Holden 304 Banana Manifold

[Wade]

They work alright in a light early girl. One of my mates ported one. And he would keep up with me off the line when I had my silver vy ss. I think he had 4.11’s and stall though, so that might of helped.

[brindo]

I was having some issues with the 70mm throttle that’s worth sharing.
Apart from it being very noisy and sticking slightly open again, it was creating a decent vacuum in the fuel tank. So much so that you could hear the fuel tank “oil canning” as the vacuum came on. The throttle body itself wasn’t something I paid a lot of attention too and clearly I should have. So once I removed it and compared it to the stock throttle body, its pretty obvious what the issue it. The workmanship on the throttle body looks good, really good in fact. But in boring them out, it exposes the 2 emissions tapping points, opening them right up. So now there is a large opening on the downstream side to the throttle blade as well as a path around the blade.
And I suspect this could be the cause of why the throttle was sticking open slightly too as it did when I tested this same throttle body on the Calais.

Anyway have pulled the bored throttle body off, and fitted the standard one in place. Immediately it is so much quieter and the fuel tank is now not exposed to full manifold vacuum. Kicking myself I wasn’t a little more thorough checking this out earlier. I think if I am to use the 70mm throttle, I will need to plug the emissions holes with Araldite so the blade seals and then drill them back out smaller to 1/16”.

Throttle Body Emissions Ports.JPG (33.94 KiB) Viewed 3640 times

[immortality]

I had similar issues. Same deal, JB weld and re-drill.

[vlad01]

Yeah thats a given. Max a v6 TB can be machined without this is 64mm and the v8 ones about 67mm before the wall collapses on those ports.

They are a pain to solve this correctly, normally with a alloy or brass slug pressed in after purposely drilling out the entire port after removing the metal barb inserts (they are hollow too), then machine the TB from this point, redrill holes and install the barbs again. Mace would press the slugs into the inside of the barbs, but this would leave a gap around the perimeter that you'd need to fill with epoxy.

On my TB enlargement, I plan to slug them all the way through, blocking them off permanently, and then install a purge solenoid like 202 did on his ecotec 808 tune via the flex table, use a corvette type carbon canister or a good used VS one, plumb the solenoid into the manifold near the TB and call it done. That will also open up the option of fine tuning the purge for your particular engine where road speeds, rpm, vac and afrs differ from factory.

[brindo]

A minor update – but no dyno results.

I have by no means finished tuning and there’s every chance I am doing something wrong, but below is the fuel map so far.

I guess there’s a huge number of variables which make it difficult to compare apples to oranges but the stock 12p 304 map has a peak at 1400 rpm, then a trough at 1600 rpm, then another peak at around 4000 rpm. I’m assuming some of this is those long runners doing their thing after which it gets asthmatic.

With this ported manifold, the first peak is at 1600 rpm but is pretty steep, then a similarly huge trough at 2200 rpm, then another steep rise to another peak at 3600 - 4000 rpm, or 4400 rpm lower down. Fuel is dropping off on the other side at 5200 rpm.
This ute is very light – 1520kg with my fat guts in it on the dump weighbridge - so it still pulls really well, even past 4000 rpm. It certainly doesn't feel asthmatic but the fuel map might suggest otherwise.
I’ve had to remove a truck load of timing down low to stop the bucking at light cruise, with still a bit more to come out yet. A better exhaust is on its way.

Anyway, right or wrong this is the fuel map so far and interpret it how you will.

Fuel Map.PNG (62.38 KiB) Viewed 606 times

[vlad01]

Looks good. The VE is pretty indicative of a tuned intake design interacting with rest of the engine dynamics, bigger cam overlap amplify this effect further with the main peak and secondary lower harmonic peak, you can get 3rd, 4th etc at decreasing strengths too, but not always visible.


In theory, there should be another such "secondary" peak mirrored on the other side of the main one, well past peak HP. We never see them as no one revs an engine that far past typically while also logging data.

When using a non tuned intake runner design, often these flatten out into the more familiar flat hill type of curve, and overall is closer in height to the trough in a peaky one like above. Often people fixate on the trough as being bad without realizing that the trough is more representative of where the baseline would be in a none tuned intake, actually tuned intake, head, cam and header package. Not just the intake. You can always make a non tuned intake become tuned if you change everything else to suit intake within reason.

Very interesting stuff!

[immortality]

I think Holden really detuned these things down low tbh.

[brindo]

I’m thinking the same thing and would like to think of the trough as just being normal rather than a power drop.
And that first peak in particular is at a pretty handy rpm to line up with normal speeds in 4th and 5th gear.

[vlad01]

I think Holden really detuned these things down low tbh.

They did for everything pretty much, VN LN3 was one if the only example that I can think of that they didn't de-tune and let it hit the public with a real tune, but as the old urban legend goes, they quickly put an end to that because of the older granny drivers complaining.

I can't imagine anyone actually complain about having good power, so I think it may have been some red tape stuff somewhere or an internal decision so that the value of the v8 wasn't tarnished or eaten into by the early vn v6.

I mean, look how the VL turbo public perception went for their VL V8 sales.