template/guide for porting heads?
02-15-2011, 07:16 AM
#1
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template/guide for porting heads? doing a cam swap on my lt1 (on a budget) soon. wondering if gm or anyone makes something to help with porting heads? dont really have the money to have them sent out, and this would be my first port job so i'd like to have a little insurance that im not going to remove too much or too little inside the runner. anyone know of anything?
02-15-2011, 08:52 AM
#3
^^ what he said, Everyone thinks that "Porting" is so simple, there are a lot of physics involved, where, how much, angle of port ect.You must understand the properties of air flow, swirl, tumble, turbulence. There was a speed shop that the owner just hogged out the ports on his own car to make a point, well he did, his car ran 3/10ths slower as all of his customers cars he ported. There is the short side of the radius, understand what this means? then don't do it.
02-15-2011, 10:56 AM
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LESS IS ALWAYS MORE !!!! just do the basics like gasket matching a inch or two in the runner and smooth all the bumps and ridges make it smooth not shiny but it is ok to polish the exhaust runners and chamber but just remember only those two areas....as for the bowl just be carful not to nick the seats or guides and use a sand cartridge roller before using a carbide cutter....
02-15-2011, 11:39 AM
#6
As stated above, if you are not going all out, bowl work will be where you see the most gains. The next would be in the short radius.
I would recommend against gasket matching. If you don't do any runner work you can create a mess. A better bet is to use the 1996-97 intake manifold.
Cam choice is also key. If you do the above work the heads will go static at about .500 lift.
You don,t have to hog everything out to make power. Velocity is your friend here.
I would recommend against gasket matching. If you don't do any runner work you can create a mess. A better bet is to use the 1996-97 intake manifold.
Cam choice is also key. If you do the above work the heads will go static at about .500 lift.
You don,t have to hog everything out to make power. Velocity is your friend here.
02-15-2011, 12:27 PM
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^^ what he said, Everyone thinks that "Porting" is so simple, there are a lot of physics involved, where, how much, angle of port ect.You must understand the properties of air flow, swirl, tumble, turbulence. There was a speed shop that the owner just hogged out the ports on his own car to make a point, well he did, his car ran 3/10ths slower as all of his customers cars he ported. There is the short side of the radius, understand what this means? then don't do it.
to answer your question i believe the short side radius is the bend on the bottom side going down into the bowl. the bend is sharp, like a right angle and this in essence 'kinks' air flow. smoothing out the top of this bend to 'straighten' air flow increases power. i also understand that making this 'arch' taller is not advantageous so more harm than good is done by messing with the top, but to widen the bend by focusing more on the bottom shelf is what you want. if i'm wrong, i'm wrong. this is just what i have been told by a few ppl that should know.
but what i was asking and still havent had answered is.. is there any kind of guide that is sold for doing this? some kind of template? figured they may be available through GM.. i know that mopar makes them as one of my friends has used them to port a couple of sets of heads for 440 builds.
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02-15-2011, 12:46 PM
#8
When I did my first port job, I had pictures galore of ported LT1 heads and how everything was shaped. Pictures and search other sites on how to's.
Take your time and you'll be fine. Everyone making it out like its the hardest thing to do, but if you know what you need to remove, you wont do more harm then good.
Take your time and you'll be fine. Everyone making it out like its the hardest thing to do, but if you know what you need to remove, you wont do more harm then good.
02-15-2011, 01:46 PM
#9
i understand that guys often think they know exactly what they are doing when they don't bc they are ignorant, egotistical etc etc.. so i see a lot of posts on here from experienced members trying to deter others from doing their own port work. i dont pretend to know exactly what i'm doing, (although i do think i know some) and i dont think that "porting" is simple either. there is a reason guys pay a lot of money to have professionals do it... i am on a budget... i've never done it b4, but everyone who has ported heads had never done it b4 at some point right? i am mechanically inclined and am confident i could have success doing it. however i AM concerned i may do more damage than good due to lack of experience, which is why i am asking questions hoping to get insightful answers.
to answer your question i believe the short side radius is the bend on the bottom side going down into the bowl. the bend is sharp, like a right angle and this in essence 'kinks' air flow. smoothing out the top of this bend to 'straighten' air flow increases power. i also understand that making this 'arch' taller is not advantageous so more harm than good is done by messing with the top, but to widen the bend by focusing more on the bottom shelf is what you want. if i'm wrong, i'm wrong. this is just what i have been told by a few ppl that should know.
