how many lb's of compression for stock engine?

[spunbearing]

i did a compression check and every cylinder is 135 to 140 .
but i cant find any specs on what is acceptable?
can anybody help?
thanks dale in arizona .

 

[onefastcar]

sounds pretty good as long as they are all within 10% of each other and approx. 130 or higher.

 

[John Wilde]

i did a compression check and every cylinder is 135 to 140 .
but i cant find any specs on what is acceptable?
can anybody help?
thanks dale in arizona .

That sounds about right.
Your holes are only ~3.5% apart.

 

[spunbearing]

hey thanks alot guys . i guess i will run it for a while longer .

 

[C-RAID]

This is what All Data online has under compression specifications for the 87 Buick Regal with Vin code 7 for the engine.

The lowest reading cylinder should not be less than 70% of the highest and no cylinder reading should be less than 689 kPa (100 psi). Perform compression test with engine at normal operating temperature, spark plugs removed and throttle wide open.


I hope this helps.

 

[TOMS86GN]

i have yet to do 1 3 and 5 cylinders but my 2 4 and 6 showed signs of 120 to 130. should i leave it or plan on a rebuild. the cars been acting funny and im about to say forget it and start fresh with the 109 i have sitting in my garage.
Any suggestions?

 

[TurboMonte 2]

Ck 1, 3 & 5 & get back to us,,,

 

[turbo nasty]

FYI ...I just did my 159k on unopened motor on the 87 and hot readings were 135-140 on all cyl.

Good luc

 

[TOMS86GN]

alright i think this is bad news but here it is

1 145 2 130
3 130 4 135
5 100 6 125


So time for a rebuild? Im not liking cyl five, and there not within 10 percent of each other which i hear is the rule of thumb

thanks

 

[spunbearing]

you need to see what the 100 is about ? valve or head gasket or ? before you jump into a rebuild. At least that is what i would do
good luck dale in arizona

 

[TurboMonte 2]

Perhaps you could do a re-test on your cyl's 1 & 5--the high & low--to verify your range,,,

 

[TOMS86GN]

alright a retest, 1) 140 5) 100, so whats next on the agenda? wet test or a leak down would you guys suggest?

 

[300kGN]

leak down is going to be your best indicator. mine, un-opened, tested 130-140 across the board. when I replaced the valve springs, my little compressor couldn't keep up with the leakage on #4. turned out to be half leakage past the exhaust valve and half past the rings. tapped the exhaust valve a couple times and the leakage dropped to about 30%. there's no smoke from the exhaust and the idle is smooth considering...I'm gonna run it as is! wet test won't help, as all the fluid will settle to the low side of the piston in a V-motor. also, you really should have all the plugs out, a very good battery, WOT, and injectors disabled.

 

[KL Mallender]

KL Mallender

Observed Cranking Cyl Pressures WILL Be Different Due To:

1. Gauge Acuracy - PSIG or PSIA
2. Altitude - Why #1 is Relevent.
3. Cranking Speed.
4. Intake Restrictions - Throttle open/closed, Manifold/Runner Design.
5. Engine Configuration - Measured Comp Ratio vs Actual Int Valve Closure.
6. Engine Condition - Hot/Cold, Leakdown - High/Low.
7. Consistency Among Cyls is What to Hope/Pray for, Inconsistency is What
to Look/Worry About.

fwiw stk Turbo Buick : Eng Warm,Throttle Open,200-250cs, 150-155psig at
sea-level. I Hope This Can Help You, KLM

 

[C-RAID]

I would recommend following up with a wet test, and then a CLT. If readings come up with the wet test it would be a ring issue. I you have leaking during the CLT, it could be a number of things. See where the air is escaping and take it from there. It would also help if you had a battery charger of some type connected to it. If the battery gets weak it will affect your readings as well.