7age rebuild for 1981 tercel

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SirFoxx
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My tercel:: 1981 Toyota Tercel w/ 7age

7age rebuild for 1981 tercel

Post by SirFoxx » Mon Nov 11, 2019 8:15 pm

Hello--

I am currently in the process of rebuilding the 7age in my tercel. I was experiencing one oil leak after another, and decided it was time to do a proper rebuild.

I currently have the engine completely torn down and ready for the machine shop, but I am waiting for the pistons to arrive so they can machine the block according to the piston specs.

I will post pictures as things progress!
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1988 DLX Tercel Wagon w/ weber (RIP)
1985 4wd Tercel SR5 (RIP)
1981 Toyota Tercel

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SirFoxx
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Re: 7age rebuild for 1981 tercel

Post by SirFoxx » Sat Dec 14, 2019 1:58 am

Progress! Block got bored over .5mm, crank got ground .5mm, and rotating assembly is:

Brian Crower H beam rods
Traum 10.5:1*** ceramic coated pistons
ACL crank and rod bearings
King thrust bearings

Also shown is the adapter plate that I am going to use with my oil pan. The indent in the 7A block has always caused me issues, and hopefully this will fix it! Forum member Chard made a thick and thin one for me, and the two black dots are the holes I need to drill as he couldnt get a good scan from the 3A oil pan gasket I sent him.

The static CR of the engine is 12.3:1. Higher than what I wanted, but, should be manageable on 93 octane. e85 is an option, but, I really dont want to deal with the side effects of e85.
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1988 DLX Tercel Wagon w/ weber (RIP)
1985 4wd Tercel SR5 (RIP)
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Re: 7age rebuild for 1981 tercel

Post by NWMO » Sat Dec 14, 2019 10:40 pm

Looking good Keegan. I picked up that parts Tercel if you are still needing a distributor.

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Re: 7age rebuild for 1981 tercel

Post by Petros » Sun Dec 15, 2019 2:02 am

That high compression might be rough on the head fast with pump gas. I would advise removing metal from the combustion chambers, clean them up, enlarge as much as practical. You might also consider taking some material off the piston crown as will, the metal is very thick there. Do it evenly so they all match combustion chamber volumes. It will improve flow, combustion and reduce the tendency for ping or preignition. When you overbore, and resufavmce the head. And add high compression pistons, you end up with high compression. You will need fo add contain booster to your gas. I think anything over 11:1 for street use will eventually cause you trouble with the head gasket or burt ex valves. I know, I have done it. Big mistake for a daily driver running pump fuel, even with premium fuel
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Re: 7age rebuild for 1981 tercel

Post by SirFoxx » Sun Dec 15, 2019 2:12 am

Petros wrote:
Sun Dec 15, 2019 2:02 am
That high compression might be rough on the head fast with pump gas. I would advise removing metal from the combustion chambers, clean them up, enlarge as much as practical. You might also consider taking some material off the piston crown as will, the metal is very thick there. Do it evenly so they all match combustion chamber volumes. It will improve flow, combustion and reduce the tendency for ping or preignition. When you overbore, and resufavmce the head. And add high compression pistons, you end up with high compression. You will need fo add contain booster to your gas. I think anything over 11:1 for street use will eventually cause you trouble with the head gasket or burt ex valves. I know, I have done it. Big mistake for a daily driver running pump fuel, even with premium fuel
I'm not touching the pistons as they are ceramic coated, tops and skirts. That copper color isn't gasket spray, its the ceramic coating. As for the head, I don't know how to modify it, and finding another 4age head for a reasonable price isnt easy if I fuck mine up. The TRD head gasket is metal, so its more robust than the standard ones, though, I know it isn't invincible. The high compression ratio is really my fault. I was aiming for 11:1, but didn't realize the longer stroke of the 7A bumps up the CR by a whole point. I may continue looking into e85 since its octane is around 100, but like I said, e85 is really nasty, and I don't know if I want to deal with that. From what I've read, 93 octane should be able to handle it. I've heard that the series 2 honda skyactive engine has a CR as high as 14:1. Granted, thats a much newer engine, but, it shows that the gas should handle it, it's just a matter of everything else on the engine...
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Re: 7age rebuild for 1981 tercel

