Stocker

A new thread it is, then. This is split from a different, unrelated thread to prevent a total hijacking

Mad John came up with:


To which I responded:


Then i8acobra says:


All of which I can follow. This begs the question: So how do you adjust the valvetrain timing on an RD?

Isn't this a pretty rigidly fixed mechanical thing?
How much does a 1mm height difference affect the timing?
Is it a matter of moving the belt 1 tooth? Is an adjustable cam sprocket required?
If it's electronics I am guessing there should be some way to accomplish it without a standalone or piggyback engine management setup, or else how would a dealership be able to reinstall a cylinder head after rework (based on the probably-faulty assumption that SOME dealer SOMEwhere actually reworks heads . . . ) Is is a scan-tool or OBD-II whatzis or is the RD designed to never be able to use a shaved head/block?
Does the stock ECM accomplish this magically?
Has anyone actually done this and lived to tell the tale in English?

I'm seriously considering a good whack off the bottom of my head (from my long-dormant port & polish thread) for increased compression, when funds finally become available again. It would be a very nasty surprise to learn my engine wouldn't run properly, AFTER I re-assmbled it.

iheartmyrd

Well, you obviously know i have been running the 1.8 pistons and 2.0 rods. witch i don't know if i mentioned before but i definitely had the head decked don't know how much but to make it true and then some. the block was also resurfaced i believe.

the only thing i did that wasn't a true 11:1 compression (witch the decking should make up for) is the head gasket,
i used the head gasket that comes on the beta motor,
two different sets of head bolts aswell
because i tryed two different Xd gaskets both identical to the beta head gasket in shape except for the one less ply.


but i kept getting an oil leak in the front of the motor, underneath the head, under the exhaust manifold.
I checked the head only to find it to be true along with the block. and i even tried giving a little extra on torque on the head bolt specs due to a one ply difference (the only thing that stoped the leak was the beta head gasket)

If you do go this rout i would love to hear (given you deck the head as well) if you have any similar problems.
Other than that the oil only leaked to the out side of the block and not in cly walls and it wasn't much but, any is enough to make a fuss.

However there was a noticeable difference in the peppyness of the engine with the thinner head gasket.
I am currently about to go low compression, so i wont be using the 1.8 pistons much longer.

maybe it is possible the timing was having an effect on the oil leaking but, i really doubt it.

P.s. i still have those extra internals saved just for you. 2.0 rods crank, and possibly 1.8 pistons depending when i get low comp ones.(i would honestly just buy the new ones for 150 from kspec tho) i only have 3k on em but still i would buy the new pistons.
Rods tho are deff saved for yah.


Long post- reply sorry

i8acobra

Dropping the head causes the pulley to spin backwards. Because the cam is rigidly fixed to the pulley, this retards the cam timing. The solution is to advance the cam timing by rotating the cam forward relative to the pulley. This is done with an adjustable pulley. Since the intake cam is driven off the exhaust cam, correcting the exhaust cam automatically corrects the intake cam.

Stocker

i8acobra, that's what I was thinking. I also seem to recall nobody makes adjustable pullies, but I've been wrong (once) before.

Since the thread is already here: Anyone know where to get an adjustable exhaust cam belt drive pulley for a Beta?

IheartmyRD, I might hit you up for the rods, or I'll post a WTB thread. The pistons, I have. It's going to be a while either way, since the bonus checks @ work have stopped for like a year now. Regular pay, thanks God, still continues!

Albuquerquefx

If you want to know how much your timing is "out", it's time to break out the math.

We really only need to know the exhaust "cog" diameter for the timing belt -- I'll make up a number, say 140mm (~5.5 inches) for the exhaust cam. I think this is pretty close from eye-balling it, but I no longer have a BETA 02.gif so I can't say exactly for sure.

We need to discover what 1mm of circumferential movement equates to in angular movement. A 140mm diameter wheel has a circumference of ~440mm. There are 360* in a full circle, which means for degree of cam rotation, we have ~1.222mm of belt travel (if, indeed, the exhaust cam diameter is 140mm)

So, if you move the belt either direction by 1mm, you've moved your cam timing by about 0.82 degrees. Is that sufficient to cause worry? Let's try some radical numbers to see how bad it really might be.

I know the exhaust cam is bigger than 4" in diameter (102mm), but let's use it as an extreme case. Do the math: circumference of 320.5mm, angular rotation with 1mm of circumferential travel means 1.14 degrees of cam timing change. Even with a smaller cog (which will be MORE affected by belt travel) we're still out only a bit more than a full degree.

Is it worth worrying about? Probably not. Could you adjust it out? Yeah, if you're very precise. Does anyone make adjustable exhaust cam gears? Yup. I had a Fidanza that went with my Tib to the new owner; I think Staauf is selling a few in his brake line GB for $100 each.

Stocker

<1º seems like a pretty minor concern to me. I guess that explains why I haven't heard those who have decked heads/blocks complaining about their cars being dogs after being put back together.

I don't know how closely you guys have been following my super-low-budget build, but "ignoring" a degree of timing is looking pretty good right about now, and is probably about the least-bodgy aspect of it. wink1.gif

i8acobra

Fidanza no longer makes them, but at SEMA today, they told me it would be no big deal to bust out the design and produce a few with confirmed orders.