$projecthp
Thanks Thanks:  0
Likes Likes:  0
Dislikes Dislikes:  0
Results 1 to 5 of 5
  1. #1
    john davis
    Guest

    Default

    I have a 1975 L-48 it says 8.5 to 1 compression ratio the L-82s have 9.0 to 1 where is the 1/2 point of compression difference they both have 76 cc heads is it in the pistons? Now that I have the edelbrock 64 cc heads any body care to guess my compression? I dont know gasket thickness all I know is it was a felpro thanks

  2. #2
    Administrator Tom Bryant's Avatar
    Join Date
    Nov 2000
    Location
    Edgerton, Ohio, United States
    Posts
    7,157
    Corvette(s)
    1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
    Post Thanks / Like
    Rides
    2

    Flag compression

    John, I would guess that the L48 had a slight dish and the L82 had flat top pistons. I'll bet your are in the 10 to 10.5:1 range now. How does it run on pump gas? You should be able to run more timing with the aluminum heads over iron.
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

  3. #3
    john davis
    Guest

    Default

    I run 87 octane with no problem I kinda figured I was tunning around 9.5 to 1 compression

  4. #4
    Member Stingray6974's Avatar
    Join Date
    Oct 2000
    Location
    Garland,Texas
    Posts
    494
    Post Thanks / Like
    Rides
    0

    Default

    Hi John,
    59Tom is correct about the pistons changing compression. Your L-48 will have a dished piston with 4 valve reliefs and a beveled outer edge. Posted compression is 8.5 but actually it's closer to 8.2. Fel-pro composition gaskets compress to .039, so with 64 cc heads your comp will be close to 9.3. If you change pistons to L2256, that will give you approx. 9.8. L2417 pistons will give you 10.1
    Hope this helps,
    Mike
    Stingray6974
    69 350 4speed base coupe
    74 L-48 coupe numbers matching
    64 GS replica

  5. #5
    Administrator Tom Bryant's Avatar
    Join Date
    Nov 2000
    Location
    Edgerton, Ohio, United States
    Posts
    7,157
    Corvette(s)
    1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
    Post Thanks / Like
    Rides
    2

    Flag thermal barrier coatings

    Thermal barrier coating on the piston tops, combustion chambers and vavle faces will greatly reduce detonation and allow more timing as well as keep the heat in the combustion chamber making more horsepower. Might be cheaper than new heads but a lot of work. Worth asking, I guess.
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

Similar Threads

  1. 82 700R4 Tailshafthouse vs. Modified 700R4 Tailshafthouse for TH400
    By Peer81 in forum C3 Technical and Performance
    Replies: 2
    Last Post: 06-06-04, 07:13 AM
  2. '81 vs. '82
    By Big Tex in forum C3 Technical and Performance
    Replies: 27
    Last Post: 01-28-04, 10:44 PM
  3. Compression ratio
    By malc350 in forum Callaway Corvette Forum
    Replies: 10
    Last Post: 11-28-03, 06:07 AM
  4. compression
    By jmp in forum General Automotive Discussion
    Replies: 9
    Last Post: 02-10-03, 09:25 AM
  5. Dilema - Keep 88 or buy 82
    By Baldie88 in forum C4 Technical and Performance
    Replies: 25
    Last Post: 08-21-02, 11:59 AM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •