By Pat Kunz


Note from TRS – Pat Kunz was a great contributor in researching modifications for the 2.9 Ranger’s. I had witness to his Nitrous Oxide powered 2.9 Ranger prior to him selling it. He use to maintain a section at entitled Kunz Korner. no longer carries it but we have preserved it here for all to read. Enjoy. ~ Jim Oaks


How to Time TFI Fords (most 86 and up Fords with distributors)

Posted by Pat Kunz on April 21, 1998 at 13:09:12:

This problem keeps on popping up now and then so I thought that I would put up this procedure for all to see. In order to time a TFI Ford you must first get the engine warm enough that it idles at the correct rpm. Next turn the engine off and look for the spout connector, It’s got two wires going into it from the bottom and has a removable pill that kinda has a mushroom shape to it, it will be located normally somewhere around the distributor. Remove this pill, and place it somewhere where it won’t get lost. Restart the engine and with a timing light adjust the distributor to the proper advance stated on the emissions label, usually 10 degrees advance on most Fords. After you got the timing set, snug down the distributor and restart and double check that the timing stayed where it was supposed to. turn off engine, and place pill back in spout connector. Restart engine, the timing should now be quite a bit higher than ten but this is normal, give the engine a little throttle and check to see if the computer is advancing the timing, if it is everything is fine and your done.

Free Floating Rockers (this one also works with 4.0L’s and 2.8’s)

Posted by Pat Kunz on April 20, 1998 at 14:26:13:

This tip comes directly from Sven Pruett’s book How to Build and Modify Ford 60 degree V6’s. If you really want to do this tip I highly recommend that you get this book, I believe that Vanir still carries it. This weeks tip is on free floating rocker assemblies. This sounds pretty exotic but its really a pretty simple mod that will cost you probably under 200 bucks, got mine done for 150 I believe. The parts required to do this modification are new rocker shafts, Aluminum to be made into spacers, possibly new pedestals if the old ones are pretty worn, and some new roll pins, and last but not least a good machine shop. The modifications include changing the rocker arm to shaft clearances by quite a bit, chamfering the oil holes in the shaft, running aluminum spacers instead of the springs, and that’s about it. now I will give you the specs.: Shaft to rocker arm clearance .0025-.003in. (stock is .0013in.) rocker arm bore diameter should be around .7836-.7842in. Aluminum spacer to rocker arm side clearance of .010-.015 for each rocker arm that, that spacer is used with so .020-.030in. for the rocker arms between the pedestals. (stock is 0 clearance between spring and rocker arm, it actually rides up against it). With the increased rocker arm to shaft clearances and now a clearance between the spacers and the rocker arm, along with increased oiling to the upper valvetrain. These combine to create a very slick and essentially pretty friction free rocker movement, in fact after the valvetrain is reassembled you should be able to flick one of the rocker arms and have it spin around the shaft numerous times. when compared to a stock rocker assembly its night and day in fact you will probably hurt your finger trying to flick one of those due to the springs actually exerting pressure on the side of the rocker arm, and the very tight clearance of the rocker arm to shaft on a stock rocker assembly will tend to drag a little. The thing that surprised me the most about it was how much I improved my upper valvetrain oiling, on most 2.9’s I can adjust the valvetrain with the valve cover off with the engine running and barely lose any oil spilled off the heads, On mine with the free floating rocker assembly, I tried it once and pumped about half a quart of Mobile one on the ground, I don’t adjust mine that way anymore. This modification tends to help most in the upper RPM bands and its a noticeable increase but not as big of an increase as I would say headers would be. Also it seem to rev a little quicker than it did before the change mostly due to the lack of friction in the rocker assembly, and as a bonus they look pretty cool when you have your valve cover off if you run polished aluminum spacers. But if you are serious about doing this mod please get the book because it goes far more in depth than I did here.

Pat Kunz

Kunz’s 2.9L tip of the week (just some general things that basically apply to all engines)

Posted by Pat Kunz on April 30, 1998 at 13:00:27:

Well I’m almost done with school now just one more final to go, till I officially have my Bachelors degree in Automotive Technology. Since I really need to send my pictures in before I can do my Ram Air tip, “its much easier to pick up from pictures than trying to explain it.” So I just decided to do a little general facts and figures sort of thing.

The first one is that every five degrees you drop your air intake temperature you increase your hp by 1%. EG. A 200hp engine that has the air intake temperature dropped 10 degrees will pick up 4 hp by this change alone, just because the air is denser. This is why it’s not a bad idea to cover all of the air intake hose with heat shielding

Another one is that any time you advance your ignition timing farther than stock its also a good idea to get a higher temperature range spark plug.

