DesertRat368 Posted November 28, 2011 Report Share Posted November 28, 2011 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 Quote Link to comment
Skib Posted November 28, 2011 Report Share Posted November 28, 2011 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. Quote Link to comment
DesertRat368 Posted November 28, 2011 Author Report Share Posted November 28, 2011 all i know is that it is an a87 peanut has been cut just shy of the numbers and letters Quote Link to comment
datzenmike Posted November 28, 2011 Report Share Posted November 28, 2011 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. Quote Link to comment
albyneau Posted November 28, 2011 Report Share Posted November 28, 2011 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? Quote Link to comment
DesertRat368 Posted November 28, 2011 Author Report Share Posted November 28, 2011 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 Quote Link to comment
Skib Posted November 28, 2011 Report Share Posted November 28, 2011 should run on 91 fine Quote Link to comment
Jester Posted November 28, 2011 Report Share Posted November 28, 2011 http://www.ozdat.com/ozdatonline/enginedesign/ Quote Link to comment
datzenmike Posted November 28, 2011 Report Share Posted November 28, 2011 What's that number again Mike~ unmilled is 4.36" or thereabouts? Should be 4.248" heard they can be 4.260" Quote Link to comment
banzai510(hainz) Posted November 28, 2011 Report Share Posted November 28, 2011 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 Quote Link to comment
datzenmike Posted November 28, 2011 Report Share Posted November 28, 2011 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 Quote Link to comment
Jester Posted November 28, 2011 Report Share Posted November 28, 2011 ^^^^^^ No pics? :rolleyes: :rolleyes: Quote Link to comment
DesertRat368 Posted November 29, 2011 Author Report Share Posted November 29, 2011 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 :) Quote Link to comment
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