bottom end

[BigElCat]

46 teeth on the B3 cam spocket.

360/46=7.8 degrees per tooth.

It's worth trying one tooth counter-clockwise. IMHO. The iginition timing would have to be set back (?)

Anybody ever try this?

I'm momentarily off topic. Sorry.

[BigElCat]

Thanks Festy...I went to lot of trouble finding my flashlight and opening my broken shed door:cry_smile:

Have you tried the 8* advance?

[BigElCat]

The Miata is a DOHC. You'd have to buy a 2 gear set. And the two gears aren't the same?

[BigElCat]

http://www.ebay.com/itm/Mazda-Miata-...05148039391507

Would these fit?

Anybody want to split a pair, if they do?

[Movin]

So a crank tooth is 16* (basically), right?

There's a way to get adjustability without cam gears, but most ppl don't like to do it.... add a second tensioner and use it to take up half tooth belt slack. You put it on the opposite side of the first one. Adjustables are easier, but I've seen ppl do it that way too.

:p so if you advance the crank one tooth and back off the cam two
teeth you have 4 deg advance ?

[Christ]

Wouldn't the cam gear for a B6T fit? Or a B8... or pretty much any other Mazda engine in the B range, maybe others.

[BigElCat]

16 - (8x2) = 0* degree, no change; only timing marks out of kilter.

The cam would have to be rotated clockwise relative to the cam sprocket in order to advance the cam timing.

[Christ]

16 - (8x2) = 0* degree, no change; only timing marks out of kilter.

The cam would have to be rotated clockwise relative to the cam sprocket in order to advance the cam timing.

I didn't answer that because I thought it was a comment made in jest... lol

[Movin]

I didn't answer that because I thought it was a comment made in jest... lol

Yes it was in jest but that late at night I should be sleeping !

[blkfordsedan]

When we talk about a cam being "advanced 4 degrees" we are talking about CRANK degrees, not cam degrees. Each tooth on the cam sprocket is 7.8 degrees which is 15.6 degrees in terms of valve timing events relative to crank position. In order to advance the cam 4 degrees, you need to move the cam 2 degrees, which is approx 1/4 of a tooth on the cam sprocket. Very soon, I'll be advancing my FMS cam about 6 degrees. I will use my degree wheel to get it exact and redrill the drive pin hole in the end of the camshaft. I'll post on it when completed.

[FestYboy]

didn't i answer all these questions on the 3rd page of this thread? :p

miata cam gears will mate to ALL B series engines.

Brian, when you want x* of cam advance or retard, you're moving the cam relative to the crank, not the other way round. so if you want 6* advance on your cam, you move the cam that many degrees, not the crank.

[windy1]

bottom end

my intuition about cars,i feel is good,that being said the b3 engine doesnt have a tough bottom end,and wasnt designed for hi rpms. not to mention ,all the engine management controls it has. without the controls,u could have more control of engine performance mods. i can understand the popular solution,of swapping a bigger engine for more power. then its not stock,any more. a fresh rebuilt b3,has a lot of pep. a bigger engine was not designed
for the other components,like brakes,radiator etc. advancing the cam / crank is a racing item,and is very precisly done. and works,i might add. changing parameters on the festy,is complicated. leaving it alone, is an alternative.

[Christ]

In contention to that, I feel that I have to mention this simple fact: The B3, despite it's shortcomings, is still "just an engine". If there's anything you want to do with it, the 3 rules still apply - Fast, Cheap, and Easy. You only get to pick two.

[blkfordsedan]

Brian, when you want x* of cam advance or retard, you're moving the cam relative to the crank, not the other way round. so if you want 6* advance on your cam, you move the cam that many degrees, not the crank.

Let me explain this in a little more detail...

When you look at any cam spec card, the valve timing events listed are referring to crankshaft degree position. That's why degree wheels are designed to mount to the crankshaft. Camshaft degree rotation is never considered, referenced or even important. Lobe Seperation Angle (LSA) is the only spec that is measured in camshaft angle degrees. In the case of when I degreed my FMS cam, I did mount the degree wheel to the cam sprocket, however, I thus had to divide all the displacement readings in half to derive the appropriate readings. That said, If a cam is listed as having an Intake Valve Open (IVO) at 30*BTDC, that means the crank position is at 30* BTDC when the Intake valve starts to open. When we want to advance the cam 4*, that means we want the Intake valve to open when the crank is at 34* BTDC (or 4* earlier than 30*BTDC). (If you mess around with the cam advance/retard feature on Dyno2000 you will see this). Obviously, the crank turns 2 revolutions (720*) for each single revolution (360*) of the camshaft, and they both turn the same direction (clockwise).
Soooo....to effect a 4* advance change in crank position when the valve opens, we can do it two different ways. First, we can leave the cam alone and simply rotate the crankshaft counterclockwise 4*. Simple and straight forward. On a typical V8, this can be done through the use of an off-the-shelf multi-indexed crank sprocket with multiple keyways. Unfortunately, no one makes them for our engines that I know of. The second way is to rotate the camshaft clockwise...but only 2*, since every single degree in camshaft displacement equals two degrees of crankshaft displacement. In other words, it doesn't matter whether you move the crank or the cam....only the direction and amount, depending on which one you move. If you move the camshaft 8* through it's own rotation (i.e. one tooth), then you are effecting the valve timing events by 16*. That's why simply moving the cam one tooth (or having it jump one tooth) has such a negative dramatic effect on engine performance.

That's about as clear as I can explain it. There are several articles that can be found on-line that may do a better job.

[FestYboy]

that's much clearer, thank you.

BUT, i have this to offer: while attempting to alieviate (sp) Caety's aspire's lack of power, i happend to mess with the cam timing +/- 1 tooth (on the cam). in either position i noticed no change in idle quality and no noticeable change in throttle response (unloaded). on the other side to that observation, last spring Ohio, Willie was complaining of a lack of power in his Aqua auto. i corrected the skipped tooth on the cam timing and the engine woke up. i'm surmising that the Aspire "tune" is much more conservative than the festiva "tune" and is the sole reason i didn't notice any change with the aspire...???? (maybe)