304 Modify bunch of bananas

[SLE 500]

So far I have cut the neck off. I will be welding an adapter plate and bolting a hand made fibre glass 90°neck mated to a 90mm tb.
I am thinking of placing a divider plate through the neck to split air to each bank. Upon cutting the neck I noticed the runners at the plenum are rough some have quite a bit of residual slag. Im contemplating cutting off the base plate and cleaning and porting the runner inlets.
Has anyone modified the bananas and if so any help, advice, heads up.
Cheers.

 

[_R_J_K_]

Extrude honing is probably about as good as you'll get. As long as you use a divider design that doesn't make one side lean out it should be fine.

You can obviously weld, why use the fibreglass neck though?

 

[Dirbatua]

Your best bet is to get rid of the 90 degree bent entirely and go with a front on style throttle body like the LS1, the 90 bend in the 304 manifold is the main problem with them.

 

[EYY]

Are you able to post some photos? I don't have any answers or advice, but I'd be interested in having a go at this myself.

 

[SLE 500]

Fibre glass is much easier to make than alloy. I wouldnt know how to make a smooth alloy neck. I have to maintain a certain angle as the thermostat housing blocks a clear access for straight on. I could make the neck straight to the TB and have an angled 45° hose.
How expensive is extrude honing? I will match port the manifold to the heads. How much benefit would I see on a mild street car?
How do I put up photos

 

[SLE 500]

So I decided to cut the bottom off to port and hone the intake runners by hand. Extrude honing was too expensive. I think I can get similar flows.
I also noticed at the back of the heads there are coolant ports that are blocked by the manifold gaskets but the manifold has bowls to match the heads that dont flow anywhere?
Should I tap thread into the manifold and run hose from one side to the other. Let coolant flow through.

 

[EYY]

I'd leave the coolant ports as is. Sounds like a good idea to remove the base of the manifold provided you're proficient in aluminium welding. Apparently most of the restriction is right at the base of the runners from the casting flaws/slag as you mentioned earlier, along with the 90 deg bend that you're replacing anyway. One of the big challenges will be keeping the manifold faces square. You'll need to try not to get too much heat into it in localised areas, and obviously will need to have the faces machined flat afterwards.

 

[Deuce]

I'd be quite interested to see a photo inside after you have cut the bottom off.

I think my bananas are the reason my car only makes 206rwkw.

 

[SLE 500]

Does anyone know why there are coolant ports at the back of vn heads but the manifold doesnt flow coolant through like at the front?
Also I wont be welding, alloy is beyond me. Im getting one of the boiler makers from work to help out.
Do you think there'd be enough heat to warp the manifold? I could make a brace to bolt the manifold to to stop it warping if its possible.

 

[EYY]

Does anyone know why there are coolant ports at the back of vn heads but the manifold doesnt flow coolant through like at the front?
Also I wont be welding, alloy is beyond me. Im getting one of the boiler makers from work to help out.
Do you think there'd be enough heat to warp the manifold? I could make a brace to bolt the manifold to to stop it warping if its possible.

There are coolant ports at the front and back because they are the same casting. There is no 'left' or 'right' head until you bolt it on and decide which is which

It doesn't take much heat to warp metal. I've never modified a manifold before, so I couldn't give you a definitive answer, but it's certainly something to check before you bolt it back on.