Opinions - B18CR Bottom End with Alaniz head

[ewendc2r]

Hi all,

Got a chance to pickup an Alaniz head which are apparently one of the better heads around with a street port -- Looking a Jun Type 3 cams ..

Question is and I've looked high and low with varied comments:

On a stock bottom end, is the Jun Type 3 too aggressive for stock bottom end? I don't want rev limited much higher than 9100rpm and I understand these cams make power through to around 9000rpm?

I also understand you really need CR of around 11.5:1 - 12.5:1 for these cams to really shine, given basic .020" machining, stock CR should approach 11.5:1 yeah?

From people with experience out there -- What are your thoughts? Apparently Jun Type 3 is like a Toda B, but can get a good deal on the Jun shafts..

[B20NA]

should get your head flow tested, as for Jun 3 cam's will best suit 12.5 : 1 comp, but you also need a good exhaust manifold and ect to get best results.

[tinkerbell]

you could use the CTR pistons to get a higher CR (12+) if you want to keep it an OEM bottom end...

[Benson]

I personally wouldn't use CTR, they dont seem to work so well in a B18c Block

[tinkerbell]

why, what happens?

[Benson]

CTR pistons work well in b16a blocks but not in b18c's for some reason. IF you can show me a set-up that is working well with CTR piston it might sway my opinion

[delsol9000rpms]

if the CTR pistons bring the comp up then why wouldnt they work well... care to share your reason?

[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.

[tinkerbell]

fair enough, piston to head contact is never desirable!

[fatboyz39]

if the CTR pistons bring the comp up then why wouldnt they work well... care to share your reason?

Compression is not the answer to good power without the rest of the combination right and so far CTR pistons in any B series with more than 77.4mm stroke is a problem.I have read of a few yank setups that work
but they have big dollar cyl heads on them.If you do it the way Toda says you cant go wrong very simple build.

[delsol9000rpms]

wasnt arguing with anyone just wanted to know why people dont use those pistons. thanks for the explanation. .

[jdmTYPE R]

a lil modification on the ctr piston will get it to work fine...