COMPRESSION?

hey guys, just needed to know what the compression should be in all 4 cylinders. its an 85 turbocoupe (didnt know if they change by years or not) thanks for any help.
zach

the way the Ford manuals spec it, the lowest cylinder should be within 75% of the highest cylinder. For example if the highest is 140, the lowest must be at least 101. This is a very wide spread according to other sources.
You really want to see numbers within about 15 psi of each other. 140 to 160 is very good. Below 115 - 110 is getting weak

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NATO Member. it's not a vice, it's an obsession
"The nice thing about each new day is nobody ever used it before" Barnaby Jones
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm

[This message has been edited by Pete D (edited 10-22-2002).]

DAMN, the highest one i have is 115, the lowest is 70....the other 2 are 85 and 95 maybe..somwhere close to that..what does that mean when my compression is that low...and how much power am i loosing from this??? please help!!!

Can be from (among other things):

Valves not seated / seating

Valve Springs weak

Worn Cam Lobes

Cam Timing incorrect (valves opening at the wrong time)

Bad Head Gasket

Piston Rings worn / not sealing (try putting 1-2 teaspoons of oil in the spark plug holes and then repeat the test).

Leaking manifolds to head

God forbid, a cracked head

I'm sure there are other causes...but it's late Yawnnnnnn.


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Dan Eaves
88TC 5spd, Crower 5.5" Sportsman Rods, Short Wiseco Pistons bored .030" Over, Ported Head with Polished Combustion Chambers, Gutted & Polished Upper, Ported & Polished Lower, Polished T/B, Ported E6, SVO T3 .63AR Turbo, Bosch Bypass Valve, 3" DP w/No Cat, 2 1/2" DynoMax single cat back w/DynoMax Super Turbo Muffler, RR Cam, K&N in Fenderwell, Gillis Boost Valve, Centerforce I Clutch, Removed A/C, Polished Wheels, Polished Valve Cover, Polished Crank and W/P Pulleys, Walbro 255LPH HP Pump, Kirban Adj FPR, and the DAMN Heater Core is new too !

http://www.geocities.com/wot_turbo/WOT.html

NATO MEMBER (Vice Chairman...if it's a vice...I deal with it)

[This message has been edited by Dan E (edited 10-23-2002).]

ahould i just not worry about it for now? or will it come back and bite me in the ass further down the road...i dont want something to mess up on me...i was thinking about a new damn block...what do you guys think?

Originally posted by POWERED BY PSI:
DAMN, the highest one i have is 115, the lowest is 70....the other 2 are 85 and 95 maybe..somwhere close to that..what does that mean when my compression is that low...and how much power am i loosing from this??? please help!!!

Did you have the throttle wide open? (it should be) Was the motor recently run? If the car sat for days before running the test, you will get lower readings.

Did you throw a teaspoon of oil in the cyls and rerun the test?

If the comp is actually that low, you should be able to boost it to 30 psi no problem... hehe [Image: smile.gif]

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Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 20 psi, forced air intercooler, water injection, bypass valve, Ranger roller cam, subframes, etc., etc.. // 86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP nitrous, ignition, gears, suspension, etc., etc.... // 91 Escort: Bone stock winter car // 00 Windstar (wifes vehicle)

Those are low figures. Compression should be checked with the engine warm, tube from the VAM to compressor inlet off, and throttle open. Each cylinder should rotate through 5 to 6 Compression strokes (10-12 engine revolutions). After doing all 4 cylinders,
put about a tablespoon of oil and each cylinder and repeat the test on all four cylinders. If the readings increase significately then your low comprssion is due to worn rings. If the readings don't change much then see the list of things Dan posted.
Leaking manifolds don't affect compression


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NATO Member. it's not a vice, it's an obsession
"The nice thing about each new day is nobody ever used it before" Barnaby Jones
88 TC X 2, 86 SVO, mods list at
http://www.turbotbird.com/showroom/pd_88tc.htm

[This message has been edited by Pete D (edited 10-23-2002).]