Increasing valve size-stock heads.

Heres what I did with my exhaust ports. I dont have any real world numbers because I found out my enigne crapped the bed before the heads could get any run time on them :rolleyes:.
 

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I was among several people at Richard Clarks shop one evening and we flowed 6 sets of iron heads and two that were aluminum. The heads were iron ESP CNC ported heads, iron Champion CNC ported heads, two sets of iron heads ported by me, two sets of iron heads that were ported by someone else and they were also done by hand. I can tell you that ALL the iron heads hit a ceiling at .500 lift with cfm maxxing out at 186 to 190. It didn't make a difference if the chambers were completely stock or CNC'd to unshroud the valves or if they were reshaped like a heart to help flow. They ALL were within a few cfm's from each other. I can also say that sticking your finger into the port while flowing at maximum lift only decreases the flow about 5 cfm. So, port matching helps but not like you would think it would. Personally, after flowing the heads below, I won't be reshaping the combustion chambers on any of my heads and I won't be spending a lot of time opening up the runner. I'll be focusing in the bowl area, cutting half of the guides out and gasket matching about an inch down into the runner.


Here are the results:

Just to clear this chart up some. The first head was bought from a head porter that supplied a flow chart. They were BEAUTIFULLY ported....you couldn't ask for anything better! However, we questioned the flow numbers that was supplied with the heads so we flowed them to see if the numbers could be duplicated...which they were not. We also flowed one of my heads that I ported myself without a spark plug in the hole the flow numbers duplicated the numbers that was supplied with the first head listedin the chart. We came to the conclusion that the guy who ported those heads must have flowed them with a spark plug out...which resulted in bloated numbers.

All IRON heads have 1.77" intake valves and was flowed at 28".

PLEASE DO NOT ASK WHO SUPPLIED THE BOGUS FLOW #'s. I won't tell you.


HeadFlowChart.gif
 
Turbo1dr said:
HeadFlowChart.gif
Click to expand...

Great info!

I am just curious as to why the aftermarket heads flow better?
Was the ports shaped much different, intake port window bigger, valves are less shrouded, larger cc's in the intake runner? etc..

What size intake valves are in the aftermarket cyl heads?
Thanks.

:cool:
 
Interesting data. It would have been cool to have done a bone stock head as a base number in your experiment.
 
Turbo1dr said:
I was among several people at Richard Clarks shop one evening and we flowed 6 sets of iron heads and two that were aluminum. The heads were iron ESP CNC ported heads, iron Champion CNC ported heads, two sets of iron heads ported by me, two sets of iron heads that were ported by someone else and they were also done by hand. I can tell you that ALL the iron heads hit a ceiling at .500 lift with cfm maxxing out at 186 to 190. It didn't make a difference if the chambers were completely stock or CNC'd to unshroud the valves or if they were reshaped like a heart to help flow. They ALL were within a few cfm's from each other. I can also say that sticking your finger into the port while flowing at maximum lift only decreases the flow about 5 cfm. So, port matching helps but not like you would think it would. Personally, after flowing the heads below, I won't be reshaping the combustion chambers on any of my heads and I won't be spending a lot of time opening up the runner. I'll be focusing in the bowl area, cutting half of the guides out and gasket matching about an inch down into the runner.


Here are the results:

Just to clear this chart up some. The first head was bought from a head porter that supplied a flow chart. They were BEAUTIFULLY ported....you couldn't ask for anything better! However, we questioned the flow numbers that was supplied with the heads so we flowed them to see if the numbers could be duplicated...which they were not. We also flowed one of my heads that I ported myself without a spark plug in the hole the flow numbers duplicated the numbers that was supplied with the first head listedin the chart. We came to the conclusion that the guy who ported those heads must have flowed them with a spark plug out...which resulted in bloated numbers.

All IRON heads have 1.77" intake valves and was flowed at 28".

PLEASE DO NOT ASK WHO SUPPLIED THE BOGUS FLOW #'s. I won't tell you.


Click to expand...

Great post. I observed almost the same exact thing in tinkering with heads on my super cheap DIY flow bench powered by two shop vacs.

I was wondering if my bench just wasn't accurate enough to see other changes but your post now has me thinking that I just may have been more accurate than I thought.

Like I said in the post above, doing anything other than the throat (to include ssr) and bowl/guide area did NOTHING for flow.

I calculated almost the same range of flow numbers as your findings and couldn't do any better no matter what I did.
I used a stock head to tweak my flow coefficient so that the stock head maxed out at 150ish cfm and then made changes relative to that.
I thought I just sucked at porting after comparing my results to the numbers I was seeing online.

