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  #46 (permalink)  
Old 01-06-2013, 03:25 PM
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Quote:
Originally Posted by Project89 View Post
u can make a simple flow bench out of a shopvac , ford 0-5v maf sensor a volt metter and some plywood/2x4's


while not an actual flow bench u can use it to see any gains picked up in each port and use it to get all ur ports close to flowing the same
That would be something I would love to try for the set I just finished.....Google here I come.....

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  #47 (permalink)  
Old 01-06-2013, 03:36 PM
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Originally Posted by bygddy View Post
That would be something I would love to try for the set I just finished.....Google here I come.....
i built one long ago , so my memory is a lil fuzy but the basics are

u build a box u can bolt the head down to one chamber at a time and seal the box up good with some calulking on the inside , i used a 3inch speaker box port on my box to make it eaier to clamp the maf sensor onto .

but u can drill a 3 inch hole in the box and use a piece of 3 inch ex tubing as well and just glue/seal it to the box .

from there u clamp ur maf sensor onto that then u clamp the vac hose onto the other end of the maf .

be sure the maf sensor is oriented so that it reads flow from the box to the shop vac

i forget exactly which maf sensor to use but u have to supply 12 volts on one pin and 5 volts on another , one pin is ground and then u take ur reading with the dvom on the reminaing pin witht he dvom's positive lead, the dvoms ground lead just goes to were ever u have the maf grounded to more then likley ur 12 volt power supply





if this is something u will use a lot build the box out of steel instead as it will last alot longer from the continuous bolting down and unbolting of the cyl heads
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Old 01-06-2013, 04:04 PM
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Quote:
Originally Posted by Project89 View Post
i built one long ago , so my memory is a lil fuzy but the basics are

u build a box u can bolt the head down to one chamber at a time and seal the box up good with some calulking on the inside , i used a 3inch speaker box port on my box to make it eaier to clamp the maf sensor onto .

but u can drill a 3 inch hole in the box and use a piece of 3 inch ex tubing as well and just glue/seal it to the box .

from there u clamp ur maf sensor onto that then u clamp the vac hose onto the other end of the maf .

be sure the maf sensor is oriented so that it reads flow from the box to the shop vac

i forget exactly which maf sensor to use but u have to supply 12 volts on one pin and 5 volts on another , one pin is ground and then u take ur reading with the dvom on the reminaing pin witht he dvom's positive lead, the dvoms ground lead just goes to were ever u have the maf grounded to more then likley ur 12 volt power supply





if this is something u will use a lot build the box out of steel instead as it will last alot longer from the continuous bolting down and unbolting of the cyl heads
Wow, thanks for the step by step. I really appreciate it and if it looks like I'm going to be doing more heads in the future I will actually give this a shot in the spring.
Thanks again
Dave
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Old 01-06-2013, 05:25 PM
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Using Some plex in a 4 or 5 inch circle. With the head on top and the shop vac under neath. Then you can use strings and smoke to tell how things are flowing. Strings are really important for flow bench testing. And you dont need an expensive meeter and test unit that will not be acurate from day to day.

If you use the maf be sure to use a regulated power supply that can produce the same 12 v everytime. If it delievers more volts when it gets more volts it will screw the readings. Everytime you wife turns on the dryer you port work will be better. One of the main reasons home made flow benchs dont really work cause ypu need lots of tech equipment to support the meeter and reading of the meeter.

String always works if a little low tech. Also works great with smoke.
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Old 01-06-2013, 05:44 PM
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Quote:
Originally Posted by hcompton View Post
Using Some plex in a 4 or 5 inch circle. With the head on top and the shop vac under neath. Then you can use strings and smoke to tell how things are flowing. Strings are really important for flow bench testing. And you dont need an expensive meeter and test unit that will not be acurate from day to day.

If you use the maf be sure to use a regulated power supply that can produce the same 12 v everytime. If it delievers more volts when it gets more volts it will screw the readings. Everytime you wife turns on the dryer you port work will be better. One of the main reasons home made flow benchs dont really work cause ypu need lots of tech equipment to support the meeter and reading of the meeter.

