Blacktop/Silvertop Throttle bodys

[4-AGE 4-LIFE]

Hello...

Well what im trying to find out is what will flow better for my engine...

I am in the process of building a high spec NA 4age.... the bottom end is a balanced silvertop, and head is blacktop which i should get back from kelfords tomorrow or early next week.

has had extensive head work, aggressive 296deg 10mm lift cams, full porting, springs etc etc...

I have 2 throttle body setups.. standard blacktop and standard silvertop face lift...

would i best to use standard blacktop

or is it possible to use the blacktop throttle body's on the silvertop face lift manifold?

or better to use the standard face lift silvertop ones?

Cheers
Ben

[matt dunn]

the blacktop ones are meant to be better and since you have the BT head,

i'd say use the BT ones.

[RedMist]

Definately use the blacktop ones. The facelift manifold has the same port shape (that of a teardrop) as the blacktop one. However blacktop is larger. If you attempt to port match the silvertop manifold to the blacktop head you will get a velocity drop from manifold to port and fuel will fall out of suspension.
You'll note a downward angle of the port then a 15 odd degree shift to the manifold. If you can downport it, ie straighten the manifold there is some good flow gains, without increasing port diameter. This means velocity is up. We flowed it using a wooden spacer block but never built the manifold necessary for downporting as I ended up going the 16 valve route.

I'm a fan of developing the silvertop (or smallport 16 valve) for a good curve 200hp engine. If your going over that the blacktop may offer advantages with its larger ports (and certainly will on the exhaust side as its massively bigger) but you are loosing velocity and hence some of the mid end torque.

I'd probably go a little longer in cam duration, but it fully depends on your application.... and Kelfords would have a considerably better idea than I.

As an aside do Kelfords have a flow bench?

[4-AGE 4-LIFE]

thanks daniel, thats exactly what i was wanting to hear, i think a adapter plate to straighten out the manifold will be on the cards next if i cant get 200whp. the cams have allrdy been made.
kelfords do not have a flow bench, probably why the job was a very good price