1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

compression test ?

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Old Jan 16, 2008 | 03:44 PM
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From: Cleveland,OH
compression test ?

i just did a compression test with a piston compression tester per the thread in the archive... front and rear were the same.. between 35-40 on the bounce test and about 70 with the button on the tester out... does this sound correct? because in the thread it says 90-100 but is that combined?... and on a side note front plugs were black and rears were light-medium brown.. what can i do to even them out?
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Old Jan 16, 2008 | 04:19 PM
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From: Lawrence KS
when was the last time the engine ran?
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Old Jan 16, 2008 | 04:33 PM
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From: Cleveland,OH
Originally Posted by Midwest 7's
when was the last time the engine ran?
its my dd so it ran today
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Old Jan 16, 2008 | 04:40 PM
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From: Lawrence KS
if the car makes good power i would say you didnt perform the test correctly.
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Old Jan 16, 2008 | 07:33 PM
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From: Washington, Iowa
nvm
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Old Jan 16, 2008 | 08:14 PM
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From: Concord, NC
NIKKI carb?? check the jet space by evening the turns on the front and back of the carb. One might be richer than the other...
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Old Jan 16, 2008 | 08:20 PM
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From: worcester, mass
arent u supposed to remove fuel wen doing a compression check anyways? mine read about 80 psi average and 2 weeks later i blew an apex seal on the rear rotor....not saying urs will but mine did....now im rebuilding it but need mo money...lol
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Old Jan 16, 2008 | 08:21 PM
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From: Concord, NC
WOW, 80 PSI!! That together or just one rotor?? I was told by a rotary shop that it was suppost to be within 50-60PSI...
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Old Jan 16, 2008 | 08:57 PM
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From: worcester, mass
Originally Posted by 2fast2rotar
WOW, 80 PSI!! That together or just one rotor?? I was told by a rotary shop that it was suppost to be within 50-60PSI...
huh? i got that for just one rotor....i think spec is supposed to be 80 or higher....not sure though...all i know is i posted this a while back and a lot of people told me that i was gonna need a rebuild soon and then a week or so later my motor shi* the bed...still ran but had shi* for power and make the worst noise ever...the thought of that poor apex seal being bullied by that rotor makes me sad
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Old Jan 16, 2008 | 09:01 PM
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From: Concord, NC
HAHAHAHA!!!

Hey man I feel your pain. When I finally had the $$ to rebuild mine you will never believe what I saw......

My rear rotar had an in-print(a perfect one) of a bolt!! I swear you could see the thread and the head of that sucker indented into my rotar.

So my car ate a bolt somehow- I have no clue how tho!!!!

Well after the rebuild, I realized I wasted $900 on a rebuild b/c that rotar was not savable...

But I got a fmoc motor now, so I'm good!
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Old Jan 16, 2008 | 09:06 PM
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From: worcester, mass
hahaha..nice man...yeah money is very hard to save for me...but yeah im trying very hard to save up for a rebuild and get my car going... sucks to hear that about ur motor....
and damn...did we hijack this guys thread or wat? lol....sorry
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Old Jan 16, 2008 | 09:32 PM
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From: Cleveland,OH
well its weird because its reading what its supposed to when doing the bounce test.. 30-35 psi per rotor face.. but when i did it with the button out it went to 70.... on both rotors so its even both ways..
NIKKI carb?? check the jet space by evening the turns on the front and back of the carb. One might be richer than the other...
ill check them the fuel level on the front seems to be a little high around 3/4 mark in the sight glass...

oh and can the fact that its like 35* outside play a roll in it? that engine wasnt completely warmed up before i did this
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Old Jan 17, 2008 | 07:08 AM
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From: Concord, NC
Its snowing in NC right now.....

I would let it run, then cool off for a while, then check them.

Also if you have some1 sit in the car and let them hold the gas at about 3-4000RPM you can tweek it by ear. You adjust the little screws until it makes an even sound from the exaust.

If they are uneven it will sound like a miss.
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Old Jan 17, 2008 | 11:59 PM
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From: St Joe MO
Compression test is supposed to be performed on a warm engine, 250 rpm cranking speed with the throttle plates fully open. The 87 FSM has 2 charts to adjust derived readings to compensate for variations in both cranking speed and altitude. Sec. 1, p. 11.

If the engine has been flooded or the throttle plates/butterflys aren't fully open, readings will be lower than actual compression.
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