String always works if a little low tech. Also works great with smoke.
thanks for pointing that out osmetimes i forget not everyone will know what i know and how to check stuff

with the maf style flow bench ur readings can very well channge from day to day so its important if u dont finish in one day to go back and re measure a port u have done so ur ports u still have to do come out to the same number.

the 12 volt supply isnt as importnant as the 5 volt , the 5 volt is what gives the readings , normally the cars ecm supplys the 5 volts to the maf this way if it reads a lil high or low on the 5 volt line the ecm can compensate


in the case of a flow bbench if u have 5,2 volts one day and then 5.4 volts the next day ur results will read artifically high . so each day of testing or when changing from port to port its just as important to stick the dvom on the 5 volt line to make sure voltage is the same from port to port.

if not u can just see what the difference is and add/sub it from the reading u get when taking the flow measurements.


u can always buy 2 cheap vlt metters as well and ties one into the 5 volt feed line permantly and then the second onto the 0-5v output of the maf so u have constant readinsg of both lines


the 12 volt feed is used for the heating of the maf, the 5volt side is were the actual readings take place
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  #51 (permalink)  
Old 01-06-2013, 08:38 PM
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The 12 v heating element is not regulated so 11 volts and 13 volts will give different temps so the readings that are taken will be different as well. Fine for the car since it adjust every few seconds and the alt provides the voltage once the engine is running.

its really important that you get the same results every day. Regular flow bench corrects for altitude and pressure. Along with temp and maybe a few other factors.

You can build a pro style flow bench. Here is a link for the best home kit i have seen. But may need more options for larger ports. Most vacums wont pull more than 200 cfm. With this kit and a vacum even the powerful one they recommend is 145 cfm at 28" and 210 cfm at 10". So totally useles for car heads that flow well.

Flow Bench | Digital Flow Bench | Flow Bench Kit

Last edited by hcompton; 01-06-2013 at 08:45 PM.
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  #52 (permalink)  
Old 01-06-2013, 09:44 PM
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Yeah,that's the link I posted earlier in this thread.
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  #53 (permalink)  
Old 01-07-2013, 10:04 AM
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Originally Posted by ChevroletSS View Post
Ill port them myself. Now I have practiced porting on heads for endless hours but what I still dont get is how Im supposed to tell if I made all the runners the same. I mean its very possible that by doing it myself that when Im done none of them will be the same. Does it matter if one flows just a little differently than others and so on?????
First is the needing of a flow bench to tell it your makeing improvements or causing degradation. In a simple sense and especially with older heads (think pre GT40P, Magnum, Vortec) it was pretty easy to improve ports. This was simply streamling the huge guide bosses and blending the rough cut of the upstream lip ahead of the seat into the wall. This make a marked improvement that was felt when you stepped on the throttle. Modern heads are much more refined in this area today so there is less impact by massaging this zone.

When you get away from the port pocket things are much more subtle, therefore, it is easy to degrade the overall flow. What seems logical to the eye is most likely not where the flow will or wants to go. Most people reporting here state that there is little to be gained by working the port between the manifold face and the turn into the pocket. This really isn't factual, but this is an area where it is easy to do more harm than good. To tease this out you really need a flow bench and a decent understanding of how gasses respond in a physics sense. There are plenty of web sites that lead you into building an inexpensive flow bench using little more than a decent shop vac as a power source.

As far as getting all ports to match the old fashion way was to arrive a good test port then make templates of the port at critical points. The uncut port is ground at the same points to fit the templates then the material between the template stations is ground to smooth connection between these points. There are people on the web that sell templates for known port shapes.

Bogie
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  #54 (permalink)  
Old 01-23-2013, 06:13 PM
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Ok guys when porting these heads can I smooth these round humps down so its nice and smooth or do I need to keep these there???
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Old 01-23-2013, 07:36 PM
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Ok guys when porting these heads can I smooth these round humps down so its nice and smooth or do I need to keep these there???
Yes make them flat they are just casting marks.

Best way is to shave a little off at a time so you can get them dead flat without cutting any metal around the area since you want it as flat as possible.
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Old 01-24-2013, 12:45 AM
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Turn the head over and work on the roof of the intake port. Get a long 6" shaft carbide burr cutter so it will reach all the way to the bowl from the intake side.

using a 3/8" cylinder shaped cutter with 6" shaft:

Raise the roof of the port approx 1/8th inch from bowl to exit and carve the flow path on the common wall side of the bowl while streamlining the guide boss. Use a felpro 1205 gasket as a guide. Never mind the BS on the floor of the port for now.
Look at the pic I posted.

Last edited by F-BIRD'88; 01-24-2013 at 12:52 AM.
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  #57 (permalink)  
Old 01-25-2013, 09:37 PM
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Thanks guys. What is the common wall side
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  #58 (permalink)  
Old 01-26-2013, 11:15 AM
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14101083 Cylinder Head

Quote:
Originally Posted by 1Gary View Post
Yeah,that's the link I posted earlier in this thread.
You must have this thread mixed up with another one. You must have got excited at the chance to argue with F-Bird'88 that you thought you posted a link to the flow bench. I only see the link for a flow bench once in post# 51.
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  #59 (permalink)  
Old 01-26-2013, 01:26 PM
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The common wall side is the side of the intake port that has the head bolt running thru the two intake ports that are right beside each other...side by each...... You need to raise the whole roof of the intake port so its taller.
right from the guide boss/bowl all the way to the intake flange.
Use the 1205 gasket as a guide. Common wall port wall porting width limit is that head bolt hole between the two intake ports. It would be nice to not bust thru into that cylinder head bolt hole.

this and the thinning shaping-streamlining of the intake valve guide boss (one side of it anyway) is primarily done with a long shaft cutter working from the intake flange side.

