4age 20v - When are heavy duty valve springs required?

[shelldrake]

Hey guys,
I'm in the process of a 20v build at the moment and it has come to the point of cam selection. I found a grind that looks the goods and should allow the vvt to still function well. I have an adjustable cam pulley for the exhaust side to optimise results. What I want to know is at what point would heavy duty/performance valve springs be required? The profile is around 270 degrees (advertised duration), with 382 (I think about9.5mm) lift. Would also be interested to know what other cam profile 20v owners have had success with. Cheers!

[Celica RA45]

1st you need to see if you get coil bind of the std spring and you also need to see what std lift is .
you need a prox 60 thou to 80 for coil bind and you better be sure you have enough room for the vvt or else you will hit pistons, 80 thou for piston to valve cover as well

[Mooro]

I think it is discussed on Bill Sherwoods 4age page. Don't quote me on this but I seem to remember something around 10mm lift being the point where you need upgrade springs.

[Sam_Q]

thats for a 16v, put 10mm into a 20v and your buckets better watch out

[Mooro]

Oh OK...sorry my mistake.

[Celica RA45]

you will have to go after market 1 s .get some TRD 1s or some from TODA
the performance springs ,dont go there ,you pay for what you get

[Sam_Q]

Celica RA45: why do think that that aftermarket springs are needed?

[Celica RA45]

he is going higher in lift and from memory 8.7 is std lift going up to 9.5 would loose the 60 thou clearence before coil bind and most likely smash a retainer or bend a few valves

[Sam_Q]

I should actually measure how much room there is before coil bind in my engine

[ed]

whats wrong with performance springs glenn - specifically?

i have heard nothing but good things

[Celica RA45]

ask mark for his opinon on them

[Celica RA45]

this is for edd


Having build a lot of 20 valves race engines I use experience rather than rules of thumbs. The standard springs only have 20lb seat pressure. The valves bounce at high rpm resulting in seat deterioration. If you have high lift camshafts this gets even worse with accelerated bucket/cam lobe wear.

I would recommend TRD or TODA springs. I've had a bad experience with failures of locally made Performance springs where I had to voluntarily recall 7 engines from the field and upgrade them to TODA. I still see 20 valves with dropped Performance springs so it doesnt look like they have addressed the problem.

TODA and TRD springs have approx 40lb of seat pressure.

You will find that you cant get much more duration before the VVT mechanism stops working. It relies on the camshaft accelerating off the back of the lobe to click it into the advanced position. Once you get to a certain duration the cam is pickup up the next cylinder before it falls off the previous one.

Speedracer

need i say any more on the subject

[shelldrake]

I understand what you're saying ra45. Do you have a part number I can quote for the trd ones?

[Celica RA45]

TRD springs no longer availible so looks like TODA are your options ,will get a price for you and get back to you tomorrow

[Celica RA45]

TODA items for ae101 about 300 dollars