7A bore and high comp piston

[PrettyCoolWagon]

I got half way through building a 7AGTE; ..but Vicroads compliance is concerning me, life is moving on and I'm getting tired of throwing money, time and brain power at how to meet their standards.

I have a built and balanced bottom end; Forged con-rods, oil squirters, 8.9:1 GZE ceramic topped pistons and hardened steel dowels in the 6-bolt crank & flywheel.

A 7AFE wouldn't raise an eye-brow as it's a completely legal transplant.
So I'm thinking of starting again, doing away with my worked 16 valve head, boring out the cylinders, fitting high comp pistons and putting a worked 7AFE head back on top, (ports and valve cuts) then maybe running it with either the 7AFE ECU with an uprated crystal OR a 3SFE ECU with an uprated crystal for more revs. (but I don't know if the 3SFE ECU would match the 7AFE distributor)

My purpose is, to build a Corolla AE95 street machine with nice pulling power that I can enjoy on club level track days, hill climbs etc.

Is there a ready available piston from another Toyota model that would suit this purpose?

Any thoughts?

[oldeskewltoy]

I got half way through building a 7AGTE; ..but Vicroads compliance is concerning me, life is moving on and I'm getting tired of throwing money, time and brain power at how to meet their standards.

I have a built and balanced bottom end; Forged con-rods, oil squirters, 8.9:1 GZE ceramic topped pistons and hardened steel dowels in the 6-bolt crank & flywheel.

A 7AFE wouldn't raise an eye-brow as it's a completely legal transplant.
So I'm thinking of starting again, doing away with my worked 16 valve head, boring out the cylinders, fitting high comp pistons and putting a worked 7AFE head back on top, (ports and valve cuts) then maybe running it with either the 7AFE ECU with an uprated crystal OR a 3SFE ECU with an uprated crystal for more revs. (but I don't know if the 3SFE ECU would match the 7AFE distributor)

My purpose is, to build a Corolla AE95 street machine with nice pulling power that I can enjoy on club level track days, hill climbs etc.

Is there a ready available piston from another Toyota model that would suit this purpose?

Any thoughts?

There was/is for the 4AF, the high comp 4AGZE pistons add a 1/2 point to static compression of a 4AF and the piston is VERY stout. The high comp 4AGZE piston is about 7cc of dish, while the largeport 4AGZE pistons are about 12.5cc dish. Do the math........ Oh AF chamber is 30cc

As to building the "F" head, it isn't all that hard, except getting the exhaust porting correct for cylinder #1. If you want to consider adding more to it, 4AG size valves can be put into an "F" head.

[PrettyCoolWagon]

Hey Dan,

You might like to have a quick re-read.
I've already got the high-comp GZE pistons in.

I'm thinking of over-boring the cylinders and want to know what high-comp pistons are readily affordable & available for the over-bored size.

(..But that's great to know about the 4AG valves in the F head - I like it! )

[oldeskewltoy]

Hey Dan,

You might like to have a quick re-read.
I've already got the high-comp GZE pistons in.

I'm thinking of over-boring the cylinders and want to know what high-comp pistons are readily affordable & available for the over-bored size.

(..But that's great to know about the 4AG valves in the F head - I like it! )

I said do the math....... the 4AGZE pistons may be "high comp" under a 30cc chamber volume( "F" head...) remember the 4AGE head is 36 cc.

As to installing the 4AG valves... it SHOULD still get O/S seats installed, and the "G" valves would need to be cut down to proper length

Finally... what is the deck measurement for your engine? A tight deck with a "squish" of between .8mm and 1.0 mm makes for a snappy "A" series engine

[PrettyCoolWagon]

The more I consider time & money the less inclined I am to strip and re-bore a freshly built & balanced bottom end. Plus I'd have to fork out more $ for custom oversized pistons. (Years of rent on properties with large garages makes my unfinished builds expensive - need to economize my grand plans into easily completed results)

I'm having trouble sourcing info on 2nd gen 4AFE/7AFE valve diameters, vs. 4AG-16v, I read somewhere that they are the same size..
According to: http://www.wheelsjamaica.com/wheels_...topic=165509.0 the 1st gen 4AFE intake valve diameter is 0.5mm bigger than the 4AGE and it's exhaust diameter is 1mm smaller.