The first key to making power out of any engine is to have the foundation sound. It doesn’t do much good to throw a lot of parts at an engine that doesn’t run right in the first place. IF its only running 50 psi on a compression test its never going to be fast, unless that problem is fixed first.

This is a problem I see all the time and some people never get it. There isn’t a six cylinder ranger on this planet that would need the airflow that completely dualed 3 inch exhaust pipe can flow. If you know the principles behind headers you already know why this is a bad idea. You want to keep the exhaust diameter small enough that the power pulses are kept separated or help pull each other out of the exhaust. This is why top fuel dragsters have 8 pipes to keep the pulses separate so they don’t run into each other thereby causing backpressure. With too large of an exhaust pipe the pulses leave the exhaust port, go through the header or manifold and reach the exhaust pipe, if the pipe is to big the exhaust air expands to fill up this volume and when it does this it slows down and cools, and the hotter a gas is the faster it will normally travel. So in essence too large of an exhaust pipe will act like a large expansion chamber, and the exhaust gasses kinda just hang around instead of hurrying to get out, therefore it doesn’t flow as well as a smaller diameter pipe would. The bigger pipe has the capacity to flow more than the smaller pipe but the engine would have to be able to move that much air through the system to take advantage of it. It would require much larger power pulses to take advantage of the larger pipe and not lose its exhaust velocity. You can over exhaust a car or truck just as much as you can over intake one.

How do you know if your air filter flows enough cfm to adequately feed your engine. It’s real easy if you have a vacuum gauge and a efficiently breathing engine. At WOT you should have atmospheric pressure or 0 vacuum in the intake if the engine is getting all of the air it wants. If the vacuum gauge doesn’t zero the gauge then it isn’t getting all the air it wants. Remove the filter and try the test again ( do this some place clean) If it zeros it after the filter is removed then you know you need a filter that is higher flowing.

Pat Kunz

Removing cats from OBD2 trucks

Posted by Pat Kunz on April 30, 1998 at 12:19:06:

Since about 96 Ford has been equipping almost all of its cars and trucks with the OBD2 system. If your curious as to if you have an OBD2 equipped truck look under the truck at the exhaust and if you see an O2 sensor before the cats and one after them than it’s OBD2. The reason for these two O2 sensors is to monitor the catalytic converters efficiency. OBD2 required all manufacturer’s to have a way of monitoring catalyst efficiency, and if this efficiency degraded to a certain point, a engine code will be set. At this point you should see why it may be a bad idea to remove cats from these systems as in an offroad pipe set-up. Because zero catalytic converters are 0 efficient therefore an engine code. Hope this saves someone from starring at a check engine light.

Pat Kunz

Kunz’s new series on how sensors work (this is on O2 sensors and how they work)

Posted by Pat Kunz on May 13, 1998 at 23:41:28:

The o2 sensor is a voltage generating device. The ECM receives exhaust gas information from the O2. The O2 sensor detects oxygen content in the exhaust, and only oxygen, it in now way detects fuel or any other gasses besides oxygen in the exhaust. The sensor detects oxygen content in the exhaust by a galvanic reaction within the sensor that produces a voltage. In much simpler words it creates a voltage by there being a difference between the oxygen content outside the O2 sensor and the oxygen content inside the O2 sensor. Internally the O2 sensor has a zirconium dioxide thimble that is shaped like a cone. The zirconium dioxide is the electrolyte. The inside and outside of the zirconium dioxide is coated with platinum to form electrodes. The inner electrode is exposed to the ambient air that is outside of the exhaust. The outer electrode is exposed to the exhaust gases. At temperatures below 662 degrees F, the zirconium dioxide does not act as an electrolyte and the sensor will not generate a voltage of its own. Once the O2 has reached a temperature of 662 degrees and above the zirconium dioxide becomes active. Instead of dissimilar metals in the presence of electolyte (how a car battery works), the oxygen sensor uses dissimilar amounts of oxygen in the presence of zirconium dioxide (electrolyte) to generate its voltage. An oxygen sensors voltage will vary from a low of 0 volts a lean condition to a reading of about 1 volt (rich condition). And of course it will read anywhere between these two extremes for the varying air/fuel ratios, such as a 14.7 to 1 ratio or the stochiometric rate would give a reading of around a .5 volt. The ECM uses these signals to vary its fuel injector pulse widths to achieve the air fuel ratio it wants, for example if the computer sees an o2 reading leaner than it wanted it to be say it saw .3 and it wants .5 it will increase the pulse width slightly to try to get the .5 volts, and if it got .6 instead it will shorten the pulse width slightly. This goes on constantly while the engine is in closed loop and why you will see the O2 sensor voltage constantly bouncing around, because the air/fuel ratio is constantly changing therefore the oxygen content in the exhaust is constantly changing.

