# Fuck interference engines **URL:** \ **Category:** The BBQ Pit\ **Created:** [April 29, 2013, 10:07pm UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050 "2013-04-29T22:07:34Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [April 30, 2013, 5:41am UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/21 "2013-04-30T05:41:01Z")
> [@pabstist](#): > > Ya know what’s fucked up? I have a '99 Subaru, last year the timing belt had about 30k miles on it. One of the pulleys for some reason shattered into pieces! The belt was perfectly fine. Of course, bent the valves. I was officially the first person ever to buy a new pulley from Subaru, “They never break!”. It took the mechanic 3 weeks to fix it, and cost about $2,000\*. Apparently, the valves have shims and you have to buy a bunch and through trial and error find the right combo. Trial and error involves removing and replacing the cylinder heads many times, at least for my mechanic… > > \*A lot to repair an old Subaru, but in Vermont they are hard to find in good shape and cost way more than that used, so worth the price if the rest of the car is mint. You need a new mechanic. First off you don’t have to pull the heads to adjust the valves. Secondly you measure the clearance with a feeler gauge then remove the cam (not the head) use a micrometer to measure the existing shim and Oder a new shim that will put the clearance in spec. Takes probably 30-45 minutes. ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [April 30, 2013, 6:26am UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/22 "2013-04-30T06:26:37Z")
This is why pushrod engines are great! No long timing belt for me! And, since most people NEVER rev their engines up anywhere near 6500 RPM, who needs overhead camshafts anyway? On second thought…gimme a two-stroke engine-who needs valves?😛 ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [April 30, 2013, 11:57am UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/23 "2013-04-30T11:57:01Z")
> [@MikeG](#): > > But back to the OP, one tooth off should not cause the destruction you suffered. I didn’t go into work yesterday because, frankly, I don’t do mechanic work for a living and I was exhausted from figuring out how to take this thing apart and get it back together. I can do it NOW in a couple hours instead of a couple weekends–so it goes. Long story short, #1 was at TDC, but the head wasn’t set that way, the #1 valves were open as I was tightening things down. :smack: ensued. The worst part is, I was following the service manual instructions. But they don’t give you the, “Yeah, _eventually_ you want the marks that way, but here’s how you REALLY do it to keep from screwing shit up” advice. ---
**Author:** ![Inigo\_Montoya](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/inigo_montoya/32/124_2.png) [@Inigo\_Montoya](https://boards.straightdope.com/u/Inigo_Montoya)\ **Post date:** [April 30, 2013, 12:05pm UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/24 "2013-04-30T12:05:07Z")
Previous post edited for speling, forgot to mention: I was going over things in my little brains yesterday when I realized I had smashed things during install, and that it was all over before I even picked up the timing belt. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [April 30, 2013, 12:07pm UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/25 "2013-04-30T12:07:46Z")
> [@jz78817](#): > > the only thing I can get behind is that interference engines should never have a timing belt. chain or gears only. Belts have a couple of great advantages. They are quiet and they are cheap. Plus you can drive the water pump with the same belt. A gear driven overhead camshaft engine? How would that work? The cam and crank are what, two feet apart? As far as chains go besides being more $ to build they wear out also. The Toyota 20R engine used a chain. Somewhere around 120,000 miles the chains would get so loose from wear that it needed to be changed. This required removal of the cylinder head. Oops. The belt on my Volvo has a 150,000 mile interval and takes about an hour to change. Chains are not necessarily superior from either a cost or serviceability standpoint. ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://boards.straightdope.com/u/Rick)\ **Post date:** [April 30, 2013, 12:14pm UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/26 "2013-04-30T12:14:28Z")
> [@The Great Sun Jester](#): > > Previous post edited for speling, forgot to mention: I was going over things in my little brains yesterday when I realized I had smashed things during install, and that it was all over before I even picked up the timing belt. One of those things you learn when you do this for a living is to glance at the bottom of the head and make sure the valves are closed for the cylinder(s) where the pistons are all the way up. ---
**Author:** ![fstbk1968](https://avatars.discourse-cdn.com/v4/letter/f/3bc359/32.png) [@fstbk1968](https://boards.straightdope.com/u/fstbk1968)\ **Post date:** [April 30, 2013, 4:28pm UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/27 "2013-04-30T16:28:58Z")
> [@ralph124c](#): > > This is why pushrod engines are great! No long timing belt for me! And, since most people NEVER rev their engines up anywhere near 6500 RPM, who needs overhead camshafts anyway? On second thought..gimme a two-stroke engine-who needs valves?😛 If the timing chain (or sometimes belt), breaks on a good old fashioned push rod engine, the valves will smash into the pistons too. The overhead cams have got nothing to do with the valve to piston clearance. ---
**Author:** ![leftfield6](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/leftfield6/32/18780_2.png) [@leftfield6](https://boards.straightdope.com/u/leftfield6)\ **Post date:** [April 30, 2013, 6:18pm UTC](https://boards.straightdope.com/t/fuck-interference-engines/657050/28 "2013-04-30T18:18:03Z")
> [@MikeG](#): > > Hey leftfield, you got a GL? I can swap the belts on a GL1200 in under two hours 🙂 dont even need to pull the radiator! > . Nope. I have a Ducati ST2. A v-twin engine with 2 toothed rubber belts driving the heads. Not a big job though, could be done in under two hours if I wanted to. I take my time, clean stuff while I’m in there, achieve one with my inner motorcycle mechanical parts zen. Always takes me about 4 hours total. [Previous page](https://boards.straightdope.com/t/fuck-interference-engines/657050.md?page=1)