Holden 304 Banana Manifold

[immortality]

That's looking a lot better.

[brindo]

I still had the banana manifold that I pulled off the VT motor that is in my one tonner. It is (or was) in pretty good order, with no real corrosion to mention. So I have invested a bit of time into cleaning it up as well so it is suitable for a stock engine.
All I have done is pretty much cleaned this manifold up and haven’t gone too stupid on the runners. Acid wise, I have just done 3 runs of water acid mix on the runners/plenum roof, 3 runs on the plenum floor, and 5 runs on the neck. The runners I have cleaned up the same way with the star flap discs on the cable and the neck with a cylinder flap disc. Spent a bit of time working on the bell mouths. Then I have run it for a week with the concrete screed motor bolted on with some ceramic media and truck wash to work on the insides just moving it around into different planes. Then attempted to port match using a gasket, but just left the port around a mm smaller.

There is still the casting trough than runs along most of the runners, and the casting lump is still right at the top of the curve, although nowhere near as pronounced. Bell mouths look a lot better. The flange where the throttle body mounts on to is just on 70.5mm and the runners come up as being between 41.9mm to 42.3mm. I guess I can’t expect each runner to be identical in flow but they are smoother than the factory finish not that the photos really show this.
Still a bit of white powder inside it which would be from the bore water we have here. I have tried to sonoclean it but it’s too big for the machine I have to do in one hit so I just hit it with Alibright and the gernie.

Long term plan is to fit this manifold to a stock engine and try and do a before and after dyno run - but the flaw in this plan is that the nearest dyno is 300km away. There is a local diesel workshop that brings a dyno in from time to time, but it’s been over a year since it was here last. Failing that I guess my options are get it flow tested, or just do logs before and after to see if there is an improvement in air flow or 0 to 100km/hr times. Could be a good thing or prove to be a complete waste of time.

Anyway the photos tell the story.

Manifold.JPG (95.59 KiB) Viewed 5011 times

[Gareth]

I am watching this with great interest, I have a 5lt to build in the not too distant future.

[brindo]

This is the concrete screed motor in action and the ceramic media. That motor has run for another week non stop without fail. It's better than I gave it credit for.
The yellow is a bit of paint on the inside I put there to see how much of it gets removed by the media.
Bit hard to judge the improvement it makes but to my eye it’s definitely smoother on the inside. After leaving it to run overnight, the truck wash and water is dark grey/black which I assume is aluminium that has been removed in the polishing process.
Shame the media gets stuck inside the runners but maybe I am using the wrong media. In the photo below I have just put a cup of media in each runner. Any more an it jams up.

Ceramic Media.JPG (50.36 KiB) Viewed 4997 times

[Cleaver]

This is the concrete screed motor in action and the ceramic media. That motor has run for another week non stop without fail. It's better than I gave it credit for.
The yellow is a bit of paint on the inside I put there to see how much of it gets removed by the media.
Bit hard to judge the improvement it makes but to my eye it’s definitely smoother on the inside. After leaving it to run overnight, the truck wash and water is dark grey/black which I assume is aluminium that has been removed in the polishing process.
Shame the media gets stuck inside the runners but maybe I am using the wrong media. In the photo below I have just put a cup of media in each runner. Any more an it jams up.

Ceramic Media.JPG

Any further progress Brindo? Great read thus far mate.. got me thinking, an aftermarket banana manifold should exist.. stock-looking but flows like a Marther Firetrucking champion

[brindo]

Unfortunately the flaw in my plan is that there is no dyno anywhere near here to get a before and after result. And I am not real keen on adding another 1200kms onto the intended vehicle I have for that last manifold I ported.
So I have tried to chase up getting both manifolds flow tested and got nowhere. But I thought I could at least compare the flow figures at -28" vacuum as a measure of improvement but it is not to be.

I also tried to find someone who bores out the standard throttle bodies to 69mm and again got nowhere. MACE only do the V6 Ecotecs now (even though their website says otherwise and that they will sell you a butterfly too) and I can’t seem to find anyone else who does this. If anyone knows of a place that still bores throttle bodies to a decent standard please let me know.
Haven’t given up, just might have to look for other options.

[vlad01]

I got some throttle plates from Mace, I believe I was the last one to get a VN-VR throttle from them as they had discontinued some months before inquired about it, but since I know them pretty well they reluctantly made one more for me, this was in 2017.


I have the plates to have my own made, I have an engineer shop who can do it they reckon but I find they tend to put small jobs on the back burner and then rush them last min when you keep asking on the progress. The issue is they forget details by the time they do it and often make mistakes even if you asked them to call you before they start the job. Frustrating!

