D0OE exhaust ports

[GARY C]

It would be nice if someone had some actual power numbers instead of just what flows better, I think it has been established over and over that exhaust flow numbers and bigger exhaust valves rarely equate to more power. You will find several race heads on the market that have a 1.55 exhaust with a 2.225 or larger intake valve which also blows a hole in the Int to Ex percentage theory...

Does that still apply if it's a 9:1 engine or 15:1?

Theory's in general or just the I/E percentage theory?

[mag2555]

Here are some pictures that go with the last batch of flow numbers that I posted.
Like those numbers show the 1.60" valve picked up a ton up to a certain lift , but peak flow really went no where and that result was expected.

Then I did more work to the short turn arc and the cylinder side wall and the opposite side wall and lost 4 percent of the peak flow and this due to the flow sheer I now have and need to deal with starting at .400" .

The photos I posted are in opposite order.
The last shoot is how the seat area was cut at first to get the 1.60" valve in there.

I now realize that I should have posted up a picture of the valve itself , and I will get that done tomorrow along with more port work that will get the mid and high lift flow numbers back on track.

[travis]

1.jpg

I guess I forgot to post this in my own exhaust port thread

On the exhaust side, as purchased. Appeared to be as cast from the factory and had a hair smaller than stock Chevy valve 1.50” vs stock 1.54”.

Exhaust
.100 45
.200 88
.300 106
.400 111
.500 112
.600 112
.700 112

Cleaned up the short turn, removed the sharp lip on the short turn, light bowl blend, and took out about 60% of the guide boss lump and blended it in. Wasn’t finished but it did better than I thought it would.

Exhaust
.100 47
.200 90
.300 117
.400 139
.500 145
.600 149
.700 150
.800 150
.900 150
1.00 150

I have since cleaned these up a little better, and shaped the valve guide lump a little better. Hoping to have flow test results in the next few days, then off to the machine shop.

[gmrocket]

It would be nice if someone had some actual power numbers instead of just what flows better, I think it has been established over and over that exhaust flow numbers and bigger exhaust valves rarely equate to more power. You will find several race heads on the market that have a 1.55 exhaust with a 2.225 or larger intake valve which also blows a hole in the Int to Ex percentage theory...

Does that still apply if it's a 9:1 engine or 15:1?

Theory's in general or just the I/E percentage theory?

You said the ex percentage theory.

[GARY C]

Does that still apply if it's a 9:1 engine or 15:1?

Theory's in general or just the I/E percentage theory?

You said the ex percentage theory.

Here is my original quote, I have never seen anything to prove it, there seem to be some pretty stout pump gas engines shown here with under 1.6 valve with 50 degree seats, CGT's Vortec 350 was a 1.5 with a 50 and made 480 hp and 460 ft, so I don't know what percentage one would use, many have been quoted over the years but I think many have moved away from looking at ex flow all together.

Bigger ex valves may have been shown to increase power on the OP's type of head and was why I wondered if anyone had actual dyno numbers showing this to be the case, preferably exhaust gains alone but it's not likely that anyone went to that extent.

It would be nice if someone had some actual power numbers instead of just what flows better, I think it has been established over and over that exhaust flow numbers and bigger exhaust valves rarely equate to more power. You will find several race heads on the market that have a 1.55 exhaust with a 2.225 or larger intake valve which also blows a hole in the Int to Ex percentage theory...

[gmrocket]

Theory's in general or just the I/E percentage theory?

You said the ex percentage theory.

Here is my original quote, I have never seen anything to prove it, there seem to be some pretty stout pump gas engines shown here with under 1.6 valve with 50 degree seats, CGT's Vortec 350 was a 1.5 with a 50 and made 480 hp and 460 ft, so I don't know what percentage one would use, many have been quoted over the years but I think many have moved away from looking at ex flow all together.

Bigger ex valves may have been shown to increase power on the OP's type of head and was why I wondered if anyone had actual dyno numbers showing this to be the case, preferably exhaust gains alone but it's not likely that anyone went to that extent.

It would be nice if someone had some actual power numbers instead of just what flows better, I think it has been established over and over that exhaust flow numbers and bigger exhaust valves rarely equate to more power. You will find several race heads on the market that have a 1.55 exhaust with a 2.225 or larger intake valve which also blows a hole in the Int to Ex percentage theory...

all I asked was if the compression ratio has anything to do with it?

Do you think it's matters?

[GARY C]

You said the ex percentage theory.

