compression ratio l20B 280z pistons

[DesertRat368]

looking to find out compression ratios for the L20B with 280z dished pistons on a87 peanut head looking to bore out block 20 over but cant find any and was told about early 280 ]z pistons work on L20 rods just a smaller dish and about a 40 overbore if someone could help out that would be awesome looking to get her to the machine shop

[Skib]

my calculator says itl bump it up 0.2 with the L28 piston as apposed to the L20B

 

 

L20B piston is 85mm with a -11.36 dish

 

L28 piston is 86mm with a -10.9 dish

 

 

idk what the over all CR will be without the chamber CC of your head.

[DesertRat368]

all i know is that it is an a87 peanut has been cut just shy of the numbers and letters

[datzenmike]

looking to find out compression ratios for the L20B with 280z dished pistons on a87 peanut head looking to bore out block 20 over but cant find any and was told about early 280 ]z pistons work on L20 rods just a smaller dish and about a 40 overbore if someone could help out that would be awesome looking to get her to the machine shop

 

L20B bored 1mm to 86mm with 10.9cc pistons and closed chamber A-87 head is 9.12 assuming the head has never been milled.

 

Measure the distance from the valve cover to the head gasket. This will tell you how much was milled off.

[albyneau]

L20B bored 1mm to 86mm with 10.9cc pistons and closed chamber A-87 head is 9.12 assuming the head has never been milled.

 

Measure the distance from the valve cover to the head gasket. This will tell you how much was milled off.

 

What's that number again Mike~ unmilled is 4.36" or thereabouts?

[DesertRat368]

even with the head shaved would it still run on pump 91 is the highest out here looking to get a cam done to but dont know what one would work best if i do go with the 280z pistons

[Skib]

should run on 91 fine

[Jester]

http://www.ozdat.com/ozdatonline/enginedesign/

[datzenmike]

What's that number again Mike~ unmilled is 4.36" or thereabouts?

 

Should be 4.248" heard they can be 4.260"

[banzai510(hainz)]

Silver Seal makes a cam tower shims also. to make up the fifference in head height after its been cut to keep the chain at exact length

http://www.silver-seal.com/results.cgis?catalog=&keywords=datsun&x=13&y=13

 

 

Just shy of the numbers is alot of material cut I believe

[datzenmike]

Silver Seal makes a cam tower shims also. to make up the fifference in head height after its been cut to keep the chain at exact length

http://www.silver-se...atsun&x=13&y=13

 

 

Just shy of the numbers is alot of material cut I believe

 

 

Only way to tell what your compression is for sure is to cc the combustion chamber. And you don't need a lab or special equipment. Here's how to cc your combustion chambers for free

[Jester]

^^^^^^ No pics? :rolleyes: :rolleyes:

[DesertRat368]

thanks for the info pistons should be here tomorrow then off to the machine shop head is going in too for an overhaul will have pics after machine work :)