Miata question

[FredK]

I'm thinking of replacing my timing belt, I don't know the history of the one in my car. I've seen lots of pictures of Miatas with the timing gears showing, do people just cut the front off the valve cover to be cool and expose the gears?, or what? O.K. I'm a little bored.
FredK

[DaveL20]

Is it a 2 piece cover like on the Focus?

I put the adjustable timing gears in my car and for ease of adjustment just left the cover off...


The Focus has an upper and lower timing belt cover the top part being plastic.

[JoeTR6]

I've heard of people cutting a hole in the upper cover to check the belt condition and/or tweeking an adjustable timing gear. You can also see any potential oil leaks from the cam seals or timing cover. The crank seal can leak eventually and get oil on the belt, too.. I left mine intact and didn't have a problem in 160k miles.

If you have a 1.6 liter Miata, make sure you have an accurate torque wrench for the main pulley bolt. Check the crankshaft nose for wear, particularly the pulley key slot and be sure to reassemble the key exactly as it came off (it's tapered on one end). When I did my belt at 120k miles, the tensioner pulley was shot. The water pump is buried under the belt and isn't too expensive.

[kyle.bowker]

I'm thinking of replacing my timing belt, I don't know the history of the one in my car.

It's not that bad. Supposed to do it every 60k miles. When I did mine I also replaced the idler pulley, tensioner, t-stat, radiator and heater core hoses (since you have to drain the coolant anyways), the valve cover gasket, cam seals, crank seal, and cam angle sensor o-ring (easiest to do with the valve cover off). And if the plastic end tanks on your radiator look brown in color it means they're about to fail so you might as well replace the radiator, too. As you can see there's a whole bunch of "while I'm at it" that makes the price and effort increase. A helpful hint: use two adjustable wrenches on the camshaft flats and a clamp to keep them together. This will prevent the cams from rotating while you slip the belt on. Remember, it's exactly 19 teeth between the marks on the cam gears. Unless you have a 90° adapter for your impact driver you're gonna need to purchase or make a tool to hold the crankshaft while you loosen the nut. Or perhaps you could put the rear end on the ground and shift the transmission into 5th gear? I don't know if that'd be enough to keep it from spinning. That bolt will be really stuck on there. And be sure to pay close attention when you put the woodruff key back in.

I've seen lots of pictures of Miatas with the timing gears showing, do people just cut the front off the valve cover to be cool and expose the gears?, or what?

Yep, that's exactly what they do. Most often they just use a bandsaw and clean it up with a file and sand paper but I've also seen people use an end mill. They do this to make it easier to access adjustable cam gears. Many people put adj. cam gears on their car for bling. On a mostly stock car I don't think they're worth it but if you have a fully built motor with ITBs and spend a lot of time tuning on the dyno they're worth it.

[Gonz]

when I did mine ( 1.6L) I did the "cut old timing belt in 1/2 lenghtwise" trick. Boy that's a mouthful.

Anyway, by cutting the old belt lenghtwise, it allowed me to slip on the new belt 1/2 way before actually taking the old belt off. Hence, no possibility of mismatching the cogs. Put hte car in gear and rock it to have access to the entire belt.

I didn't do any of that seals, water pump, etc etc stuff. Guess I left all that for Francois
I did put covers back on. I've seen cars without them. I'd hate to be checking the oil and get a finger stuck in there!

[Wade Chamberlain]

Fred - you could have Larry mill the front of your valve-cover off.....shouldn't take more than 8-10 weeks.

[FredK]

Thanks for all the input guys. I don't know if I need one, but WTH. I think I'll leave the cover intact, though I might get it powder coated since I can't afford a turbo.

My favorite post is "the cutting the old one in half trick" I love that, and can't wait to do it. My least favorite is Wades, boy kick a guy when he's down.

Anyone know what are the best tires with a 141 tread wear?

[kyle.bowker]

That's a great tip about cutting the belt in half so you can slip the new belt on easier. I'll keep that in mind for the next time.