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Discussion Starter · #1 ·
Hey all! I'm porting and polishing up my LIM, and the heads are next. The intake manifold is easy, because I'm just cleaning up all the casting flaws (it's disgusting) and making it nice and shiney (leaving it rough where the injector meets airflow). I have no idea what I'm doing with the heads, though. I'm reading up on some of the stuff the ranger guys have done.

Link 1: http://www.rangerpowersports.com/forum/sho...ad.php?t=146485

Link 2: http://www.rangerpowersports.com/forum/sho...ad.php?t=138637

According to the OP in the first link, these heads can get pretty decent with the right amount of work. I've heard multiple times that the intake ports on our heads are good for 7k rpm, so to not touch them. But what do I do to the exhaust? There's tons of mismatch between the port and the exhaust manifold, but that's good to alleviate exhaust reversion. I'm new to head work, too, so if somebody can tell me what I'm supposed to be doing, I'd appreciate it.

Also, I wanted to do some combustion chamber (CC) work. I was looking at the picture from the 2nd link, and "Boss 3.0" highlighted all the material between the CC and the gasket. If I took all that out, it would drastically lower compression, which is a bad thing. I took two pictures, one with and one without the gasket, of the heads off my old engine. There's some sharp points coming off the wall surrounding the valves. Is it there for a reason, or should I smooth it off to let the valves move air easier? Also, should I push the material closer to the gasket? There seems to be a couple mm I can cut away around the valves.






Also, I found stainless valves from SI, and oversize valves from rockauto, but I can't find oversize stainless anywhere. Is it better for 3k-5k rpm power to go stainless or bigger?

-Dan
 

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Ok, the 3.0L vulcan is restricted on the exhaust side. You can go with either larger exhaust valve, or you can get a cam that opens the exhaust ports longer and more. Stainless valves are more resistant to heat, making them suitable for forced induction or other situations where they might get hotter than normal. For a naturally aspirated engine, I would opt for the larger valves versus stainless.

I would not worry about the combustion chamber mods unless I wanted to reduce compression. The primary reason to do that is forced induction, the stock compression is to high reliable turbo applications, so reducing the compression allows you to use higher boost. I would pursue a shorter stoke as a better way to do that. Messing with the combustion chamber can have all sorts of unintended consequences. Those areas that seemingly restricting airflow that you can marked are probably involved with directing the flame front and making it propagate properly, remove it, and the performance of the engine might decrease or you could have engine balance or fuel economy issues.

I like the idea of porting the head, but remember, a polished surface does not necessarily flow better than a semi-rough surface. Think golf ball effect. Smooth surfaces create boundary layers which can actually resist airflow.
 

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Discussion Starter · #3 ·
QUOTE (KhanTyranitar @ May 31 2010, 07:11 PM) index.php?act=findpost&pid=808190
Ok, the 3.0L vulcan is restricted on the exhaust side. You can go with either larger exhaust valve, or you can get a cam that opens the exhaust ports longer and more. Stainless valves are more resistant to heat, making them suitable for forced induction or other situations where they might get hotter than normal. For a naturally aspirated engine, I would opt for the larger valves versus stainless.

I would not worry about the combustion chamber mods unless I wanted to reduce compression. The primary reason to do that is forced induction, the stock compression is to high reliable turbo applications, so reducing the compression allows you to use higher boost. I would pursue a shorter stoke as a better way to do that. Messing with the combustion chamber can have all sorts of unintended consequences. Those areas that seemingly restricting airflow that you can marked are probably involved with directing the flame front and making it propagate properly, remove it, and the performance of the engine might decrease or you could have engine balance or fuel economy issues.

I like the idea of porting the head, but remember, a polished surface does not necessarily flow better than a semi-rough surface. Think golf ball effect. Smooth surfaces create boundary layers which can actually resist airflow.[/b]
True say about the polishing. As for the areas marked in my photos, I just talked to my neighbor about it (he's been a car enthusiast for years & ported, blueprinted, balanced, all that jazz a 302W a while back) and he said to stay away from anything combustion chamber side. I thought I had to clean up in there, but the castings aren't too bad. The only thing I'd need to do is blueprint the CC which isn't really worth it in a street engine that idles well enough before modification. FI seems like a fun goal, but I don't think I'll pursue it and therefore have no intention of lowering my compression.

I know the exhaust side is the most restrictive, & both those links I posted refer to the bowl work, but neither had pictures, and I have no clue what they're talking about. Can somebody step in and explain please what I need to do to my exhaust ports? (Other than bigger valves)
 

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QUOTE (Palach @ May 31 2010, 09:39 PM) index.php?act=findpost&pid=808230
QUOTE (Spock Power @ May 31 2010, 10:23 PM) index.php?act=findpost&pid=808226
http://www.rangerpowersports.com/forum/sho...ad.php?t=264562
You might have seen this thread, but this guy built up some nice looking heads. The exhaust port and valve pics are about halfway down.[/b]
Nice find! Thanks!
[/b][/quote]


Ported heads have little effect if you don't modify your exhaust. I would also look into a high flow air cleaner.
 

