7 replies to this topic

[luvin_the_rings]

Hello All,  

 

I want to thank you all for your continued support for all us new SM'ers.  I know its repetitive to keep answering the same ole' questions from us youngins who are too lazy or broke to buy the Advanced Autosport Ultimate Constructors book.  

 

This brings me to my question.  I want to make sure, without a shadow of a doubt, that my Cam timing is correct on my 1.6. The manual that I have gives a picture of how the cam gears should be oriented, but there is too much room for error in my opinion.   I was thinking that I could put the engine at TDC with my dial indicator, then measure the valve lift on the intake and exhaust side on Cyl 4.  This combined with counting the teeth on the belt between the two arrows on the cam gears should ensure that it is correct.  As I know, there are supposed to be 19 teeth between the arrows on the cam gears.  This I already know is correct.  Does anybody have a measurement on exhaust valve lift on cyl 4 at TDC?  If you could include your measurement for valve lash also that would help even more, although it is not necessary.  

 

If anybody knows a different  way to directly measure cam timing so we know it is correct, any help is welcomed.   

 

Just want to make sure before we really start shaking the car down.  

 

Thank You, 

 

-Z

[Bench Racer]

Welcome and have fun.

 

If you have a 1.6 Mazda Factory Shop Manual, please follow the picture/written instructions, they work very well.

[davew]

Valve lash should be zero. Your 1.6 has hydralic lifters (technically called "hydralic lash adjusters" or HLA's).

 

Insert a long stick (screwdriver or 1/4" drive extention) into #1 spark plug hole. Turn engine and watch for stick to reach the top of its travel. This will not give you exact to the 0.001" of measurement, but works fine for setting the timing belt

 

dave

[ScratchRob13]

Valve lash should be zero. Your 1.6 has hydralic lifters (technically called "hydralic lash adjusters" or HLA's).

 

Insert a long stick (screwdriver or 1/4" drive extention) into #1 spark plug hole. Turn engine and watch for stick to reach the top of its travel. This will not give you exact to the 0.001" of measurement, but works fine for setting the timing belt

 

dave

That's what I do for most of my 4 bangers.

[luvin_the_rings]

thanks guys, 

 

we took it to Buttonwillow, CA and realized that the "freshly rebuilt" trans we purchased is actually "freshly blown"

 

motherf**kers on craigslist i swear...

 

-Z

[Jamz14]

.

[RWP80000]

-Z,

 

Your are correct in thinking you can use a dial indicator to measure the intake and exhaust valve lifts as a method to accurately verify the cams are positioned correctly.  Also, even though your engine has HLA's, the measurement you make using this method is valid regardless whether or not the HLA bleeds down while performing this measurement as you are measuring what is happening at the cam/lifter interface independent of actual valve movement.  

 

I use this method but rather than measure each cam lobe separately at TDC, I measure both the intake and exhaust lobes at the same time on the overlap stroke (where the Exhaust valve is closing and Intake valve is opening).  The dial indicator reading to observe is where the lift of both the Intake and Exhaust valves are exactly the same. This is commonly called "split overlap" position.   When measuring this way, you see exactly where "split overlap" occurs with respect to TDC.  Split Overlap is normally referenced as happening at TDC (also considered as cams being installed "straight up"- a position where the cams are considered to be neither advanced or retarded).  You will find for Miatas' that split overlap happens more like 2 or more degrees after TDC and the split overlap lift measurement value will be in the range of .014 to .020 inch on the dial indicator.

 

Rich Powers

[luvin_the_rings]

Rich, 

 

Great info.  Thanks.  So, if the marks on the head are dirty, hidden or otherwise not visible, I can just set the engine to 2 degrees ATDC and set the cams to split overlap on Cyl 4; then put the timing belt on?

 

Thanks, 

 

-Z