Silvertop and Blacktop VVT pulleys

[Leon]

Are they the same, or not so much?

Pulley in wagon rattling like a bastard (blacktop).

Previous pulley was not rattling, but was leaking like a leaky leak.

Scored a random pulley off a silvertop engine today for $9 so wondering if they are interchangable.

Mark (Toyota) tells me that the parts listing is different.

[fxgt race]

The blacktop cam belt is 21mm wide and silvertop 19mm wide so i would say the belt will hang over the side, in saying that my old race engine was a silvertop block with blacktop head and silvertop cam wheels so i was running a 19mm belt. The new engine is all blacktop but still running silver to cam wheels using 21 belt and the belt runs right on the edge of the cam wheels, had to file the sharp machining edge off the side off the cam wheels so it didn't chew the belt up and that is how i am running my race car at the moment. I don't run vvt so I have a solid centre on that cam wheel. I would say as long as the oil galleries line up and you file of the sharp edges of the cam wheel I would say it could work.

I've not I have a blacktop vvt pulley, $60 plus postage

[matt dunn]

As above the pulley are different width,

and they are also timed differently,

There is 5 deg of difference in the ST and BT cam timing,
abd the difference is in the location of the hole in the cam wheel for the locating pin,

so if you fit the wrong cam wheel the cam timing is out.

[fxgt race]

Thats interesting matt as my blacktop engine is running silvertop cam wheels, these have been made adjustabe by machining new centers and is running like this at the moment, I guess that being adjustabe when they set the timing they could account for the 5degs between svtop and bktop engines.

[matt dunn]

Yeah, I spent ages working out where the differences in the cam timings came from,

As Toda list different adjustable wheels for a ST and a BT
and I have a set af aftermarket turbo cams designed for standard silvertop camwheels,
so bought a set of silvertop Toda Adjustables,

and then wanted to use them on standard Blacktop cams in the 7A.

Once I get my engine back
and have the old block and a spare head setup,
going to investigate if purposefully using the wrong standard wheel can correct the cam timing issue casued by raising the head on the 7A engines.

[Leon]

hmmmm ... wonder what the vvt pulley is that I chucked on the car when it was replaced due to oil leakages ...

[fxgt race]

they must be the same diameter and same teeth just different widths and centers, the blktop cam belt is longer than silvertop as well, I had problems when I got my new engine built because the old block was a svtop and the new block was blktop and they used the old svtop crank cam pulley on the new engine which is narrower because it ran the 19mm cam belt so the new belt at 21mm hung over the side of the crank cam pulley.
The crank pulley wheels are different widths as well to compensate for the crank cam sprockets being different sizes.
Just need to measure the parts if interchanging them.

Makes me wonder if they made me a blacktop centres for my adjustable cam wheels as they were for blacktop cams but I suppled them with silvertop cam wheels to fit to them, might do a little investigating.

[matt dunn]

The blacktop cam belt is longer due to the hydraulic tensioner which moves in further,

so far that is covers where the TDC marks are on the oil pump so the blacktop oil pumps and crankshaft cambelt drive wheel have th TDC markings in a different place.

The location of the actual cambelt to the crank is the same, so the cam timing on not affected if you use the wrong parts, just that when you line up TDC oil the cam drive to oil pump, it's not TDC. Found that out the hard way too.

[fxgt race]

Yer the slivertop crank cam wheel has a different tdc mark on it compared to the the blacktop one.
Found this out when my new engine came back from the builders, they had marked the cam wheels with marks for me for tdc but when I looked at the bottom crank cam wheel being slivertop the tdc mark didn't line up with the tdc mark on the block.
When I changed it for the correct blktop crank cam sprocket all the tdc's lined up.

Can't really use svtop lower cam sprocket on blacktop as they are not wide enough for the wider blktop cam belt and also the crank pulley for ps,alt and water pump is machined smaller for the wider cam sprocket.
I've you use a slivrtop pulley on a blktop the belts will be out of alignment.

Best to stick with blacktop parts for blacktops and vice verser with silvertop.

[neo]

Leon I have a set of blacktop cams + sprockets here for comparison if you wanna look.

Next question is, will blacktop cams simply bolt into a silvertop head? I've been told the lobes will fowl on something.. myth?