Race Engine Forum UK

Hello All,

I am looking for a drawing to get Exhaust Manifold Flange to head plates lazer cut.

Can anyone help or must I start drawing it out?

Kind Regards,

Ernst

Sorry I do not have a dwg of that,

G

I've got something that was floating around on the web. Only has 3 dimensions or so but could easily be imported into your cad software and the rest would be derived from there. Saves some time in measuring up everything yourself.
Not much, but it's a start. I'll send you a PM.

regards
Tom

This is my drawing!

Any comment Please!

Ciao,

Ernst

I do not want to check the data but I will remark on this:

The primary pipe ID should always be bigger than the port diameter. This gives a proven anti-reversionary effect against ex gas flowing back to the cylinder. Yes I have proven fact on this from Jaguar 6cyl simulation.

Irrespective of port size the controlling section for flow from the cylinder is the ex valve throat, so 36mm ex valve gives a controllling section of about 33mm and 40mm ex valve about 37mm. Ideally the port cross-sectional area will be the same as the controlling section or fractionally bigger but NOT smaller.

As a reasonable rule-of-thumb the ex primary pipe ID should be 5mm bigger so 38mm - 42mm (respectively) is perfect though you could go bigger without losing power (so to speak, up to 8mm bigger than the controlling section. No point doing so except to say that much depends on available pipe size - which is not gauged by ID - but OD and wall (gauge) thickness. Which is very annoying but there we are.

Whether you have factored for this Ernst depends how the pipe is welded to the flange. Inside the flange or outside. As the port face is slanted and thus elliptical I would suggest outside in which case your hole size is about right. Be sure to check on this with the intended manufacturer/pipe supplier.

A primary pipe system designed for a 40mm TC Fiat ex valve will work equally well with a head with 36mm valves. NO need to have two different sizes if you are thinking of selling flanges.

Small primary pipes on atmo engines cause more problems than big ones.

If you want advice on pipework ask me here.

Sincerely,

G

hi Ernst

Haven't checked the sizes either (maybe later this week) but some remarks:
- the holes look to circular too me. 38 x 44 or 40 x 46 seems closer to it.
- any real reason why you have the straight upper edge between the middle two ports 1,5mm below the contour of your blank? Might be you need to clear something but I can't think of it.
- why do you have a different lower contour between ports 1,2 and 3,4? Might be you're following an existing flange or gasket shape that was influenced by eg. casting requirements.
- same for the asymmetrical shape between ports 2 and 3.

In general: looking nice. I'd make life as easy as possible for myself and avoid complex and/or unneeded shapes even if you're going to have it laser-cut. Save yourself time measuring and marking up. Personally I'd prefer the pipes to be inside the flange and then welded, so your holes would be pipe OD and then some. Mind the angle between the port / pipe axis and the flange face.

Gegroet uit het oude Holland ;-)

regards
Tom

It has been a long time since I have posted on this thread!

Firstly to Guy, thank you for all your input and help. You make life so much easier for idiots like me.

I have spent a lot of time on other jobs and helping around on other projects.

I have been busy developing my own head and then got to learn a lot in regards to the angles of holes!! (smile)

I have redrawn the exhaust manifold plate and found a lot of mistakes. I also improved it through feedback and proper measurements.

Thank you Tom for your input and observations as well.

I have measured the angles of a few cylinder heads with different casting numbers.

The exhaust ports are sitting at an angle of 56 degrees at the flange area.

The flange plate will have the holes cut for the ports at this angle and at the right height to match up with the head.

We will be using 48mm OD pipe that has a 44mm ID.

The port width is 37mm and if measured without the angle is 37mm high. If the hole is measured across from top to bottom it is 42mm.

So we can say 42 x 37mm. The header pipes will go through the flange and will exit at a level angle perpendicular to the head surface