Opinions - B18CR Bottom End with Alaniz head

[TODA AU]

I’ve gotta say I’m with Benny on this one…
If you use B16C CTR pistons,
Without machining the block, you’re already approaching a zero deck
(0.006” to move on a virgin block)
The pin height of the B16B piston is 30.73mm
The B18CR piston pin height is 30.23mm
With only 0.005” machined off the head & block combined,
You’ll have a compression ratio of 12.9:1
This can be troublesome with 98RON fuel & short duration cams.
(With comp this high, you’re better off with E85 or race fuel)
If 0.010” of material is removed, you’ll have to look a 0.8mm or even 1.0mm head gaskets to maintain acceptable piston to head clearance.
As a side note, I don’t like the crowns on CTR pistons either.

If you’re on a budget & want respectable gains from the head & cam swap
& the bottom end is actually in good condition & fine to re-use…
Pull it down, tickle it a bit here & there & strap it back together.
It’ll only cost you a bit of time, some machining & a set of gaskets
(You're swapping the head anyway so it's not much extra work IMO)
.
Keep your original B18C7 pistons…
& machine no more than 0.020” off the top of the block…
This will give you a comp of 12.1:1 (assuming the chambers aren’t bigger & the head isn’t shaved)
To get it right, you will have to do a bit of measuring & a few sums,
But, you can have 12.0:1 C/R with little spent
IMO this will work better on 98RON pump fuel than moving the CTR pistons.
& you’ve maintain acceptable piston to head clearance with original head gasket.
Once it’s ready to go back together, you’ll need to get the cam timing right or your piston to valve clearance will become an issue.

[ewendc2r]

I’ve gotta say I’m with Benny on this one…
If you use B16C CTR pistons,
Without machining the block, you’re already approaching a zero deck
(0.006” to move on a virgin block)
The pin height of the B16B piston is 30.73mm
The B18CR piston pin height is 30.23mm
With only 0.005” machined off the head & block combined,
You’ll have a compression ratio of 12.9:1
This can be troublesome with 98RON fuel & short duration cams.
(With comp this high, you’re better off with E85 or race fuel)
If 0.010” of material is removed, you’ll have to look a 0.8mm or even 1.0mm head gaskets to maintain acceptable piston to head clearance.
As a side note, I don’t like the crowns on CTR pistons either.

If you’re on a budget & want respectable gains from the head & cam swap
& the bottom end is actually in good condition & fine to re-use…
Pull it down, tickle it a bit here & there & strap it back together.
It’ll only cost you a bit of time, some machining & a set of gaskets
(You're swapping the head anyway so it's not much extra work IMO)
.
Keep your original B18C7 pistons…
& machine no more than 0.020” off the top of the block…
This will give you a comp of 12.1:1 (assuming the chambers aren’t bigger & the head isn’t shaved)
To get it right, you will have to do a bit of measuring & a few sums,
But, you can have 12.0:1 C/R with little spent
IMO this will work better on 98RON pump fuel than moving the CTR pistons.
& you’ve maintain acceptable piston to head clearance with original head gasket.
Once it’s ready to go back together, you’ll need to get the cam timing right or your piston to valve clearance will become an issue.

Thanks for that -- when you say a tickle, you mean rebore,hone etc new rings yada yada -- I don't want to pull the block out at the moment, much bigger job for one person that replacing a head.. Can I do anything worthwhile with the block still in the car? (Guessing I can drop the bottom end out and replace bearings etc too.. ) given the engine now has 120,000kms you may be right ... this is getting expensive quickly lol ..