4agze pistons ina 7afe???, will they fit? Options

[playr158]

you pulled those numbers from where?

[nik]

Using 4AGZE pistons in a 7AFE will give you 11:1 compression. However, if you swap a 4AGE head on there, you'll be all set, 8.5:1 or 8.9:1 depending on which version you use. Plus the GE head is better anyway.
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do you have any info to back that up i know edo's comp rose but what proof do you have on the 4ag head ??

[playr158]

exactly ^^

[Dr_Tweak]

The difference in compression between the two engines is because of the head, so even using 4AGZE pistons ends up with high compression.

I haven't done this personally but I know several people that are running 7AGEs with 4AGZE pistons.

-Doc

[doGGy]

WRONG.

The diffetrence is not only in heads, the difference is in pistons - 7A pistons are DISHED, GZE almost flat, with the dished valve places. Pistons are the same height, but the difference is in these 10 cc that 7A piston Dish has.

The difference in compression between the two engines is because of the head, so even using 4AGZE pistons ends up with high compression.

I haven't done this personally but I know several people that are running 7AGEs with 4AGZE pistons.

-Doc
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[Dr_Tweak]

WRONG.

The diffetrence is not only in heads, the difference is in pistons - 7A pistons are DISHED, GZE almost flat, with the dished valve places. Pistons are the same height, but the difference is in these 10 cc that 7A piston Dish has.

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Think about what you're saying. If you swap the GZE pistons in, the compression goes up. Why is this not the case when you use the GE head? Because of the combustion chamber. Yes, the piston of the 7AFE is dished, which is part of it (I should have added that), but we're talking about using GZE pistons in a 7AFE.

When you use 4AGZE pistons in a 7AFE with a 7AFE head, the compression goes up.
When you use 4AGZE pistons in a 7AFE with a 4AGE head, the compression goes down.

Why? Because the head is different. End of story.

I wonder what the compresssion ratio would be in a 4AGE using 7AFE pistons?!

[doGGy]

here im talking about 7AFE with GZE pistons. Not the 7AGE. And CR with GZE pistons in 7AFE will be 10.8 if not using oversized pistons. With 82 Bore, and GZE pistons, the CR is at 11.02. This been proved on Edos car. As on stock 7A, you can count the CR, it will be 10.8 without overboring.

As for head swap, yes, the combusion chamber on GE head is bigger then on 7A, so the CR will drop noticibly.

WRONG.

The diffetrence is not only in heads, the difference is in pistons - 7A pistons are DISHED, GZE almost flat, with the dished valve places. Pistons are the same height, but the difference is in these 10 cc that 7A piston Dish has.

[right][snapback]277244[/snapback][/right]

Think about what you're saying. If you swap the GZE pistons in, the compression goes up. Why is this not the case when you use the GE head? Because of the combustion chamber. Yes, the piston of the 7AFE is dished, which is part of it (I should have added that), but we're talking about using GZE pistons in a 7AFE.

When you use 4AGZE pistons in a 7AFE with a 7AFE head, the compression goes up.
When you use 4AGZE pistons in a 7AFE with a 4AGE head, the compression goes down.

Why? Because the head is different. End of story.

I wonder what the compresssion ratio would be in a 4AGE using 7AFE pistons?!
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[Kwanza26]

Think about what you're saying. If you swap the GZE pistons in, the compression goes up. Why is this not the case when you use the GE head? Because of the combustion chamber. Yes, the piston of the 7AFE is dished, which is part of it (I should have added that), but we're talking about using GZE pistons in a 7AFE.

When you use 4AGZE pistons in a 7AFE with a 7AFE head, the compression goes up.
When you use 4AGZE pistons in a 7AFE with a 4AGE head, the compression goes down.

Why? Because the head is different. End of story.

It's equally the piston and the head. The older FE head designs had part of the combustion chamber carved into the piston top. Likewise, compression increase with the 4AGZ pistons is both because of the pistons and the stroke ratio. The 7A has a larger stroke ratio and that adds to the compression increase along with the flat topp-ed pistons. In a 7AGE, things will look more similar to the 4AGZE as far as compression goes, but it'll still be higher. I would estimate around 8:5 (7AGE) with the 8:0:1 4AGZE pistons and around 9:2 to 9:3 with the 8:9 pistons...

I wonder what the compresssion ratio would be in a 4AGE using 7AFE pistons?!
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Very low...

