This is a TRD copy valve spring that I used in my 4age on the left and the original 4age 16v valve spring on the right, as you can see the TRD copy valve spring will coil bind much later then the original one would and it is also a stiffer spring.
Reduced: 97% of original size [ 526 x 398 ] - Click to view full image
Using a lift as high as 9mm or over can turn into a disaster as the cam lobe can flick the shims out of the valve buckets, 9mm lift cams are boarder line so if I had a cam that size I would install some shim under buckets, This can be very expensive for what they are.
But apparently the Shim under buckets from a Toyota 1SZ-FE 1.0 liter 4 cylinder engine use a bucket that's compatible with the 4age 16v.
More info on this:
http://www.club4ag.com/faq%20and%20t...%20Tuning.html
With camshafts that size you would also defiantly need to run a higher compression of around 11:1 or better 11.5:1 though milling the head down heaps might not be a good
as the valve to piston clearance will be much less due to the bigger lift and lower sitting head, So it is a good
to use some aftermarket forged pistons with +dome to give the compression you need. They are also normally stronger pistons designed to take the extra HP & RPM.
Arias Pistons make a 4age 16v piston with a +Dome CC of 7.5cc and are listed that with stock head and gaskets it will give a 10.7:1 compression ratio. Though they are only made to suit bore size of 81.5mm (standard size is 81mm) so the engine block will have to be pulled down and bored out to that oversize. To bump it up a bit more you could use a TRD head gasket 0.5mm thick, this should give you around an 11.3:1 CR.
If you are willing to go that far it would be a good
to replace your old worn out & most likely stretched rod bolts with some ARP ones. They are much stronger and can take more abuse from revs, though the big ends must be closed and honed back to size when you install new rod bolts.
Also if you are going to be revving the engine up to or over 8500rpm it would be good to have the bottom end balanced as the forged pistons will most likely be a different weight then the standard cast pistons and throw out the balance.
The Standard rods should take 9000rpm maximum with some ARP bolts so if your not going to rev the engine past that the standard rods should be fine as long as you have some ARP in them,
As you can see the Smallport 7 rib block rods (20mm pin, 42mm big-end) are very strong and are the same rods used in the 4AGZE supercharged engine.
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Though if the rpm concerns you, you can have the side’s lynished to remove any stress points and then have the rods shotpeened as well.
If you really wanted to have a strong engine you could install a ARP head bolt stud kit and an ARP main cap (crankshaft main bearing cap) stud kit , Though with the main cap kit you should have it tunnel bored with the new studs fitted to ensure 100% alignment just like the rod bolts. Anything past 9000rpm you will defiantly need Aftermarket Forged rods.
There is also aftermarket 215mm Aluminium and Chrome Moly flywheels that weigh around 3.6kg available for the 4AGE but street driven engines with aggressive cams you may prefer the Lightweight Chrome-Moly flywheel because the lower weight of the Lightweight Aluminium may hamper idle at lower rpm running.
In my opinion if your going to go to the expense of getting forged pistons and rods you may as well build a 7AGE using the 1762cc 7AFE bottom end and get the Forged rods and pistons to suit that engine. If you bore that block out to an 81.5mm bore it becomes a 1782cc engine. You will have to use the 4AGE 16v crank timing gear and a longer timing belt as the 7A block is taller to take the extra stroke of 85.5mm, Porsche 924/944 belt has been rumored to fit. You will also need a custom exhaust manifold so it can have clearance under the sump if the engine is in a FWD car. The 7A also does not have oil squirters (piston coolers) like the Smallport 4age 16v (100kw engine) douse.
The 7A uses a 6 bolt fly wheel apposed to the 8 bolt 4age flywheel, The 7A 6 bolt can be made stronger using 3 solid steel dowel pins and some ARP replacement bolts.
One advantage with the 7A engine is due to the extra capacity you will not need to rev the engine out so much to make the same power as a 4AGE making power @ 9000rpm.
So you could probably get away with using some standard cast pistons and use a 82mm over size to increase the capacity to 1803cc and save $$ on forged pistons, I would still recommend replacing the rods with forged items as the standard 7A rods have a very narrow neck, they also use a 18mm press fit pin and would most likely brake after constantly seeing 8500rpm every day.
This is a standard 7A rod Vs a Forged item with a 20mm floating pin little end to suit the later 4AGE pitons. The big end is machined to suit the standard 7A crank size.
As you can see the 7 rib 4AGE block (painted orange) and the 7AFE block (bare) are nearly the same, just the 7A is taller to accommodate longer stroke, so you will need to use the 6-bolt 7A crank.
Both blocks are a standard 81mm bore.
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If you are going to be running over a 11:1 compression ratio it is a good
to not have any sharp points removed in the combustion chamber that will cause pre ignition due to hot spots.
As you can see in the pic below on the standard 4age (left) you can see an example of a hot spot. The pic on the left is an engine that would be running high compression and has had the spots taken away.
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While you’re playing around with that you may as well clean the ports up of any sand casting marks left from when the head was cast.
You can also open up under the valve a little bit but don’t go 2 crazy as you will loose power, its best just to keep to cleaning the ports out and putting nice round edges on things that have sharp turns.
If you’re planning to run up to a 272 you will fined the Smallport head with light port work is all that is needed. With 288’s I would start playing with throttle bodies.
A 290 cam or bigger it would probably be best to run a Bigport head and ported intake manifold with over size throttle body or run a Quad throttle body set up.
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