ExhIntake Cam Swap

This mod has been gaining a lot of popularity recently due to how cheap and effective it is. For me it felt like a 14 deg timing bump without actually advancing the timing. Basically what happens in the ExhIntake cam swap is the exhaust cam is installed on the intake side, then clocked accordingly. This mod is only available for NA and NB 1.8Ls due to the CAS being on the exhaust cam. In a nutshell, you obtain an exhaust cam from a 1.8L head (BP from a 1.8L Mazda Protege, 1.8L Mazda Miata, 1.8L Ford Escort GT), cut the CAS tangs off of the cam, redrill a stock cam gear to 197.5 deg off of in I tick mark (or use an adjustable one), and install. The cam specs from SoloMiata show the same amount of total lift, but the exhaust has a longer duration.

	94-97 (Hydraulic Lifters)		99-00 (Solid Lifters)
Duration @	Intake (BP05)	Exhaust (BP06)	Intake	Exhaust
.010''	218	232	257	278
.020''	208	220	224	232
.040''	195	208	209	215
.050''	190	202	204	210
.080''	176	190	190	196
.100''	167	180	181	187
.150''	145	158	158	164
.200''	119	134	132	141
.250''	89	108	102	114
.300''	43	70	59	79
Valve Timing	5 BTDC	56 BBDC	8 BTDC	53 BBDC
	48 ABDC	14 ATDC	49 ABDC	9 ATDC
Overlap	19 (-5-14)		17 (-8-9)
Base Circle Dia.	1.415''	1.415''	1.418''	1.418''
Total Lift	.338''	.338''	.326''	.350''

*Data taken from: http://members.aol.com/solomiata/cams.html

Here is a 1:1 template that I made in order to redrill the cam gear.

If you're doing this on the cheap, you'll want to redrill a stock cam gear, otherwise just use an adjustable cam gear. A new hole will be drilled in the cam gear to reposition the locator peg on the front face of the cam 197.5 degrees from the I tick mark. Use this template that I created to make an overlay of the cam gear to help you centerpunch the hole. After you drill the holl you'll need to slot it slightly toward the center of the gear. I did this using a carbide bit on my dremel, just go slow and keep fitting the gear to the cam until you get it correct.

Here's all the supplies you'll need, not including tools of course. You're basically doing a timing belt change with a little extra step in the middle. For the timing belt I like to use whiteout to locate the belt on the gears, and binder clips or zip ties to hold the belt on the gears while assembling it all. You'll also need your recut cam gear, a new camshaft seal, assembly lube, and of course your BP06 camshaft with the CAS tang cut off. My camshaft is in the plastic bag to preserve the oil film while it sat outside the car. If you haven't done your timing belt before, I'd recommend getting a new one as well as replacing both camshaft seals and the crank seal. You will also want to replace the valve cover gasket if you haven't done so recently.

You should see something like this when you open your hood. If this is unfamiliar to you, please stop now :). Remove your intake crossover tube. You can also remove your upper radiator hose, but I chose not too as you should have adequate space. Afterwards remove the accessory belts.

Next, remove the 3 plastic front engine covers. Then unbolt the cam cover from the coil pack and the head and pop it open. Rotate the crank so that the I on the intake cam is vertical and the E on the exhaust cam is vertical, the front cylinder should now be at top dead center. Before remove the intake cam and gear, you'll want to mark the timing belt and gears with whiteout to help you locate the belt when you put it all back together. This isn't necessary but I'd recommend it as a good way to double check yourself. I ziptied and clipped the timing belt to the exhaust cam gear and used the white out to make marks on the belt and both gears. Loosen up the belt tensioner and zip tie the intake side of the timing belt to the side to hold it in place. Lastly, before remove the gear and cam caps, CLEARLY LABEL the order of the caps. You want the caps to go back to their original locations when you reassemble them.

Now go ahead and remove the gear and the caps. The caps will be a little difficult to remove to do the oil film suction and the bearing areas. CAREFULLY remove the 10mm bolts hold the caps to the head, you definitely do not want to strip the head out. This next part took the most amount of time. I used a rubber mallet to tap each cap to break the oil film, then wiggled each cap back and forth until it loosened up. This will take some time, so please be patient, you don't want to damage anything. As you take them out keep them organized along with the bolts because you want them to go back in the their original location. Once you get all the caps off (4 for the body of the cam and 1 more at the front of the head), pull the intake cam out. With the assembly lube, put a light film on each bearing area and lobe of the "new" cam you are going to install and place it in the head. Now get the recut cam gear and the original cam gear with the whiteout mark on it and transfer that mark to get same spot on the recut gear.

Using the recut cam gear I rotated the new cam into roughly the same position. Put the cam caps back on and SLOWLY tighten them down in a circular fashion. Again, you DO NOT WANT TO STRIP THE HEAD. Put the cams back in the same location as they came from. Hopefully you labeled it and are organized. Also, do not forget to replace the cam seal!

This is where all those zipties, clips, and whiteout marks come into play. Now you'll have to put the timing belt back on. Make sure the front cylinder is at top dead center. I just put a long ziptie in the cylinder and rotated the crank with a wrench. The belt should still be ziptied to the exhaust gear, so now you'll just have to make sure you get the belt on the correct teeth of the new gear. With the I on the gear vertical, slip the belt onto the gear. Your whiteout marks should match up if you did it correctly. Again, double check your work, and tension the belt with the pulley.

Once the belt is tensioned properly. Start bolting everything back together. There's the front engine covers, the cam cover (to the head AND coil pack), accessory belts, intake crossover. Cross your fingers and start it up! Hopefully everything works without a problem. You'll probably hear a ticking sound due to the HLAs, so if you do, just check your oil level and rev the engine so it builds up oil pressure to fill the cam bearing areas. In all the mod took about 4 hours to install, but allow enough time just in case a mistake is made or you've never changed the timing belt before. Enjoy your new cam!