[playr158]

ok basically all we need to know is

4agze pistons at a 82mm bore
with a 7afe motor (no headswap)

[StreetRacing10PS...]

all i really wanna know is what do i have to do to lower my compression with forged 4age pistons in my 7aFE. is a thicker head gasket all i need?

[Kwanza26]

It'll raise your compression to higher than stock. Even with a thick headgasket, you're still looking at compression at stock levels... so it would really serve no purpose. One might think strength will increase... but that all comes down to tuning. 4AGZ pistons will be a bigger tuning hazard because relative compression increase will be mostly unknown, but expected in the high 10's... 4AGZE pistons is NOT a good way to go if you're looking to boost a 7AFE... Sure they're stronger pistons... but so what if tuning is gonna be that much harder...

[StreetRacing10PS...]

ok, so i get my turbo probly some time this week or when ever it gets mailed. and ill b runing around 8 PSI. but i wanna get the boost up to around 15+PSI but for that to b safe i would have to run forged internals, but if 4age pistons raise my compression to over 10:1 then it wont be safe on the engine. so is it worth getting the forged pistons or should i leave it stock??

[playr158]

you can boost a 10:1 cr fine at 10-15psi you just have to make sure that your emanager is tunned

but i'm goin to run
82mm bore with a 2mm headgasket
ported and polished head
shot peen'd rods
3 angle valve job
4agze pistons


imo don't use stock pistons if you wanna shoot for 10psi and over

[StreetRacing10PS...]

i no, i posted a pic in the off topic forum i think it was a few weeks ago of my friends eclipse that blew a piston runnin 13 PSI on his stock internals....not a pretty site..... too much boost

This post has been edited by StreetRacing10PSI: Apr 24, 2005 - 10:16 PM

[Kwanza26]

you can boost a 10:1 cr fine at 10-15psi you just have to make sure that your emanager is tunned

but i'm goin to run
82mm bore with a 2mm headgasket
ported and polished head
shot peen'd rods
3 angle valve job
4agze pistons


imo don't use stock pistons if you wanna shoot for 10psi and over
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why not use stock pistons? Your logic sometimes is just totally wrong. Even forged, because the compression is significantly higher, the heat will be significantly higher, putting just as much, if not more stress on the 4AGZ pistons as would a stock 7A with stock pistons... In the end... it's all about tuning.

You keep listing your little list of "soon to be" modifications... but I'm still not convinced you know what they actually do to the motor.

In the end, IMO, it's really not worth it to go through the trouble of installing 4AGZE pistons. If you must have pistons... get proper ones. Short cuts is what almost always kills custom turbo builds.

I'll still say though... if you're looking for 15 psi+... you can't look to do it cheap.

[Dr_Tweak]

The answer to your question is in this thread. But to lay it right out, it's like this:

If you want 15 psi, you have two options.

1. Do a 4AGE head swap and use the 4AGZE 8:1 pistons which will give you about 8.5:1 CR

2. Get custom forged low compression pistons. Have a look at http://www.importperformanceparts.net/ they have a complete 7AFE rebuild kit with ROSS/Wiseco forged pistons in any compression ratio you want for only $889... that's a sweet deal.

-Dr Tweak

*edit* Oh and I forgot: Never ever ever ever use a thicker head gasket to lower your compression. By doing that, you eliminate the quench (squish) area in the combustion chamber which will increase combustion temperatures and cause massive detonation and preignition problems. Worse than if you had left it at stock compression.

This post has been edited by raven_101: Apr 25, 2005 - 3:07 AM

[playr158]

well then thank you for the piston link
i knew goin to wit the thickerheadgasket always isn't a best way to do but hey its not like anyone has gotten the 7afte to the levels like these
and ha if i can get the custom compression pistons then i'm happier

[playr158]

oh and just so we get the line down
i refuse to swap heads or my motor
so give me the best info for a straight up 7afe
cause its goin to be an original motor project

[nik]

you can boost a 10:1 cr fine at 10-15psi you just have to make sure that your emanager is tunned

but i'm goin to run
82mm bore with a 2mm headgasket
ported and polished head
shot peen'd rods
3 angle valve job
4agze pistons


imo don't use stock pistons if you wanna shoot for 10psi and over
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i wouldnt use stock rods for 15psi even if they are shot peend

[nik]

oh and just so we get the line down
i refuse to swap heads or my motor
so give me the best info for a straight up 7afe
cause its goin to be an original motor project
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with the set up you are going with heat soak is a big factor because of the head design so the longer you run the less power