S30TRBO Posted September 25, 2005 Author Share Posted September 25, 2005 you might want to consider just enlarging the bore on all of them. How big would that one cylinder need to be bored to 'clean it up'? .080 overbore is a lot... If anyting you might consider going as big as you need IF that will be enough to fix the problem' date=' if only because that will increase displacement and power. Or is it going to cost much more to overbore them all evenly?[/quote'] I will find out and get a price in comparsion to sleeving one and overbore all of them, but what I need to know is what works and what is over kill. I am not trying to pinch penny's here... I did some research and I read if you go over .60 it will run hot. I plan on running electric fans, 4 core radiator, and 160 thermostat. Is this a B.S. statement? I just want to make sure since some people are saying sleeve the one cylinder and you'll be fine and others are saying overbore them all .60-.80. For a turbo application (I know L are strong) what is the best method to ensure a strong block that will last? Thanks Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted September 25, 2005 Share Posted September 25, 2005 Again, I had no problems with an N42 block I had overbored .060 over. Never heard from anyone that that would cause it to 'run hot'. With mine it was not an issue. But this was with a non-turbo'd motor. I ran the stock 280zx radiator... everything to do with cooling was stock. It was a moderately built up motor that put 170 hp to the wheels. I used to drive it every day, living in Southern California with some pretty hot ambient temps, 100+ degrees during summer was not uncommon, and never had a problem with overheating. I'm not saying I know which is better, as far as comparing sleeving one cylinder or just overboring all of them. I wanted a pretty big overbore to get more power... with an N/A motor every little thing you do counts. With a turbo motor increasing displacement isn't nearly as important, as you can just turn up the boost It just depends what you want to do, not sure there's really a 'better' way, but if it was me and the cost was either close or not enough of a difference to be an issue, I'd probably go with overboring all of them. Quote Link to comment Share on other sites More sharing options...
AK-Z Posted September 25, 2005 Share Posted September 25, 2005 If you do run hot then I would think that the problem would be the amount of fuel to the cylinders is a bit lean. I would upgrade injector sizes and bump up the fuel preasure a bit. Quote Link to comment Share on other sites More sharing options...
Mikelly Posted September 25, 2005 Share Posted September 25, 2005 I had one block bored .80 over and it never ran hot, but the comment about running hot should be taken seriously. Go much more than .60 over and the block does require attention and a stock cooling system may not work... All depends on how well that individual block sheds the heat. I think sleeving it would be the way to go, but wouldn't think twice about boring it out to .60 over on all cylinders if that would "fix" that problem cylinder. Mike Quote Link to comment Share on other sites More sharing options...
S30TRBO Posted September 25, 2005 Author Share Posted September 25, 2005 ok I think .60 will be the way to go (on all), if that cylinder still won't clean up then I'll cross that bridge if I get there... Keep you posted. Joe Quote Link to comment Share on other sites More sharing options...
240Z Turbo Posted September 26, 2005 Share Posted September 26, 2005 how about pickin up another turbo block? With all the cash you are spending whats another couple hundred for another block. Agreed, seems to be most economical solution. No need to sleeve block on 400rwhp and no need to overbore that large as it really buys you very little. Quote Link to comment Share on other sites More sharing options...
Clifton Posted September 26, 2005 Share Posted September 26, 2005 Luckily he is boring this before ordering the pistons or I would be screwed.. That's brave. I hope the pistons are whatever they are expected to be. If the pistons are .002" +/- than expected, that would screw everything up. I know my guy won't touch a block without pistons in hand. Quote Link to comment Share on other sites More sharing options...
ezzzzzzz Posted September 26, 2005 Share Posted September 26, 2005 Without sonic testing you don't know how much wall is in the cylinder(s). You can bore over and take the risk or sleeve and know all is okay. I'd want to know how much meat is there before I bored more that .040". I don't see any advantage to an overbore except it's salvaging the block for another rebuild. I've seen chevy blocks with shifted cores that would not allow a .060" overbore due to porosity. Maybe the L block is thicker and or more accurately cast. Siamesed blocks are stronger but require more attention to cooling since there is less surface area in contact with the coolant. If it were me (and I can get anal) I'd look for another block or sleeve all six cylinders to run stock pistons. If you decide to sleeve even one cylinder be SURE the machinist doesn't bore all the way through and fit the sleeve. You want a step at the bottom of the bore to stop the sleeve from possibly dropping. It is retained at the top by the head. If you haven't heard of or seen a sleeve that moved...well, lets' say things come apart rapidly and it ain't purty. Quote Link to comment Share on other sites More sharing options...
S30TRBO Posted September 27, 2005 Author Share Posted September 27, 2005 That's brave. I hope the pistons are whatever they are expected to be. If the pistons are .002" +/- than expected' date=' that would screw everything up. I know my guy won't touch a block without pistons in hand.[/quote'] It makes sence to me to check the bore before having pistons ordered. In my case a .40 over bore worked on all but 1 cylinder, if I had .40 pistons I would have .40 pistons that I couldn't use. He is overboring the one cylinder today to .60 and if that doesn't work then I will be in search for another block. Quote Link to comment Share on other sites More sharing options...
1 fast z Posted September 28, 2005 Share Posted September 28, 2005 You do know that I have seen people actually just over bore ONE cylinder, and make the over bored piston the same mass as the others, to obtain the balence. Quote Link to comment Share on other sites More sharing options...
S30TRBO Posted September 29, 2005 Author Share Posted September 29, 2005 You do know that I have seen people actually just over bore ONE cylinder, and make the over bored piston the same mass as the others, to obtain the balence. No I don't but thanks for the info... Quote Link to comment Share on other sites More sharing options...
S30TRBO Posted September 29, 2005 Author Share Posted September 29, 2005 .60 worked and it cleaned up. Now it's time to decide on the C/R so we can get the pistons ordered. I have looked into Ross and when I called I was told for turbo application to use the tapered wall pins. Does anyone have anything bad to say about Ross pistons? Back to C/R according to my Sydney Z Car Club L series engine calculator on a L28 base line w/ P90 head, HKS 2mm and .60 overbore using flattop pistons the C/R is 8.24:1, using dished pistons yielded 7.21:1. All the reading I have done says to keep the C/R between 8 - 8.50:1 is this a fair estimation? My machinist lives by the John Lingenfelter book and he was explaining the squish theory (.40-.50) that I should have some room from the top of the block to the bottom of the cylinder head. He also suggested to maybe use a HKS 1mm verses the 2mm to allow me some more play. So what I am asking is what should I use flattop pistons, dished, or a custom flattop with a D shaped dished (his suggestion)? I want to make sure I am not over looking anything since this is my first build. Quote Link to comment Share on other sites More sharing options...
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