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1,999 Posts
Discussion Starter · #1 ·
Here we go, the how-to for installing an Exhaust cam on the intake cam journals. Of course, all usual disclaimers apply. These steps worked for me, but I cannot guarantee they'll work for you, or that I didn't accidentally leave something out. If you're not comfortable with tearing your engine down, this is probably not a great project for you. It's certainly not a "first project" for anyone, and I'd give it about a 7-out-of-10 on the difficulty scale. If you can do a timing belt, you can do this.

It's really not too tough, but you do need to make sure you have a few things in line before you start. If everything is lined up for you in advance, this isn't a difficult install at all. :)

Exhaust cam that corresponds to your model-range head.
Abrasive saw/bandsaw
handheld grinder
Coffee can with solvent/solvent brush
Assembly lube
10, 12, 14, 21mm sockets, and a few ratchets
Needlenose pliers
rubber mallet (hammer and block of wood in a pinch.)
new cam seal (optional.)

First step: go to the machine shop (unless you have the tools) and have them drill your cam-gear to the following specs:

- Find the notch in the lip of the gear on the "I"-marked spoke, and go 197.5 degrees clockwise from that notch.
- Mark a line from the 197.5° point on the outside of the gear to the center of the gear.
- Drill a hole in the gear on that line. The hole should be set at the same distance from center as the outer edge of the existing slots.
- Slot the hole towards center slightly. The cam locating pin will be just barely inboard from that point, so they need to slot the hole towards center just slightly (1mm?). I don't know if this distance varies, hence the "start at X and work inward" methodology.

Next, take your exhaust cam and wrap it in a T-shirt or towel. Wrap the shirt tightly around the last narrow point of the cam, leaving only the CAS flange exposed. Now, clamp it into your abrasive or band saw. Chuck the cam so you'll cut off all but roughly 1/4 inch of the final CAS flange on the cam. Hold it up to a stock intake cam for comparison, but you're going to cut off just over 1 inch of the end, leaving about 1/4 inch of the exposed portion of the cam.

Cut the cam, and then de-burr the end with the handheld grinder. Remove the T-shirt/towel and if the cam was kept outside of an engine for any length of time, use the solvent to clean the journals and lobes of the cam.

You should now have a shortened cam, and a re-drilled gear that fits the cam. Set these aside somewhere clean and start pulling apart your engine. I left the upper radiator hose connected, you can remove it if you so choose.

Remove the following:
-Intake crossover tube.
-Accessory belts
-Water pump pulley (and coolant lines if needed. Mine are bypassed)
-Accessory pulley (just the 4 10mm bolts, NOT the center one.)
-Timing covers
-unbolt Coil Pack from valvecover
-Valve cover

Up to this point, everything you're removing is the same as if you were to do a timing belt, so if you need more focused directions for that part, google up directions for doing a timing belt swap.

Next, set the engine as if you were going to time it. Turn the crank by putting a 21mm ratchet on the crank and turning it clockwise until:
- The notch on the crank pulley matches the arrow on the oil pump
- "I" is at 12:00 on the Intake cam
- "E" is at 12:00 on the Exhaust cam.

Now, take a 14mm socket and loosen the cam gear on the left.

Next, remove the following pieces:
-Timing belt tensioner
-Timing belt
-Intake cam gear.

At this point, take your 10mm ratchet and start unbolting the intake cam. Work in a spiral pattern outwards from center, and evenly loosen the cam over 4 or 5 passes around the spiral. Remove the caps, and ensure that you do not get them out of order. You may have to lightly tap the caps with your rubber mallet to break the oil suction.

Remove the cam and cam seal. Go over to your clean dry place you left your cam, and bring it to the car. Set the cam into the cam journals and replace the cam caps. Make sure the cam caps are replaced on the journal they came off of, and in the same orientation. Liberally apply assembly lube or oil to the cam journals and lobes as you reassemble them.

In a spiral pattern, slowly tighten the cam down over 4 or 5 passes around the cam. Once all of the cam cap bolts are snug with the head, make one further pass around with a 1/4 drive ratchet, and add 1/8th of a turn or so to each. I don't have a torque spec for this, but I treated it like a spark plug for comparison's sake. You do NOT want to strip the head out.

Replace your cam-seal. Set it flush with the leading edge of the head, with the flat side out. Do not bottom the seal out. Now, replace the cam gear. I have no torque spec for this either, but make it reasonably tight, you do not want this coming undone on the road.

Next, re-time the motor according to the instructions you found elsewhere online. Once you have the belt on AND TENSIONED, bolt the valvecover and coilpack on without any timing covers or accessories. Start the engine to ensure everything is timed properly. Ensure you don't run the car for more than about 30 seconds, as you're not circulating coolant. Shut it off, and either re-time the motor until it runs smoothly, or re-fasten all the covers, pulleys and accessories.

At this point, you should be good to go. Take that inaugural drive, and enjoy the byproduct of your last 3 or so hours worth of work!

If I forgot anything and you see my mistake, let me know. I'll add it into these directions. So far, I've put 200 or so miles on my cam, and everything checks out normal. Oil pressure is the same, coolant temps are normal. Car idles wonderfully, and if anything runs smoother than before. Good Luck!

1,999 Posts
Discussion Starter · #4 ·
Slydin'... I unfortunately kinda flew through the install pretty quick. I tossed the car up on the lift, and went for it. I can get pics of where to cut the cam, etc... but I didn't take any pics as I went.

I had no apprehension in doing this. That said, I've also had the motor out of the car 3x now, and rebuilt it once. I've also rebuilt innumerable other motors. I'm going to just restate my disclaimer from below. If you're not comfortable with tearing your engine down, this is probably not a great project for you. It's certainly not a "first project" for anyone, and I'd give it about a 7-out-of-10 on the difficulty scale. If you can do a timing belt, you can do this.

Airbrush, I can't comment. I'm not familiar enough with the math of how cams work to determine what overlap/lobe center changes occurred, etc to know if this'd help or harm a FI application.

Mufasa in Training
34,673 Posts
The answer is that the Exhintake won't work on a 1.6 because the CAS is on the intake cam instead of exhaust, so you can't just move over the exhaust cam because it doesn't have the cut-out for the CAS.

1,017 Posts
oh crap..... you were'nt talking to me......

my question was regarding gains in a forced induction application.... IE: my turbo'd miata..... which is a 1.8 by the way
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