What size bore did you flow it on? I used a 4" bore due to the schedule 40 pvc pipe I used being that size. I was wondering how that affected flow. On the stock bore the chambers are larger than the bore in a couple of spots so I was figuring that must kill some flow. I sprayed some fluid down the port to see where it was flowing and most of it doesn't come near the overhang anyway so it might not be hurting flow that much.

If you want to see something really neat, grab some modeling clay and put it at the floor of the port to raise the hump. I.e. make a larger radius.
This blocks a huge amount of the port but I was amazed to see that the flow INCREASES and the port flow even sounds a ton smoother. I don't remember exactly how much the flow increased but I think it was around 7 cfm or so on top of what I could already max out at.

I didn't have the guts to try and actually fill a port like this and run it. Someone with more time and money to blow should try it.
 
Pablo said:
Great post. I observed almost the same exact thing in tinkering with heads on my super cheap DIY flow bench powered by two shop vacs.

If you want to see something really neat, grab some modeling clay and put it at the floor of the port to raise the hump. I.e. make a larger radius.
This blocks a huge amount of the port but I was amazed to see that the flow INCREASES and the port flow even sounds a ton smoother. I don't remember exactly how much the flow increased but I think it was around 7 cfm or so on top of what I could already max out at.

I didn't have the guts to try and actually fill a port like this and run it. Someone with more time and money to blow should try it.
Click to expand...

This is done on the Chevy inline 6 to increase flow as well. You can actually buy a pre made "lump" that is epoxied and screwed into place to help with the numbers.
 
it's just a six said:
Could you tell us what is the largest valve you can fit & bennefit from?

Unshroud the chambers is all that is needed?

What is the limiting factor for installing larger valves,,the bore size or the chamber wall or both?:cool:
Click to expand...
It appears that the cyl diameter is the limiting factor for flow. Unshrouding the val ves and notching the bores will help. Imo on iron heads the spring seats are the limiting factor. You just cant easily get enough spring on them. Flow doesnt mean chit if the engine isnt capable of revving to take advantage of the added flow. Ive seen a set of 1.83 intakes in iron heads. Ive heard of 1.90's if i recall properly
 
Were any of these flow bench testing done with a pipe in the exhaust port and some puddy around the intake port ?
Allan G.
 
Good thread with some interesting data/theories ...fits well with some of the current discussions.
 
Too bad the chart is missing. BTW, thessman did my iron heads...
 
My ANS heads have 1.83 valves in them. I have also heard of 1.90's also but would have no idea how much work would have to go into them to make that happen.
 
Turbo1dr said:
I was among several people at Richard Clarks shop one evening and we flowed 6 sets of iron heads and two that were aluminum. The heads were iron ESP CNC ported heads, iron Champion CNC ported heads, two sets of iron heads ported by me, two sets of iron heads that were ported by someone else and they were also done by hand. I can tell you that ALL the iron heads hit a ceiling at .500 lift with cfm maxxing out at 186 to 190. It didn't make a difference if the chambers were completely stock or CNC'd to unshroud the valves or if they were reshaped like a heart to help flow. They ALL were within a few cfm's from each other. I can also say that sticking your finger into the port while flowing at maximum lift only decreases the flow about 5 cfm. So, port matching helps but not like you would think it would. Personally, after flowing the heads below, I won't be reshaping the combustion chambers on any of my heads and I won't be spending a lot of time opening up the runner. I'll be focusing in the bowl area, cutting half of the guides out and gasket matching about an inch down into the runner.


Here are the results:

Just to clear this chart up some. The first head was bought from a head porter that supplied a flow chart. They were BEAUTIFULLY ported....you couldn't ask for anything better! However, we questioned the flow numbers that was supplied with the heads so we flowed them to see if the numbers could be duplicated...which they were not. We also flowed one of my heads that I ported myself without a spark plug in the hole the flow numbers duplicated the numbers that was supplied with the first head listedin the chart. We came to the conclusion that the guy who ported those heads must have flowed them with a spark plug out...which resulted in bloated numbers.

All IRON heads have 1.77" intake valves and was flowed at 28".

PLEASE DO NOT ASK WHO SUPPLIED THE BOGUS FLOW #'s. I won't tell you.


HeadFlowChart.gif
Click to expand...



This was the most interesting post of all.........testing seems to have been done in an unbiased environment.

190 cfm with 1.77 valves @28 was the ceiling on the irons.
 
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