yay got my spark racing pistons and rods today (had to wait a week to clear customs....********)

anyway very good value for money, pistons not bad for a cast at 300 grams, rods just short of 500 grams (pin around 85 grams) puts it in the same bracket as the oem b20z1 piston/rod combo i had.

just need to check the ring end gap and piston to wall (not 100% sure what gap they should be being 0.5mm oversize units, have asked spark for the info, i shall post it up here)

i could not find any pics of peoples pistons.rods on here, sorry for the quality the lighting was niknak and i was in a rush. block is red btw...my camrea is a bugger for messing up the color under bright light

















old psiton and rod (yum....)

 

right been outside and done some measuring of the piston rings.

got the following gaps.

cylinder 1:

top 0.20
mid 0.40 (feeler gauge just fits in but has a fair bit of drag on it when going in/out)
bottom1 0.30
bottom2 0.30

cylinder 2

top 0.20
mid 0.40
bottom1 0.30
bottom2 0.25

cylinder 3

top 0.20
mid 0.40
bottom1 0.30
bottom2 0.30

cylinder 4

top 0.20
mid 0.40 (tight)
bottom1 0.35
bottom2 0.30


now for piston to wall. manual says i need 0.01-0.04mm in the cylinder wall. now. do i measure the piston diameter at multiple points and subtract that from the bore diameter?

do i put a feeler gauge down between the wall and piston (poses problems due to piston hot being held) or is there another way to get a measurement?

also in regards to the gray coating on the skirts? i am guessing as its a coating do i need to include its measurement to the piston to wall or not? (ie: if it was 0.01 thick etc)

thanks!

 

right according to spark they say i should be running these gaps on their pistons: so i should file my rings until they are those gaps correct? (first i assume is the measurement in inches, i converted it to mm)

.015 = 0.38 (top)
.017 = 0.43 (mid)
.0020 = 0.050 (piston to wall)

i still cant find a guide on how to check the piston to wall clearance. anyone? (even google gives me very little on the procedure)

 

This should have everything you need.
GSR Rebuild

 

awesome thanks.

all my oem bearings in the rods and mains were all green and brown. im guessing it would be worth buying an acl standard set of bearings and running those as they should give me the 0.008 -0.015 clearance i need right? (bar the rod as they are aftermarket)
only going to run this engine on ctr cams as its a dailey and i want to keep the revs low (er) and power under 250 flywheel

gonna drop my block back to a builder and get him to re-hone the block to correct specs, align hone the gsr caps and crank girdle to the b20 main block journals and then slap the bottom end together.

hone needs to be a 60 degree cross hatch correct?

cheers

 

The clearance is .0008"-.0015". However, I am going to be running .002" which is the service limit. It should give me some extra room and hopefully prolong the engine life. Many people have recommended including the machinist at the automotive machine shop I use. Many people like to use OEM bearings since they have a much wider variety in sizes. Follow that guide for choosing bearings and go by that.