Post by Petros » Mon Dec 16, 2019 4:40 pm

the area around the combustion chamber has the most amount of metal on it, you can take out a fair amount of metal around the combustion chamber without worry (I have cut into a lot of heads, including toyota heads). up to 1/8" without issues, but mostly you want to smooth out any ridges, corners or machining marks, lumps and ridges. it will reduce the chance of preignition. Also, add some grooves cut into the squish area, I show it on my headgasket repair guide, will also reduced the tendency to ping. This is a simple mod that works remarkably well, I do it to every head I have off of cars now. do not be afraid to modify the head, by cleaning it up you will improve the performance and actually reduce stress on it.

also, do not run too much timing advance, you want to run the most advance you can without getting ping. it may take some experimenting (acceratle hard on an up hill run with the engine warm, than adjust the timing if necessary). but I suspect you will be good in the 7 to 10 deg before TDC. too little advance has the problem of overheating the exhaust valves, because the exhaust temperatures are much higher with retarded timing. I have seen many engines that were destroyed by setting at the federally mandated 5 deg BTDC, and the exhaust valves overheated and broke off into the combustion chamber, causing severe damage, sometimes trashing the whole engine.

the last thing you an do is use an octane booster with each tank of gas, you can mix up your own pretty cheaply from commonly available chemicals used as solvents and cleaning fluids. look it up. you can push the pump premium from 92 octane to about 97-100 for just pennies per tank if you mix up your own octane booster. Another thing I used to do when I was running 11.25:1 CR, mix half and half unleaded regular/unleaded premium it is supposed to result in higher octane than the premium because of the different formulation, bit of a neusance, but easy to do at a pump island.

here is one formula I read about: mix 2 parts 93/94 octane fuel to 1 part xylene(115) or toulene(/114), and yoiu get about 100 octain mix, and it will not harm the catalytic converter. if you want to run this fuel all the time it is suggested adding in a bottle or 2 of Marvels Mystery Oil it will add back in a bunch of lubricants that you thinned out mixing in the xylene/toulene and not really affect total octane.

I highly recommend using toluene instead of xylene. and keep it off your skin (I would wear eye protection too). Xylene tends to dissolve plastics, not sure how much plastic there is in the old Toyota fuel system, but Xylene is pretty aggressive solvent (I have used it thin certain specialty paints, it will melt typical paint brushes, and dissolve plastic paint mixing buckets and roller trays unless you use a metal one). there is also a concern that is is a mild carcinogen.

After my experiance with the 11.25 to 1 CR street engine it is my general feeling that anything above 11:1 is unsuited for a daily driver. 10.5:1 or less is better.

Do not get me wrong, the higher compression ratio the more efficient the engine (more power, and better fuel economy) IF you can keep the per-ignistion under control. on the racing engines I help design and build were were typically running 13.5:1 CR, but we were using 115 octane racing fuel. if you have a source of high octane fuel, typically from a local race track or fuel supplier, that would be best, but troublesome and costly for a daily driver. Aviation gas is also high octane, but that contains lead which may have a very undesirable effect on a catalytic converter if you are running one.

Unfortuantaly because of federal regulations, you can not buy the fuel you want for your car. 100 octane pump gasoline was common when I was young, and than came federal emissions regulations, when the feds started regulation the kind of gasoline formulation retailers were allow to sell.
'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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SirFoxx
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Re: 7age rebuild for 1981 tercel

Post by SirFoxx » Mon Dec 16, 2019 5:45 pm

Petros wrote:
Mon Dec 16, 2019 4:40 pm
the area around the combustion chamber has the most amount of metal on it, you can take out a fair amount of metal around the combustion chamber without worry (I have cut into a lot of heads, including toyota heads). up to 1/8" without issues, but mostly you want to smooth out any ridges, corners or machining marks, lumps and ridges. it will reduce the chance of preignition. Also, add some grooves cut into the squish area, I show it on my headgasket repair guide, will also reduced the tendency to ping. This is a simple mod that works remarkably well, I do it to every head I have off of cars now. do not be afraid to modify the head, by cleaning it up you will improve the performance and actually reduce stress on it.
I will have to revisit that thread when I'm off work. Photobucket is unfortunately blocked here... However, I will post a closeup of one of the combustion areas so you can give me some proper advice as to what to clean up, and where to put those grooves at.
also, do not run too much timing advance, you want to run the most advance you can without getting ping. it may take some experimenting (acceratle hard on an up hill run with the engine warm, than adjust the timing if necessary). but I suspect you will be good in the 7 to 10 deg before TDC. too little advance has the problem of overheating the exhaust valves, because the exhaust temperatures are much higher with retarded timing. I have seen many engines that were destroyed by setting at the federally mandated 5 deg BTDC, and the exhaust valves overheated and broke off into the combustion chamber, causing severe damage, sometimes trashing the whole engine.
Definitely will be trial and error involved. I thought about getting one of those self-learning knock sensors that just flashes a light when it detects detonation. As for the exhaust valves, I know haha. On my first wagon, I burned a valve, and it looked like someone used a dremel to cut a slot through the seat face.
the last thing you an do is use an octane booster with each tank of gas, you can mix up your own pretty cheaply from commonly available chemicals used as solvents and cleaning fluids. look it up. you can push the pump premium from 92 octane to about 97-100 for just pennies per tank if you mix up your own octane booster. Another thing I used to do when I was running 11.25:1 CR, mix half and half unleaded regular/unleaded premium it is supposed to result in higher octane than the premium because of the different formulation, bit of a neusance, but easy to do at a pump island.

