Small chamber,big squish 2L

http://www.performanceforums.com/forums/sh...old-datsun-head


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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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Nice work,makin it better.

Cool thread. (might be OT though)! I think he ended up hitting 240 after tuning, not bad for a 50 year old 2.0L!

Who let Freaky out of the sandbox?

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.

excess pressure on the shaft
causes oil shear
big hot mess of things

That was a good read. What a shit ton of work.

Neat forensics there....noodling out what happened is always good for the brain.

Ya might want to consider replacing the front & rear crank seals just for the comfort of it......