Porting a slant six head

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1930

1930

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I have been reading and saving posts that I find whilst searching the slant sites, I have some questions.

I am also hoping I can get some of you more knowledgeable on the subject to chime in with opinions/observations.

I will try and keep identical threads on this site and the slant.org site as I know some of you do not visit the others sites and Id like all the opinions I can get.

Original poster asked..........'Im in the process of porting a 1980 p/u cylinder head. I was wondering what to do with the small emissions breather holes in each exhaust bowl.
Is there an epoxy that will withstand the temp. or is this mod unecessary?

Doc answered..........You can just grind down the tops of the air injection ports and then plug the main feed hole at the rear of the head. (tap it for a pipe plug or use the air tube flange and flatten / weld the tube closed) ..............

Here is a piss poor picture of that air injection hole on my own head, my camera is not the latest and greatest.

I plan to do as mentioned and grind away the top portion or the area where the casting is raised to eliminate that hump.

I am a little concerned that by doing so I will making the hole that is there larger and more pronounced.

Am I being overcautious?
 

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You could just leave it alone too... Is it gonna flow that much better if you do or don't? Probably not. Porting really only helps high RPM situations as far as I'm concerned. What's the intended usage?
 
PoisonDart74 said:
You could just leave it alone too... Is it gonna flow that much better if you do or don't? Probably not. Porting really only helps high RPM situations as far as I'm concerned. What's the intended usage?
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Id like to optimize flow of the head, improve the engines efficiency. I understand that some of the mods I am planning to do wont make a wink of difference in themselves but I am assuming that these few mods together will make a perceptible difference.

Slant 6, manual trans 4 wheel drive big heavy truck.

Higher engine efficiency is my goal.
 
PoisonDart74 said:
You could just leave it alone too... Is it gonna flow that much better if you do or don't? Probably not. Porting really only helps high RPM situations as far as I'm concerned. What's the intended usage?
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these heads suck, the later ones are even worse. I would be willing to bet a good ported head would be just about perfect for a STOCK engine in terms of efficiency...
 
Its a shame that first things that comes to mind is negativity toward the cylinder head. Dosent make any sense to me why we cant be happy making what little improvements we can make and be satisfied with that.

I am sold on the slant six cause of its ruggedness and spunk, not cause I thought it could take me down the 1/4 mile at 11 seconds and on the cheap.

If I wanted that I would have built a small block Chevrolet.
 
Any smoothing you do will give some results. Whther or not it's enough when combined with other mods to make a feelable difference is anyone's guess. But - you won't hurt anything by leaving a larger hole there. It does add a small amount of volume to the port itself, but like Kid mentioned - these heads are so bad that it takes a lot to make them good. It's just reality - not bashing. If you really want to "fix it right" then have the holes welded up and reshape the bowl. This will require the entire head be rebuilt because of the heating required and the distortion - but if that's also part of the plan then welding isn't a big expense. I also don't think it will give you much better performance so the cost vs reward issue comes into play there too.
 
1930 said:
Its a shame that first things that comes to mind is negativity toward the cylinder head. Dosent make any sense to me why we cant be happy making what little improvements we can make and be satisfied with that.

I am sold on the slant six cause of its ruggedness and spunk, not cause I thought it could take me down the 1/4 mile at 11 seconds and on the cheap.

If I wanted that I would have built a small block Chevrolet.
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the trick is to MAKE it do 11's lol which a number of guys have, im still working on the 13's
 
moper said:
Any smoothing you do will give some results. Whther or not it's enough when combined with other mods to make a feelable difference is anyone's guess. But - you won't hurt anything by leaving a larger hole there. It does add a small amount of volume to the port itself, but like Kid mentioned - these heads are so bad that it takes a lot to make them good. It's just reality - not bashing. If you really want to "fix it right" then have the holes welded up and reshape the bowl. This will require the entire head be rebuilt because of the heating required and the distortion - but if that's also part of the plan then welding isn't a big expense. I also don't think it will give you much better performance so the cost vs reward issue comes into play there too.
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Thanks for the thoughts, these are what I was looking for.
 