here is one formula I read about: mix 2 parts 93/94 octane fuel to 1 part xylene(115) or toulene(/114), and yoiu get about 100 octain mix, and it will not harm the catalytic converter. if you want to run this fuel all the time it is suggested adding in a bottle or 2 of Marvels Mystery Oil it will add back in a bunch of lubricants that you thinned out mixing in the xylene/toulene and not really affect total octane.

I highly recommend using toluene instead of xylene. and keep it off your skin (I would wear eye protection too). Xylene tends to dissolve plastics, not sure how much plastic there is in the old Toyota fuel system, but Xylene is pretty aggressive solvent (I have used it thin certain specialty paints, it will melt typical paint brushes, and dissolve plastic paint mixing buckets and roller trays unless you use a metal one). there is also a concern that is is a mild carcinogen.

Hmmm...I may try the half and half gas mixture first before buying xylene / toluene. The car didn't have a cat when I got it, and we don't do emissions where I'm at, so I'm good there. My only concern is it may clog up the wideband O2 sensor.
After my experiance with the 11.25 to 1 CR street engine it is my general feeling that anything above 11:1 is unsuited for a daily driver. 10.5:1 or less is better.

Do not get me wrong, the higher compression ratio the more efficient the engine (more power, and better fuel economy) IF you can keep the per-ignistion under control. on the racing engines I help design and build were were typically running 13.5:1 CR, but we were using 115 octane racing fuel. if you have a source of high octane fuel, typically from a local race track or fuel supplier, that would be best, but troublesome and costly for a daily driver. Aviation gas is also high octane, but that contains lead which may have a very undesirable effect on a catalytic converter if you are running one.

Unfortuantaly because of federal regulations, you can not buy the fuel you want for your car. 100 octane pump gasoline was common when I was young, and than came federal emissions regulations, when the feds started regulation the kind of gasoline formulation retailers were allow to sell.
Why is it unsuited for a daily driver?

One of the reasons I'm leaning away from e85 is cause this car isn't going to be daily'd. e85 attracts moisture, and when the water content is over 2%, organic acids start forming, which is where the problems start. The old toyota fuel systems have no plastic in them (unless you retain the factory fuel filter), but, I am worried the xylol mixture may damage the fuel pump or the injectors on the holley sniper tbi.
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Re: 7age rebuild for 1981 tercel

Post by Petros » Mon Dec 16, 2019 10:30 pm

SirFoxx wrote:
Mon Dec 16, 2019 5:45 pm

Why is it unsuited for a daily driver?
Very troublesome and constant maintance requirments: on a 3ac with 11.25:1 compression ratio, and fully polished and grooved combustion chamber, I would have to replace the head gasket every 3-4 months, running premium. with careful surfacing of the block deck and head face, chased and cleaned threads, modified head gasket (to improve coolant flow around the exhaust ports), and with precision aircraft type torque wrench I could get it to last longer, but one accidental filling with regular fuel caused the head gasket to leak. I have also broken rings from the detonation, eventually one of the flat top pistons failed and damaged the cylinder walls. I gave up on it after 3-4 years of this. went to 4ac and limited the CR to 10.5:1, it has been a lot more reliable, but the head gasket is still very sensitive, you must keep the cooling system in top condition, doing preventative maintenance on the cooling system (like preemptively replacing water pump, t-stat, and all hoses every 3 years). Now it needs another head gasket after the last overhaul after bout 25,000 miles, not sure what went wrong on it, last one lasted about 90k miles, and I have not overheated it. I may open up the combustion chamber a bit more. it needs to come apart again. I may go for a costly toyota head gasket.

the 4age head may be a lot more durable and reliable, I know it cools much better because of a better water jacket and cooling system design. but a lot of ping in the engine will do damage to internal parts over the long term.

