D0OE exhaust port

[mag2555]

I could not agree more with Steve’s post about turbulence!
If a exh port under a flow test display’s such at whatever lift less then the peak lift being tested at then to me the peak flow numbers are flat out useless!

It’s too bad that people who pay to get a head(s) flow tested are rarely told about such conditions when they pick up there heads !

How was that for a reply Mr or Miss Adimin, will you ban me again for 30 days for this reply post?

[blackford]

Every head is different, but based on my experience, you can remove the boss completely and more. This pic shows the exhaust port boss completely gone plus the roof was raised 1/8" to 3/16" and blended. An important note is that you have to have headers that can be port matched to this port or otherwise, it could be for not. I used Dougs headers tri-ys that had enough material to allow port matching. A few other headers I checked out were a no go. These were 1-5/8 tube headers. The port measured 1.48 x 1.25. If you can use 1-3/4 tube headers, you'll have more room. I can provide more pics of the exhaust and intake ports if you are interested.

What engine are these going to go onto?

That is a borderline sadistic amount of cutting Does that leave enough guide left for long term street usage?

1 3/4” headers are not available for this application. Well, they are, but are WAY outside the budget and are really too big for the application anyway. The port exit will be sized for a 1 1/2” header.

No it doesn't. The final config was a bronze guide sticking out about 1/4" and it was shaped.

[mag2555]

Probably more times then not I have found during flow test with different type Mule heads used for port development on my bench that completely removing the guide will cause a low lift flow loss and can introduce turbulence at some .300” lift or so.

This is especially the case on heads with exh valve bowls depth wise in which the top of the valve guide is not in the bowl as deep as the diameter of the exh valve used.

By top of the valve guide I mean the chamber side of the guide, not where the valve guide meets the roof.

Canted valve heads can be a bit of a different story since all things being equal they will flow more air with a smaller valve bowl throat.

[n2omike]

Probably more times then not I have found during flow test with different type Mule heads used for port development on my bench that completely removing the guide will cause a low lift flow loss and can introduce turbulence at some .300” lift or so.

This is especially the case on heads with exh valve bowls depth wise in which the top of the valve guide is not in the bowl as deep as the diameter of the exh valve used.

By top of the valve guide I mean the chamber side of the guide, not where the valve guide meets the roof.

Canted valve heads can be a bit of a different story since all things being equal they will flow more air with a smaller valve bowl throat.

The valve guide boss on a SBF is nothing more than a major intrusion/choke point in the port. I make it disappear completely like Blackford's photo, and don't worry about that 1/4" or so of guide that is lost. I ran the 289 heads that were done like this on a daily driver and put thousands of street/strip miles on the car over a 12 year period. It had the occasional valve job, but never did need guides. Yes, they were bronze, and the geometry was spot on. The rockers were the old Dove units... who made almost everyone's rockers back then, including the Comp aluminum. They are better/tighter/last longer than what you can buy now in an aluminum stud mount rocker.

[mag2555]

Can you post up flow numbers up to .300” lift of before and after total guide removal?

[n2omike]

Can you post up flow numbers up to .300” lift of before and after total guide removal?

I've posted the full numbers somewhere in the past... but would have to dig them up.
Very busy, so you'll have to be patient. lol

[mag2555]

Mike, I will save you the trouble of digging out your flow sheets!
While not a direct A/B test I just slapped a E7TZ head on the bench and got these numbers.
The second test was after I fully blended in the valve guide without going any deeper with the troughs on either side of the guide.
This is with the stock valve .
The first column is stock, the second is the rework, and the 3rd the flow difference.

.050”. 18. 16.4. -1.6 cfm

.100”. 37.3. 36.6. -.7 cfm

.200”. 76.9. 74.9. -2 cfm

.300”. 103. 103. =

.400”. 112.6. 113.3. +.7 cfm

.450”. 113.3. 114.8. +1.5 cfm

If one was to blend out the lower rear wall of the bowl then more low lift flow would be lost.

[n2omike]

I found a post I made back in the day that included flow numbers:

Coming from someone who has ported their fair share of 289 heads, those look really good! I ported mine without the aid of a flow bench, and they did pretty well. They pushed my 3300# pump gas, flat tappet 6800 rpm 306ci mustang to a best of 7.48 @ 93 in the 1/8 naturally aspirated, and 6.74 @ 103 with a 200hp plate. Toploader 4-speed car, and served as a daily driver. Car ran 10.63 @ 126 in the 1/4 on the bottle.

I had the heads flowed after a decade or more of abuse, old valves and a worn out valve job... and they flowed:

Intake -- Exhaust

.1 063 -- 050.9
.2 119 -- 101.3
.3 168 -- 132.8
.4 201 -- 157.1
.5 210 -- 175
.6 218 -- 176.6

The intakes came out to around 155cc, and the exhaust 55cc. (1.94"/1.60" valves) They were just ported by 'eye', and seemed to work pretty well for what they were. This was done back in the days before the internet, right before all the aftermarket heads came out. They whooped up on more than their fair share of Chevies back in my late night street racing days.

