|01-30-2013 12:32 PM|
Goodson is nice stuff.
you only really need two of them with a long 6" shaft for this SBC head porting job.
LFR-34C and LFR-46C
Yes these Double cut style are for cast iron. Not good on alumunum.
Use single cut for aluminum.
There are other sources that are a little less pricey.
But avoid cheap chinese junk.
Welding supply and industrial tool supply stores usually have all this stuff.
google search carbide burr The same onces but with a 3/8" cutting head diameter are about half the price.
I use the various shaped mounted stones to shape the short side radius. The amount of material that needs to be removed is not that much to shape the short side. radius.
You don't need to run these at 10,000 rpm.
Ebay: remember good quality tools are not sold for dirt cheap. Can be real hit and miss.
|01-30-2013 10:45 AM|
You can use a coarse aluminum bit on iron all that will happen is a rougher surface finish from some chatter the wider flutes create, but they'll cut just fine. Aluminum will gum up the smoother fine iron flute almost instantly. You can kind of get away with the fine flute on aluminum if you frequently run the bit into a piece of bar bath soap. This lubricates the flutes preventing the aluminum from sticking. Same thing if you're cutting aluminum with a rotary stone or drum sander, run the stone or drum sander into piece of bar soap every few cuts and it'll stay pretty clean of imbedded aluminum. This of course leaves your bits and stones smelling clean and refreshing.
|01-30-2013 09:06 AM|
Hey F-Bird check out these bits. will these work ok. They are similar to what you have below.
I guess these are made for cast iron??? I have no idea.
|01-29-2013 09:33 PM|
|vinniekq2||1gary,do you have any experience with super stock engines? How do you measure cfm flow on stock castings|
|01-29-2013 09:19 PM|
We all know as casted OEM heads are all the same.Right??. I'm call it BS. So to follow the same pattern reaps the same results without a flow bench to check if your just hacking away at a pc of metal or really doing better or worst. Taking tech back to what amounts to caveman times is illogical.
The first set of heads done right usually the response is OH!!!. That's what I have been missing..........
|01-29-2013 02:52 PM|
The whole purpose of marketing and advertising is to separate you from your money in exchange
for what ever is being offered by the advertiser. And convince you that you need it.
And they will go to what ever lengths thats nessessary to "tell you what you want to hear", to get the sale.
|01-29-2013 02:45 AM|
Now that just doesn't make any sense.
|01-29-2013 12:22 AM|
get these two with a 6" shaft
2.5" shaft for this one
|01-28-2013 09:28 PM|
|ChevroletSS||Thanks for the info. Greatly appreciate it. Can you point me in the right direction on some bits to use for porting. All I have is the port and polish kit from jegs which is ok but not efficient. I need something about six inches long id say and one maybe three inches long. A good carbide bit I guess. What do you suggest|
|01-26-2013 03:22 PM|
None of this general porting on this stock SBC head requires a flow bench. You got to put some air in a tire first before messing with the tire gauge.
A picture says a 1000 words.
i did not do this head. Buts a really good pic of the desired finished form. Look at the chamber too.
|01-26-2013 03:17 PM|
You can make you own go no go gauges from sheet metal or welding rod to compare port width height dimensions by hand. Or use calipers. Just make then visually as close the same as practical.
Its the size of the "choke" that counts. (point of minimum cross sectional area)
Air flow gets real funky at supersonic speeds. Running Engines do not flow air like a flow bench.
|01-26-2013 03:01 PM|
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.
|01-26-2013 02:26 PM|
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.
|01-26-2013 12:15 PM|
14101083 Cylinder Head
|01-25-2013 10:37 PM|
|ChevroletSS||Thanks guys. What is the common wall side|
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