An after market ping sensor would be an excellent addition, it will help you dial in your best timing, and it should very quickly tell you if you have sub standard octane fuel in the car. I did not know they were available to retro fit on to an engine.
'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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Re: 7age rebuild for 1981 tercel

Post by SirFoxx » Tue Dec 17, 2019 3:03 am

Petros wrote:
Mon Dec 16, 2019 10:30 pm

Very troublesome and constant maintance requirments: on a 3ac with 11.25:1 compression ratio, and fully polished and grooved combustion chamber, I would have to replace the head gasket every 3-4 months, running premium. with careful surfacing of the block deck and head face, chased and cleaned threads, modified head gasket (to improve coolant flow around the exhaust ports), and with precision aircraft type torque wrench I could get it to last longer, but one accidental filling with regular fuel caused the head gasket to leak. I have also broken rings from the detonation, eventually one of the flat top pistons failed and damaged the cylinder walls. I gave up on it after 3-4 years of this. went to 4ac and limited the CR to 10.5:1, it has been a lot more reliable, but the head gasket is still very sensitive, you must keep the cooling system in top condition, doing preventative maintenance on the cooling system (like preemptively replacing water pump, t-stat, and all hoses every 3 years). Now it needs another head gasket after the last overhaul after bout 25,000 miles, not sure what went wrong on it, last one lasted about 90k miles, and I have not overheated it. I may open up the combustion chamber a bit more. it needs to come apart again. I may go for a costly toyota head gasket.

the 4age head may be a lot more durable and reliable, I know it cools much better because of a better water jacket and cooling system design. but a lot of ping in the engine will do damage to internal parts over the long term.

An after market ping sensor would be an excellent addition, it will help you dial in your best timing, and it should very quickly tell you if you have sub standard octane fuel in the car. I did not know they were available to retro fit on to an engine.

That makes sense. Granted, the 3ac is a turd of a motor haha. I won't put nearly as many miles on my tercel as you do, so hopefully the TRD head gasket is the last head gasket job I do to this motor.

Attached are two pictures. One is the location of where the factory knock sensor goes. The factory style is a screw in type, and looks similar to an oil pressure sensor. It's located on the passenger side of the motor, towards the top, between the #2 and #3 cylinder. The "universal" bosche wide band sensor is a donut style, but, I will probably bolt it on in the same spot. I will be using it with the G4 knocklink unit. I've read good things with it. Only downside, it can pick up random noise and think its detonation.

(http://www.matrixgarage.com/store/knock-monitoring-0)

The other picture is of one combustion area of the head. Where would you put those anit-ping notches at on this head?
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Re: 7age rebuild for 1981 tercel

Post by teranfirbt » Tue Dec 17, 2019 8:09 am

The 4AGE head is an entirely different beast from the 3AC, it has a combustion chamber that doesn't need more more than a touch of valve deshrouding and a good polishing to be excellent. The key to 4AGE's is to get the squish gap set as tight as you dare, I set mine at ~0.75mm when I built the turbo engine for my MR2.

As for the knock sensor, I've had good luck with connecting one of the Bosch donut style connectors to a headphone amplifier, that way I can listen to the engine directly. Think of it like an advanced det can. I'm not monitoring all of the time, but if you find you have issues with the knocklink, you can switch over and see if it's really knock or just mechanical noise inside the engine.

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Re: 7age rebuild for 1981 tercel

Post by Petros » Tue Dec 17, 2019 11:17 pm

Teranfirbt is correct, it does not need a lot. and the head design is better than the crappy obsolete 3a head, but with that high a compression ratio I think you need to give it all the help it can get to prevent knocking.

attached is how I would modify the head. to lower the compression, and improve breathing around the valves, you can cut back and remove material at the edges on the top and bottom edge of the combustion chamber in the pic. up to the edge of the head gasket, and round it out so intake air, and exhaust gases, flow more smoothly into and out of the valves.

