7MGTE - Should I get the block decked?

[terryo]

I run an engine shop and always machine the block & head with a special tool, before using a metal HG. I can get you a good price on one, if you dont already have it. If you can't affort the time/$ to strip the block, then get a professional to "flatten" the block by hand with a decking plate. they should tell you beforehand, if you are wasting your time.

[doobs]

Cheers terryo, Im going to stick with the stock one for now, what would you suggest i used to give the block a better finish, judgeing by the pics above?

[gianttomato]

You really need to put a straight edge over the deck. Seeing as you haven't done this and can't tell anybody what sort of flatness the deck has, nobody here can confidently tell you what to do.

From memory, Ed's block and my mate's block (who recently did a Cressida motor after a BHG) had enormous undulations (around 20 thou) across the deck. Not confident how long you could seal something across such an uneven surface should yours be the same. Of course, everyone then blames the motor but, of course, the head gasket's failure is actually due to the retard doing the head gasket who has no idea what they're doing. Machining one surface perfectly flat, using the world's best head studs, a metal head gasket and head sealing compound will not improve the ability to seal if the other surface is as hilly as the Himalayas.

Your call. Of course, you might decide that repeating the process in a couple of months is something you want to do.

[ed]

enormous undulations

teeheehe.... titties!!

ahem - he speaks the truth.

and remember - please dont contribute to further "i rebuilt my engine and got another BHG" whinging stories in 6months if you dont do it right the first time.

cheers
ed

[doobs]

I appreciate the advice, and yes I do understand a metal gasket requires a perfectly flat surface, both sides, to seal correctly, but like I said before I WILL NOT be using a MHG, I will be opting for a stock gasket, followig the advice I have been given.
Unlike some around here my pockets are not so deep, and I can not afford to rip the block apart right now. 6 Months from now, I will have saved the cash for the rebuild... as I will be expecting it to fuck up.
Please keep in mind, I'm learning as I go, I've never done this before...

Now after all that here are some pics with the ruler on the block:

[doobs]

You really need to put a straight edge over the deck. Seeing as you haven't done this and can't tell anybody what sort of flatness the deck has, nobody here can confidently tell you what to do.

How do you check the "flatness" of the block?

[ed]

feeler gauge under the sraight edge. and youll need something a little more robust/stiff than a rule to use as a stright edge

[EldarO]

peice of box section aluminium does wonders, mind you i have this at easy disposal because we use it at work.

have a look around work and house, youll find something a bit better than a rule

Eldar.O.

[doobs]

Yeah if only I could take it to work, I'm an apprentice sparky at ford, in the engine plant, where we make the F6 engine amoungst others, the tools we have there are awsome, and some of the blokes are pretty cluey, but my toyota engine will never see the insides of that building

[Cressida91GLX]

/quote as for the mechanics version of 'thats why they blow' - remind me how come so many cressidas have bhgs ?? no validity to that statement /end quote

Yeah so true, but there is more than just simple torque specification issue.

Ruler might not be as robust to check for flatness. borrow something from your workshop and do a good flat job.

[thechuckster]

opinion: unless you can take the block to a workshop to flatten/polish both surfaces, treat it like a disposable engine.

You will have to re-do this at a later stage (12-18 months or less if you give the engine a lot of hard work) so spend the intervening months collecting another block to rebuild at yoru leasure.

personally, i wouldn't even bother checking the surfaces for flatness - because any remedial work will require the engine to be pulled apart and you've already ruled that out. Just clean the crap off both sides, make sure no rubbish gets down the bores, drains and oil-feed then re-assemble with a good coating of hylomar on bioth sides of every gasket.

hint: to keep gunk out of bores and drains etc - make large balls of gaffa tape (cloth tape) to fit down various holes ike a bung - but with the sticky side facing outwards. You will have to clean a residue off afterwards (metho works fine) but metal shavings/ dirt etc will stick to the surface before you remove the 'bung'. An alternative is cloth with grease on it. A loose cloth will let dust thru and when you remove it, all the loose suff will fall down the crevasses. Having the engine on a stand makes it even easier as you can just tip the block upside down to shake off loose stuff.

[AeRoKaBn]

on the topic of block and deck machining, i read that a MHG is useless without having the block and deck faced to 1ra (roughness average). I asked the guy who rebiult my 7m head whats the smoothest he could get it n he rekoned if he used a new diamond he could get it down to 9-10ra... I noticed quite a few ppl on here are running mhg's and was wondering if anyones discussed this with there machinists on how to get a 1ra finish

Apparently some aircraft engines run with no hg so i was wondering if an aircraft machinist could get it that smooth

[kemicalx]

on the topic of block and deck machining, i read that a MHG is useless without having the block and deck faced to 1ra (roughness average). I asked the guy who rebiult my 7m head whats the smoothest he could get it n he rekoned if he used a new diamond he could get it down to 9-10ra... I noticed quite a few ppl on here are running mhg's and was wondering if anyones discussed this with there machinists on how to get a 1ra finish

Apparently some aircraft engines run with no hg so i was wondering if an aircraft machinist could get it that smooth

I'm pretty sure a cometic headgasket will be fine with a 9-10ra I wouldn't worry about finding an aircraft machinist