Some things that will kill O2’s are certain types of non-sensor safe RTV’s, anti-freeze, and the one I unfortunately found out about, Castrol super clean,( I was cleaning the underside of my truck and must of hit the O2, because it was instantly killed dead after that.) the other is time, after time the O2’s have a tendency to get lazy and unresponsive so that the ecm is not getting an immediate feedback from its air fuel changes, so changing them at about 60k is often a good idea.

Pat Kunz

The answer to the frequently asked question of what is open loop and closed loop operation

Posted by Pat Kunz on May 19, 1998 at 22:25:16:

Its a relatively simple difference, in open loop the ecm is either ignoring the O2 sensor or the o2 sensor isn’t working, and closed loop refers to when the ecm is paying attention to the O2, and using these readings to correct its air/fuel ratio, and for certain diagnostic tests.

conditions that the engine would be running open loop.

1. Wide open throttle 2. Cold start 3. restart when O2 is not up to tempreture yet 4 when O2 is not funtioning due to either mechanical failure , or contamination. 5. When ECT is still giving a cold reading and the timer for the O2 has not expired yet.

Closed Loop 1. anytime the ECT is up to temp and the O2 is functional and hot enough for operation. 2. after the closed loop timer has expired even though the ECT is not up to temp, normally around 145 seconds after start as long as O2 is hot enough.

Pat Kunz

Kunz’s 2.9L tip of the week (this is actually a new one)

Posted by Pat Kunz on May 25, 1998 at 23:48:00:

Well my clutch fan broke this last Friday (stuck fully engaged, really noisy and quite an engine drag). So I decided to switch to an electric puller along with my electric pusher, and I just wanted all you 2.9 guys and gals to know that a 16 inch electric will actually fit on that little radiator, barely but it fits. The removal of the clutch fan and its shroud also clears up a ton of room in the front of the engine. My engine is no longer equipped with A/C, but with the 16 inch puller and a 12 inch pusher, I could basically keep the engine at almost any temperature desired by turning off and on fans (had to turn the big electric off for a while to even get the temp above 180). As far as performance gains, the jury is still out since I just did this Saturday, but it definitely couldn’t hurt the horsepower any, and could only help. Plus the extra room in that tight engine compartment is almost worth the change in itself.

Pat Kunz

I am redoing some of the Kunz’s 2.9L tips of the week because I lost them and maybe someone hasn’t caught them before, (this works for all engines except there maybe some problems with this and OBD2 equipped trucks)

Posted by Pat Kunz on May 25, 1998 at 23:34:39:

How can a cooler thermostat increase horsepower? well its relatively simple if you learn this simple formula. For every 5 degrees you drop your air intake temperature you increase your horsepower by 1 percent. Keep this formula in the back of your mind why I explain this. As everyone surely knows there is coolant circulation through your lower intake on fuel injected engines and the intake on carbureted engines. Normally this coolant has to warm up to a temperature of between 192 and 196 degrees or so before it is allowed to circulate through the radiator where it can dissipate some of the engine heat. So what does this hot coolant do the intake, well it heats it up of course. The thermostat can only control minimum engine temperature and does not affect maximum temperature so keep this in mind. So in essence it will make the minimum intake temperature on a warmed up engine around 192-196 degrees with some leeway on either side depending on engine and cooling system design. Well lets say we put a 180 degree thermostat in there, well that’s 12 to 16 degrees cooler than the stock thermostat. If you could maintain that 180 degrees constantly that could possibly drop you air intake temperature around 12 degrees or so. What does this mean to power output, well on a 200 hp engine that comes out to around 5 horsepower for basically 4 bucks. But in order to take advantage of this your engine must be capable of maintaining this 180 degree, this is normally accomplished through high flow thermostats, auxiliary electric fans, running a high water content in the coolant, etc. But this isn’t without its drawbacks. the major drawback is a loss in gas mileage due to the internal combustion engine losing efficiency at lower temperatures and that denser air charges also require more fuel to maintain the proper air fuel ratio. So many people may be asking the question why not run a 160 thermostat. Well my answer to this question is that yes you will probably make a little more power with a 160, but it comes at the cost of terrible gas mileage, increased engine wear due to the lack of part expansion which is calculated in to the engine design to take up certain clearances, increased particulate matter in the oil due to less efficient combustion and much richer mixtures. This is why I don’t recommend these in anything besides competition use only engines. So why the deal about OBD2 engines? Well, OBD2 equipped engines have many diagnostic tests that OBD 1 engines do not, and some of these tests may require that the coolant temperature be above the rating of the stock thermostat, and if this test can not be run after a certain amount of time a code may be set. I am not certain about there being any OBD2 tests that depend on coolant temperature being above 196 degrees or so, but its possible, but as I said before you can get around these by forcing your engine to run a little warmer, remember thermostats only control minimum temperature, such as turning off your auxiliary fan or partially blocking your radiator during normal driving to get the temperature up around the normal range if your engine runs right on the thermostat minimum normally.