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Discussion Starter · #7 ·
QUOTE (kgrantkey @ Jun 1 2010, 06:53 AM) index.php?act=findpost&pid=808334
QUOTE (Palach @ May 31 2010, 09:39 PM) index.php?act=findpost&pid=808230
QUOTE (Spock Power @ May 31 2010, 10:23 PM) index.php?act=findpost&pid=808226
http://www.rangerpowersports.com/forum/sho...ad.php?t=264562
You might have seen this thread, but this guy built up some nice looking heads. The exhaust port and valve pics are about halfway down.[/b]
Nice find! Thanks!
[/b][/quote]


Ported heads have little effect if you don't modify your exhaust. I would also look into a high flow air cleaner.
[/b][/quote]

I appreciate the tip, but don't assume. Also, with our engines, the worst thing exhaust-side is the head, so I'm sure it'll do plenty with a stock setup. Along with cleaning up the LIM, I have the composite UIM off an '01, plus a 60mm TB & whatever-sized MAF off a 'tec, K&N filter, and 3" of piping into my fender from my stock airbox (which flows plenty). The same time the heads are being installed, I'm throwing in 1.8:1 roller rockers from Tom Morana, and hopefully the stainless high-flow y-pipe from SHOsource. I then have plans for that y-pipe to cut it off before the collecter and get a muffler shop to run stainless from there on to the back for some sick true duals. And before someone says it, I'll be getting another tune. But back to cylinder heads...

So I'm looking at the pictures of that guy's exhaust port, and I can't tell if he port matched or not, because his head is so shiny. When I talked to my neighbor, he pointed out all the material I could take off exhaust-side. I told him that I wanted to avoid exhaust reversion, but he looked at me funny & told me it doesn't exist. I've read plenty of articles since that highlight the dangers of reversion, so I'll stick with not hogging them out. Should I be opening them up a little, though? Or just focus on re-shaping the bowl?
 

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You do NOT want to run true duals if it is performance you seek. Allow me to explain and bring up some examples.

To get the best scavenging effect, you need a smooth and fast flow. As the exhaust travels down the exhaust, it cools and slows, but it slows faster than it cools. This creates backpressure. This effect can be minimized by reducing the surface area of the tubing that the exhaust comes in contact with. The less heat that can escape, the less the exhaust slows down, and the stronger the scavenging effect is.

Some examples? High performance enthusiasts use heat shields and warps to stop heat loss, not just to protect fuel and brake lines, but because it can add a couple of horsepower, the effect is measurable (though you won't feel the difference).

Dual exhausts have more than double the surface area of a properly sized single exhaust of a similar cross section. But the effect goes further, the fact that the exhaust coming off the two banks flows together actually reduces the parasitic losses, the pulses push each other out with less effort than if they had to take their own paths. This is assuming of course that the pipe is sized properly and that bends and other power robbing designs are kept to a minimum.

Now I know someone will cite some things to the contrary, such that man high performance cars have dual exhausts, that many track cars have dual exhausts, etc. First off, lets make one thing clear, many of these dual exhausts on stock systems are not true duals, they run as a single system at least part of the way. Furthermore, many true duals have an x-pipe or h-pipe which offsets some of the balance issues often found in true duals (single exhausts balance themselves). Then there is the issue of whether many of these true dual systems couldn't produce more power if they were properly designed and sized singles. A lot of maybes there, but I feel that the difference would be small, but in favor of the single system.

So where do duals have an advantage? Well sound is one, the dual system tends to project sound better. They also tend to produce deeper tones, and the synchronized sound coming from two sources is very appealing to the ear. I do feel that dual exhausts also look better, adding a balanced look to the car. My car has duals, and I like the sound.

Running duals of a single will still give good results, because after the exhaust has combined, it balances out, and by the time the exhaust gets that far back, it has less effect on the engine performance if it does slow down from cooling.

Hopefully that was clear and didn't confuse anyone.
 

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Discussion Starter · #9 ·
A bit tender there, Khan? Back to cylinder heads.

Once you get started, it's pretty easy and straight-forward what needs to be done. Anything rough needs to be smoothed out, and any harsh transitions need to be smoothed out. Any change in direction needs to be as gentle as possible, without increasing the volume too much to reduce the air velocity.

Somebody's going to raise the porous point again. A rough surface traps air, which has less friction against fellow air molecules, and therefore has less resistance to airflow. Mirror-polished surfaces still have unimaginably small pores, but they aren't big enough to trap enough air to form a flow-encouraging pocket. Instead, the air slides by and slows due to the forces of friction between the air and the iron.

But! A polished surface, with it's tiny tiny pores, doesn't grab onto carbon. Instead, it blows on by like everything else. If the surface were still rough, the carbon would build up on it (which is the case if you look inside your engine right now) and carbon will build on the carbon, which will build on the carbon, et cetera. This isn't a drag engine that's going to be disassembled and overhauled 3 times a week, it's going to be my street machine for hopefully years to come. The clear answer for both flow and maintenance ease is to cut golf-ball like grooves all over the manifold path and cylinder heads. That way, the surface of the material is still smooth enough to discourage carbon build-up, but it's irregular enough to encourage flow. But you know what? I don't think it's worth the 200+ hours of tedious labor for 0.05 hp gains, especially if that 0.05 hp will never be realized since the intake is overdesigned, but the exhaust port is constrictive.

And while I'm ranting, I'm putting duals on because it's my car. I'll give up 0.14 hp and a couple lb-ft to make my car sound bad-ass. Honestly, if I had 1,200 whp but my car sounded like a civic... I wouldn't drive it.
 

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Discussion Starter · #10 ·
Does anybody know how much we can take off our heads before things get complicated? The valve cover seals over the LIM, so if the heads drop too much, it won't seal properly. I want to take 1mm off. Some simple math shows 1mm off the heads will raise compression up to around 10:1. I don't know what it will be exactly, because the CCs aren't geometrically friendly to find the volume of without the use of a buret.
 

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One of the more respected members of the Vulcan/Ranger community suggests that head/deck milling should not be used to raise the compression. You'd have to equally mill the LIM, and get shorter pushrods or adjustable rocker arms.
 
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