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BigWorm
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May 2002

Re: how big is your turbo on your 4a-gte?

Mon, 24 October 2005 15:21

TE72_Turbo wrote

I actually tried Wade's 280 degree cams first with almost 8.5mm lift, but despite their initial advice, they cams actually lifted one side of the shim about 1.5mm off the bucket/lifter when turned over by hand! Thank god I didnt start it up and give it a rev before noticing. Now Wade don't recommend those cams without a "shim under" conversion kit Smile

Interesting, I've been looking into cam profiles & lifts (only half-arsedly so far) and came across the following website which lists cams for standard bucket & shims & cams for shimless or shim under buckets, and the standard shim cams went up to .493" (just under 10mm) with 300+* of duration!
http://www.camshaftshop.com/camsha fts/view/27/toyota-camshaft/

It makes you wonder just how many of these cams these guys have sold...

I've almost pretty much decided to go with some of the Toyota 1sz-fe shimless buckets so I don't have to be too restrained when it comes to cam selection. Then I just need to work out how big I want to go. Rolling Eyes

Whadaya reckon Phil? I'm also interested to see what the 2510 can handle, currently power drops off very gradually up to revlimit, so it doesn't look to be struggling. I s'pose it'll come down to how mental I go when I choose a profile, but, if I find it is getting a bit strenuous for the old girl, then dammit I just might have to get something a little bigger! Evil or Very Mad

oldcorollas wrote

as for seat pressures.
stock 4AG seat pressure is what? 35lbs?

intake valve area is 1.06 square inches... sayy roughly 1sq" taking away the valve stem area (if we want to get exact.. 6mm valve stem = 0.0558 sq", 29.5mm valve = 1.0594sq", so..= 1.0036sq" minus the area shrouded by valve seats)

so yeah, Joels rough calc is dead on the money Wink

1pound boost = 1pound heavier seat pressure.. for a 29.5mm dameter valve.

Sweet!

That does get me a bit worried though, the springs I used have 50lb seat pressure, so during my occasional ( Wink

) 25 pounds of boost my 50lb valve springs are now 25lb springs! I guess that's just another very good reason to rev limit it to 7000rpm, rather than it's standard 7700rpm redline; anyone know when standard rev limiters kicked in?

So when I do get stuck into cams & buckets etc I'm going to have to shim them up to increase the seat pressure, to at least 60lb I reckon, which depending on what lift cams I choose (maybe around 9mm?) will leave the springs about 1.125mm away from binding. It's a bit of a fine balance between spring seat pressure & cam lift (and boost!).

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