Quick easy 18.4cfm gain for old Single port heads

[Brian_e]

DISCLAIMER!!! This is how I do things. It works, and I have had very good luck doing it this way. I am certain someone will be on here to tell me I am doing it all wrong. That's fine. They can show me all their tools, successful jobs, and teach me a different way if they want. I am always eager to learn more.

So here goes.
I was doing a quick valve job for a local guy building a stock 1600sp. I decided to do a quick bowl blend while the guides were out, and then my usual 3 angle valve job. I also tested it with a back cut on the intake. I thought it would be fun to test a before and after on my flow bench to see what kind of improvement I could make with minimal time, and almost zero physics involved.

Only port work done was to blend the valve seat into the bowl, and knock the ridges out. This can all be done with a harbor freight 1/4" die grinder and their cartridge roll assortment pack. Just use common sense. Don't remove anything off the port walls making them larger, just remove the ridges that stick out into the ports making the walls smooth. Really this could be done with the guides still in if you used a narrow cartridge roll.

This next part I do myself because I have the available tools. Most guys will need to take this part to their local engine machine shop to have done. It is nothing VW specific, and most any decent shop should be able to handle it.

Now take the heads to a local machine shop, and have them core out the old guides, press in new guides and have them size the guides properly. I like .0015" on the intakes, and .0025" on the exhausts. Have them cut new valve seats with a 3 angle cutter. I use a .040" intake seat, and a .060" exhaust seat. Again, this is all a daily routine for any decent engine machine shop. Also have them reface your intake valves and have them grind a backcut on them. ALWAYS replace the exhaust valves.

Once you get your heads back, I always like to lap my valves to make sure everything looks good. Clean the heads really good. Use a small bottle brush in the valve guides. Lube the valve stems good with fresh gear oil, and assemble the heads with new HD springs, and grind the keepers so they don't butt.

At this point you should probably get the cylinder seating surface cleaned up as well. Most of these old heads are in rough shape and need the clean up cut.

Ok. Here are a few crappy phone pictures I took after I was done. Remember this was all done very quickly, and is no where near perfect. This is a good easy improvement to do on any heads while you are rebuilding them.

Here is a shot of what a backcut valve looks like. I know the seat is a little wide. It was a test valve.

Again...This is how I do it, and it does work. The stock head before I started flowed 96.6cfm at .450", 28"h20. After the quick bowl blend and a real valve job, the head flowed 115.0cfm @ .450".

This is NOT a ported head at this point. This is a cleaned up head with a valve job. Fully porting will take a bunch more time, tools, and might yield better results. My ported single port heads are usually in the 125-130cfm range.

Hope some of you found this a little interesting. Its always good to see a modification done with real world before and after data.

Now Jpaul should do the same to a set of heads and dyno it while watching TV in the living room so we can have dyno number so match the flowbench numbers.

Brian

[atticus finch]

No it is not being done wrong.

30 degree backcut on the valves? About 0.040-0.050 width?

If so, same for a s / b chevy and has the same result, especially on the intake side.
Single angle only on the backcut for both intake & exhaust, multi angle doesn't work at all.

Cleaning up the bowl underneath the valve seat (blending the ridge left from the seat being cut) is a proven and simple way to gain an increase in total airflow, you'll see a larger increase in the intake velocity than you'd see in mass airflow through the intake.

add edit: in looking at the two pictures where it shows the short-side radius from the chamber side looking into the intake port. I see where you didn't remove the protrusion on the side of the bowl where the short-side radius transitions into the bowl wall.
I have no experience with VW heads so I'm only taking an experienced guess at this, why not remove that protrusion there? It looks to be possible without sharpening the short-side radius? It appears it'd smooth out the transition from the short-side radius and promote additional intake velocity? or would that take too much support metal from underneath the valve seat?

[Alstrup]

That´s almost exactly what I did here, apart from a full balance and the "classic" correction of deck height and a raise in Cr to 8,2 and Otherwise completely stock.

Later the muffler was replaced with a NOS Sebring muffler. After that the weired drop in hp around 4000 went away and it pulled 57 hp at 4200 and about the same torque, but held the plateau to about 3400 before dropping off.
The stock 1600 sgl port is rated 46 hp din @ 3900, so it is almost a 10 hp gain with very little work actually. and it really wakes the sgl port up.

So Jeff can relax on this one

T

[bugguy1967]

Nice gains for the work! It just goes to show that factory heads are faaaaar from optimal.

