Crawford Performance & LIC Motorsport adjustable Timing Belt idlers - Perth-WRX.com

Rossco · #1 03-01-2011, 03:11 AM

Just thought I'd throw this out there.....

Has anyone used eccentric timing idles to zero their cams in as opposed to vernier cam gears?

they're like this:

crawfords blurb:

"For changing timing, we recommend using one adjuster for fine tuning 3-4 degrees. Moving the timing belt one tooth on the cam gears will net a 7-8 degree change. Then using the adjuster will allow the user to fine tune above or below that 7-8 degree change.

For those who have changed the math from the OEM specs of the long block - ie using different thickness head gaskets, using decked heads, using phase two heads with a phase 1 block etc - Using two adjusters will allow you to ensure timing is accurate, and each side of the engine is working harmoniously.

***ONE ADJUSTER IS NEEDED FOR ADJUSTING CAM TIMING ON OEM-SPEC LONG BLOCKS***

***TWO ADJUSTERS ARE NEEDED FOR SITUATIONS WHERE THE MATH OF THE LONG BLOCK AS BEEN CHANGED - THICKER HEAD GASKETS, DECKED HEADS...ETC***"

LIC Motorsport has the same thing (in their own branding):

Thoughts gents?

Please discuss.....

tuna · #2 03-01-2011, 07:24 AM

theres a lot of slop in the factory tensioner and stretch in the belt from standard (even with the sti belt).

not seen any japanese equivelent replacements for these pulleys, so i'd be surprised if they actually made a significant difference...

Rossco · #3 03-01-2011, 09:54 AM

Yeah I didn't get it at first Stace,

But it affectively changes the timing belt length between the crank & and cams.

When you adjust the upper idler on the RH side,...it ends up adjusting all of the cams. (everything between it and the tensioner,... (the tensioner being the only thing that takes up, or gives out slack)).

The lower idler on the RH side is after the RH side cams but before the LH side cams,.. and just like the top one,.. it adjusts everything between it and the tensioner. And being that only the LH side cams are located between it and the tensioner,....adjusting that lower idler eccentric only affects the LH side cams.

Practical example:
Lets say you've narrowed your engine by decking the heads and the block (after a rebuild or two). Doing this will retard all 4 of the cams. And because the belt goes past both heads before passing the tensioner (where the resulting slack is taken up) the LH side will be off twice as much as the RH side.

So if your narrowed engine has caused your RH side cams to become retarded by 2 degrees,...your LH side cams will be retarded 4 degrees. You can just buy one eccentric for the top idler... and crank it in (pushing the belt downwards) until any one of the cams has advanced 3 degrees (All the cams wil be advancing the same amount as you rotate the upper adjuster). Your RH side will now advance by 3 degrees to become 1 degree advanced from factory, and the LH side will improve from 4 deg retarded to only 1 deg retarded. Close enough.

If you're a stickler for perfection,..you can get two adjusters and adjust them each +2 degrees & have both sides back to the zero reference.

dtrally · #4 03-01-2011, 12:56 PM

I don't like the Bunnings spec screw they provide. It should be a proper bolt, with a shank. I see no advantage over vernier camwheels other than a cost saving perhaps.
Also, if the inlet is advanced, so is the exhaust, you can't adjust them separately.