Hello everyone;

After took out the engine and did the research, I believed I have red top and 7 rid block. My goal is put T3 turbo and run around 8 to 10 psi of boost. Some people said that I can use the stock pistons and connecting rod with 8 to 10 psi of boost. What is your recommendation? If I have to use the low compression pistons and connecting rod, what brand do you recommend? I saw a lot of members in forum are selling use low compression pistons, can I use the used pistons and connecting rod?

danhtruong wrote:Hello everyone;

After took out the engine and did the research, I believed I have red top and 7 rid block. My goal is put T3 turbo and run around 8 to 10 psi of boost. Some people said that I can use the stock pistons and connecting rod with 8 to 10 psi of boost. What is your recommendation? If I have to use the low compression pistons and connecting rod, what brand do you recommend? I saw a lot of members in forum are selling use low compression pistons, can I use the used pistons and connecting rod?

It is possible to add boost to the 9.4 to 1 stock pistons, BUT the piston ring lands are weak, and the tune needs to be perfect, and even then it might just be a matter of time before something breaks.

just because you have a 7 rib block doesn't guarantee you have the "larger" internals. "larger" = there are 2 different sizes of crankshaft, rods, and pistons. Earlier engines use a rod with a 40mm big end, with a 18mm small end. Later engines use rods with 42mm big end, and a 20mm small end. Because of this size difference, the crankshaft and the pistons are designed to fit their accompanying rods, and so don't cross over. Earlier engines have less "performance" options then later engines because of the differences in rod dimensions.

**IF** you do have the "larger" internals, then you can purchase a set of pistons better designed for boost. Used pistons in some cases can be re-used, but before you purchase, have your machinist tell you if they are reusable.

Yeah the compression ratio is not the concern with the NA pistons. The super weak ring lands are the concern.

If someone has a healthy motor and wants to start playing with boost I tell them they can do it on their stock motor. If something takes out the motor it will most likely be a tuning mistake or old age and if it's a tuning mistake then better to make that mistake on an old motor than a new one with high performance parts.

But if you are already in the motor then I suggest taking the safer route of putting good pistons in the motor while you are in there.

I am not a fan of using used pistons or standard bores in a stock motor. Like OST said if you do either you need to get it inspected and make sure everything is absolutely in spec but even then there will be some wear that will put you starting out with some wear that will likely just get worse over time. If it starts in spec that should be a long time but it's still not as ideal as starting out with fresh pistons and cylinder bores.

If you inspect the motor and find you have the 42mm crank and rods then the stock components are plenty for your goals as long as they are healthy and those rods have the bigger wristpins which have the best options for pistons.
The compression ratio will depend on how aggressive you want your tune to be and how closely you plan on monitoring it.
PSI is also not a good measure. With a poor build or mistake you could only hit 140 WHP at 10 PSI. With an off the wall build with high compression and big cams you could make 300+ hp at 10 PSI.
So it is more important to have goals for peak power, power curve and efficiency.
Now guessing you are thinking in mostly stockish terms 10 PSI could get a stock 4A to 150-180 WHP.
Personally in that range I would run about 11:1 with a mild cam and maybe 6 PSI to get to the same power range with the potential to crank it up to 10+ PSI for even more power.
For my customers I'll often suggest something a little milder but my recommendation would depend on their goals, budget, commitment and comfort level.

Thanks a lot guys.

Can you let me know which Pistons can I buy for the low compression? I don't want to spend a lot of money, I just need the decent one. Do I have to buy the connecting rod or just the piston? My goal is to get up to 250 HP. With that HP, do I have to change the bigger injection and fuel pump?

danhtruong wrote:Thanks a lot guys.

Can you let me know which Pistons can I buy for the low compression? I don't want to spend a lot of money, I just need the decent one. Do I have to buy the connecting rod or just the piston? My goal is to get up to 250 HP. With that HP, do I have to change the bigger injection and fuel pump?

until you know what is inside, no one can tell you what you need to buy. It isn't easy to rebuild these engines on a very tight budget. Expect a minimum of $800, and with machining and the correct parts, it could run as much as $2000, and maybe more.....

