I've had my car (mk2 polo w/AEE) on bike carbs for about a month now, but had constant trouble with my pretty shoddy inlet manifold (lots of air leaks and not been able to get the carbs well mounted :( )

I wanted to start again, but this time have it done properly. So i enlisted to help of my dad and his CAD skillz to draw up the flange plate, based on the original plastic inlet manifold for the AEE.

here it is before the dims were added:

I wanted to drop this into somewhere for CNC'ing but nowhere was able to get it done for my by friday just gone, so i figured that i may as well have a go myself at making it

I went to a friend at an engineering shop and picked up a bit of stock steel, 9mm thick by the approximate dimensions i needed. Gave him a £5 for it for his trouble.

I already had plenty of mild steel tube for the job. It actually happens to be roll cage tubing but its 34mm o/d (perfect for the mounting rubbers i've got) and 30mm I/D which is the exact size of the inlet ports on the head

So with the help of my dad, and with the CAD drawing in hand, we set about knocking up a manifold.

I spent a few hours transposing all the dimensions onto the stock...

I then went onto to making the runners. I calculated the angle they needed to be at in order to mate up with carbs from the ports on the head. It was 10 degrees over 70mm. I wanted them to meet the carbs straight on, which meant putting a dog leg into them. Wasn't too much trouble after i worked out the trig. Needed a tiny bit of tweaking but end result was this

they are on a transfer of the old inlet manifold, as a rough guide. We got them in the lathe and cleaned up the ousides, and put a chamfer (sp?) on the ends that marry up to the carbs to elimate any hard edges. I also get the dremel out and cleaned out the insides of them, not fully polished, but a lot cleaner than they were.

With those done i put them to one side and carried on with the flange plate.

I started by drilling out all the mounting holes. The holes in the factory manifold were 9mm but we drilled these out to 9.1mm to allow for any tolerances in our measuring equipment and tools.

here it is offered up to the old manifold, not too bad

the three groups of three holes are along the line where we needed to cut out the excess, it meant i just had to cut up to them, and then file out the rest.

Unfortunately i'm missing a few photo's here, but the next thing was to cut the grooves for the o-rings. I wanted to go with o-rings like the factory manifold rather than cutting a custom gasket as i've never been happy with them.

For these grooves, and then subsequently, the holes for the runners, we used a fly cutter on the mill. Again, i'm a bit gutted i didn't take any pics :(

Here it is with all the holes drilled and with the runners sat in place...

after this, the joins in the two outer runners were gas'd up and then repolished. and then i started removing the excess from the flange plate to allow for spark plug access.

I had a mate round for a new sill on his mini, and while he was here i figured i may as well get him to muck in!

He's griding down the rough edges after the first few cuts.

After about an hour, we were left with this...

it still needed some bits grinding down, but by this point i was knackered so left it there for that night

All the components of the manifold... inc the o-rings and mounting rubbers...

and the back side of the flange plate

and the top... w/hand

Next job was fitting the runners into the plate, this was pretty time consuming as i needed to get the angles just right before they were attached.

in order to get them just right, i fitted the carbs. This was a nightmare as the runners were moving all over the place and trying to get all 4 to line up at once was v.difficult

And voila!

99% done The runners were brazed onto the flange since it requires less heat and would be less likely to warp it.

I then had it apart to paint, gave it an undercoat of VHT and then a top coat of gloss black.

and finally got it all assembled back on the car 8)

All in all it came in at £9 (5 for the metal, and £1ea for the red mounting rubbers from GSF). It took around 25 hours to complete.

It is running noticably better than it ever has done. and definately feels quicker than it ever has before :D fun fun fun hehehehe

Edited 18 May, 200818 yr by Joel

amazing stuff that :)

Nice one! you going to get it on the rollers and find out what its ptting out?

mmmm sexual minimalist bay and a great conversion. maybe u coudl sell plans for these :p

great stuff!

cheers guys.

yeah i'll get it on the rollers asap. probably be start of next month now after i've got some more money

good work there mate. nice to see abit of custom fab'ing going on.

am I right in thinking you cut a circular groove and then placed the 'branches' in the groove before welding them up. If so wouldn't this have created a step?

good work there mate. nice to see abit of custom fab'ing going on.

am I right in thinking you cut a circular groove and then placed the 'branches' in the groove before welding them up. If so wouldn't this have created a step?

There for the manifold gaskets which are rubber o-rings, which is how the original manifold has them, joel you should sell/make some base plates up

Superb work mate .

Fabrication work can be rather testing . Did a course on it myself and man it can annoy you but once its all done and sorted your so impressed withthe work you have done .

Looks like a top job though youhave done

You must have alot of tooling to do such a good job thats my only problem .

Tools arnt cheap at any sence of the imaginaton .

Respect to you mate respect .

I see now. thought he welded it up the other way. Sure there will be alot of people who will buy a DIY manifold kit

thats such a good job you have made !!!

thanks guys 8)

sorry, i didn't make it very clear, as has been said, the grooves are on the mating surface so i could fit the o-rings rather than making a custom gasket. The runners slide into the holes and were then welded on the face.

awesome work there, inspirational. Might have a crack at making one myself for a GT head...

thanks. if you've got the facilities and the patience then go for it!

i do need to say a huge thanks to my dad too. Basically wouldn't have been able to do this without his help! He used to teach welding and engineering and such at the plymouth polytechnic, and has a lot of knowledge and skill, i really appreciated him helping me along with this

oh, and he's the one who has bought all the tools through they years

Awesome work

Given me a few things to think about for when i make mine :-)

i want bike carbs so bad

what power gains have you got since fittin them??

Looks sooo good and must be so worth while!

Good work man

good work lad, you guys should start up a bogg bros rival daaaan saaarf

smart work there fella, I'm sure some people on here would pay for them

and the right tools do help alot, sounds like you got a pretty decent setup there

thanks peeps

I'd love to start making these to sell, but its really labour intensive. Its when you make one yourself, that you appreciate why you pay what you pay for a Bogg Bros manifold (I've got a manifold from them for my mini), and they look sexual in aluminium unfortunately neither me or my dad has any experience in working with aluminium so that kinda rules that out.

The gains? well i never drove it with the standard AEE injection/inlet, but its an absolute hoot on bike carbs. I'm really keen to get it rolling roaded to see what actual hp gains i have considering its just a stock AEE with the carbs and a 4 branch, the weight of the car obviously helps a lot (it was 700kgs last time i weighed it) Not sure what to compare it too really, its like nothing i've driven before for the fun factor, and sounds better than anythin else i've driven too :p hehe.

Driving it to college this morning though (thats where i am now... ) in the rain on greasy roads in rush hour was a 'challenge' to say the least. Pulling away with involuntary wheelspin everytime kinda gets a bit embarassing when you're just moving a few feet in a traffic jam. had to resort to second gear pull aways

Going to have to take a look around this beast at some point

Were the Carbs dificult to set up ?

I hope to be at some shows this year

They weren't that difficult to set up. they needed a bit of tinkering with the mixture screws and a jet needed blocking. I've got the standard jets in them (as they were on the bike), the mains are 1.5mm, i may need to go bigger, but it runs well now. only a rolling road session with a wideband lambda would tell me if i needed bigger mains :)

Very nice work dude!

awesome work dude, really wanna do my gt now.