhaust side. TheGuide boss in the bottom of the bowl is a major flow loss now. You need to slim and streamline the guide boss and carve flow paths on either side of it.
I probably could do more here. I really didn't want to do the guide bosses anymore, but if you think major porting here helps, I'll reconsider.
The roof again can be raised some. The port opening can be opened some especially the roof area. But again huge will only get you gasket sealing problems. I use a 1/5/8" round header
gasket as a guide, but i don't make the port opening round.
The floor of both the intake and exhaust port just need to be cleaned up.
I need to get some new header gaskets then to do my exhaust side.
BTW...
I took some templates from one of Vader's replies to another of my posts, and my ports matched up real close to them after I was done...except maybe the guide bosses on the template were steeper than what I ended up with. Mine ended up not being quite so steep. I was trying to be conservative in my approach though.
Question: Will any port work of the combustion chamber help flow...the inch into the chamber above the valve head? Unshrouding the valves help flow, or does it just help in combustion?
I'm hoping to put these on my basically stock 350, and then place on an inexpensive rebuild of a 383 with the hopes of 400 hp and 500 ft-lb torque at the crank. You think these heads are on their way?
Appreciate the comments and help F-bird.
I have a digital camera...but no way currently to post pics. If anybody is wiling to "host" them for me I will take some pictures.
Yes when you install bigger valves, unshrouding the chamber a bit will help flow.
Take the head out side and squirt the garden hose through the port. Hug the floor with the water stream and watch the water flow pattern as it leaves the port into the chamber.
Notice how the water hugs the shortside.
Now do the same only hug the roof of the port with the water stream. See how it curves toward the plug as it exits.
These are the areas to work. Since your planning on useing them on a 383 don't have to worry about compression ratio loss
from removeing metal from the combustion chamber.
Use a head gasket to mark out the cylinder wall so you don't get carried away.
Pictures say a thousand words. You should be able to "host" them your self on "Yahoo photos". You should be able to get a serial cable to connect your camera to your computer and download the right camera driver for it from the manufacturers site.
Then any good photo program will allow you to "aquire" the shots off your camera and save them.
You then may want to adjust the picture size and resave a copy
as most good cameras are capable of takeing a much better pic than nessessary for a computer monitor. Makes for smaller file size. I'm very interested in seeing them.
Got my ported "416" heads off the motor again and am going to get my friend to come over and take some pics of the ports for me so I can post them so others can see.
Not that they are any where near the last word on porting heads but they did do well on the bench and worked real well on the car.
Real well, right up until the motor let go a piston at 6500+ rpm.
LOL. Oh well, thats racing.....
You can really work the area of the green square.
Widen it alot. make it deeper. Widen it by laying back the wall
(left red line) straighten this wall as much as you dare all the way from the bowl to the port entrance. The only danger is where it passes the cylinder head bolt.
Widening this area increases flow and port bias.
"Port bias" is what gives the flow a swirl action towards the center of the chamber as it enters the chamber.
Make the whole roof of the port higher, and wider.
Make the floor of the port wider but not lower. (blue arrows)
The purple area at the bottom of the pic can be "unshrouded"
radiused and layed back. this is where the flow wants to swirl towards. Do not shorted the plug hole thou or plug threads will be exposed to combustion (bad)
Again work the area of the red square. Wider and deeper.
Lay back and straighten this wall (blue arrow) Widen and make the whole roof of the port deeper.
You can lay back this wall some too.(green line)
Widen and blend the floor at the walls ( purple arrows)
radius the short side to the floor but do not lower the floor.
Ya need that arch. Just clean it up.
On the exhaust side You can open up the areas marked by the red squares some more. This is where the flow goes around the valve and boss in the port.
You can widen, and raise the port {green lines} some more (use your header gasket as a guide) You'll notice on aftermarket SB heads the port is rectangular. There is still a visable cast parting line on your port walls so I know not enough metal has been removed.
See how fat and deep this area is..(light blue arrow)
When you start your thumb will not fit in here.
When your done your thumb should get lost in there.
For a header gasket to use as a guide...what options do I have besides the SLP gaskets that came with my headers.
Headers are 1-5/8"...
Felpro 1404 ??? Would be cheaper than the SLP by $10, plus might can pick them up at the auto parts store.
BTW: I feel like I'm hogging out the pockets now. They also don't have a valve job yet, but have been cut for bigger 2.02/1.6 valves...Not confident getting near the seat. One port was done at shop by their head porter...and he basically ported the seat too. I didn't think you were supposed to do that. Is it ok??? Same on intake and exhaust.
I have finished the carbide cutting again of one head except for the exhaust exits. Almost like starting all over. I'll see about getting a few pictures up.
DO NOT let any of the header flange or gasket block any of the exhaust port flow area. That's a performance killer.
Your choices, if you have this condition, are:
1) Weld around the tube & flange on the outside and grind away the offending material (gasket match to the port, basically), or;
2) Get bigger primary tube headers.
