Bob Posted December 3, 2005 Share Posted December 3, 2005 Hey guys, I'm fairly new to actual engine work but interested in learning about my TT engine; in particular the head. I'm hoping at some point in the near future to take the head off to change the stem seals - I know you don't need to but I'd like to just in case I ever want to fiddle with the valves. As I said, I'm new to block work, so can someone clear these questions up for me?: a.) What does 'skimming' the head entail; why is it necessary? b.) Is there any point in uprating the head gasket if I don't aim to go higher than 500bhp (in the VERY long run!) Thanks guys! Bob Link to comment Share on other sites More sharing options...
LeeT Posted December 3, 2005 Share Posted December 3, 2005 the standard metal toyota head gasket is very good and there would be no reason to upgrade it Link to comment Share on other sites More sharing options...
veilsideTT Posted December 3, 2005 Share Posted December 3, 2005 unless you skim too much off the head! Link to comment Share on other sites More sharing options...
Bob Posted December 3, 2005 Author Share Posted December 3, 2005 Phew, thought I was going to have to fork out even more for another gasket! So, what's this 'skimming' malarky then? Link to comment Share on other sites More sharing options...
Bolsius Posted December 3, 2005 Share Posted December 3, 2005 Skimming is like it says. If the head is slightly warped, or you want to increase the compression, you can, within tolerances set by the manufacturer, skim very small amounts off the mating surface of the head (being the surface of the head which meets the block). By very small amounts we are talking thousands of an inch in some cases (dont know about the supra). If you take more of than recommended, you run the risk of the piston striking the valves at higher revs. If you rebuild and find the pistons strike the valves at all revs, you used an angle grinder Link to comment Share on other sites More sharing options...
Bob Posted December 3, 2005 Author Share Posted December 3, 2005 So would the head need skimming if you're replacing an okay head gasket? Link to comment Share on other sites More sharing options...
terribleturner Posted December 4, 2005 Share Posted December 4, 2005 **Hijack** When would one consider upgrading the head gasket?? Link to comment Share on other sites More sharing options...
Robert Posted December 4, 2005 Share Posted December 4, 2005 when one is making more power than you will be james, so clear off Link to comment Share on other sites More sharing options...
terribleturner Posted December 4, 2005 Share Posted December 4, 2005 I'm just thinking that when i finally push the kit up to 700bh, should i think about it then?? Or is it worth doing for a measly 550/600bh?? Link to comment Share on other sites More sharing options...
Robert Posted December 4, 2005 Share Posted December 4, 2005 probably when you pushing 700-800bhp it might be in order but someone will give a more technical answer Link to comment Share on other sites More sharing options...
LeeT Posted December 4, 2005 Share Posted December 4, 2005 I'm just thinking that when i finally push the kit up to 700bh, should i think about it then?? Or is it worth doing for a measly 550/600bh?? people in the states run 1000hp+ with stock gasket Link to comment Share on other sites More sharing options...
terribleturner Posted December 4, 2005 Share Posted December 4, 2005 Good, one less thing to worry about then. Link to comment Share on other sites More sharing options...
tDR Posted December 4, 2005 Share Posted December 4, 2005 So long as you haven't had any overheating issues, the head should be fine and not need skimmed as long as you untorque the bolts in the correct order and torque them up (new head bolts required!) in the correct order which ensures even clamping force is applied. Standard gasket is of the metal type and doesn't really need replaced but if I had the head off I'd choose to replace it with another standard gasket to ensure no chance for problems. Remember to properly clean the mating faces of the head and block! Cheers, Brian. Link to comment Share on other sites More sharing options...
Bob Posted December 4, 2005 Author Share Posted December 4, 2005 Thanks Brian, that's what I was hoping Got me a little gasket scraper kit - that should do the trick for the gasket, right? Link to comment Share on other sites More sharing options...
paul_y3k Posted December 4, 2005 Share Posted December 4, 2005 then of course there's manual skimming or doing it with a machine .... machine is safer, but Im told that the best way is manually and you get lots of little scrapes which mate better when everything is re joined. Link to comment Share on other sites More sharing options...
Chris Wilson Posted December 4, 2005 Share Posted December 4, 2005 The only reason to skim a head that has had no head gasket or overheating issues is if the the fire rings of the gasket, around the chambers, have "bitten into" the alloy head material and left dents. Then a light skim is advisable. A warped head may well skim flat, within tolerances, but you MUST MUST MUST ensure that the warping has not also put the camshaft bearings out of line. If so these need the caps machining and the journals then line boring back to round and straight, the cost of which may well make the repair uneconomic. Heads need skimming on a proper resurfacer, either ground or fly cut, and NOT by hand. Even a toolmaker would be hard pressed to get a warped head truly flat with scrapers, although in theory it's possible. Use a machine! Link to comment Share on other sites More sharing options...
TLicense Posted December 4, 2005 Share Posted December 4, 2005 then of course there's manual skimming or doing it with a machine .... machine is safer, but Im told that the best way is manually and you get lots of little scrapes which mate better when everything is re joined. BY HAND!! Machined and surface ground is the best way. You'll never get it as flat by hand. NEVER I tell thee. Link to comment Share on other sites More sharing options...
Bob Posted December 4, 2005 Author Share Posted December 4, 2005 Ah, I think I understand now. So an undamaged head gasket replacement won't need the head skimmed as long as the bolts are torqued off and on in the right sequence, and the standard head gasket is fine. Luverly! Cheers folks, that's my mind at rest! Link to comment Share on other sites More sharing options...
paul_y3k Posted December 4, 2005 Share Posted December 4, 2005 BY HAND!! Machined and surface ground is the best way. You'll never get it as flat by hand. NEVER I tell thee. I'm just going on what one of engineers was telling me the other day. basically that you use a pan of red led place the surface on it and remove and you'll see the bumps as the have led and the lower surfaces wont. you then skim away until the whole surface is red. and apparently by doing that and havng lots of mini score marks it gives everything more purchase when put together ? personally I struggle with the 710 cap, but he's an old boy that seems to know what he's on about most of the time. Link to comment Share on other sites More sharing options...
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