Perfect240z Posted March 16, 2012 Share Posted March 16, 2012 (edited) I just looked at this website and on the bottom it said that e31 head was changed to the e88 head because of detonation problems. Anyone hear of this? I tried searching this and couldn't find anything, reason why I ask is this stock E31 head/block need higher octane fuel then regular unleaded? Maybe 89 octane? Heres the site, its' on the bottom. http://www.zshop.net.au/240tech.htm Edited March 16, 2012 by Alex731 Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted March 16, 2012 Share Posted March 16, 2012 When the original z hit the market there was still leaded premium gas at a reasonable price and most cars got 10 mpg.Combustion chamber design was still kind of a guessing game.If you are building your own engine it is up to you to get the correct combination of parts to suit the purpose of what the engine will be used for.Combustion chamber shape,spark plug location,Ignition timing,air fuel ratios have a lot to do with an engines likelyhood of preignition.most modern dohc 4 valve engines have the spark plug in the center of the combustion chamber .this allows for less ignition advance used and a shorter flame front that burns faster.with the amount of old datsun parts around you should be able to build an engine to run on lower octane fuel.I used that ozdat engine calculator to work out the combination of parts for my turbo engine. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted March 16, 2012 Share Posted March 16, 2012 detonate with poor fuel and tuning Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted March 16, 2012 Author Share Posted March 16, 2012 Well I guess I'm just wondering if the e31 head e31 block that's all stock will have detonation? That's just what I was reading. If its true would I have to use maybe better fuel then reg unleaded? Like 89? 91 would be to high I thinke. Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted March 16, 2012 Author Share Posted March 16, 2012 OZdat said I think 9.1 for cr, with the stock set up like that wouldn't it have to use better gas then regular? Quote Link to comment Share on other sites More sharing options...
PMC raceengines Posted March 16, 2012 Share Posted March 16, 2012 In Aus the fuel was not as good we had 2 fuels back then reg and super , and most people were to tight to pay for super and most cars pinged very badly ... so most car makers droped comp and made new heads, it was mad in the 80s head gaskets and head repers all day ever day ,all from pore fuel Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted March 16, 2012 Author Share Posted March 16, 2012 In Aus the fuel was not as good we had 2 fuels back then reg and super , and most people were to tight to pay for super and most cars pinged very badly ... so most car makers droped comp and made new heads, it was mad in the 80s head gaskets and head repers all day ever day ,all from pore fuel That's interesting, so I wonder then if reg will be fine with the stock cr for my rebuild. Quote Link to comment Share on other sites More sharing options...
Leon Posted March 16, 2012 Share Posted March 16, 2012 That's interesting, so I wonder then if reg will be fine with the stock cr for my rebuild. Only one way to find out... If the head is not shaved and you have spark and fuel tuned right, you can probably get away with regular with a stock E31/L24. Otherwise, you may need to bump to a higher octane. Dynos help determine this. Oh, how I wish I had pressure transducers inside each combustion chamber and a data-logging software for it... one can dream, right! Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 16, 2012 Share Posted March 16, 2012 OZdat said I think 9.1 for cr, with the stock set up like that wouldn't it have to use better gas then regular? The octane rating specified by Nissan for the stock 8.3 CR L28 in the 280Zs is 91. Are you planning your build for the capability to run low octane gas? If you're doing a stock rebuild, the octane rating specified is probably in the Owners Manual for the year of the engine. For whatever it's worth... Quote Link to comment Share on other sites More sharing options...
Leon Posted March 16, 2012 Share Posted March 16, 2012 The octane rating specified by Nissan for the stock 8.3 CR L28 in the 280Zs is 91. Are you planning your build for the capability to run low octane gas? If you're doing a stock rebuild, the octane rating specified is probably in the Owners Manual for the year of the engine. For whatever it's worth... Could you elaborate on whether the aforementioned required octane rating is RON, MON or API? An N42/N42 will run on 87 octane with ease. I run 89 in my L24/E88 and the E88 has machine shop scribes, so it's possibly slightly shaved (don't remember if it has cam tower shims, but comp is likely a bit over 9:1). Quote Link to comment Share on other sites More sharing options...
NewZed Posted March 16, 2012 Share Posted March 16, 2012 I was just pointing out the recommendations a for stock Nissan engine. Hence the trailing "For whatever it's worth". The PO said he's doing a stock rebuild. Since Nissan wrote the Owner's Manual for the domestic market, I assume that they meant whatever standard was used in the USA in the 70s, but were probably erring on the side of caution, like they did with their timing specs. From what I've gathered, fuel quality is so variable around the country that the PO won't really know until he drives it. So he'll just have to gather as many facts as he can and make an educated guess on what might work and how much risk he wants to take. Don't forget to factor in 15% ethanol if you're in Oregon. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted March 16, 2012 Share Posted March 16, 2012 The 1970 Owner's Manual recommend 95 octane fuel but does not specify RON, MON, or other. Here in Los Angeles the octane ratings are R+M/2 and we have 87, 89, and 91 commonly available. I suspect that means that the 91 octane fuel would be required for the early Z with the E31 head. Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted March 17, 2012 Author Share Posted March 17, 2012 Ahh sounds right...but now I had a dumb moment and never looked in the owners manual...doh! I'll look but I suspected if the car had that high of a cr for stock that it would need 89-91 but I'll look in the book. Quote Link to comment Share on other sites More sharing options...
getoffmyinternet Posted March 17, 2012 Share Posted March 17, 2012 Doesn't seem like the block would make much difference (piston shape though obviously). One head could be more likely to detonate than the other simply because of the chamber size. I don't see the Z cars requiring higher octane though either way... Quote Link to comment Share on other sites More sharing options...
Tony D Posted March 18, 2012 Share Posted March 18, 2012 I run 91 in the 260zotherwise it's ping city. Even with 91 it rattles. Probably time to retard the timing a tad, or go EFI... Fuel distribution does wonders some times! Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted March 19, 2012 Author Share Posted March 19, 2012 Time will tell, the head should be shipping this week. Then I can get my stock motor back together. If it pings on 91 still, I did find a gas station that has 94, 95 and 100 or something along those lines, but if it's safe to say...maybe back in 1970 95 leaded octane might be the same as 91 unleaded by now right? Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted March 19, 2012 Author Share Posted March 19, 2012 I should talk to you tony about getting the horse power up in my l24 like you said they did in Japan at around 300hp is what you said right? Quote Link to comment Share on other sites More sharing options...
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