Here is my original quote, I have never seen anything to prove it, there seem to be some pretty stout pump gas engines shown here with under 1.6 valve with 50 degree seats, CGT's Vortec 350 was a 1.5 with a 50 and made 480 hp and 460 ft, so I don't know what percentage one would use, many have been quoted over the years but I think many have moved away from looking at ex flow all together.

Bigger ex valves may have been shown to increase power on the OP's type of head and was why I wondered if anyone had actual dyno numbers showing this to be the case, preferably exhaust gains alone but it's not likely that anyone went to that extent.

It would be nice if someone had some actual power numbers instead of just what flows better, I think it has been established over and over that exhaust flow numbers and bigger exhaust valves rarely equate to more power. You will find several race heads on the market that have a 1.55 exhaust with a 2.225 or larger intake valve which also blows a hole in the Int to Ex percentage theory...

all I asked was if the compression ratio has anything to do with it?

Do you think it's matters?

The consensus seems to be that higher compression engines favor smaller ex ports and headers, I am just not sure at what point going bigger is better or if one would be safer staying on the small side and adding ex duration?

I will say that the OP's exhaust port was the quietest one I have had on my bench, I will curious to see how it acts to the 1.6 valve.

[gmrocket]

Here is my original quote, I have never seen anything to prove it, there seem to be some pretty stout pump gas engines shown here with under 1.6 valve with 50 degree seats, CGT's Vortec 350 was a 1.5 with a 50 and made 480 hp and 460 ft, so I don't know what percentage one would use, many have been quoted over the years but I think many have moved away from looking at ex flow all together.

Bigger ex valves may have been shown to increase power on the OP's type of head and was why I wondered if anyone had actual dyno numbers showing this to be the case, preferably exhaust gains alone but it's not likely that anyone went to that extent.

all I asked was if the compression ratio has anything to do with it?

Do you think it's matters?

The consensus seems to be that higher compression engines favor smaller ex ports and headers, I am just not sure at what point going bigger is better or if one would be safer staying on the small side and adding ex duration?

I will say that the OP's exhaust port was the quietest one I have had on my bench, I will curious to see how it acts to the 1.6 valve.

Oh , this head is being done in your shop on your bench?

When you say quiet,, how are you testing that?

I have a db meter set up on mine I use sometimes...so I do have a reference.

[Carnut1]

all I asked was if the compression ratio has anything to do with it?

Do you think it's matters?

The consensus seems to be that higher compression engines favor smaller ex ports and headers, I am just not sure at what point going bigger is better or if one would be safer staying on the small side and adding ex duration?

I will say that the OP's exhaust port was the quietest one I have had on my bench, I will curious to see how it acts to the 1.6 valve.

Oh , this head is being done in your shop on your bench?

When you say quiet,, how are you testing that?

I have a db meter set up on mine I use sometimes...so I do have a reference.

Db meter is an interesting idea, I like that. I am not sure what exactly it is quantifying but it is a good idea. Thanks, Charlie

[GARY C]

all I asked was if the compression ratio has anything to do with it?

Do you think it's matters?

The consensus seems to be that higher compression engines favor smaller ex ports and headers, I am just not sure at what point going bigger is better or if one would be safer staying on the small side and adding ex duration?

I will say that the OP's exhaust port was the quietest one I have had on my bench, I will curious to see how it acts to the 1.6 valve.

Oh , this head is being done in your shop on your bench?

When you say quiet,, how are you testing that?

I have a db meter set up on mine I use sometimes...so I do have a reference.

I always wondered if a DB meter could be a good tool for that, if you could build data with dyno comparisons there may be something to learn there but I am just going off of sound and stability.

I live close to him so I agreed to flow the head for him, he is doing his own porting.

[gmrocket]

The consensus seems to be that higher compression engines favor smaller ex ports and headers, I am just not sure at what point going bigger is better or if one would be safer staying on the small side and adding ex duration?

I will say that the OP's exhaust port was the quietest one I have had on my bench, I will curious to see how it acts to the 1.6 valve.

Oh , this head is being done in your shop on your bench?

When you say quiet,, how are you testing that?

I have a db meter set up on mine I use sometimes...so I do have a reference.

Db meter is an interesting idea, I like that. I am not sure what exactly it is quantifying but it is a good idea. Thanks, Charlie

I don't know what it's quantifying either..other than I think less screeching relates to reduced pumping losses.

I'll post some pics and readings from what I gathered when experimenting .