2.9 Promaxx Aftermarket Head Porting

[PetroleumJunkie412]

@Jim Oaks, trying to set this up as a info page on 2.9 area of tech section. Want to get some feedback here first.






Now that we've let the 2.9 heads jokes run their course, I am moving on into figuring out how to port these things as part of my build. If I'm going to push the envelope on this engine, I want to do as much as possible now so as to not regret it later.

Snoranger has been a great help so far (you suck Bobby ) on helping me look at these things.

There's almost nothing out there on it. Pruett gives one sh*tty paragraph and diagram on the intake side only,and as far as exhaust, his only comment:

"get rid of the egr bumpand it's all sh*t and let's not discuss it further other than 220 grit and don't think about it."




(pretty sure that's a valve cover bolt boss there Sven, but uh, sure, you gave the world Hemi so we'll play along)








Well sven. I disagree. Strongly.


Theres ponies to be had in them ports.





Pruett was probably correct for n/a and carbureted with his comments.


My engine is being built to handle 21psi at 7000 rpm on sequential efi. His advice doesn't apply here.









So. This is what I think I know about porting. I'm probably wrong. I'm not a mechanic. I'm a computer nerd that f*cks with old engines. Please chime in..



From my understanding, when running tbi/carb n/a, the goal is to rely on what oem gave you and cause airflow to scavenge itself. With A perfect job on intake runner shape and path and other necessary modifications, a volumetric efficiency of >100 is possible, and is evidence of a perfect intake design for a given rpm range. Air will develop minute levels of boost when entering the combustion chamber if the combination of displacement, rpms, intake runner shape, intake runner length, valve selection, crank throws, etc are tuned perfectly. This is why variable length intake runners work. When you can adjust runner shape and length on the flu, you can keep optimal volumetric efficiency.

I now see the beauty in the massive carbureted engines of the Golden age of drag racing. The lifetimes that have gone into perfecting that is awe inspiring. I am humbled.



With fuel injection, same principal, sorta.

Efi goal seems to be to force your fuel to become atomized as quickly as possible when entering the combustion chamber. Tbi/carburetor has an advantage of higher atomization. Mfi wins out due to precision of control. Intake runners are tuned around the injectors to atomizer fuel as fast as possible. Multi hole injectors help this, so does coarse textures around your intake ports so you can get a wall wetting effect. Off gassing fuel droplets means atomization. Atomization means better burn.

This is how I ****Ed up the first lower I ported. I hogged ports and trimmed down injector bosses. Which led to carbon. I learned my lesson.

Injector bosses provide turbulence. Tighter turns and twisting ports creates turbulence. Blend to just shy of gasket surface. Blend within 1/4 inch, not 3 inches. scuff with 80-150-180 and send it. Like don't waste time in the runners. Bust up the droplets. That's the goal. The bare coarse aluminum will do that once you break the casting skin. That's all it needs.



Side note:
I see why gdi is so cool now. It's insane how perfect you can get them. You can form different types of combustion in the chambers depending on your piston tops and injector programming. The level of complexity is beautiful. And I still ****ing hate it.




So. I read somewhere that if you're dealing with a terrible runner design head, like the 460, take silicone castings first, then if in doubt then look, for photos of a cut up head.

Pruett didn't talk about this. I could find no forum posts, so I took some silicone castings.


Guess what??

Yeah they look obscene. It's the f*cking apocalypse, all they had was purple, cut me some slack

Easy AF to do. Silicone molding kit from Amazon. Mask with compatible tape (read f*cking instructions). I used powder coat masking tape, worked. Brush ports down with carnuba wax, follow silicone instructions, pop out when cured.

There. Tech section article. Send it.





Anyway.... They look like sh*t!


So then they suggested to find photos of a cut up head when in doubt.


And then I couldn't find photos of a cut up head. And that's a whole Lotta doubt in those purple ports...

Oh. And another thing.


For all these head cracking rumors, I see very few photos... Hell, photos of my set of blown ones posted here has come up in my searches.


Here's the head perched on the saw, head courtesy of @lil_Blue_Ford.

See how it cracked on the back half, but not on the decks? That's a non stress relieved or machined surface with the mother of all coolant pouches in it. If it's half full and builds up steam.... Boom.

It was half full. It built up steam.


Because casting residue and a horrible head gasket didn't allow coolant to flow.

That's after being run through my commercial parts washer, descaled with aluminum oxide, and cut in half with a chop saw. There's still ****ing casting residue.

It wasn't a bad f*cking design, it was p*ss poor quality control.









**** your 4.0.









Ok I feel better.









Anyway.


Here's photos of a blown 2.9 head cut into port runner profiles.

This may become my new avatar:

Profiles:

Just hit me how nice this one came out:

Well. There you have it.

And there where I'm at as of now. Looking for suggestions on shape and porting.

I think I can get away with leveling valve guide bosses and blending. But other questions about supporting valves, wear, etc.

If it's OK with @snoranger, I'll upload his suggestions, along with pruetts terrible sketch.

 

[snoranger]

TL;DR
2 things:

1 - Your silicone molds...

2 - You’re really want to post my fat finger on an iPhone scribbles... go ahead.

 

[PetroleumJunkie412]

@snoranger s mentioned suggestions on porting:

Reference photo of a how to port a small block ford head:

And the entirety from Pruett:

And a fraction of his notes dealing with the terrible coolant design on the 2.8... I will be dealing with this in a separate post, but it gets the point across on what's in store for 2.9 gaskets. Goal will be to open up the head gasket coolant passage holes around the exhaust ports in order to keel exhaust side temperatures down.

Remember: Detroit's primary concern is emissions, not performance or longevity. Betting the 2.9's coolant passages are the same as the 2.8's: small and restrictive to keep exhaust ports hot for emissions purposes. We're gonna change that. Look for a separate post.

