1985 L98
Thread Starter
Intermediate
Joined: May 2000
Posts: 42
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From: pendelton in in
1985 L98
i just had my cylinder compresion checked it's 150 anyone with a manual is this about normal for a L 98? am i still all right on power. thanks baldeagle
[Modified by bald1eagle, 5:38 PM 3/1/2003]
[Modified by bald1eagle, 5:38 PM 3/1/2003]
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Re: 1985 L98 (bald1eagle)
I think that's a bit low.
I had mine done on my 104K motor last year and they were all 167-168.
As long as it is uniform though I don't think it is very bad.. Or so I heard.
I had mine done on my 104K motor last year and they were all 167-168.
As long as it is uniform though I don't think it is very bad.. Or so I heard.
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: 1985 L98 (bald1eagle)
The 1985 GM manual says verbatim:
When checking cylinder compression, the throttle should be opened and all spark plugs removed, and the battery at or near full charge. The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds.
When checking cylinder compression, the throttle should be opened and all spark plugs removed, and the battery at or near full charge. The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: 1985 L98 (ld85)
The 1985 GM manual says verbatim:
When checking cylinder compression, the throttle should be opened and all spark plugs removed, and the battery at or near full charge. The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds.
When checking cylinder compression, the throttle should be opened and all spark plugs removed, and the battery at or near full charge. The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds.
Guage accuracy... lubrication of rings... air filter on or off... block temperature... air temperature... cranking speed, etc. Youre better off just comparing your cylinders to each other. I noticed a significant decrease in pressure during the second test.. and pressures dropped a bunch as air temp went down.
I got readings between 175 and 185 doing my stock 85. (Prolly carbon deposits.) I think 150-160 is fine. How fast did the pressure build up on the gage? How many strokes before you got your max pressure?
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Re: 1985 L98 (CentralCoaster)
[QUOTE]The 1985 GM manual says verbatim:
When checking cylinder compression, the throttle should be opened and all spark plugs removed, and the battery at or near full charge. The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds.
Youre better off just comparing your cylinders to each other. QUOTE]
Thats what the GM manual says, " The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds."
I agree and when you read the Haynes manual it explains some more about how the compression is acheived in relation to the Piston Rings Leaking, Valves Leaking etc.
When checking cylinder compression, the throttle should be opened and all spark plugs removed, and the battery at or near full charge. The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds.
Youre better off just comparing your cylinders to each other. QUOTE]
Thats what the GM manual says, " The lowest reading cylinder should be no less than 70% of the highest and no cylinder reading should be less than 100 pounds."
I agree and when you read the Haynes manual it explains some more about how the compression is acheived in relation to the Piston Rings Leaking, Valves Leaking etc.
Team Owner
Joined: May 2002
Posts: 24,337
Likes: 25
From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Re: 1985 L98 (ld85)
No offense intended BTW.. I was referring tho the manual being crap, at least in this case. You woulda thought they'd err on the side of scaring more poeple to take their cars in to the dealerships for engine rebuilds. :smash:
Also, baldeagle... you stated one value for cylinder pressure. Did you measure all 8 or just one? You should post em here, and let us look at the values.
Also, baldeagle... you stated one value for cylinder pressure. Did you measure all 8 or just one? You should post em here, and let us look at the values.
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