Too Much Machining?

  • HD block is machined, pistons now sit slightly above deck

  • Cylinder head also machined

  • Running stock HD flat top pistons

I’ve tried fitting different head gaskets four times, with the same result. As soon as I turn the key over it leaks straight away. Bubbles out of radiator or overflows, top hose gets hot, bottom hose stays cold - thermostat doesn’t open. Each time I’ve pulled it apart, leaks on all 4 cylinders - worse than when I got the engine originally lol. Fire rings aren’t sealing.

Used new head bolts on two occasions, have also tried oem gasket. Don’t want to give up on this project! I also posted in the old daiforum but unfortunately with this problem things have come to a halt.

Any thoughts on why this would happen? Any information would be much appreciated.

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would it be worth getting the piston machined down or seeing if there is a torque plate or even as dodgey as running 2 head gaskets? to get it working.

What’s the head to piston distance? Comp ratio?

How much came off the head and block?
Have you straight edged both surfaces?
Same gasket each time or different brands?

I am running 0.4mm of the block and 1.5mm off the head.

Although I never listened I did once have an experienced Dai engine tuner advise me not to machine too much off the head as he reckoned it could cause problems, but I have never had anything along the lines of what you describe.

Head and block are both straight

Don’t know how much has been machined off, don’t know the compression ratio either. Learning the hard way… unfortunately lol this g102 is older than me. Luckily it’s a Daihatsu so the mistakes aren’t so expensive :grin:

Head will be going back to the machine shop to double check flatness and to measure the volume of the chamber. Any specs on the HD pistons volume? They are close to flat but not quite.

Used different brands each time. Payen, Durapro, Reinz, OEM from Toyota Parts.

Thanks for the replies, I’ll keep you posted on what happens. This thing is going to run, it’s just doing my head in at the moment.

Lastly, this new forum is excellent. The new layout makes it really enjoyable to browse, great job :+1:

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Stock HC and HD combustion chamber is around 42cc.

My HE head with 1.5mm machined off is 35cc.

Good luck!

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I’d be doing a clay/Plasticine dummy build and boroscope the thing too. I have a spare head with a cut out so it is possible to do a build with it and check the remaining ex and in valve clearance for real as it’s turned over. Also cc the head and calc the effective bore displacement taking ring clearance cc and head gasket cc into consideration. With all this knowledge you can gain an understanding of what might be going wrong.


Sorry to keep adding ideas. For perhaps the last decade I’ve not done a rebuild with out switching over from head bolts to studs (typically ARP - though the exception might be when I finally do the EJ-DE or EJ-VE build that I’m yet to do since: the bolts are way short [and won’t twist much]; the ARP route is a mix of internal wrenching nuts and custom studs; and Jono M figured out Nissan VG head bolts can be made to work [oversize diameter compared to std]). Also just check the head and block water galleries are a match - check about ten times with an old headgasket and then get someone else to check about ten times also. Do you have any pictures of headgaskets that show the sealing ring failures?

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Hey lads, it’s been a while but check this out

HD block - exhaust side - cyl 3 & 4

Looks like a crack in the sleeve. What do you think?

Still haven’t given up on the Charade, it’s just getting hard to source a decent engine these days.

Had the head pressure tested, checked for flatness and it came back all good. Valve clearance and compression ratio is all good.

Head bolt clearance is fine, they are not bottoming out in the holes.

The cylinder sleeve appears to be separating from the block. Going to get it down to the shop and get it looked at.

Here is one more pic with block cleaned up.

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now I can see it sometimes pics are hard to see what is what

Any luck with the block?

Sorry to ask a silly question, but are the dowels in the block seated properly? They could prevent the head from contacting the gasket fully.

Is there anything else in the engine bay preventing the head and block contacting?