Info:- Pistons & Headgaskets
MK1 4A-GE Pistons
The compression ratio on the MK1 was changed from 10:1 to 9.4:1 on the later cars, this was achieved by slightly changing the piston crown.
1a (bluetop) 1985-86 and crossover cars 1986-87 were 10:1
1b (redtop) 1988-90) were 9.4:1
The two pictures below show both types of pistons, you can see that the 10:1 piston has a slightly raised crown in comparrison with the 9.4:1 piston
All models including the GZE use the same headgasket
As far as can be determined (not 100%) the standard toyota gasket is 1.2mm thick and reduces to 1mm after torqueing
After market gaskets can vary in thickness and some have been measured at as much as 1.8mm thick
TRD do a range of multilayer steel headgaskets which are still available from various places, but are expensive £75+.
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