Hello from Slovakia

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Jojo
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Posts: 19
Joined: Thu Jun 29, 2017 5:09 am
My tercel:: 1986 4wd

Re: Hello from Slovakia

Post by Jojo »

My decision to overhaul engine head was a good one. Watch for inlet valve guides on first and fourth cylinder. What could be a reason?
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Petros
Highest Ranking Member
Posts: 11930
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Hello from Slovakia

Post by Petros »

exhaust guides got over heated and worked loose. You should replace all the guides, or at the very least, all the exhaust valve guides.

take it to a machine shop. They will knurl the inside of the valve guild bore and than install new valve guides, they are interference fit and if it runs hot, typically in the exhaust side, the heat expands the head too much and the friction fit is reduced. I have had it happen on my daily driver.

Also, IMPORTANT; replace the exhaust valves, they likely have heat damage as well and should not be trusted. I have seen them brake off or fail, and do a lot of damage to the engine (once I have seen the stem was driven up through the head, another time the valve head embedded into the top of the piston, bending the connecting rod and the crank!). Not worth the risk, the exhaust valves are cheap and should be replaced, along with the exhaust valve guilds.

the intake valves should be okay to regrind the face and reuse.

to lower the exhaust temp while running you should run the spark timing at 10 deg BTDC, not the factory 5 deg BTDC. It will improve your fuel economy slightly as well.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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Mattel
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Posts: 1788
Joined: Tue Aug 17, 2004 12:11 am
My tercel:: 1988 Corolla 4wd Wagon (AKA Corolla All-trac) 5speed, AC, Power Sunroof, Windows, Mirrors, Steering, Locking, Diff Lock, 14" Corolla SX Alloys with Silica Hankook Tyres, 4afe, King Springs, Upgraded Headlights, Full Synth oils, 210,000kms
Location: Melbourne, Australia

Re: Hello from Slovakia

Post by Mattel »

Thank you Petros. I'm not sure what we would do without you on this forum! Your dedication and knowledge is always appreciated.
Previous: 83 Tercel SR5 4wd, 84 Tercel SR5 4wd
88 Corolla 4wd Wagon 5speed, All power options, Fact Sunroof, Diff Lock, 14" SX Alloys, Hankook Tyres, 4afe, King Springs, Upgraded Headlights, Full Synth oils, Tow Bar, 210,000kms
Jojo
Newbie
Posts: 19
Joined: Thu Jun 29, 2017 5:09 am
My tercel:: 1986 4wd

Re: Hello from Slovakia

Post by Jojo »

This is some deposit! :-)
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Petros
Highest Ranking Member
Posts: 11930
Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: Hello from Slovakia

Post by Petros »

that is fairly normal, and a real bear to get off. I use a wood chisel as a scraper. fuel particles against the cooler intake valve do not burn completely, leaving trace deposits. of course after 30 plus years, those trace deposits build up. it gets worse when it runs too lean, less of the fuel burns at the edges because the mixture burns cooler being lean.

You get the same build up on the piston top, and to a lesser exent on the inside of the combustion chamber. This thin layer of fuel air mix that does not burn is known as the "quench area" where the cooler engine parts (200-300 F; 100-190 C) in the combustion chamber the inside cools the boundary layer and prevents complete combustion. the flame front in combustion is well over a 1200 deg F (700 deg C), so when it is "quenched" at the cylinder walls, incomplete combustion occurs.

That is why that build up occurs. No way to avoid it. other than pulling the head and scrapping it all off, many chemical products like Gumout, Seafoam, etc can be used to flood the engine, let sit overnight, and than restart in the morning and allow it all to blow out...filling the cat converter.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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