but what i was asking and still havent had answered is.. is there any kind of guide that is sold for doing this? some kind of template? figured they may be available through GM.. i know that mopar makes them as one of my friends has used them to port a couple of sets of heads for 440 builds.
to answer your question i believe the short side radius is the bend on the bottom side going down into the bowl. the bend is sharp, like a right angle and this in essence 'kinks' air flow. smoothing out the top of this bend to 'straighten' air flow increases power. i also understand that making this 'arch' taller is not advantageous so more harm than good is done by messing with the top, but to widen the bend by focusing more on the bottom shelf is what you want. if i'm wrong, i'm wrong. this is just what i have been told by a few ppl that should know.
but what i was asking and still havent had answered is.. is there any kind of guide that is sold for doing this? some kind of template? figured they may be available through GM.. i know that mopar makes them as one of my friends has used them to port a couple of sets of heads for 440 builds.
Its VHS so that how long ago it was..
02-15-2011, 07:27 PM
#10
I beleive you're referring to "Standard Abrasives" they offer a basic porting video and they have all kinds/shapes of porting tools. Google them and you'll see what I mean and good luck with your project, just don't forget to take it to a good machine shop and get your valve job done.
02-16-2011, 05:22 AM
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You really need a flow bench if you want to port heads right, or access to one that you can use an unlimited amount of time. LT1 heads really need work just about everywhere but the port floor, and the gasket area. Pushrod pinch and venturi need to be opened up, roof needs to be raised, short sideradius reworked. Once the port roof, bowl, shortside radius is done then you need a flow bench. Find the venturi size that works best for your port but usually 88-91%. If the shortside is laid back pretty good and the port is real wide over the shortside with the roof raised a lot over shortside, you can get by with 91% and get over 270 CFM from the 1.94 intake valve. If you open the venturi up too much, it will allow more air coming thru than you want and the air speed over the short side will be way too high. I would start at 88% and measure the velocity over the shortside. As long as you can keep the air below 260 FPS, keep going larger until it is in the 260 FPS range. this will offer the most CFM with the air being the right speed.
If you understand and can do all of that above go ahead and port them.
If you understand and can do all of that above go ahead and port them.
02-16-2011, 08:03 AM
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You really need a flow bench if you want to port heads right, or access to one that you can use an unlimited amount of time. LT1 heads really need work just about everywhere but the port floor, and the gasket area. Pushrod pinch and venturi need to be opened up, roof needs to be raised, short sideradius reworked. Once the port roof, bowl, shortside radius is done then you need a flow bench. Find the venturi size that works best for your port but usually 88-91%. If the shortside is laid back pretty good and the port is real wide over the shortside with the roof raised a lot over shortside, you can get by with 91% and get over 270 CFM from the 1.94 intake valve. If you open the venturi up too much, it will allow more air coming thru than you want and the air speed over the short side will be way too high. I would start at 88% and measure the velocity over the shortside. As long as you can keep the air below 260 FPS, keep going larger until it is in the 260 FPS range. this will offer the most CFM with the air being the right speed.
If you understand and can do all of that above go ahead and port them.
If you understand and can do all of that above go ahead and port them.
02-16-2011, 03:33 PM
#13
You really need a flow bench if you want to port heads right, or access to one that you can use an unlimited amount of time. LT1 heads really need work just about everywhere but the port floor, and the gasket area. Pushrod pinch and venturi need to be opened up, roof needs to be raised, short sideradius reworked. Once the port roof, bowl, shortside radius is done then you need a flow bench. Find the venturi size that works best for your port but usually 88-91%. If the shortside is laid back pretty good and the port is real wide over the shortside with the roof raised a lot over shortside, you can get by with 91% and get over 270 CFM from the 1.94 intake valve. If you open the venturi up too much, it will allow more air coming thru than you want and the air speed over the short side will be way too high. I would start at 88% and measure the velocity over the shortside. As long as you can keep the air below 260 FPS, keep going larger until it is in the 260 FPS range. this will offer the most CFM with the air being the right speed
If you understand and can do all of that above go ahead and port them.
If you understand and can do all of that above go ahead and port them.