Pat Kunz

2.9’s WHAT WORKS!!

Posted by Pat Kunz on July 17, 1999 at 21:22:07:

This is all stuff that pertains to the engine and engine controls only, I’m not about to go into drivetrains but gears are important to a small engine so remember that as well, I’m going to start with induction and work my way back then to ignition and controls. First off I wrote this for those of you serious about making as much power possible without having to have a NASA computer with you or a team of engineers.

Lets start with a simple concept, an engine is an air pump, the more air you can move in and out of it in a given time period (with the appropriate amount of fuel as well) the more power it will make.

Lets start off with the air filter, first off buy a K&N or equivalent, cones are better since they have more surface area in which to pull in air. If you don’t want to buy a high flow air filter of some sort you might as well stop reading this now because your not very serious about power, this is one of those required things, now that you have your air filter, now you have to go about feeding air to it, now the denser the air you can feed an engine the more power you make since dense air will carry more oxygen per a given amount of volume then say hotter air will, this is how a supercharger works, it makes the air extremely dense and packed with oxygen. So to take advantage of this you need to feed the engine cool outside air, how do you do this, by making the distance and restriction that the outside air takes to the filter as small as possible, because the longer that air sits around the engine compartment the more heat it will take up and the less dense it will be. This is the reason for the power boosts from things such as ram airs and cowl induction setups, simply feeding the engine denser air, there have been enough posts on here about ram air that I think most of you have an idea of how to go about it.

Next on induction if the throttle body, this is a relatively simple choice, the ones on the 86-87 2.9’s are much larger and basically your only bolt on piece and tend to increase power in the 3k and up range, without one of these I would find it very difficult to make much power normally aspirated, so I would include this on the must have list. now you can modify the 86-87 TB by sharpening the throttle blade edges, shaving the throttle shaft etc. if you think you need more cfm, also check that they open up all the way, I did have one that didn’t.

Next is the upper intake, here is a mod that I just kinda stumbled on while goofing around one day cleaning my intake out. the upper and lower intake are very poorly matched (real bad), so having these port matched and also taking some material of the inside turn of the upper intake to straighten the flow will make significant improvements across the entire RPM band, so much so that it really surprised me, it also made a surprising improvement in the exhaust tone (when an intake mod makes a noticeable change in exhaust tone you know you changed something pretty substantial). I would also put this on the must do list because this is a rather substantial bottleneck.

Before I get to the lower intake let me also recommend phenolic spacers between the upper and lower intakes, this is a non heat conductive material that keep the heat from the heads lower intake etc. from finding there way up to the upper intake, thereby keeping the upper intake substantially cooler, and I already explained why that helps above.

Now the lower intake, this one I have a hard time telling you how much gain you get out of doing some port work on the lower since I did the headers and lower intake at the same time, but let me say it’s probably worth your while, while you have it out to port match the lower ports to the heads, make them slightly smaller than the head ports though, nothing is worse than running air into a wall, better to have it expand slightly. also it helps to reduce the injector bosses protrusion into the ports, so trim these down a bit but not so much as to reduce their integrity. there’s some little restrictions in the lower as well that you can easily find by running you hand through them that you can smooth out to help flow. I don’t count this as a must do but it won’t hurt anything.

Now the Heads, since 2.9 heads are relatively expensive, and there is a book out on how to port them I highly recommend Sven Pruett’s book, “how to build and modify ford 60 degree v6’s” this will run you through it, and gives you excellent advice on building the short block as well, plus Sven helps us out here so please support him.

Now that I’m at the heads lets look at the upper valvetrain, now in Sven’s book it goes into all the up and downsides of the upper valvetrain especially the rocker assembly. Now you can modify it and fix almost all of it’s problems with about 150 bucks of parts and machine work. what you are going for is a modified stock valvetrain which is frictionless as possible otherwise known as a free floating valvetrain. this replaces your stock spring spacers with solid aluminum spacers and changes your rocker arm to shaft clearances to help prevent seizing at higher RPM’s, I also think it helps with upper end oiling as well, and you come out with a bulletproof rocker assembly, all the specs for these can be found in Sven’s book. If you plan to use your engine in any sort of competition I highly recommend you do this, If you don’t then I still recommend it but it’s not a necessity and moist gains are found at higher RPM’s from it.

