Mazda 1.8l Head tear down-Tech Info


The basic views

Front

Rear


Notice the casting number in the middle to right corner of the casting.
BP4W 2-1

AREA dose not have this head casting listed for in it’s head and block book, but it still may be listed in the CD rom.


Intake side


Exhaust side


Top view



Combustion chamber




Head thickness Measured from VC rail to head gasket surface is Between 5.270 and 5.272 at four corner points around the head.


Intake valve head measured 1.300



Exhaust valve head measured 1.103


The valves were slipped back into the head, and valve tip height was checked.
Intake range 1.792 – 1.799
Exhaust range 1.791 – 1.798



Next I checked spring installed height on one Intake valve
Measured 1.565 w/out spring seat shim installed

Spring seat shim measures .020 thick

Now to figure out what my seat pressure is.

1.565 - .020 = 1.545 +/- .004

Now setting up the spring tester to 1.545


Most springs were 35-37 lbs @ 1.545
A low was 33 lbs and a high of 39 lbs

Spring specs.
1.027 OD

1.800 free length


Looking at my SBI Catalog (2007)

Pg 545 Block 12
1.8l 16v “BP”

Spring part number 160-1250 (90-97)
SBI spring spec (Pg 760)

1.831 Free length
46 lbs @ 1.600

But due to the difference in years and no listing for the 99/00 head I am working with.
These springs, are asking for taller installed heights from what I measured by .055

Looking at the supertech springs they as for a much shorter installed height.

Catalog - SuperTechPerformance.com

SPRK-MM16D1 56 lbs @ 34.2mm /1.346

That is the loan single spring they list.


It makes me what to think there is miss listings in both SBI and Supertech.

.200 is a lot of shims to be used and no good way to locate it with out the use of special thick spring seats.