Porting 4AG: My 1st O/S valve porting job

[oldeskewltoy]

I haven't posted many recent porting jobs, but I decided I'd post this one... being that it is my 1st porting job that incorporates over-sized (Atlantic) valves.

Intakes....



and exhausts



This is also the first head I've worked on that was previously in another porters hands prior to my involvement

I explained to the client I would do what I could, but that there had already been some "damage" done to the short side radius's of the intake bowls






The original intent of the owner, and the original porter was to retain the standard valve seats. This can be done with no issues when using 1mm O/S valves, but when using 2mm O/S valves the seat becomes too small, too much machining is required, and once finished you are left with not very much seat, and so seat failure is more likely. I explained this to my client, and persuaded him to invest the money to have the proper seats installed. He agreed, a side benefit to the O/S valve seats is it MAY allow me some additional material to "fix" the short radius's.

Oh, this is a smallport head, and for the numbers....

bore = 3.2680"
stroke = 3.0315"
Deck = .025"
gasket = .020"
piston volume = 9.5cc
final desired static CR = 12.5 to 1
Kelford 193HV-B. 300 max duration, 10.5mm maximum lift


now for some views of the ports.... the intakes, are just roughed out ports - more will be done once the O/S valves are fitted

#1 \/



#2 \/



#3 \/



#4 \/



The significant differences in these views are 2 fold... 1) to "remove the sagging eye brows", and to open up the entire roof of the port. 2) to add as much of a taper as possible from the gasket flange to the leading edge of the bowl - this adds a bit more slope to the port roof. The view below demonstrates what I mean



although rough, the right hand side shows the roof taper beginning to materialize. The left hand side is fully shrouded and the roof of the port adds nothing to the flow the right hand side(as you are viewing it) has a small slope from the gaskets edge to the beginning of the bowls roof. What I did was to remove the quick and sudden taper designed into the head for manifold mis-matches, and made a gradual slope where there wasn't a slope before.

[oldeskewltoy]

I'll be doing quite a bit more once the O/S seats have been installed. Now onto the exhaust side of the head.....


Exh #1 \/



Exh #2 \/ - note the actual change in overall size from 29.5-30.5mm out to 33mm



Exh #3 \/ - using the gasket to show the change



Exh #4 - a slightly different view.... showing material removed




A before, and mostly after view of all the ports from nearly identical perspectives

[oldeskewltoy]

#4 intake port - almost there.... O/S valves not yet fitted, but the port and bowl work to allow those O/S valve to breath is quite evident

[MorGo]

The port floor needs some reshaping.What about the quides/quide bosses?
And 10,5 mm lift cam is small even for stock valves when properly ported.Sure,it's about there but much of the potential remains unused.
What's the throat diameter?

[oldeskewltoy]

As I pointed out, this is going to get O/S seats installed, once the seats are in, I'll attempt to put a radius on the port floor, but it would be ill-advised to attempt that before the new seats are in. 10.5mm lift cams in a 4AGE are quite tall actually, 7.1mm is stock in this head. From memory(could be faulty), the Atlantic cams were under 12mm. As it is the head will need to be machined so the 10.5mm cams will clear the bucket cradles. "Throat diameter"? Do you mean what is the cross width? I'm currently between 49.25mm and 49.40mm at the mounting flange.


Here are the other 3 ports....
#1 \/



#2 \/



#3 \/






As far as guides go.... each with before, and after views


#1 intake guides \/



#2 intake guides \/



#3 intake guides \/



#4 intake guides \/

[MorGo]

Oh,it's still stock seats.Might be better that I don't comment anymore..

[takai]

Could do with a lot more taken out. For reference:

That is my head, same valves, roughly 190hp at the rears.

[dumbass]

have u match ported the manifold to the gasket and the gasket to the head
we used to fit small 3mm locating dowels between heads and manifolds on most engines if possible
so everything is match ported so no step and then we dowel them so they dont move tiny amounts on the bolts

[oldeskewltoy]

takai - 190 whp is very good on stock valves I'm debating removing the valve guide bosses.


Here are a pair 3 panel views.... The first one is the intake side of a smallport - top = stock, middle = typical OST smallport porting, bottom = Oversize valve head by F/A builder Loynings






now for a similar 3 panel, but the exhaust side... Same variables - stock, OST, Loyning O/S




I believe now you can understand where I borrowed my ideas for porting an O/S valve equipped head from

[oldeskewltoy]

have u match ported the manifold to the gasket and the gasket to the head
we used to fit small 3mm locating dowels between heads and manifolds on most engines if possible
so everything is match ported so no step and then we dowel them so they dont move tiny amounts on the bolts

I have not match ported the intake manifold. Here is what I have done... I've ported the intake to a steel OEM gasket. I've noted that although the smallport gasket is reversible/flip-able, it isn't a perfect flip. I'll be including instruction to fit the gasket they choose and feel its fit on the port before the manifold is attached... and if ANY part of the gasket can be felt(is in the air stream) the gasket should, 1st be flipped and seen if the fit is better, but if not to get the gasket ported to get it out of the air-stream. I'm going to recommend he use an OEM, because it being steel is easier to accurately port, and maintain its integrity.

The VERY first time I delved into the head of my TVIS 4AGE (back in 1999) I found that the TVIS plate-to-head uses dowels, but the TVIS plate to manifold didn't! I used tiny roll pins to pin the intake to the TVIS plate and then ported accordingly

[takai]

That head has FA valves, hence why i suggested you would want to go wider on your intake, and much larger on the exhaust.

[oldeskewltoy]

What's the throat diameter?

The valve seat throat diameter currently is.....




I'll know more about the after once I get the head back with the O/S seats installed

[toyota1515]

Looking good, good luck with it.

[oldeskewltoy]

The valve seat throat diameter



I'll know more about the after once I get the head back with the O/S seats installed

The intake throat went from around 26.07mm, out to 27.7mm a gain of 1.6mm, or a gain of about 6.3%

The exhaust just GREW.... from 20.97mm out to 23.84mm, a gain of 2.87mm or a WHOPPING increase of OVER 13%


Here are a pair of unique views... top is the exhausts, bottom the intakes.

Left side have the seats roughed out, right side is raw uncut seat






and last for this post... the progression of chamber #3... top view as it arrived, the next view shows it with the un-machined seats







More to come

[oldeskewltoy]

All the intake ports are now finished. I've done what I could with the short radius, and the overall size is now set.


Now that the intakes are set, we move on to the exhaust side. Now that the O/S seats are in, the exhaust sees a cutting bit to get the "new" shape correct.



The first thing you notice is the overall increase in size... if you are careful you can see this expansion proceeds beyond the valve guide. Note the increase between the bowl wall and guide, and the splitter and the guide



This increase in volume is evident from the port view as well. Top view was the "finished till O/S seats installed"....



and in the bottom view... the lopsided look with the left bowl now shaped to accommodate the volume needed for the O/S valve.... the right hand bowl awaiting its massaging