NB8A blown head gasket

wydra · Postby **wydra** » Mon Mar 24, 2014 1:58 pm

Got the head back from Harris Engines on Friday but unfortunately there were some "issues" so it couldn't just be skimmed.
My wallet is now $600 lighter but I have a head that can be bolted back to the block.

Should be running again in a week or two

project.r.racing · Postby **project.r.racing** » Mon Mar 24, 2014 2:02 pm

In other words, it was bent like a banana...

See page one, post seven.

wydra · Postby **wydra** » Mon Mar 24, 2014 2:31 pm

nope, it failed the hardness test in some spots. It was actually rather straight which was annoying.

wydra · Postby **wydra** » Tue Mar 25, 2014 2:26 pm

I cleaned the deck of the block and tops of the pistons yesterday, thankfully it all looks good, really good actually.
I rotated the engine and checked all the bores and everything is looking as I think it should.
I have now got the ARP head studs into the block and will be bolting the head back up this afternoon

Should be driving again shortly :mrgreen:

hks_kansei · Postby **hks_kansei** » Tue Mar 25, 2014 2:56 pm

Don't forget to oil up the cams before it goes back in.

Last thing you want is to ruin the lobes with a dry start.

I'd also be priming the HLAs if your car has them (can't remember what MX5 you have)

wydra · Postby **wydra** » Tue Mar 25, 2014 3:16 pm

Yeah will give the cams a good oil bath before starting (will fill the engine with oil with the cam cover off).
I believe I am ok for the HLA's, Looks like the NB8A engine has solid buckets and shims.

wydra · Postby **wydra** » Thu Mar 27, 2014 7:35 pm

Can anyone offer some advice?

My head is back together, block deck cleaned off, studs are in the block, all I need to do is chuck the head on and torque it down.

First question,
when you clean the old head gasket "crap" off the head using a sharp blade scraper and carby-clean it must leave a small amount of crap in the oil galleries right? I know it wouldn't be much as it is just a metal multi-layered from factory but there was some gunk coming off on the blade. Is it worth removing the oil filter (which I have done already), putting something under it to catch liquid and run some methylated spirits down all the oil holes?

Second question,
There is a lot of discussion about the torque of the ARP head studs. The box says 80 foot pounds, the general consensus is that 65 foot pounds should be more than enough and is better to stick to this. What to do? 65 or 80?

Cheers

wydra · Postby **wydra** » Fri Mar 28, 2014 6:45 pm

Ignore question 1, I have answered it myself with some help from this image:
http://www.miataturbo.net/attachments/d ... 1383092190

As for question 2, I am leaning towards 65 ft-lb unless someone has a reason why 80 ft-lb is needed (and I wont crush the aluminium head bosses). I believe Flyin Miata actually ship another set of instructions to only torque the stud bolts up to something less than 80 (mixed results on the forums, somewhere between 50ish and 70).

sailaholic · Postby **sailaholic** » Fri Mar 28, 2014 7:57 pm

I took mine up to what the instructions in the box said.

More clamp better seal is my thoughts.

If you haven't already figured it out, the new nuts for the studs are a imperial size. Half inch for memory. The metric socket that worked on the Mazda ones doesn't work on the Arp ones anyway.

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wydra · Postby **wydra** » Fri Mar 28, 2014 9:56 pm

Cheers for that, will use an imperial bit for the top nuts and not the 12mm that took out the standard bolts.

So you went to 80ft-lb? It just seems so much more than standard, and the new thread pitch amplifies this even more. More clamp force is better unless you start to crush the head.

sailaholic · Postby **sailaholic** » Fri Mar 28, 2014 11:38 pm

That's what I was told by the head builder. Seems to have held up.

Having said that, you seem to more susceptible to head problems?

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wydra · Postby **wydra** » Mon Mar 31, 2014 1:52 pm

I ended up torqueing to 22, 44, 66 ft.lb then nipped them up between 72-73 ft.lb
Got the rest of the engine back together and it started right up and is running great

Still have a few more hours work to get the car back on the road again and give it a full test but so far so good.

Aussie Stig · Postby **Aussie Stig** » Mon Mar 31, 2014 3:21 pm

You have a turbo set up don't you?

Common sense would dictate the higher torques for boosting.

The mturbo guys should be able to offer some advice. Surprised nitrodann hasn't stuck his nose in this thread.

wydra · Postby **wydra** » Mon Mar 31, 2014 5:48 pm

general consensus on mturbo is to go to 65 ft.lb, from what I read anyway. I split the difference and went to 72-73. meh its done now and it wont be getting changed. Even at 65 you have considerable more clamp force than stock and the only reason that let go was due to an overheat situation. It will be fine