 

[bobbywalter]

I have seen piles of cracked 2.9 and 4.0 heads with 6.2 heads. Piles.

Even if I had taken pictures...it was the late 80s early 90s.....they would have been lost by now....and poloroids suk anyway.


Great work here mang.

 

[Uncle Gump]

As far as you're into this thing... you need to build a flow bench... or befriend someone that has one.

All the grinding/reshaping in the world doesn't prove a thing without the data.

 

[bobbywalter]

Absolutely.


Naturally Aspirated....
Yates heads and Intake and 363 with a 850 bg .... We can get 116 percent v/e right off of peak tq.

Wrong whittle job will reduce that.

 

[rusty ol ranger]

You guys are way above my paygrade here.

 

[PetroleumJunkie412]

As far as you're into this thing... you need to build a flow bench... or befriend someone that has one.

All the grinding/reshaping in the world doesn't prove a thing without the data.

Exactly my plan. Manometer can be built out of a shop vac and poly tubing, so that's the plan.

Was going to put one together to measure cfms, but the electronics are going to be entirely too expensive.

 

[8thTon]

Exactly my plan. Manometer can be built out of a shop vac and poly tubing, so that's the plan.

Was going to put one together to measure cfms, but the electronics are going to be entirely too expensive.

Exactly my plan. Manometer can be built out of a shop vac and poly tubing, so that's the plan.

Was going to put one together to measure cfms, but the electronics are going to be entirely too expensive.

Use a big MAFS from something?

 

[PetroleumJunkie412]

Have thought about that as well. I would need a MAF with transfer tables that are available, and use a arduino to read and produce data. Haven't done my homework on available maf sensors yet, though. I'm all ears if anyone knows of one

 

[8thTon]

Have thought about that as well. I would need a MAF with transfer tables that are available, and use a arduino to read and produce data. Haven't done my homework on available maf sensors yet, though. I'm all ears if anyone knows of one

If you could find data on what CFM some specific geometry would flow at a known pressure drop (say a simple circle of a given thickness, etc.), you could use that to roughly calibrate you MAFS output. Also if the MAFS isn't big enough get two identical ones, and just hook up one. You know it will be flowing half the air.

 

[gw33gp]

I am not an expert in this, but I have been racing in SCCA for over 30 years. I build my own engines, but send the heads out for professional work. I still have learned some things about porting head. You can certainly gain power by porting heads but it is usually in the form of higher rpm HP while reducing low rpm torque. Boosting should help with the torque though. My experience with race engine are normally aspirated so may not carry over to boosted engines.

First, be careful not to just open the ports as mush as you can. I have seen race engines lose power by doing this. Opening the ports can increase flow volume but it also reduces flow velocity. This can result in reduce effect of ram tuning. I suspect a boosted engine will take larger ports before reduced flow velocity will become a problem. You should try to maintain a relatively uniform cross section area through the ports. Changing the port area (opening area) up and down from where it starts to where it ends causes compression and expansion of the air locally which can ultimately act as a partial restriction (almost like reversion).

You certainly want to eliminate or reduce anything that restricts flow like bumps, sharp corners and so on. Also anything that can cause turbulence is bad. Turbulence can act like a bump and restrict air flow. Once you get optimum air flow, you may want to consider larger valves because they could become the limiting factor in air flow and not allow you to take full advantage of the improved air flow. If you do go to larger valves, try to maintain the size ratio between intake and exhaust valves. If you get that off, it can disrupt the balance of flow.

You should also look at the combustion chamber. There can be things inside there that can interupt flow especially in exhaust.

Be careful with making your own flow bench. You need to understand exactly what you are doing and how to read the results. You need to get the flow rate in the range the engine can produce or your information could be meaningless.

Flowing a head can be complicated when optimizing it. That is why I let an expert do it. If you just want to clean up the ports to get a little better flow, you should be okay, but will probably leave much that can be done. When I first started racing, I followed a book by David Vizard on how to tune British Leyland A Series engines. I got some decent power improvements with everything advised, including the head work. When I wanted to run with the really fast guys I came across a guy in Ohio that does a lot of engine work (especially heads) for all kind of race engines, including Indy Cars. I gave him a head that I had worked on per the book and he said it was not much better than stock. Once, I gave him a head that someone else had flowed and he would not work on it. He said too much had been take out in some areas which meant he could not optimize it. From then on, I only sent him stock heads. I can tell you, the heads that he flowed for me were by far the most improvement in power of anything that was done to my engines. Of course, without all the other stuff that was done to the engine, the improvement of the flow of the heads would be lost.

I by no means am inferring you should not do it. It can be a great learning experience and from what you have done so far, I can see you are serious about it and are using the right approaching. Good luck.

 

[Ramcharger90]

If you remove material from the valve guide area can you redrill for a larger valve with a thicker stem?

P.s get the sodium filled valves.... they draw heat away.

 

[gw33gp]

A thicker stem is also a source for air flow restriction. Race engines typically have the valve stem area that is exposed to air/gas flow, cut down to a smaller diameter. Of course, the valve guide area has material removed from it too.

Cutting down the valve stem diameter is a tricky thing. They are usually ground then polished to make sure fatigue life is not reduced. The shape of the valve from the stem to the head is also important and is different depending on if it is an intake or exhaust.

 

[Uncle Gump]

Then you put that big thick sodium filled valve stem right in the middle of the port work you just did... It's been awhile... are sodium filled valves still a thing?

In my experience with cylinder head porting... I've done it myself... I've bought mass produced stuff... and I've paid to have it done right. There is no comparison... let someone that knows what they're doing do it. They aren't usually cheap... but go fast stuff never is.