Also, taking out the standing machine ridges from around the valves will improve breathing and reduce tendency to ping by reducing turbulence around the valves. these can be completely removed to make a smooth combustion chamber around the valves seats. you will not harm the head, it is excess metal from the manufacturing process.

I show where to put the grooves, they should "point" right at the spark plug. they are best made with a round file, tapering from the near the gasket so they are deepest at combustion chamber end. the idea is when the spark plug fires off the mixture, the super heated flame gets funneled into the "squish" area to ignite the mixture trapped there than normally gets left out of full combustion. it both improves economy, and power output, but also reduces knock (prevents uncontrolled and uneven combustion of the end gases at the far end of the chamber). A simple mod that has good benefits all around. this has been tested to prove the value, and I have used it to good and noticeable effect.
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Re: 7age rebuild for 1981 tercel

Post by Petros » Tue Dec 17, 2019 11:32 pm

here are some videos showing how to groove the combustion chamber. the inventor is from India, and I think he is a genius. he demonstrates on a Suzuki engine with a similar combustion chamber shape as the 4age. ignore the foreign language dubbing, they speak in English.

https://www.youtube.com/watch?reload=9&v=5YbcOhiwmkE

more info.

https://somender-singh.com/

in my early life as an engineer I studies combustion chemistry, I was going to work in the auto industry to help design better cars and engines. there are a lot of interesting but subtle changes to the combustion chamber that most manufacturers do these days to get a similar effect (while avoiding this guy's patent), so this is a known effect. All of Singh's claims are more or less correct, the genius is that it is easy to put into any older style engine.
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Re: 7age rebuild for 1981 tercel

Post by The Professor » Wed Dec 18, 2019 9:27 am

Stay away from home-brewed high octane fuel, buy the highest octane pump gas you can find or just buy a drum of Sunoco or other boutique high-octane fuel. It's not worth the risk of damage to the fuel system to play backyard chemist.

Also mixing regular unleaded with premium unleaded nets you... mid-grade unleaded.
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Re: 7age rebuild for 1981 tercel

Post by Petros » Wed Dec 18, 2019 4:51 pm

The Professor wrote:
Wed Dec 18, 2019 9:27 am
Also mixing regular unleaded with premium unleaded nets you... mid-grade unleaded.
this has been tested in the past, and is not true. you do not just average octane ratings, there is a complex relationship between octane rating and the fuel formulations. the idea is the octane improvers they add in the regular gasoline has the effect, when combined with the premium fuel, that it nets a higher overall octane rating.

I can not vouch for the current formulations, these always seem to be changed based on arbitrary EPA mandates (likely driven by large corporations making campaign contribution to their favorite law maker). But a car magazine actually tested this idea back in the 1980's, and it results in octane rating higher than the premium fuel alone. At the time I was running 11.25 to 1 in my daily driver it seemed to work. However, current formulations are likely different, so I would not know if this is still valid. Though if one would install the aftermarket knock sensor, it would be easy enough to test for yourself.

the octane rating is a measured ability of a fuel to resist knock or ping in a spark ignition gasoline engine. It has nothing to do with energy content of the fuel. it is measured with a standardized test engine, and they use three sample fuels: pure cetane for the "0" point, and pure octane fuel for the "100" point, and then they test the sample fuel for the timing point where ping or knock occurs when the spark timing is advanced. I actually ran one of these test engines we had in our engineering lab in collage, it is a massive cast iron one cylinder engine. Various additives will change how much the fuel resist knocking, the most infamous was tetra-ethyl lead. They used to call premium fuel "ethyl", and the term "get the lead out" meant to stomp on the gas pedal. they learned this is very bad for our health and the environment so it was banned from auto fuels in the 1970s as I recall. now they use other additives, or they recombine the fuel differently when cracking it. it is possible to get 110 octane without any additives if the raw fuel is processed more, which is more costly so they use chemical additives (like xylene or toulene, which will not harm the sensors or the cat). there is no reason you can not mix your own fuel, except that it is against federal law if you use it on the street (if that worries you). It is common for racing teams to have their own special racing fuel formulations custom made for use on the track. When you buy the octane booster additives from the auto parts store you are essentially mixing your own fuel.
'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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Re: 7age rebuild for 1981 tercel

Post by teranfirbt » Thu Dec 19, 2019 11:10 am

Per Sunoco it's pretty much a straight averaging game https://www.sunocoracefuels.com/tech-ar ... ing-octane.

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