Der_Idiot

iTrader: (2)

Hey guys, going through the process of ordering some high lift 264 duration cams for my build. I've heard that some high lift cams require machining the lifter bosses to clearance the lobes. Does anyone know whereabouts folks start seeing clearance issues?

I'd really like to install these without pulling the head. Again.

NiklasFalk

iTrader: (1)

It's all about max radius. Easiest is to measure the clearance with the current cam.

Rebuilding the valvetrain for smaller basecircle might require pulling the head, unless just thicker shims is an option.

Maruha are really conservative and only assume the stock radius have clearance (going to smaller base circle for all higher lifts), but that can also be to push sales of SUBs.
Maruha's BP Camshaft Lineup Mazda MX-5 Miata

Der_Idiot

iTrader: (2)

Thanks for the response! I do already have SUBs installed, from what I'm reading if the lobes aren't hitting the lifter boss (with at least a mm or two between the lobe and boss) I should be able to re-shim the buckets and break in the cam no?

NiklasFalk

iTrader: (1)

No need for that large clearance if I've understood this right (the cams don't flex that much).
Then you have this with lifter diameter and profile (tilting the lifter etc)...

I've seen no downside with a little smaller base circle.

my97miata

For the 99-00 engine heads, Maruha (Tomei from 949racing) have 10 mm of lift. You could also go with the BP-5A intake camshaft to save a few bucks, but you're probably looking at a 10-15 whp drop with the BP5A camshaft.
The BP-5A has 8.9 mm of lift.

Der_Idiot

iTrader: (2)

I've been talking with a Kelford agent and he advised ~9.05-9.1mm lift are my maximum without damage on 264s (inertia and valve seals I'm guessing). He took my SUB weight and size and did some maths to get to that info. The 99-00 OEM intake/exhaust is 257/277 and 8.28/8.89.

From my reading almost all of the gains from a cam with a turbo come from increased Intake flow not Exhaust so a minor increase in exhaust lift doesn't appear to be an issue. But is a .8mm lift increase for the lifter and a 7* duration increase on the Intake side and a 13* shortening of the exhaust cam with a ~.2mm lift increase actually net a gain? If %flow increase can equate to %hp/tq increase that's a 9-10% increase assuming the shortened exhaust duration doesn't affect things too badly, no?

Is he right? Is 9.1 as high as I can go? I read about folks with 10mm lift Maruha cams and feel like I'm missing something; even with heads having HLAs that can't be all the difference can it?

NiklasFalk

iTrader: (1)

With that reasoning, I'd advise you to copy someone else's setup.
A lot less chance for ordering mismatched parts and getting into problems (which can be a lot worse than not reaching the results you want).

Otherwise, the cam you have designed dictates the rest of the valvetrain buildup, and anything can be made to work, including 13mm lift cams (Cat cams have a brutal set, note that all their cams are for HLA unless a lash ramp is specified).
I suggest reading up on reduced base circle.

Der_Idiot

iTrader: (2)

Niklas,

I agree. I've been trying to find a similar setup but haven't had any luck yet. I'm debating ordering some off the shelf Maruha cams and having the head lifter bosses machined to suit extra lift if need be. The local machine shops aren't very helpful, and of the four local shops I called three wanted me to use shimless lifters and the third tried to convince me to go back to OEM.

Now this page here indicates the cams should work fine with SUB setup in a NB8C before M/C(w/o VVT)

Anyone know what the "BEFORE M/C" is supposed to mean...?

NiklasFalk

iTrader: (1)

"(w/o VVT)", witout VVT, NB1, 98-00, BP4W, ...