For the exhaust port, I remove the 'step' and make the roof a straight shot to the back of the bowl. You lose a small amount of the guide, but it still works just fine.

Mine are C6 castings with the dog-leg exhaust port with the bosses made for the thermactors. I don't believe your C5 heads have that, and are probably more efficient.

I will also agree that 1.94"/1.60" valves are probably not optimal on these little heads. The 351W size of 1.84"/1.56" (I believe, that's the measurements) fits better. The bowl is getting really thin with the bigger valves, and the short side turn seems to get compromised.

[n2omike]

Better exhaust ports don't need as much duration to run good. Some guys used to shape those bosses into super sexy guide veins, it doesnt have to be all or nothing. Those exhaust port can flow 180 cfm or better without big outlet size. You don't need that much cfm for your goal but I'd make it better than stock. 150 cfm would work well with your intake flow.

Is this you Mummert? Came across this looking for my numbers...

https://www.fordmuscleforums.com/thread ... ds.493012/

[Mummert]

No, I'm Geoff Mummert in San Diego , no Facebook.

[Walter R. Malik]

Forget about percentages and just make both the intake and exhaust ports as good as you can ... then cam it accordingly.

[Helmantel]

Every head is different, but based on my experience, you can remove the boss completely and more. This pic shows the exhaust port boss completely gone plus the roof was raised 1/8" to 3/16" and blended. An important note is that you have to have headers that can be port matched to this port or otherwise, it could be for not. I used Dougs headers tri-ys that had enough material to allow port matching. A few other headers I checked out were a no go. These were 1-5/8 tube headers. The port measured 1.48 x 1.25. If you can use 1-3/4 tube headers, you'll have more room. I can provide more pics of the exhaust and intake ports if you are interested.

What engine are these going to go onto?

I agree that you should be a bit careful on the port exit size. I matched mine to the same 1.48 x 1.25 inch dimensions of the Fel Pro gaskets I had but regretted that when I hardly could match the 1 5/8" Hooker headers to that size (they were taller but narrower). I should have kept the ports a little smaller in hindsight. Or at least waited with grinding the last bit until I knew the header entry dimensions.

[mag2555]

Walt, I need to ask, how does someone without a flow bench and some pretty good knowledge and experience " make them as good as you can"?

How does someone without a flow bench know if there rework has taken a lesser flowing but smooth flowing port @ let's say .300" lift into being a gurgling turbulent port?

Once you screw up the short turn , and especially if your already using a larger Exh valve size the odds are that atleast in terms of a iron head it's time then to find another's one to restart on!

[n2omike]

Walt, I need to ask, how does someone without a flow bench and some pretty good knowledge and experience " make them as good as you can"?

How does someone without a flow bench know if there rework has taken a lesser flowing but smooth flowing port @ let's say .300" lift into being a gurgling turbulent port?

Once you screw up the short turn , and especially if your already using a larger Exh valve size the odds are that atleast in terms of a iron head it's time then to find another's one to restart on!

The exhaust ports on these stock heads are VERY BAD. It's amazing that they would even be created like this in the first place. Performance was definitely ZERO concern for them. This being said, they were originally designed for a 221 ci engine, and never changed THAT much as displacement grew to 260, 289, 302 and even 351 ci.

Look at some pictures of 'good' bowls, and make yours look similar without risking grinding all the way to water. With stock or 351W sized (1.84/1.56) valves, you can make the bowl look pretty nice without a lot of risk. As for the exhaust, make them look like the picture Blackford posted. Remove the valve guide boss, and make the roof a straight shot to the back of the bowl.

The C5 289 heads have a much straighter port without the 'dog leg' shape and thermactor bump in the top corner. These will make for a much more efficient final product than the C6 and later with the thermactor bump. Mine are the C6. The C5 should produce better mid lift numbers.

The 'obvious' will go far with these heads. If the heads need a rebuild, I'd put that money towards a set of aftermarket units, as these are pretty terrible and require a LOT of work to make usable. However, it will definitely be a learning experience if you decide to make chips.

Good Luck!

[Mummert]

Why does everyone always dogg the exhaust port in the SBF iron heads. With 2hrs worth of work they will be capable of making more HP than any thing the intake ports can do with a weeks worth of work. After working these heads on too many occasions the exhaust ports impress me more everytime.
C5AE heads are for sure my favorites I like them better than 351W heads especially for 289-302 builds.

The intake port has always been the sheep in wolves clothing. They are up to the task, but shoturn is finicky and they are very sensitive to the valve head shape, and the amount of grinding is not for the timid.