cjh said:
Can't use an earlier head ????
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Yeah I could but I would like to work what I have, this was only one of a long list of questions that I have, please stay tuned cause I know that you have alot to add to this thread. Thanks
 
805moparkid said:
the trick is to MAKE it do 11's lol which a number of guys have, im still working on the 13's
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Again in my opinion be happy with what we have, be content with the fact that these cars can be made to run in the 14 and faster ( if thats what your into ) and it was done with goodolfashioned handsontinkering instead of opening a Jegs catalog and a fat wallet and buying all pre-fabbed ****.
 
Doc over on slant.org made this comment..............A 'dead-end" hole in that location has little to no impact on what we need to do on the exhaust side of a SL6 head.

The porting "goals" on the SL6 exhaust side is to have smooth flow out of the chamber, across the valve seat and into the port "pocket".

The flow is pretty good once the "fire" is past the valve head and in the pocket area / exhaust port.
You do want to "round-off" the sharp edges, especially around the valve guide, so you can minimize turbulance as the gases transition from the pocket area and into the port "runner".
As for the exhaust pocket inself... having some open volume, right under the valve seat, simply gives the "fire" a place to go and that little EGR "hole" and the indentation it sits in, helps create additional pocket volume.
 
Duster-idiot of on slant.org added this helpful info............I used a late model "447" head that has the ports as you have pictured on my last hi-comp engine, I just plugged the port at the back of the head and called it good...After some bowl work there wasn't enough meat in those holes to tap and install a threaded plug, and if it came loose I didn't want it falling into the chamber on an engine with a deck height in the .0x area.

With headers and the 4 barrels, it never skipped a beat (until the clutch started to die...and I threw the fan belt...but those weren't exhaust related...LOL)...

On "torque" and street porting, as Doc noted smooth out the sharp edges, take some of the restriction out of the ports, but don't go too overboard as you want to keep port velocity up...you don't have to polish the intake ports since you want something to break up the excess fuel that tends to ride the port walls. Do only minimal work to the floor (remove casting flash, don't reduce). Make sure to have a good large compressor and/or reserve tank and get an assortment of carbides from your local tool store (Long and short shank, I use balls, flames, and cylinder with the rounded tip for best bet). A fistful of modelling clay can sometimes be used around the areas you don't want to 'booger" up if you slip (valve seat area and milled surfaces are a good place to protect).
 
One of the questions that I was going to post here was if any of you guys had a way of helping me with terms like FLOOR, CEILING, Bowl, Most of the in port grinding is done on the bump in the floor.

Its difficult to understand what needs to be done if I cant figure out what part of the head is being referred to.

I was hoping someone here could take the image of one of the cut-aways and use a program like paint ( that the one I have and the only one I know of ) and add some text with arrows showing where are these different areas were.

Maybe also where exactly the areas are that can be cleaned up/hogged out a bit.

I would be willing to pay someone for their time and experience.

Can anyone help with this?
 
I have no pics, but here are some simple terms:

Looking directly at the port in normal installed position: the floor is the bottom, the walls are the sides and the roof is the top. Now flip the head on its back, with the chambers up toward you.
With the valve removed, the bowl is what you see if you look down pass the valve seat.
Doc's recommendations are what I have always done as well; I think we may have read the same books when we were kids, :)

You don't want to lower the floor, or the bottom of the runner. I have found that the most "bang for the buck" ( the most effect with the least effort and time involved) is to "blend the bowls", that is, removing the casting flash just below the valve seat ( careful not to hit your valve seats!) and grinding off the big blockey bosses that often stick down where the valves stems come through the head into the bowls. Then you can "gasket match", which is matching up the openings between your intake manifold and the head so they run directly into each other without a "step" where the two meet.

Another thing I do is to open my headers or exhaust manifold slightly larger ( about 3/32) than the exhaust port opening in order to create an anti-reversing effect, or A.R., and polish the exhaust ports. This is easy to do, since headers are usually larger than stock openings anyway.
 