For 250hp it is advised to run more piston then your stock ones. As yoshi pointed out, a higher compression piston, well supported with a good tune should have no problems getting to your goal. Piston options, at the very bottom is the original 4AGZE supercharged 4AGE piston @ 8.0 to one compression, this is not the best choice, but they are plentiful, and likely the least costly. Next would be the 2nd generation 4AGZE, those pistons are 8.9 to 1, and are more expensive because there just are not as many, and those that are out there are mostly Toyota, so you pay a little premium. Next would be one of yoshi's pistons. So pistons could be as cheap as $200 including rings (used pistons, new rings), or upto about $500 ish for yoshi's slugs. If you can afford the $300 difference, your smile will appreciate it... To fit new pistons, plan on at least $500 for machine work (likely more).

At this stage you might consider headwork. The 4AG combustion chambers can lead to detonation/ping if not properly deshrouded.



A "good" chamber can handle more boost/ignition timing then one not deshouded.

oldeskewltoy wrote:

danhtruong wrote:Thanks a lot guys.

Can you let me know which Pistons can I buy for the low compression? I don't want to spend a lot of money, I just need the decent one. Do I have to buy the connecting rod or just the piston? My goal is to get up to 250 HP. With that HP, do I have to change the bigger injection and fuel pump?

until you know what is inside, no one can tell you what you need to buy. It isn't easy to rebuild these engines on a very tight budget. Expect a minimum of $800, and with machining and the correct parts, it could run as much as $2000, and maybe more.....

For 250hp it is advised to run more piston then your stock ones. As yoshi pointed out, a higher compression piston, well supported with a good tune should have no problems getting to your goal. Piston options, at the very bottom is the original 4AGZE supercharged 4AGE piston @ 8.0 to one compression, this is not the best choice, but they are plentiful, and likely the least costly. Next would be the 2nd generation 4AGZE, those pistons are 8.9 to 1, and are more expensive because there just are not as many, and those that are out there are mostly Toyota, so you pay a little premium. Next would be one of yoshi's pistons. So pistons could be as cheap as $200 including rings (used pistons, new rings), or upto about $500 ish for yoshi's slugs. If you can afford the $300 difference, your smile will appreciate it... To fit new pistons, plan on at least $500 for machine work (likely more).

At this stage you might consider headwork. The 4AG combustion chambers can lead to detonation/ping if not properly deshrouded.



A "good" chamber can handle more boost/ignition timing then one not deshouded.

So, I just need to buy the new pistons. I don't have to buy the new Connecting Rod?

danhtruong wrote:
So, I just need to buy the new pistons. I don't have to buy the new Connecting Rod?

You will not know until you disassemble what you have.....

danhtruong wrote:
So, I just need to buy the new pistons. I don't have to buy the new Connecting Rod?

It seems as though you aren't really listening to us.
Was my post too long for you? Or perhaps you have trouble understanding English?

I would recommend you find out which motor you have. If you do not have the later larger 20/42 rotating assembly I would find one or at least a crank. The 20mm wrispin pistons are much easier to find in much better selections.

Stock rods, especially 20/42 rods will be more than enough for your goals.
However if you end up needing new rods these are not much more than stock rods and are stronger and lighter so if you do need to buy rods this is what I would get.
http://www.matrixgarage.com/products/br ... tsman-rods

My Arias pistons are barely more expensive than stock GZE pistons and available in more options for compression and style so I definitely think it's worth paying a couple bucks more for them.
http://www.matrixgarage.com/store/pistons-1?page=1

You mentioned buying used pistons. I would never do this.
If you do end up doing it then I would have the seller have them inspected by a machinist to make sure they are in spec before you buy them. Then once you get them I would have them inspected again, either yourself if you don't have the tools/skills then by someone who does. In my opinion it's just not worth the time, cost or risk.

Now for me to make more of an educated suggestion on your setup.
Where are you located? What octane do you want to run and is it rated in RON, MON or AKI?
Is response more important or is making more power with more room to grow more important?
Do you want a build that pushes the limits a little more and takes a little more work and monitoring but gets you better efficiency, power and performance? Or would you rather a safer build that has more margin for error at the cost of efficiency and performance?

You might find some info in here useful.
http://matrixgarage.com/content/yoshimi ... oing-4a-ge