Guess my compression...
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 3,470
Likes: 18
From: Lake Ozark, MO
Guess (help me with) my compression...
Over the past several months I've been looking for a cam for my wife's car...selection advice of forum has been based on current compression....I was guessing high, but maybe too high. Here's what I have - what do you think the CR actually is?
454 bored 30 over (not a tall deck)
Stock crank
Stock flat top pistons notched for valve relief
3931063 closed chamber heads 100.9 cc WITH bigger 2.19/1.88 valves
Some machine work was done to surface the heads not sure how much was removed, If I remember right it was 6-8 thousands.
Minor bowl work to increase flow
Using Felpro gaskets at .039 thickness
454 bored 30 over (not a tall deck)
Stock crank
Stock flat top pistons notched for valve relief
3931063 closed chamber heads 100.9 cc WITH bigger 2.19/1.88 valves
Some machine work was done to surface the heads not sure how much was removed, If I remember right it was 6-8 thousands.
Minor bowl work to increase flow
Using Felpro gaskets at .039 thickness
Last edited by Hvymtlc5; Jul 8, 2010 at 12:10 PM.
Race Director
Joined: Apr 2000
Posts: 17,665
Likes: 194
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
18:1 run at least rum 87 octane 
Or on the other hand give us the correct specs to determine compression ratio if you don't know what specs you need just google it and you will get 112,033 reply's
Or on the other hand give us the correct specs to determine compression ratio if you don't know what specs you need just google it and you will get 112,033 reply's
Instructor
Joined: Jun 2010
Posts: 199
Likes: 0
ok with whats there i came up with around 9.4-9.6ish:1 not knowing exacts but
this is the numbers i guessed at lol
stock crank so 4in throw
stock 454 bore 4.250 which he went..030 over takes that to 4.280
casket bore unknown threw a standard 4.250
crompressed casket uknown used the .039 thickness
chamber 100.9
piston deck clearance unknown 0
the few thousands of the head may make up for pistons deck clearance hence my guessing high side of 9.6:1 low side of 9.4:1 lol
so go with the middle and just say 9.5:1
if any of my figures seem wrong please feel free to correct me i am not perfect.
this is the numbers i guessed at lol
stock crank so 4in throw
stock 454 bore 4.250 which he went..030 over takes that to 4.280
casket bore unknown threw a standard 4.250
crompressed casket uknown used the .039 thickness
chamber 100.9
piston deck clearance unknown 0
the few thousands of the head may make up for pistons deck clearance hence my guessing high side of 9.6:1 low side of 9.4:1 lol
so go with the middle and just say 9.5:1
if any of my figures seem wrong please feel free to correct me i am not perfect.
Thread Starter
Melting Slicks
Joined: Mar 2004
Posts: 3,470
Likes: 18
From: Lake Ozark, MO
Thanks to all the responded - that's all the info I had so with those estimates I can safely go to a different cam based upon my earlier "WAG guess" of a CR of 10.4
as far as:
that will be perfect for my supercharger application - thanks! 
as far as:
18:1 run at least rum 87 octane
Last edited by Hvymtlc5; Jul 9, 2010 at 07:56 AM.