1930 said:
Again in my opinion be happy with what we have, be content with the fact that these cars can be made to run in the 14 and faster ( if thats what your into ) and it was done with goodolfashioned handsontinkering instead of opening a Jegs catalog and a fat wallet and buying all pre-fabbed ****.
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Your really going to come after me about a catalog car? Ive worked my *** off to get where I am with my car, and most everything I have done has been fabbed in, so don't try to belittle me with the catalog BS. Perfect example is the water neck I machined for MY PROJECT. That said im also building an 65 AWB that ive done all the chassis and fab work on.

My point in trying to help you is you cant go wrong with headwork and you want to try to turn around and bite me, go for it. Much easier to skip past your threads where you ask for help... :wack:
 
805moparkid said:
Your really going to come after me about a catalog car? Ive worked my *** off to get where I am with my car, and most everything I have done has been fabbed in, so don't try to belittle me with the catalog BS. Perfect example is the water neck I machined for MY PROJECT. That said im also building an 65 AWB that ive done all the chassis and fab work on.

My point in trying to help you is you cant go wrong with headwork and you want to try to turn around and bite me, go for it. Much easier to skip past your threads where you ask for help... :wack:
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I was not trying to belittle you, not sure where you get that idea.

You are of course more than welcome to read and respond to any post you wish.
 
LTOP said:
I have no pics, but here are some simple terms:

Looking directly at the port in normal installed position: the floor is the bottom, the walls are the sides and the roof is the top. Now flip the head on its back, with the chambers up toward you.
With the valve removed, the bowl is what you see if you look down pass the valve seat.
Doc's recommendations are what I have always done as well; I think we may have read the same books when we were kids, :)

You don't want to lower the floor, or the bottom of the runner. I have found that the most "bang for the buck" ( the most effect with the least effort and time involved) is to "blend the bowls", that is, removing the casting flash just below the valve seat ( careful not to hit your valve seats!) and grinding off the big blockey bosses that often stick down where the valves stems come through the head into the bowls. Then you can "gasket match", which is matching up the openings between your intake manifold and the head so they run directly into each other without a "step" where the two meet.

Another thing I do is to open my headers or exhaust manifold slightly larger ( about 3/32) than the exhaust port opening in order to create an anti-reversing effect, or A.R., and polish the exhaust ports. This is easy to do, since headers are usually larger than stock openings anyway.
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Thanks for the feedback, Ill digest the info and may get back with you if I have more questions.

It is appreciated
 
1930 said:
I was not trying to belittle you, not sure where you get that idea.

You are of course more than welcome to read and respond to any post you wish.
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Your below post

1930 said:
Again in my opinion be happy with what we have, be content with the fact that these cars can be made to run in the 14 and faster ( if thats what your into ) and it was done with goodolfashioned handsontinkering instead of opening a Jegs catalog and a fat wallet and buying all pre-fabbed ****.
Click to expand...

As i was the one bitchin about the head i thought this was directed at me. And BTW my new job gives me access to a big vertical mill and a big lathe so who knows what might happen to a stock head!
 
805moparkid said:
Your below post



As i was the one bitchin about the head i thought this was directed at me. And BTW my new job gives me access to a big vertical mill and a big lathe so who knows what might happen to a stock head!
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Quite the contrary, I enjoy what pics you have posted and like very much your car. Trust me, I would not knock a young man that is interested in slants.

I also envy your knowledge if that helps.
 
1930 said:
Quite the contrary, I enjoy what pics you have posted and like very much your car. Trust me, I would not knock a young man that is interested in slants.

I also envy your knowledge if that helps.
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im sorry i took it that way and i apologize.
 
No problem.

Just to show my ignorance before I call it a night I have thought all of these years that when people worked on heads for performance modifications that they were working on this part of the head that I am pointing to.

I am pretty sure this is called the chamber?

The more I look at this head the smaller it gets.

I have done a few performance V-8 heads or I should say paid someone else to do them. This little slant head really is pathetic but again I will work with what I have.
 

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Here's a little brighter shot of the original picture. Hope it helps...
 

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