1st gen 4AFE = 12.440696 ²cm of air coming in through the intake valve.
2nd gen 4AFE = 14.803172 ²cm of air coming in through the intake valve.

4AGE 16v SP = 13.160121 ²cm of air coming in through the intake valve
4AGE 16v BP = 14.012748 ²cm of air coming in through the intake valve.

4AGE specs ( quoted from bill sherwoods page )
Inlet valve diameter - 29.5mm
- Exhaust valve diameter - 25.5mm
- Both valves have 6mm diameter stems.
(Are valve diameters different between bigport & smallport)


OST: That's interesting about the 30cc chamber of the F head bumping up static compression. Which generation F head are you referring to? They're quite different and used different pistons amongst other things. Here's some stat's between them.

4AFE

1st GEN
Overlap: 9.00 degrees
Intake Duration: 220.00 degrees
Exhaust Duration: 220.00 degrees
Intake Installed Centerline of 104.00 degrees ATDC.
Exhaust Installed Centerline of 107.00 degrees BTDC.
6.6MM lift in/ex
30mm int diameter 24.5mm ex dia
the amount of ²cm of air coming in through the intake valve is 12.440696 ²cm

2nd GEN (4AFE / 7AFE = same head / different injectors)
Overlap: 8.00 degrees
Intake Duration: 224.00 degrees
Exhaust Duration: 224.00 degrees
Intake Installed Centerline of 106.00 degrees ATDC.
Exhaust Installed Centerline of 110.00 degrees BTDC.
7.6MM lift in/ex
the amount of ²cm of air coming in through the intake valve is 14.803172 ²cm


Sorry, maths is not my strong point and I have far less experience than you in this area. What static comp would I be left with using the following combo:
7A block/con-rod
8.9:1 GZE piston
7A head gasket
7AFE head

[oldeskewltoy]

I did my 4AFE... the intake valves are 30mm (4AGE are 30.5), the exhaust valves are 24.5mm(4AGE are 25.5) There is another advantage to running the G valves besides a small gain in valve head diameter... the 4AG valves are FAR superior in their shape...

Note the back cut on the G valve (on left) is far more uniform then the F valve on right



As to the math.... https://www.rbracing-rsr.com/compstaticcalc.html

F chamber = 30cc, 7AF gasket is .7mm, I believe (but am unsure) the stroke is 85.5mm. The only thing you need to add is the deck... how far above/below the blocks surface any piston is @ its TDC

[PrettyCoolWagon]

I did my 4AFE... the intake valves are 30mm (4AGE are 30.5), the exhaust valves are 24.5mm(4AGE are 25.5) There is another advantage to running the G valves besides a small gain in valve head diameter... the 4AG valves are FAR superior in their shape...

Note the back cut on the G valve (on left) is far more uniform then the F valve on right



As to the math.... https://www.rbracing-rsr.com/compstaticcalc.html

F chamber = 30cc, 7AF gasket is .7mm, I believe (but am unsure) the stroke is 85.5mm. The only thing you need to add is the deck... how far above/below the blocks surface any piston is @ its TDC

OK, I can measure the distance from piston at TDC to the deck - thanks.

Yours is the 1st generation F-head right?
A friend has a 2nd gen F-head, I'll measure the valves on that - they might be different

[PrettyCoolWagon]

The worked bottom end is all greased/oild and wrapped up in storage at the moment, (vvv it's linked in the bottom of my posts vvv)

so I don't know what the deck measurement is. It's a good point (to measure the deck) I will have to check / take some photo's etc. 'cause I'm also wondering about interference..

With the AE101 GZE pistons I have in place now, would the valves in the 7AFE head hit or miss?

I'm thinking of using a standard 7AFE head gasket.
How can I tell if the engine would be interferance or not?
The diameter of the FE valves are only 0.5mm smaller in diameter, but their angle-position in the head is different to 4AG and so I'm concerned about whether not the cuts in the piston for valve clearance will match up or not. The 7AFE valvle angle is closer to vertical than 4AG making the valve's head surface less intrusive - down towards the piston.

So I'm really not sure. I guess I'll have to put it all together and test it by slowly rotating it all by hand.

http://s127.photobucket.com/user/dau...-f-f1.jpg.html

[oldeskewltoy]

This pic shows early cammed head @ full lift (exhaust)



I seriously doubt you'll have any interference issues... even with another mm of lift