Modifying intake runners 4age blue/redtop tvis

[crispy'86]

I'm toying with the idea to do this in my race car, had several ideas,
1: Get larger diameter intake runners and weld them to the original manifold keeping them same length
2: Making the intake runners a bit shorter and making the intake closer to the cylinder head.
I looked at a 4afe intake and thought it'd be doable, and retain the flange off the 4age intake.
It's for my race car, 4age redtop spec tvis, looking to run aftermarket cams, bit of porting, larger throttle body.

What are everyone's thoughts? I'd be interested to hear

[Trls250s]

Generation 1 3sgte's have a TVIS manifold on them. Might consider using them if your going to do this mod.


Sounds interesting though.

[barryogen]

I'm toying with the idea to do this in my race car, had several ideas,
1: Get larger diameter intake runners and weld them to the original manifold keeping them same length
2: Making the intake runners a bit shorter and making the intake closer to the cylinder head.
I looked at a 4afe intake and thought it'd be doable, and retain the flange off the 4age intake.
It's for my race car, 4age redtop spec tvis, looking to run aftermarket cams, bit of porting, larger throttle body.

What are everyone's thoughts? I'd be interested to hear

I'm by no means an expert, but...

1. In NA cars, don't you want to keep the velocity up on the intake charge? so going too wide with the intakes would slow it down meaning less power... not too sure on how big is too big though.

2. Making the intake runners shorter would make it more optimised for higher revs... which by the sounds is probably where you are heading anyway, but just so you know.

Google around for Helmholts, or Helmholtz or similar... it's all about how the air reacts with the opening and closing of the valves...

[Mr Revhead]

longer runners after the TB is for HP at higher revs....

[RedMist]

longer runners after the TB is for HP at higher revs....

Ahhh... but he's talking wider, which means more volume, and in turn shorter for the same capicity.

Wider is certainly NOT recommended for non compressed applications. If you want more power then REDUCE the size of the ports. My 4age had ports that were about 10mm smaller in large axis (width) than the smallport and still flowed enough for 210 flowbench HP. IE considerably smaller than the smallport. It gave a great spread of torque, from 5k rpm with 304 degree 415thou lift cams. It did run out of puff just under 8k as the ports began to restrict flow.
In regards to runner length you want to do some research on Helmholtz frequencies. From memory I ended up with 19.5 inches from bellmouth to valve tuned for 5.5k (the bottom of my percieved power band) with the cams above and ports as described. I also ran silvertop throttle bodies and the silvertop manifold with a custom made 60mm adaptor plate. The blacktop TB's were percieved too big for the 200hp I was aiming for.

[Mr Revhead]

yeah..... wtf was i reading?

[frost]

would it be worth while changing to straight runners to get rid of the dog lets on runner 1 and 4 on a small port, keeping the same length and making the 90 deg bend smoother rather then its sharp turn in,

[crispy'86]

would it be worth while changing to straight runners to get rid of the dog lets on runner 1 and 4 on a small port, keeping the same length and making the 90 deg bend smoother rather then its sharp turn in,

This is also partly what i was referring to achieve but forgot to mention it.

[RedMist]

Personally I think you're better off trying to get velocity out of the ports. Your approach should, in theroy, generate holes in your torque curve and probably reduce peak HP. Although you are right in trying to reduce any restriction in the intake path, volume and length of the runners are critical for ram charging. The HP numbers are staggering for correct Helmholtz tuning hence the eloborate castings on most modern engines, some with variable length runners.

If you're after a cheap NA HP solution then you cant go past a 20 valve. Considerably smaller ports, tonnes more valve area, quad TB's.... a better responce, higher HP engine.

[crispy'86]

If you're after a cheap NA HP solution then you cant go past a 20 valve. Considerably smaller ports, tonnes more valve area, quad TB's.... a better responce, higher HP engine.

Yes that would be my next step/option although nothing wrong with experimenting with setups.