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Interference motor?

 
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  #1 (permalink)  
Old 20 Aug 2010, 11:22 pm
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Join Date: Aug 2010
Location: CA
Posts: 9
Default Interference motor?

Hey, all...
Just got my daughter a 2002 PT cruser touring in dark grey, (not sure of the official name), but just 77,000 miles, and a new auto transmission!
It's banged up a little on the body, the bumpers are really faded, but the interior is near perfect and it runs alot stronger on top(over 4000 rpm) than the 2007 we drove, (typical??) so my 16 year old is pretty happy!
Im a mechanic, and I have learned alot about these cars using searches on this sight (thanks to all!), to help me with repairs, but one fact has eluded me...are these interference engines?
Im gonna replace the timing belt at my first opportunity, but I feel this fact is good to know...
It also has the pull to the left under full throttle, but the tires are worn unevenly, and I have yet to inspect the suspension.
It does feel very solid on the road, much better than my tinny 2001 Saturn SL-2, so I think there is some potential here...
BTW, are cold-air boxes just added noise on these cars, rather than an HP upgrade, and has anyone ported thier throttle body?
Chris
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Old 21 Aug 2010, 01:48 am
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Join Date: Jan 2010
Posts: 157
Default Re: Interference motor?

The engine is not an Interference engine...however since it is a dual cam the valves could contact each other and bend or break...does not seem to happen often, but a few owners have reported it happening.
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Old 21 Aug 2010, 07:13 am
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Default Re: Interference motor?

Chris,

Welcome to the forum. azphotog has already told you about our non-interference engine. I'll try and fill you in on your other questions.The timing belt, according to the book can go till 120K but the recommendation is to change it at 100K along with the water pump,a new belt tensioner and the two drive belts (Serpentine and alternator). It's good that your a mechanic because replacing the timing belt is not easy chore. It's 5 to 7 hours labor and that's if you know what your doing.

The non-turbo PT is not a racer but any means but it will keep up with 99% of the traffic out there on the roads. All the add-ons you can buy isn't going to change that but some can make it feel a little stronger. The cold air intake, even the not-so-cold intake (short ram) will give it a better feel from the stop lights allowing more air to get to the throttle body. Porting the TB or thowing in that TB spacer won't do a darn bit of good. You need to to some internal engine work for porting to do any good and the spacer is just a $100 paper weight. A lighter flow thru exhaust can hep in weight savings and help the engine breathe better but increases the sound output to something your daughter might not like.

Good luck with your daughter's PT. Watch the front suspension especially the front wheel bearings. Lots of people having to replace parts earlier than you would expect.
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Old 21 Aug 2010, 06:24 pm
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Join Date: Aug 2010
Location: CA
Posts: 9
Default Re: Interference motor?

Thanks for the good info!
My daughter and I have already caught the PT bug!
We're already thinking of ways to customize it!
Cool PT, BTW Crewzin! Love the paint and hood struts!!
CB
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Old 22 Aug 2010, 01:09 am
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Join Date: Mar 2010
Location: Billings, MT
Posts: 745
Default Re: Interference motor?

Several of the Chrysler techs at our shop say the engine is an interference engine. However, they also state that it's usually fairly rare for valves to bend if the timing belt breaks.

According to the techs, all Chrysler FWD engines are interference. If they were non-interference, the valves would never get damaged when the belt breaks, but we have had a few in our shop with valve damage.

I don't have too much experience on this topic myself, but am just repeating what the techs told me.
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-Chris
2010 PT Cruiser Classic, Deep Water Blue
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  #6 (permalink)  
Old 22 Aug 2010, 07:14 am
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Default Re: Interference motor?

The terms were around before the overhead valves really caught on where almost every car has them. So whoever coined the terms was only thinking of clearance between the valves and pistons.

In a non-interference engine, overhead valves can hit each other when the timing belt breaks if certain conditions exists (but it happens rarely) but cannot hit the piston tops.

The interference engine does not have enough clearance between the valves and pistons tops so they will collide when the belt breaks.
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Old 22 Aug 2010, 12:41 pm
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Join Date: Aug 2010
Location: CA
Posts: 9
Default Re: Interference motor?

Good points...
The only truly NON-interference motor is a two-stroke...
CB
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