Finding TRUE TDC on a 7AGE

[oldeskewltoy]

I FINALLY got my hands on an assembled 7AGE and the owner allowed me to check TDC by using a piston stop. You CAN'T do cam timing... if you don't KNOW where TDC is......... well... here it is



Above is TRUE TDC... as measured by using a piston stop. 2 teeth off AT the CRANK!

I always figured that Toyota changed the position of the TDC dot on the 7A oil pumps and crank timing pulley. I figured (correctly... in many cases) that people had no idea where true TDC was because they were using a 4AG timing pulley, and using a 7A reference........

[BrianGT]

That's amazing! Timing a cam to the original marks would be way off!

When I change my cams on my 3TG I am going to check for true TDC as I have been told by others that it's not always where the manufacturer would like it to be.

There's the proof.

[trdee]

or you could get a crank sprocket from bazda that has been modified to allow for the change in TDC position

[oldeskewltoy]

or you could get a crank sprocket from bazda that has been modified to allow for the change in TDC position

You MIGHT do that........ but you still would NOT KNOW where TDC was....

TDC means TOP, DEAD center..... not... oh..pretty close to it

IF you are setting cam timing... you need to KNOW EXACTLY where TDC is... and NOT a dot and a notch

[Fantapants]

im curious why bazdas recut keyway would be any less accurate than toyotas own? not a dig, genuine curiosity because im in the process of putting together one myself, and can think of several ways to be as accurate or probably moreso than a mass produced item like this for a budget engine???

or have i missunderstodd and the toyota markings may also be not quite right in most cases?

[dnegative]

Dial gauge down the spark plug tube....... if thats not close enough I dont know what is.

[fixeruperer]

piston stop / degree wheel.

[bermy]

Just use the 7A timing gear, you need an extra 7A cam pulley and a 2JZ t-belt...



...that you need to narrow down a bit...




Bonus, I'll have to put a dial gauge on the valves but cam timing seems unaltered compared to using a porsche timing belt... will have to check with the dial gauge but by eye it's dead on spot

[Fantapants]

interdasting.....

[DX20VT]

I always figured that Toyota changed the position of the TDC dot on the 7A oil pumps and crank timing pulley. I figured (correctly... in many cases) that people had no idea where true TDC was because they were using a 4AG timing pulley, and using a 7A reference........

But if you use a 4AGE oil pump and a 4AGE crank timing gear they do line up perfect.

The location of the keyway in the crank to TDC is the same across 7A and 4A,
so as long as you use the oil pump and cambelt drive that match, there is no issue with finding TDC.

If you put a 7A oil pump and a 4AGE sprocket on any motor, 4A, 5A, 7A, they will all be out.

Why do people use the 7A pump anyway?