The motor rebuild plan:
I'm looking for good driveability and torque. I want good turbo response. An all-around type of motor, nothing too wild (for now). I'm shooting for at least 250hp for my XR, which I feel I should have no problem getting. Right now I have a stock IHI turbo, and combined with Mass-Air, it should be fun in the low and mid range :)
Rods: The stock rods are more than adequate for 300 hp, so I had them balanced, peened, and reconditioned
Head: See below for some pics. I installed larger exhaust valves, and used stock size intake valves. In theory the stock intake valves will help keep the intake velocities up, for better off-turbo response. The larger exhaust valves help flow, and hopefully get the turbo spooled up quicker.
The chambers were also CC'd to get a 9:1 compression ratio. The stock ratio is about 8.5:1. Raising the compression is good for low-end power, but can cause detonation at higher boost levels.
Cam: I am using a ranger/mustang roller. I have valve springs and lifters from Racer Walsh that are better suited for a roller cam.
Intake: The intake ports were opened up to the size of the head ports. The bosses on injectors #2 and #3 were welded up. I matched the upper to the lower as well, no big size increase though.
Exhaust: I'm using the old style manifold. I opened the ports up a little, with the most work done on the "D" shaped area.
Fuel System: I had the injectors cleaned and flow matched by AE Technologies. New hats, filters, and o-rings were also installed. Not bad for $10 per injector. The report can be seen here: Injector Report
I also installed a 255lph hi-pressure fuel pump purchased from Auto Performance Engineering Get the kit for an 85-97 Mustang.
Installation instructions can be found in the Merkur Encyclopedia
Misc: I put in a windage tray, see pics below. I also installed a DIS system off a ranger and have an EEC-Tuner for even more power.
An adjustable cam gear will be purchased as soon as the car is up and running.
Some good engine rebuild and head porting articles can be found on the Merkur Encyclopedia and Ryan Mattson's site
I also did a little preventative maintenance on the transmission. Some things to replace while it is out is the clutch, pressure plate, input shaft bearing, and shifter bushings. Also check the guibo for cracks, and make sure the center support bearing doesn't have too much play in it.
The clutch and pressure plate were like new, and BAT did not have the input shaft bearing in stock, and they wouldn't have it in time before I installed the trans. They also didn't have the shifter bushing cup, but that can be installed by just removing the shifter later.
Head Porting (click on any pic to enlarge)
I got the head back from the machine shop. Following instructions from the above sites, I started on the exhaust side first. The stock port is about 1.25" in diameter, and I opened it up to 1.375" (leaving the bottom alone, just cutting into the top) going 1" into the port as suggested in David Godfrey's article. The carbide bit I had was 1" long, making for a perfect depth guide. Then blended into the bowl.
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| Exhaust before porting | Exhaust after opening up to 1.375" |
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| Exhaust after blending to bowl |
For the intake side I didn't open the ports up at all. The walls are reported as being thin in this area, all I did was smooth them, and blend into the bowl. The intake ports come in two different shapes.
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| Intake style 1 (cyl 1, 4) | Intake style 2 (cyl 2, 3) |
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| Shot of the intakes after. |
For the bowl areas, the most work can be done on the intake side. The exhaust side is a PITA due to it's small size. The intake is much easier to get to. I opened the intake bowl and blended to the seat. On the walls, make it straight, and on the short side radius (SSR), there is a sharp lip that can be removed. I made the walls straighter on the exhaust side, but there isn't a whole lot to be done with the SSR. I was afraid of cutting too deep into the seat. When the machine shop inserted the seats for the larger valves, they blended them in a little. On both the intake and exhaust bowls I rounded off the tops of the valve guides, and got rid of the sharp corners. Then I used the "shoeshine method" to smooth the SSR of both ports.
I highly recommend having the machine shop wait until you are done porting before doing the valve grind. Mine did the valve grind even though I asked for them to wait. Of course, I nicked a couple of the seats. Fortunately, it wasn't enough to wreck anything.
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| Bowls before | Bowls after |
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| Shot of smoothed chambers | You can also see the steam holes |
I didn't open the chambers up at all. There is bump in the chambers that I removed (check above pictures), and then smoothed all the surfaces.
I used the Merkur Encyclopedia to figure out what CC to get a 9.0:1 compression ratio.
Here is a pic of the front of the engine, where you can see the Crankshaft sensor, and yes, everything is upside-down in the background.
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| Crank sensor for DIS |
Miscellaneous Pics:
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| Windage tray top view | Windage tray side view |
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| Windage tray installed side view | Windage tray installed rear view |
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| Trans parts |