[Brian_e]

Next time I have a set of dual ports I will do the same. I was hoping this would help people see how important a good valve job is, especially on smaller valves with low lifts.

One thing to note for people looking to do this at home. Do not do anything with the exhaust port. The stock exhaust port is really close to 75% of the intake flow after the intake has been blended, and the valve job has been done.

Brian

[Rome]

Thanks for the details of your work and the clear photos, Brian. Looks like you also trimmed back the valve guide boss slightly in the exhaust port.

Had you considered using the cartridge roll to slightly trim back the ledge at the intake manifold flange on the head where the copper sealing ring sits? In my experience the ledge extends maybe half to one millimeter into the port after the ring is squashed/compressed by the intake manifold. Trimming off that protrusion so that the head material is flush with the inner diameter of the compressed gasket ring would be another easy gain. Takes maybe 4 min. per head. This might not be needed if the inner diameter of the intake manifold is smaller than the newly enlarged intake port diameter...

[Brian_e]

[Brian_e]

[Alstrup]

Yes. The same thing can be done to an engine with dual port heads.
Below is a pull with such an engine which resides in a nice ´71 vert.

Stock 1600 type 1.
All balanced.
1,05 mm deck height.
113 heads. Cleared behind the valve guides on intake, casting inaccuracies smoothed out. Non plug side laid back a tad. SS valves, 30 degree back cut. 8,1 CR
1,25 rockers on intake.
34 mm Pict3 with 27 mm venturi. Stock ´71 vert aircleaner with the outer 1½" cut off of the snout.
NOS Leistritz muffler with CSP "hi flow" tail pipes.
That´s it.

[jpaull]

That's a great write up! When you are using your flow bench many times, and constantly comparing your numbers to advertised numbers, I bet you feel comfortable with your results.

Good points regarding the area under the seat that needs desperate help!

Your flowing with the intakes bolted up correct?

How much time does it take to set up your flow bench with some heads and flow test them?

Those 050 Mofocos I have were flowed at headflowmasters on a 110 superflow, and I don't trust the numbers cause that bench maxes out at 160cfm so I don't know how he estimated these numbers that were over 160, and I have done more work to chambers so its all "up in the air lol".
_________________
[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg

Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[Alstrup]

Jeff, if Headflowmasters have a 110 bench with either the Flowcom or PT flow analyzer hooked up to it, the 110 can handle flow up to about 270 cfm @ 25" The software will correct the numbers even though the surpression is only 10" or lower. However, the higher the overclock the higher the inaccuracy in numbers.
I have acces to a SF110, SF600, a Quickflow and a homebrewed PT unit. When we compare numbers there are usually very little variance up to about 160 Cfm (corrected to 25") The real difference between them is that when you start looking away from just getting a lot of air through the ports (chasing high flow numbers!) and begin looking at port velocity, air speed decrease in some parts of the port, (dead spots) tumble and cylinder distribution, the SF110 sort of "gets in trouble" because the air speed at 10" is not enough to really determine where the issues are. 25" is usually fine, but sometimes you have to go to 28" or more to really find the issues. That´s when I rent the Quickflow since it can flow up to 600 Cfm @ 50" Remember to wear ear protection there

I have more than once dynoed engines that have basicly fallen on the face in terms of lack of power compared to what the owner thought it would pull, many times according to some ads here and there. Then taken the heads off of the engine and DECREASED and reshaped or simply corrected the size and shape of the ports if possible, sometimes simply replaced them with something appropriate for the engine and pulled 10 - 20% more power and torque with a cooler running engine.
About 4 years ago I had one customer wiho had built a "kit" 2332 with supposidly 200+ hp. At the moment of truth it pulled 178 hp and 210 Nm torque. Needless to say that the guy was pissed. This was a little more than just the heads. But after a cam swop to another brand with basicly the same seat duration, swop of heads to another brand of CNC heads, a raise from 10,3 to 11 CR along with a 40 minute correction of the intake manifolds we pulled 202 hp and 262 Nm torque the next time. And again, with a cooler running engine. Ohh, this was a deroute

I guess you can say that port flow is one thing. Once you learn to make the ports so the quality and distribution of the incoming mix is good, THEN you can really make a difference.
T

[Longy]

Would be any benefit & extra ponnies along with 1.25 rockers just on the intakes on such 1600sp??? Or aleready on the limit with cfm

