Unusual High Compression - Engine Timing Related?

[TurboChrged93]

Compression was 150 across the board right before we pulled the motor. Replaced the timing belt. And after replacing the timing belt compression was 171, 165, 150, 160. Then after scratching my head for about 3 minutes I check the timing again. It appears it has jumped. Although, the cam gears didn't jump, the crank jumped... about 5 teeth. And car still runs, drives, boosts, and everything. Only thing is it misses when idling. How did compression increase!!! And how do I not have any bent valves???

 

[VelocitàPaola]

The timing has to be advanced a little bit more than five teeth (although that is quite alot) to seriously damage your engine: people advance or retard timing all the time with adjustable cam gears.
I'm not completely sure about the compression though. Several things could've happened to cause this, but I can't say for sure without more information.
I'd fix that timing though... unless you're car is so heavily modified that you need adjusted timing, it's not doing you any favors.

 

[larsenracing]

How did compression increase!!! And how do I not have any bent valves???

The compression went up because the different place ment when everythign opens and closes your exhaust valve hangs shut for a second longer and your intake hangs open alittle longer allowing more air to get in and less to get out which inturne at tdc there is more pressure. its all about timing of the piston placement and valve position thats why its called timing. good luck if its 5 teeth off your lucky you never hit any valves i wouldnt run it at all till you get it fixed also hope you didnt hit any high rpm's or you probably did nick one. best regards

 

[Spyderman7]

You need to be a litt;e more concerned about how and why your timing jumped after you just replaced the belt.Either you did something wrong or something is wrong in your engine.You should'nt drive it because you might bend the valves when it skips a few more teeth.

 

[TurboChrged93]

By the way, the motor is in my Plymout Colt. 4g63 swap Anywho, just got done redoing the timing. Skipped due to a failed auto tensioner. Compression is now 150 across the board again. NO BENT VALVES!!! WOW! Thanks guys.

 

[TurboChrged93]

One more thing. It jumped 8 teeth.