Milling head and deck change cam timing?

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cars-guy
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Milling head and deck change cam timing?

Post by cars-guy »

Hi everyone, new to the forums and to tercels. Just got an 84 sr5 with 220,000 on it for just 600 bucks. So far runs great, every thing works and cruises at 75 on the highway getting 27 mpg. Being that the motor does have 220,000 thousand it and i plan on racking up a lot of miles on this car, Im certain that the motor is gonna give out at some point. Whether its in 10,000 or another 200,000 miles. I know I'm gonna need a new motor at some point and i want to plan ahead for it. I also just want to learn as much as i can. Im not new to cars or toyotas. Ive built plenty of 22r motors. When this 3ac does give up the ghost Im planning on yanking it out and throwing a dnj rebuild kit in it (used dnj in all my cars with great results). Whenever I have done 22rs I've always made sure to mill the deck and head 10 thou each so i can use a 20 thou thicker head gasket and keep the cam timing on point. On the 22r for every 10 thou taken off, it retards cam timing by 1 degree.

My two questions are
1) does milling the head and or block affect the cam timing and if so, by how much per thou
2) In all your experience, how much longer (assuming good maintenance, consistent oil changes etc) can i realistically except to get out of this 3ac motor before needing to pull it

I am also aware of the 4ac swap as well. In the end when this motor dies i may do that if i can get a super cheap un molested core. If not its only gonna cost me around 500 bucks to rebuild the 3ac. 200 for the dnj kit and 300 for machining. and i would assume all info about rebuilding the 4ac is the same as the 3ac
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Petros
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Re: Milling head and deck change cam timing?

Post by Petros »

change in timing would be about the same, but I have not seen it written down. I suppose one could calculate it based on the sprocket dia. most people just live with what they get. I have not seen different thickness gaskets available for the 3a or 4ac engines, unless it is some kind of special order item. You can get generic adjustable cam sprockets, that were for other models of toyota's that should work. I plan on do that with my 4age swap project, and than using it to detune the peak RPM hp, and improve low end power and hopefully the economy as well. changing the cam timing affects the shape of the peak hp and toque curves, lower peak hp, but more toque and hp in the lower end of the rpm range, which would be more desirable than having all the power up at 7400 rpm.

I would not waste time rebuilding the 3ac, it has some intern problems (cooling in the head, see my thread on head gasket replacement), which seems to be improved in the 4ac (depute it being a similar design, there are a few minor improvements). Also, the 3ac will not reliably yeild any more hp, going with the 4ac you pick up more HP for "free", improved reliability, and can push it for a few more hp without harming the reliability.

The best performance set up is to get a first gen 4age, they are easiest to adapt. Larry MacGrath installed a 20 valve 4age, but he has some useful skills and access to auto shop tools that most of us do not. It is not an easy swap. Even so the early 4age, doubles the hp, and should also improve the fuel economy, and mostly bolts into the Tercel engine compartment. But you will need to covert to EFI, make a custom header and exhaust, alter the flywheel in a machine shop, and work out a few other details.

so either enjoy the 3ac in stock form, or go for the 4ac or even better the 4age swap.
'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)
cars-guy
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Re: Milling head and deck change cam timing?

Post by cars-guy »

Petros wrote: Fri Feb 23, 2018 5:11 pm change in timing would be about the same, but I have not seen it written down. I suppose one could calculate it based on the sprocket dia. most people just live with what they get. I have not seen different thickness gaskets available for the 3a or 4ac engines, unless it is some kind of special order item. You can get generic adjustable cam sprockets, that were for other models of toyota's that should work. I plan on do that with my 4age swap project, and than using it to detune the peak RPM hp, and improve low end power and hopefully the economy as well. changing the cam timing affects the shape of the peak hp and toque curves, lower peak hp, but more toque and hp in the lower end of the rpm range, which would be more desirable than having all the power up at 7400 rpm.

I would not waste time rebuilding the 3ac, it has some intern problems (cooling in the head, see my thread on head gasket replacement), which seems to be improved in the 4ac (depute it being a similar design, there are a few minor improvements). Also, the 3ac will not reliably yeild any more hp, going with the 4ac you pick up more HP for "free", improved reliability, and can push it for a few more hp without harming the reliability.

The best performance set up is to get a first gen 4age, they are easiest to adapt. Larry MacGrath installed a 20 valve 4age, but he has some useful skills and access to auto shop tools that most of us do not. It is not an easy swap. Even so the early 4age, doubles the hp, and should also improve the fuel economy, and mostly bolts into the Tercel engine compartment. But you will need to covert to EFI, make a custom header and exhaust, alter the flywheel in a machine shop, and work out a few other details.

so either enjoy the 3ac in stock form, or go for the 4ac or even better the 4age swap.
Thanks for the info. I may end up swapping to the 4ac when this motor gives up the ghost. The one thing I'm worried about is just how much longer this motor will last. It has 220,000 miles on it but otherwise runs fine. smooth idle, ran it at 75mph on the highway on a three hour road trip so far no issues. granted it was turning about 3500-3700 rpm but I assume thats normal and fine for the motor. I've put a thousand miles on it since i got it and all is good.

In your experience how many more miles can i get out of this motor with good maintenance before any major repairs or rebuild would be needed

Only reason i ask is because i plan on road tripping it for like a week all up and down the west coast and don't want to be 1000 miles from home and have it explode
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LowBuckCanuck
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My tercel:: 1986 DLX 4wd Wagon "Jenny"

Re: Milling head and deck change cam timing?

Post by LowBuckCanuck »

Legend tells of a tercel that went 750000 miles before the transmission disintegrated, so its difficult to say how many more miles your engine has in it.
teranfirbt
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My tercel:: '86 SR5 4WD, 5AFE, lifted rear, 195/70/14 tires
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Re: Milling head and deck change cam timing?

Post by teranfirbt »

Keep up on maintenance and don't rag on it and 300k shouldn't be too much of an issue. The high revs that these run at speed tend to make them not last as long as Toyotas that run slower (22RE"s and such). Give it a good inspection (compression, leak down, etc.) to make sure it's in good shape and it should last a good while.
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Petros
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My tercel:: '84 Tercel4wd w/extensive mods
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Re: Milling head and deck change cam timing?

Post by Petros »

about 300k miles sounds about right, I have seen a number go to about 375k without particularly good care.

I live and drive dusty gravel roads daily, I suspect that may contribute to my short piston ring life (about 100k ring life with oil changes in the 5-6k miles range). perhaps I should change the oil more often, or go with an external aftermarket super filter to keep it clean.
'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)
xirdneh
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My tercel:: 87 tercel 4x4 wagon w/reringed engine, 83 tercel 4x4 wagon w/salvaged engine and 4.1 Diff's
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Re: Milling head and deck change cam timing?

Post by xirdneh »

I have always changed at 2500 max
Pretty much every tercel i have had started losing oil at around 2000. So thats why i change before 2500. I figured something must be going wrong with the oil.
Love those Tercell 4x4 wagons but they sure suffer from road noise.
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