Some of my work mates have found a supposedly great engineer shop close by to the one I was using that have really good attention to detail and fast turn around so this will help keep things fresh in the mind. They mainly work on making/repairing parts for machinery in the print/offset industry. I don't know what they are like with car parts yet, I need to pop in and see them. They are called Dorax engineering, no website or info other than a yellow pages type business listing etc... on google.

[Cleaver]

Unfortunately the flaw in my plan is that there is no dyno anywhere near here to get a before and after result. And I am not real keen on adding another 1200kms onto the intended vehicle I have for that last manifold I ported.
So I have tried to chase up getting both manifolds flow tested and got nowhere. But I thought I could at least compare the flow figures at -28" vacuum as a measure of improvement but it is not to be.

I also tried to find someone who bores out the standard throttle bodies to 69mm and again got nowhere. MACE only do the V6 Ecotecs now (even though their website says otherwise and that they will sell you a butterfly too) and I can’t seem to find anyone else who does this. If anyone knows of a place that still bores throttle bodies to a decent standard please let me know.
Haven’t given up, just might have to look for other options.

https://jhp.com.au/shop/performance/per ... -suit-5lt/
Certain you probably have seen these before, this is what I'm running.. The only downside is that the original Starr throttle body is non-existent, but the best option I have found is a Proflow 90mm TB, the bolt pattern is off, so the threads in the Starr elbow will need to be welded and drilled to suit the proflow 90mm TB.. This elbow mod and in conjunction with your runner porting will prove to provide the biggest flow figure for the banana manifold period.

[brindo]

Yes I have one of those weld on necks. Bought it a while back just to have one put aside before they disappear. A 90mm throttle I think would be too big but it certainly won’t do any harm. But as you say the Pro Flow throttle probably has the closest bolt spacing. The LS throttles are quite short in comparison to the stock 304 throttle body so a 1” adaptor plate would easily fit in there. That way you get to use the stock IAC arrangement. And the LS engines seem to make reasonable horsepower on a 75mm throttle so just needs the cable actuator swapped over.

Welding the JHP neck on is clearly the ultimate solution but I guess what I was trying to do was just see what could be done by the average bloke at home with ordinary tools to make these manifolds as good as they can be for minimal cost. Most people wouldn’t have access to the gear to TIG these elbows on and its getting expensive by the time you pay someone to do the welding then get the faces milled. But as yet I haven’t proved anything as to whether any of this porting is beneficial or not.

As I said before I am not an expert in anything, and maybe I am thinking about this too simplistically – more than happy to be corrected – and am just trying to understand this better and hopefully learn a bit along the way.
But my understanding is that the stock 304 VN-VT heads flow around 240 cfm at -28”H2O on the intake with a decent set of ported heads flowing up at 270 cfm at -28”H2O. But this flow is at 0.600” valve lift. The stock VN-VT cams have don’t have much over 0.420” lift at the valve, so a set of factory heads with a factory cam would be probably be around the 200 cfm range at -28”H2O.

For the life of me I can’t find the thread now, but I do recall seeing some flow testing figures on an untouched factory banana manifold. From memory, the individual runners flow around the 200-210 cfm at -28”Hg per runner when measured individually. So for a stock engine, the banana manifold is probably around the same flow as the heads. But add a performance cam, such as the usual 276/284/286 type cams, all with lifts approaching up around the 0.500” at the valve, the stock heads are flowing 220 cfm at that lift, and the banana manifold is now a restriction. Obviously it can’t be quite as simple as that as there are a lot more variables than a flow figure at -28”H2O, but for the average 304 engine with ported heads and a 220 to 230 duration cam, I’m thinking each runner needs to be up closer to or above the 240 cfm at -28”Hg or the engine won’t get to -2”Hg at WOT.

I think that other OEM 65mm throttle bodies flow around the 600 cfm mark so the stock Holden one must flow somewhere around that. So surely a bored out throttle body won’t be a restriction. So it will be the neck that is holding the show up which is probably what everyone who has gone down this path before has already found out. So even if I can get the runner flow up to 240 cfm, it’s the neck that needs to be up around 600 cfm.

So yesterday I have tried to measure the neck of the first manifold I ported to compare to a stock one, and its not that easy. My best guess is that I have only taken just a bit over 1mm from off all the walls so there is scope to go more but any improvement is difficult to prove. So I guess the goal is to get a ported neck and a bored out throttle body to be up around the 600 cfm @ -28”H2O and if I can’t then the TIG welder needs to come out for the JHP neck.

I also measured the runners of that first manifold I acid ported and in the section I can access (about 4” down into the port) they are all around the 44.0 to 44.3mm. So a bit more than what I thought but that is a bit over a 12% increase in runner cross section area.

[Gareth]

Just remembered I have this, came from the back of a wrecked car a long time ago, it's all pretty poor quality work but interesting all the same.

I wonder if the throttle body size increase is required at all...