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Doing some stupid shit to an old datsun head

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    pinging on E85? really?
    This is a post i wrote by mistake, which is nice...

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      Timing is an indication of how slow and poor the burn is.

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        Yup, stock head needed 36 deg on avgas with 12:1 comp, this looks like it's going to end up at around 26 deg at 13.5:1 with a slower burning fuel.
        So likely around 10 deg less ignition timing required with a slower burning fuel - that's a very good thing.

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          I thought a slower burning fuel would want more advance, to spark it earlier because of the slow burn??
          My l20b on e85 I have the timing set at 36 deg total and it's not pinging but I only have 11.2-1 comp(pings badly with 98+octane booster) I couldn't even run any advance at idle 0 deg.

          Would I be better running less advance with the e85?? Sorry if thats to off topic

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            Slower burning fuels do need more advance, hence it's impressive that we're back at 30 deg & it's into det - shows how much faster this chamber is burning compared to a stock one.

            Tune for the timing the motor wants, more/less is not necessarily better, just find the sweet spot.

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                Well, clean bill of health on the motor - other than the fucking oil pump.

                Got the head gasket about 1, headed to Bills & screwed the head back on, got it fired up about 3, got part way though some mapping etc when smoke started coming out the breathers.
                WTF's were said, pulled it back to idle & fucking bang - the oil/fuel vapour in the sump ignited with an almightly bang.

                We thought it'd hurt something - plugs out, comp test - all good, 195-200psi on all 4, plugs looked good, cranked it to fire it again & no fire, traced it to having no pulse for #1.
                The dissy is just used to tell the ecu when she's on #1, so we pulled the blanking cap off - dissy no spin. Pull the dissy out - shaft no spin. Oil pump off - drive gear has lost most of it's teeth.

                Best we can figure the centre shaft in the new oil pump is too long, it's been pushing the shaft up hard into the bottom of the lug where the shaft runs in the front cover, the heat from that has burned the oil off the gear & the gear has overheated & come apart.
                The explosion was the heat from the gear (it had gone past blue to silver hot) igniting crankcase gasses - happened coming back to idle as windage etc was keeping the flames under control (that was the smoke from the breathers), as it came back to idle the windage dropped & fucking wham.

                It took out the front cover, oil pump drive shaft, pump drive gear on the crank & put metal all through the front cover.

                On the bright side the motor itself is fine.

                Owner is chasing up another front cover, drive gear & drive shaft right now, I've got the sump etc off for a clean.
                I'll have to mill the new front cover to the same height as the now munted one, it'll go back together in the morning & we'll use the old, slightly beat up oil pump coz we know the fucking shaft in that one is not too fucking long.

                During mapping we did see 184hp @ 6000rpm on 24 deg timing tho - so looking good once it's back together (again).

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                  Damn, that's shitty luck.

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                    PS - 184hp @ 6000rpm = 113% VE & we ain't even in to the intake runner tuned length zone yet..........

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                      One word = Winning!

                      Looking forward to seeing what i'll do once the oil pump is sorted.

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                        "Old Datsun head" = 260GLE?
                        Soft roaders represent an excellent compromise between the needs of the hardcore 4x4 user and the convenience of a city hatchback. Its clear to see why they have become so popular in todays society.

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                          Power is impressive, bad luck on the pump, good that nothing serious is broken!
                          Originally posted by thebluerx7
                          The fact they want to ban cash makes me want to go out and use it full time again now .

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                            Originally posted by TK View Post
                            Yup, stock head needed 36 deg on avgas with 12:1 comp, this looks like it's going to end up at around 26 deg at 13.5:1 with a slower burning fuel.
                            So likely around 10 deg less ignition timing required with a slower burning fuel - that's a very good thing.
                            That's interesting, I'm running 26 on your motor in the Hako too. Any more and I hear a wee bit of ping in the mid range.
                            Japanese Nostalgic Car - Dedicated to classic japanese cars

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                              Yup, if you're gonna get ping you'll get it 1st around peak torque, be carefull, if you can hear it it's more than a little ping!

                              Front cover sourced, cleaned up, milled to height & painted, all the other little bits came out of a spare engine (that had a dead front cover, doh), so everything is ready to go back together in the morning.

                              I can't get down there tho, got a very large pile of work that needs to be done yesterday, so I'll just have to keep in touch by phone.

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                                Thanks all who contributed for the interesting discussion on ignition advance and timing and the relevant theory. Learnt something.
                                Richard's DatsunZ lappin LakesidZ http://www.youtube.com/watch?v=47OSh...&feature=g-upl

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