cam profile mod gains

[andrew_mx83]

lol.... rockers...


we arent in the dark ages anymore

[JadeEstevez]

For dark age's technology, My dads XB with a Cleveland 351 kicked late model Holden Senator asses!

But this is a Toyota forum, I'll shut up... =P

[andrew_mx83]

pushrods vs pushrods

its like a cripple wrestling a retard.

[JadeEstevez]

Don't say that to my dad, Bahaha! I've still got some of the banana shaped push rods from the engine ;P Still ran good with them like that hehe.

[metcap]

I've got my uni exams comin up soon so i dont have a lot of free time but i can give you a better breakdown of the valve train in a week probably if you like.

I'll eventually be doing a breakdown on complete engine tuning for my website so if you've got some interest in customising other parts i should be able to help out

any info you can share here is greatly appreciated, I'll be anxiously waiting for your update BTW where the link to your website?

Are your springs and shims capable of the cam's rpm range

How do we determine this? Any references you can share, and for a hi rpm range is it that a single valve spring better than double springs? Whats the recommended spring rate for an engine pushing 8k rpms to prevent spring float? Is spring float more critical on pushrod engines as compared to over head cams/buckets?

[MWP]

How do we determine this? Any references you can share, and for a hi rpm range is it that a single valve spring better than double springs? Whats the recommended spring rate for an engine pushing 8k rpms to prevent spring float? Is spring float more critical on pushrod engines as compared to over head cams/buckets?

Double springs are better for high RPMs.
There is no easy way to determine what spring weight is required. It depends on many factors (valve assy weight, lift, cam profile, etc, etc).

[metcap]

Double springs are better for high RPMs.
There is no easy way to determine what spring weight is required. It depends on many factors (valve assy weight, lift, cam profile, etc, etc

Hmm, possible to clue me in on whats the hard way? Anyone know whats the valve spring rate that Toyhead sells for the 2tg 10krpm?

[oldeskewltoy]

when doing a long duration, hi lift cam conversion what important details need to be taken to upgrade the valvetrain parts?

How long is the duration?

How much lift?

Are springs capable of the lift and rpm?

Some things occasionally overlooked.... Valve to piston clearance... Valve to valve clearance...

[J-M kujala]

Hmm, possible to clue me in on whats the hard way? Anyone know whats the valve spring rate that Toyhead sells for the 2tg 10krpm?

Stock double springs.. just to weak (exept full stock motor) singles are stiffer..

First step up is use 2TG Singles with double inner springs.. (oem parts)
then there is some other cheapos available, BugPack double springs.. from VW beetle aircooled engine.. have use different combination with outer and inner with bought stock type outer springs.. and only outer BugPacks
also some CatCam Springs and From Kameari is available..

Kameari specs what i measure ~5 years a go. 38 mm install height ~65 kg at intake side, and ~45 kg in exhaust side.
with ~12 mm lift at bought side. 80-90 kg open pressure.

i have buy those Springs directly from Kameari.. (toyhead sells same with $$$ added) they are not 10 Krpm springs with all Hardest profiles (really fast ramps) but they are enough to almost all aplications..

Also when you got 2 spring (inner&outer) what are tight together, they resonate at different frequencies and kill resonance at each other. (Kameari ones are tight fit to each other.)

also when big boost added, had to raise valve spring rates... the pressure try to open those valves..

to 2TG ~15Kg more spring load to every added 1 Bar of boost..

[Duk]

I haven't read all of this thread, but I thought I'd add some info.

Being involved in all sorts of other cars, also has me playing with Alfa Romeo's.
I own a 3 litre V6, 12 valve, 1990 Alfa 75 that has about 142KW in standard form.
There is a (American) guy on 1 of the Alfa forums I'm on that has been modifying these things for a very long time (20+ years). 1 of the things that he constantly harps on about is the importance of cam design and how the right cam profile can deliver really good power and really good torque when the camshaft profiles matches the inlet manifold (diameter and length of the inlet runners).
What is really impressive is that he has consistently got 100hp/litre (on an engine dyno) from pretty aggressive, but still road going, 2 valve per cylinder engines (even more on outright track engines).
Think of a 3 litre V6 with standard sized, single, 44mm inlet valves (so no where near the valve cross sectional area to capacity ratio of a 4 valve per cylinder engine), breathing through 38-39mm inlet runners (that are pretty short) with good tractable torque and 300HP, below 7000rpm.

His emphasis is on having the valves open as long as possible without having too much valve overlap.

Now that sounds like a contradiction, but the idea is to get the valves open as quickly (and ultimately, abruptly) as possible, as high as is worth while (25% of the valve head diameter) and closed as quickly as possible.
So (as mentioned by someone else) an almost rectangular cam lobe.

Why should I, or anybody else, listen to this guy?
Appart from the results mentioned above, he talks about the different requirements of the same 3 litre Alfa 12 valve V6 that were factory built with longer, larger diameter runner inlet manifolds and they required different cam overlap numbers to get the same results.
He was also scathing of aftermarket over sized valves that actually impeded flow because the edge closest to the cylinder bore was even closer to the cylinder bore. These were his tested results rather than some opinion.

[andrew_mx83]

ive never seen the logic in using oversize valves unless the seats are bored out or replaced with larger ones to suit. as you say if anything OS valves on stock seats would seem to impede flow.

[metcap]

He was also scathing of aftermarket over sized valves that actually impeded flow because the edge closest to the cylinder bore was even closer to the cylinder bore. These were his tested results rather than some opinion.

sorry for my ignorance, but why is getting the valve edge closer to the bore a bad thing? Also when fitting oversized valves on stock seats won't the seat be bored out to suit?

2TG ~15Kg more spring load to every added 1 Bar of boost..

do you know whats the stock 2tg spring rate?

[JadeEstevez]

I'm guessing it's a bad thing because there is less flow between the bore walls and the edge of the valve closest to the bore wall.

[J-M kujala]

do you know whats the stock 2tg spring rate?

Depends. There is different springs/age and different km:s behind them

Weakest double springs was 17kg at intake side !! What i have measure. Up to ~30kg (seat pressure)
I have once use totally stock 2tg top end (260) and when boost raise near 2 bar i pop out my intake side valve adjusting shim at turbo spool in ~ 4500 rpm.. That was some test drivings to get some base tune to wastegate.. In that time i was thinki g that stocks are ok with stock cams and stock rpm limits when only boost is added. But nooo.



And to that valve case, bigger is not always better, and need a lot more than just drop them in. And some combustion chamber do not like at big valves. These real hemi heads accept big valves.. Some "pool" type combustions wont like them. So combustion needs a real porting work..

[metcap]

I'm guessing it's a bad thing because there is less flow between the bore walls and the edge of the valve closest to the bore wall.

But on the 2tg stock head the intake valve already borders on the bore edge so does this means the stock config is doomed to start with? Also, for oversize valve jobs I'd assume most would go bigger bore, so I'd think the valves sitting too near the bore dun come into the question?