[jpaull]

Alstrup wrote:

Jeff, if Headflowmasters have a 110 bench with either the Flowcom or PT flow analyzer hooked up to it, the 110 can handle flow up to about 270 cfm @ 25" The software will correct the numbers even though the surpression is only 10" or lower. However, the higher the overclock the higher the inaccuracy in numbers. I have acces to a SF110, SF600, a Quickflow and a homebrewed PT unit. When we compare numbers there are usually very little variance up to about 160 Cfm (corrected to 25") The real difference between them is that when you start looking away from just getting a lot of air through the ports (chasing high flow numbers!) and begin looking at port velocity, air speed decrease in some parts of the port, (dead spots) tumble and cylinder distribution, the SF110 sort of "gets in trouble" because the air speed at 10" is not enough to really determine where the issues are. 25" is usually fine, but sometimes you have to go to 28" or more to really find the issues. That´s when I rent the Quickflow since it can flow up to 600 Cfm @ 50" Remember to wear ear protection there I have more than once dynoed engines that have basicly fallen on the face in terms of lack of power compared to what the owner thought it would pull, many times according to some ads here and there. Then taken the heads off of the engine and DECREASED and reshaped or simply corrected the size and shape of the ports if possible, sometimes simply replaced them with something appropriate for the engine and pulled 10 - 20% more power and torque with a cooler running engine. About 4 years ago I had one customer wiho had built a "kit" 2332 with supposidly 200+ hp. At the moment of truth it pulled 178 hp and 210 Nm torque. Needless to say that the guy was pissed. This was a little more than just the heads. But after a cam swop to another brand with basicly the same seat duration, swop of heads to another brand of CNC heads, a raise from 10,3 to 11 CR along with a 40 minute correction of the intake manifolds we pulled 202 hp and 262 Nm torque the next time. And again, with a cooler running engine. Ohh, this was a deroute I guess you can say that port flow is one thing. Once you learn to make the ports so the quality and distribution of the incoming mix is good, THEN you can really make a difference. T

You have so much valuable information in this ONE post, I couldn't even figure out what to say for a day, cause I been reading it over and over taking it all in.

All of that makes so much since, I'm Jealous of the fun you must be having with all those flow bench's available!

It would be nice to have a "VW Head Porting and Flow Numbers" Sticky to capture all of this valuable info. People like you, Brian, Modok and some of the others that are constantly Hot Rodding everything available in the current market is priceless info.
_________________
[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg

Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[frenchroast]

[oprn]

I wonder the same thing. On this last SP engine I chucked the intakes up in my lathe and trimmed that edge away. I just blended it into the bell shape of the backside of the valve. I have no flow bench or dyno so really don't know if I improved it or not.
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)

[Brian_e]

I would imagine the valve manufacturer uses the same valve blank for many different sizes. They would just need to turn the OD, and then grind the 45 face on it. The smaller the valve diameter from the original blank, the taller that ridge will end up because its getting closer to the stem. Some valves are worse than others. It's just the end of the 45 face that makes the ridge.

Doing a back cut will increase the flow on most heads I have measured around 3-5cfm. It really depends how bad the ridge is to begin with. I usually lap the valve to see where the seat surface ends, and then grind the back cut just shy of the lap line. At lower lifts, it is almost like adding lift. The ridge hangs down in the way, making the curtain area around the valve at that point shorter. Remove the ridge, and it essentially makes the lift higher.

Similar thing happens when you move the 45deg. seat surface out toward the edge of the valve and make it narrower. It gets the material out of the way of the valve head, so the air can get around the head of the valve easier. The additional valve seat bottom cuts help set the air up to make the turn around the valve head easier.

Brian
_________________
www.type-emotorsports.com

[frenchroast]

[frenchroast]

[Brian_e]

It could work with the file. You could also chuck the valve in a drill, and run it on the side of the bench grinder wheel. Both ways are just as crude, but they will both work.

Any machine shop can back cut the valve for you in about 10min. It’s very quick. I would lap the valves after you get the seats cut to show the shop where the 45 seat ends on the valve face.

Brian
_________________
www.type-emotorsports.com

[oprn]

Very easy to slip though and mark the sealing surface with the file. You are working right up next to it. If you have a steady hand, go for it.
_________________
We had the stone age, the bronze age, the industrial age and now we are in the age of mass deception and mind control for corporate profit. (The mass media age)