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10 Posts
Discussion Starter · #1 · (Edited)
I know I know not another timing question!!!! I'm just as sick of them as you are

I can't figure out this mess I'm is what I have so far. I have probably over complicated things

Engine Spec
D15b2 block w/Pm3 pistons (not decked)
D16y8 Head milled -0.045
D16y8 Distributor
D16z6 AEM Tru Time cam pulley
Composite Head Gasket .048? thick

Calculated to 11.71:1 Compression Ratio

This is where it gets crazy:

Correct me if my facts are off:

-B7 Head Gasket = .048 thick
-Y8 head Gasket = .028 thick
-D?s Lose (retard themselves) 1 degree per .012? of milling
-D-series Cam teeth are worth 9.5 degrees each
-Z6 Pulley is 4.5 degrees Retarded from Y8 Pulley

This is where I'm at now:
-Advanced 4.5 degrees on cam pulley to get to Y8?s 0 degree.
-Advanced 4 degrees for head milling .045/.012 = 3.75
-Retarded 2 degrees from stock Y8 gasket (.028 thick)

Total = 6.5 degrees +/- advanced @ cam pulley

Ok so here are my problems:

-Car idles nice and runs to 7k smoothly?always, just not too quickly
-Emissions idle HC is like twice the limit (500+)
-Car isn?t as zippy as I feel it should be.. kinda lugs itself around

-From the calculated stuff above I experimented with the half tooth off theory. From where it was I just moved the timing belt over a tooth one way (advanced) and then over one tooth the other way (retarded). Neither made any difference whatsoever in power. To time it to the center of the 3 timing marks I just had to put the distributor from one side of max adjustment to the other.

#1-Where am I supposed to add the 4 degrees from milling?
The answer is "A" the cam. Via Tranzex
??-B timing belt?
??-C cam pulley?

#2-What is the range of degrees on a Y8 distributor?

#3-if I had the answer to #2 I could answer this but, could I get the timing marks to line up (timing light looking at crank pulley turning distributor and adjusting cam pulley) if I was 2 teeth off? And would it be running?.. like at all?

Sorry for the long post I?m just throwing my ideas and struggles at you all.

Thank you for reading!

Brokedick Millionaire
40,760 Posts
the amount of milling that effects cam timing, your number is off by a factor of Pi.

.012 x Pi = 1 degree

You have lots of numbers there that don't matter, ignition timing and Y8 HG thickness don't matter.

You did get the compression ratio correct :)

1/2 tooth = 4.75 degrees, not 4 degrees.

I would install the cam gear to D15 (flat) marks, which is how a Y8 cam is normally indexed.

10 Posts
Discussion Starter · #3 · (Edited)
Alright man!
Sorry about all my numbers. I'm just trying to understand why it's doing what it's doing so I'm not just throwing things at the wind.
So just to restate what you said so I know I have it clear.

When you mill a head, you account for it in the cam timing. aka adjustable cam pulley...correct?

Ok now how or why does pi affect my numbers? .012 x 3.14 = .037...not sure what this means. What is .037?

100mm pulley = 3.93" sorta
360/3.93=.010 and thats 1 degree...I think

IDK what I'm talking about tho...I saw that pic that you or someone Drew up showing why .012 was the number, that when removed equaled a degree of

Sorry I'm only asking because I don't know..but why don't the head gasket thicknesses matter? Isn't putting a composite hg on a .045" milled head like rebuilding a stock Y8 and only milling .025"?

And what is flat timing? Like set my pulley at 0? It's sorta old and doesn't have any alignment marks anymore. other than the degree marks for timing.
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Brokedick Millionaire
40,760 Posts
Larry Widmer, aka T.O.O. or The Old One originally posted the .012" = 1 degree, which I and other passed on as correct info. Once I was working on the maths for the 1/2 tooth cam timing error.....found out he forget about Pi.

D cam gears are 380mm in circumference, 38 teeth, 10mm belt spacing.

360 degrees / 380 mm = 9.474 degrees per tooth, we'll call it 9.5 for ease, 4.75 for 1/2 tooth.

.25 mill is like retard the cam a 1/2 tooth, nothing to worry about IMHO as I liked 3 degrees of cam retard most of the time on my old builds.

Set crank to TDC, the Y8 cam gear set using the D15 marks...aka flat with the valve cover surface.

Simple math 1 mm = 1 degree cam timing change

10 Posts
Discussion Starter · #5 ·
all right! this is the information I'm looking for!..almost there couple more...

I have a Z6 adjustable pulley visible timing marks

So with what you said I could basically install the stock y8 pulley that has the timing marks. Install with marks at like 9 o' clock and 3 o' clock and I would be about 1 degree retarded due to the head milling, correct? or is it more?

converted and extended simple math 1mm =.050" = 1 degree right?

if that was true would that explain why I'm not in the half tooth territory?

.025" is where I basically stand with the thicker gasket right? retarding a half tooth puts my timing belt that was a half tooth off with the vtec swap back in line.

But isn't a half tooth worth 4.75 degrees??

Thank you very much for the help and for reading my posts!!
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