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Does having cam gear's +1in. -3ex. effect compression #'s? A friend tell's me this is the case. my #"s are 1=140 2=140 3=142 4=140 5=140 6=135 toy. man. say's 156+- 14psi limit 128 car still run's strong last night [email protected] no nos on dr's.
 
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Im pretty sure cam gears play no role in cylinder compression.... to my recollection, those numbers are pretty low.... arent they supposed to be in the 160 range?
 
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Those #s are a little low. The good thing, though is that they're pretty even. I'd just run it until you notice more symptoms like oil burning/usage. I'd start to stash some $$ for that day, though.

#6 with the lowest may indicate that its running hotter. EGT's a little high causing extra stress, maybe? EGR block off mod may help prolong #6 until the time you rebuild.
 
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I don't really think the #'s are all that low, If you read the spec's from toyota. And the car is still so strong. But i may be wrong. And i did the egr block. Thank's for the input though.
 
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Cam gears should not have any effect on compression #'s. Correct me if I'm wrong, but changing valve lift wouldn't change anything on the compression side.
 

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deavenly1, dont listen to the people that are telling you the cam gears wont change you comp. numbers...of course they will! You're changing the amount of overlap between the cams when you adjust them(ie the int and exh valves are open at the same time for a longer time), which creates lower compression #s. This is a good example of how compression ratio and compression pressure are (and arent) related.
 
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Discussion Starter #7
Ya after hearing it explained, he's definately right. They should yield lower numbers.
 
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Shooo. Thank's for the good news! I was getting worried. I thought my car was running strong still, But that it might be in trouble.:blue:
 

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Also, did you do the compression test with the throttle wide open? Often people forget to do this, with the throttle blade wide open, it will read about 10psi higher, also, did you have all the spark plugs removed? Don't foget to do that....and was the engine warm or cold...
Sounds like good numbers to me...
 

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AZMongoose said:
deavenly1, dont listen to the people that are telling you the cam gears wont change you comp. numbers...of course they will! You're changing the amount of overlap between the cams when you adjust them(ie the int and exh valves are open at the same time for a longer time), which creates lower compression #s. This is a good example of how compression ratio and compression pressure are (and arent) related.

Not on my car.

I tested at 165 on all cyliders recently with cam gears installed!!! Go figure.

-4.5ex/+1intake
 
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turbodg said:
Also, did you do the compression test with the throttle wide open? Often people forget to do this, with the throttle blade wide open, it will read about 10psi higher, also, did you have all the spark plugs removed? Don't foget to do that....and was the engine warm or cold...
Sounds like good numbers to me...
Is the correct way to do the test when the engine is warm or cold?
 

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Spool said:



Not on my car.

I tested at 165 on all cyliders recently with cam gears installed!!! Go figure.

-4.5ex/+1intake
Did you do a before/after? How COULDN'T the intake cam gear change the compression? Think about it, the more intake cam duration, the less compression at lower RPMs...

If the #s are all close to each other, don't worry about it. I've seem a gauge be as much as 40 psi off.
 
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....But no valves even within 90 degrees of being open during the compression stroke, how can valve overlap affect the compression#? Valve overlap would only happen at the end of the exhaust stroke and the beginning of the intake stroke.

My gauge was off (high) by around 20psi or so. I guess it makes sense to find a way to calibrate the gauge. Perhaps do compression on a known new car, or feed it air from an air compressor and cross check the compressors gauge.
 
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Oh, i did'nt have throttle open,plug's out or engine warm. Im going to try this and see what i get . TIA.
 
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