The other side of the valve guide boss in the bowl is done from the bowl side, for the most part.
Leave the 1st inch of the intake port, for last. Most people get carried away there cause its easy to see and reach.
You need to carve two strong flow paths around the valve guide boss, in the bowl. Just like in the pic.
and generally make the roof of the intake port taller.
There is very little flow at the floor of the intake port where those little casting bumps are.
This area only needs cleaning up. Do not lower the floor of the intake port. The critical part of the floor of the intake port is the short side radius shape and width as it aproaches the valve bowl.
The shape the "short side" decides the flow balance between a low lift friendly port job or a port job that is high valve lift friendly. The short side radius shape causes the air to hug it as it turns.
If the air does not hug the shape, it separates and creates turbulence in the port.
On a stock GM SBC you only ahve what you have to work with to reshape it. It is not optimum.
and won;t be when you are done, without epoxy or port welding.. You have to work with whats there.

All 8 intake ports don't flow the same stock as cast and they won't all flow exactly the same when you are done. And if you attemp to chase that and get them all exactly the same, you will probabily F*&^% it up.
+/- 2-3-4 cfm port to port variance don;t mean squat. its the shape and overall ports performance that counts.

Just look at a big block chevy head. They do not all flow the same at all. Runs just fine with 4 long ports and 4 short port that enter the chamber differently.

On all SBC intake manifolds the intake manifold runners DO NOT FLOW THE SAME.
Do not chase port to port flow little differences. The point is to make a better Stock head, not a prostock CNC head. ALL the ports will flow a ton more than stock. Thats the point.

Do not keep running back and forth to the flow bench. Port the whole port to the desired finished shape.
1000's of stock SBC heads have been ported before. You are not going to invent anything.

once you are all done porting the ports then you can check the ports flow on a flow bench. for braggin rights.
On a street motor witha stock SBC head and a stret cam the important zone and a good benchmark is the flow @ .400" lift.
If it flows good at .400" it will make good power. The absolut peak hgih lift port flow is not that critical and won't tell you the engines real power by the number alone. Its all about flow balance. Low lift flow is important too. Especially with smaller street cams where the valve never gets that far away from the seat (relatively). If you get the intake port up to 230-240cfm peak you did a great job and it will make very good power in a street motor. It will make well over 400hp on a decent 350.
somewhere around 217 to 224@.400" indicates a good small block chev street port on this type of OEM SBC head ,too.
If you think you are the next Joe Mondello, your not and you won;t reinvent the SBC racing head.
you will get to a point where you just trade off low lift flow for high lift flow by trying to be a hero.

The funnel venturii shape just under the valve job in the bowl is critical to low lift flow. remember air wants to follow a curved surface. that curved surface venturii shape under the valve job helps the air come around the intake valve into the port at lower lifts. and sets the port curtain area velocity profile as the valve moves away from the seat.

This venturii shape just under the valve job should be approx 88% of the diameter of the valve.

The head in the pic is a finished 083 head with a 2.08" valve. It flows well over 260cfm at high lift.
And they don't all flow the same.
Takes a .600"roller cam to use the high lift flow.

Its how much horsepower and torque the engine actually makes and how well that engine accelerates up thru the power curve that counts. Not the flow bench numbers.

Last edited by F-BIRD'88; 01-26-2013 at 01:47 PM.
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Old 01-26-2013, 02:01 PM
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Its how much horsepower and torque the engine actually makes and how well that engine accelerates up thru the power curve that counts. Not the flow bench numbers. You will be removing about 10cc of metal from each port.
The limit on how big you can open up the push rod pinch is the push rod hole. Nice to not bust thru there either.
The minimum intake port cross sectional area size. (the smallest area of the port) pretty much detemines the rpm where peak HP is created. You can have 240+cfm flow at high lift, but of the MCSA is too small the port "chokes" ( air goes supersonic in the port) and chokes off the top end power.
Thats why just working the first inch and last inch of the stock port leaves a lot on the table. its hard to make these ports too big. but its far too easy to over work the port entrance.. Unless you are using a big full race single plane race manifold, felpro 1205 gasket size is plenty big. Its just right for the Performer RPM and Vic Jr on a street motor.

The two point you got to watch for when porting is the push rod pinch wall and the common wall where the cylinder head bolt hole is. this is where you are likely to make a hole. Use common good sense here.
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