Now to the exhaust, fist off the stock exhaust manifold suck. and are a contributor to the head cracking problems of 2.9’s, so what do you do about this problem, HEADERS, not only do they help get the exhaust gasses out of the engine faster they keep the heat build up in the heads down to a more manageable level. Now header choices for a 2.9 are relatively small, JBA’s for the 4×4’s, or JBA or Pacesetter for the 2wd’s, both I believe come with an H or Y-pipe depending on year. these are one of those must have deals since their benefit is two fold and they do give you a noticeable power increase.

Note from forum member jnunez86: Pacesetter headers will work on a 4WD, they just don’t bolt up to the stock cat back on some years. They are also not street legal and need a weld on bung for 02 sensor and band clamps for y pipe to headers.

The H or Y pipe, now the 86 and 87 2.9’s had an advantage in that they have an H-pipe rather than a Y-pipe like the 88 and later do, meaning that with an 86 or 87 h-pipe you can run full duals while this is impossible with the later 88 and up y-pipe. therefore the 86-87 h-pipe is the more desirable one to have, but depending on your emissions situation you may be forced to run the y-pipe with an 88 and up 2.9.

If you have to run Cats and yours have some age on them 50-60k or more I advise you change them, with some high flows, cost has gone down quite a bit the last few years so they may not be as bad as you thing, make sure that your old cats are bad before you have them changed by a shop, such as a big rock hit it or a hammer accidentally hit it, or the EPA may be upset.

Now for the ever controversial exhaust pipe size dilemma. Here’s my recommendations, take it or leave it for what it is, bur for full duals stay with 2″ pipe as long as you can at least 3 or 4 feet after the h-pipe then you can go slightly larger for the muffler etc, but stay 2.25 or under if possible (2.5 at the tip won’t hurt though) but stay 2″ or above. now for single exhaust I recommend 2.5″ for any modified 2.9. 2.25″ at a minimum, and if you split the single pipe the dualed pipes should use the size recommend for the duals meaning when you first do the split stay 2″s for a bit then you can go larger down the line.

As far as Mufflers are concerned (this is a large personal preference I know) I prefer Flowmasters, especially if done with all the mods above, I personally run 2 2.5″ 2 chamber flowmasters on mine and I like them albeit a bit loud (not for me) at WOT but If I’m on it I want everyone to know anyway.

now to the ignition system, there’s been more gimicks here than probably anywhere else, but to get 95% of what you want out of the ignition system here’s what you buy, a Crane PS-91 coil, a good set of spiral core plug wires, motorcraft plugs 44 heat range with the timing set at 12 btdc, a good cap and rotor with copper or brass terminals, then if you want to give it that little bit of extra effort get yourself an ignition box such as an MSD or Crane Hi-6, this will be more than enough ignition to feed a 2.9 to excess of 6 grand.

Of course there are always the cheap mods like the 180 thermostat and stuff which are under the tips section if you want a more detailed explanation.

Oh yea, one of the things on a 2.9 owners mind all the time, cooling. Fist off get the 180 thermostat Robert shaw high flow preferred, also make sure the cooling system is in top shape, I flush both of mine every year and change the coolant from 50/50 winter to 25/75 summer (anti/water). Now there is often talk about electric fans, first off I don’t recommend electrics with A/C still in use or the condenser still on the vehicle, but if the A/C is gone I recommend a 16″ puller electric and a 12″ pusher electric in front, this is more than adequate for mine in the midwest Summers, plus it free up a lot of room in the engine compartment, I didn’t notice a whole lot of performance gain without the clutch fan however, but I’m sure the water pump appreciates the lighter load.

Now for injectors, the best I can recommend are the ADS sold in Summit Racing (Lucas actually makes them for ADS), but these are the best injectors on the market and will flow better at a higher fuel rate than some injectors rated higher, these will feed about any 2.9 that I’ve seen, I’m running ADS only of a slightly higher fuel rate than stock and they feed mine wonderfully.

Now to chips, do they work? most definitely. are they worth the money? I think so. but don’t get the generic stock chips if you plan to modify the engine quite a bit go with someone who will make you a custom chip and will reprogram for a modest fee if you add something later or you have a slight problem, (too lean at idle for example).

I think that covered most of the basics, If I think of something later I will add to it.

Pat Kunz

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