Porting AMC heads

[AMBROSIA]

Done a bit of trawling on here trying to get some pictures showing what porting is worth doing.
I'm probably gonna pull the engine from my bug soon to sort out a pressurisation issue that's causing coolant loss.
I figure whilst the heads are off why not do some porting and polishing after checking everything is ok.
Anyone got any tips as I don't want to grind through any water channels!

[Ol'fogasaurus]

In order to make a positive statement, I am going to sound negative so please bear with me on this.

It is considered common practice to port match the heads and manifolds by using the gasket as a guide; you only want to go inside the heads or manifolds about and inch or so to be safe. You can de-burr any flashing found in the heads and smooth out radius’s as long as you do not do too much contouring.

Porting and polishing, cc-ing the combustion pockets, and reshaping of the bowls is something that should be done in conjunction with the use of a flow bench to be safe in what you are doing and trying to accomplish. Improper work (matching flow from all cylinders) can cause you to end up losing horse power and torque so it is (in my opinion) very important to not get too happy with the metal rasp or sanding discs without the proper knowledge or tools. To do a proper job, you will want to cc the heads also can mean re-setting the seats or valves lower in the combustion chamber to even out the cylinders volume. Doing the bowls, and working around the valve guides can really make of break a port job.

The heads also must match the other components or there is a lot of waste of time, money and performance potential (some will consider this rubbish but I think it is good advice. I have seen unbalanced, components wise, engines run and the owner can’t figure out why it doesn’t perform like he/she was told it would.

Although what I have said is not going to be everyone’s opinion; I think this is a pretty common recommendation for all engines, air or water cooled. I’m not trying to stop you from doing a port job, just warning you of some of the pit-falls.

If you do decide to "hog out a set of heads", I would advise getting the book: 'How to Hot Rod Volkswagen Engines' by Bill Fisher, published by HPBooks. Starting on page 46 they cover VW heads quite well and staring around page 65 they have pictures of porting the runners. I still recommend bench flowing to ensure that all the cylinders are flowing easily.

The last set of heads I did was to have the new, larger valves’ hard valve seats roughed in and installed; then I carefully tapered the seats into the pockets. I left the valve pockets pretty much alone only cleaning up and burrs I found. From the other end, I blued the surfaces, scribed the gaskets port opening to the heads and started to go in about and inch, doing as smooth of a taper as I could. I took out some flashing farther down the port/runner and smoothed down some rough radius’s on the bends. I did not worry about polishing too much, especially the exhaust ports because as soon as the engine starts, it starts to lay carbon in the port which defeats the mirror like polish you could achieve. In the intakes, some people feel that some roughness is good as it disturbs the flow enough to keep the fuel and air mixed. I ended up doing a lot of work with tapered and flat sanding rolls mounted on a mandrel. I always started the die grinder (33,000 RPMs) with the mandrel inside of the head just in case anything happened during startup. I forgot one time and the new mandrel bent to 90 degrees as soon as the grinder turned on. Luckily the sanding roll did not fly off. A friend of mine had borrowed my first die grinder to do a set of Chev heads and while he was in the port, the chuck disintegrated on him. Again, the head protected him and there was only minimal damage that was easily fixed. Also, be prepared for the grinder to jump some when it starts up, you don’t want it to make contact with anything.

Lee

[fastback]

well the WBX heads are pretty good size stock.
2,1 ones have the largest port.
i would recomend a small job with taking away casting burr etc and smooth the transition from seat to port
what is your engine plans?

[AMBROSIA]

I read 'How to Hot Rod Volkswagen Engines' many years ago so i'm familiar with the porting process but I was after some specifics on the wbx head.
I port matched the manifolds for the current build so no worries there.
My initial thoughts were indeed casting marks as that's an obvious area of improvement.
Research has indicated that the wbx heads have greatly improved ports over aircooled heads.
I'll pop the valves out and see what I can do with the seat/port areas as suggested.
I was toying with the idea of 2.2 p&l's but as i'm using oem german 2.1 pistons I would loose compression and possibly end up with similar overall hp.
The current spec puts out over 120hp which is a good percentage increase over the stock 112hp but i'm used the the power after 3 years and was looking for a little boost
TBH i'm just being a bit opportunist as it's a pita stripping the top end down just to locate a small combusion leak.

Cheers guys,

Iain.

[Ol'fogasaurus]

Confession, you talked about AMC heads and I wasn't sure if you were talking about American Motor Company (AMC) or from the rest of you thread, a/c VW heads… or what (sorry, I didn’t know what WBX heads meant) so I tried to stay very general in my response (reference to the Hot VW book was an after thought). On a water cooled engine, if there is often a bump inside the runners (I forget its name); on some heads you can remove it and some you don’t want to do much with it. Just remember, you may be closer to discovering water than you think.

Don’t spend too much time reshaping the valve pocket under the valves, especially where the built up area where guides enter the pocket as you can mess up the flow on the floor of the pocket and change airflow to the negative. A lot of guys used to streamline the valve guide boss instead of leaving the shape round but unless you have a spare head to practice on and a flow bench to check it out as you go, it is often best to be conservative and just polish the area.

Hope the grinding and polishing works out for you; it is fun to do and at the same time scary (on many levels).

Lee

[buildabiggerboxer]

Hi mate, as has been said, the port flow is good stock, so about all you can do now, without re configuring the whole engine, is a good seat and valve flow job, no polishing, that's retail b/s, finish the inlet ports to a worn 120 grit, AND LEAVE THE BUMP ALONE, as you may be cutting below them... i do manifolds 40 grit at the top, graduating to 60 mid point, worn 120 bottom and to match the port, 240 on the exhaust port, polish here if you fancy, match it to the stock gasket. cut the chambers to the bore line adjacent to the inlet valve, leave the exhaust end alone. fly cut the chambers . 030" and the seal face to match to compensate for the chamber work, for about 10.6 comp with D.J pistons. fly cut the valve spring seats .040, then you can use 1.4 rockers safely. thats why you leave the inlet bump, you may need new valve springs for seat pressure. you will need to check valve to piston on the overlap, and for full lift coil bind, it may well be fine depending on your cam specs, if its too tight, fit berg retainer 281a. 1" 5/8 exhaust may help also, plus up the vent size and re jet to suit the new flow rate, that lot is about it without bigger cams and valves, but may well find you 10/12 hp. also consider electronic cooling control and ditch the mechanical water pump for another 5 or 6 hp

[sideshow]

Confession, you talked about AMC heads and I wasn't sure if you were talking about American Motor Company (AMC) or from the rest of you thread, a/c VW heads… or what ...

WBX is the once optional water cooled boxer engine (later standard equipment) offered for the air cooled Vanagons.
AMC is an aftermarket manufacturer that make OEM like parts, in this case stock replacement cylinder heads in Spain.

[Ol'fogasaurus]

Thank you Mr. Show. Me being an offie, you can see how I was confused.

Lee

[AMBROSIA]

All food for thought guys, thanks.
I have tried 1.25 ratio rockers but had trouble getting the geometry correct so I went back to stock.
Sadly I don't have direct access to cutting machines.
Sounds like the potential gains are fairly small so I will focus my efforts on a FI solution I guess.

[fastback]

just booooost it and forget this post

[AMBROSIA]

just booooost it and forget this post

That's the long term plan, got a 1.9 wbx engine in bits but nowhere to properly build it for now.