silver top or black top ITB's

[jesse dreadz08]

Iv got a redtop small port 4age that i'm rebuilding and wont to run ITB's, just wondering whether be better to use blacktop or silvertop ITB's, what injectors would be best to run whether its worth lightening the fly wheel and what would be an ideal weight, i'm making some long 4 to 1 extractors and i'm going to make the ITB manifold so whats a good length. I'm going to keep the motor pretty standed internally maybe some aftermarket cams. I am an engineer and have rebuilt old motors before but don't no much about tuning or what set ups to run but i wont to do as much as i can my self and not spend much money so any help much appreciated.

[totta crolla]

Hi welcome.
In order to run itb's you really need to use a after market ecu and once you have that sorted you might as well put a decent pair of cams in to make the most of the itb's.
The 4age is fairly reliable up to around 8000rpm so 272 degree cams are about the maximum on stock internals.
A light flywheel is a good investment, personally I wouldn't lighten the stock one.

[burdickjp]

For the greater majority of 4A-Gs, silvertop throttles are more ideal.

If you can find an OEM blacktop flywheel they're a great weight for street use.

I have a preference for Tomei's PonCams, but there are many camshafts with similar lifts and durations.

[yoshimitsuspeed]

Near stock there will be no noticeable power difference between stock TB, ST or BT ITBs. Anywhere under 200 hp anyone paying for ITBs is paying for looks, sound and cool factor so don't worry about it too much.
You can run ITBs on the stock ECU but you need a plenum that pipes to the AFM and most people concerned with looks, sound and cool factor aren't willing to cover up their ITBS with a plenum.

To get the most out of a build you want to plan everything around that particular build.
Here is a build I helped a customer with. We decided on Tomei Poncams and 11:1 pistons that I designed specifically for his build and goals.
http://mr2oc.com/showthread.php?t=468649

Cams without upping the compression is loosing efficiency and leaving power on the table.

[Rogue-AE95]

Cams without upping the compression is loosing efficiency and leaving power on the table.

This made me wonder why Toyota kept the smaller profile cams when they upped compression for the smallport. Does raising compression without changing the cams bring about more low end torque?

[yoshimitsuspeed]

More compression will raise power across the board. Bigger cams will move the power band and the VE curve higher in the RPM.
Detonation is most likely in the low to mid RPM where everything is happening slower. As RPM goes up and events happen faster detonation is less likely.
So yes 10.3:1 on stock 16v cams will tend to make more mid range power than 10.3:1 on bigger cams. Of course with bigger cams you could run more compression before getting detonation. This would allow you to retain similar power in the mid RPM and get more power in higher RPM.

Unfortunately manufacturers have to be concerned with a lot more than power or even BSFC. They have to worry about emissions, fuel availability NVH and all kinds of other things. If your cams are big enough you can get exhaust in the intake or worse for emissions you can get air and fuel passing unburnt through the system. This may be why the first 4A to run significantly bigger cams ran VVT where they could reduce the overlap where it was needed. Likely as much for emissions as for power.

[Sam_Q]

Unless you're making a real high end engine then you will likely make more power with silvertop throttles

[burdickjp]

Unless you're making a real high end engine then you will likely make more power with silvertop throttles

I would say that's a dubious claim, but would argue that just as importantly you'll have more linear throttle delivery with the silvertop throttles than you would with the blacktop throttles.

[oldeskewltoy]

Iv got a redtop small port 4age that i'm rebuilding and wont to run ITB's, just wondering whether be better to use blacktop or silvertop ITB's, what injectors would be best to run whether its worth lightening the fly wheel and what would be an ideal weight, i'm making some long 4 to 1 extractors and i'm going to make the ITB manifold so whats a good length. I'm going to keep the motor pretty standed internally maybe some aftermarket cams. I am an engineer and have rebuilt old motors before but don't no much about tuning or what set ups to run but i wont to do as much as i can my self and not spend much money so any help much appreciated.

Welcome....

WHY do you want to run ITBs?

Injectors... it depends, on what type injectors your electronics support... low ohm(under 4 ohms), or high ohm(over 10 ohms) but 210cc-240cc will cover you...

4-1 headers - 38mm(1.5") O/D piping mandrel bent, make the length of the primaries 28"-30", use a 60mm(2 1/4") collector

Total length of intake (intake, ITBs, and velocity stacks) should be about 10" (+ or - an inch)