m20 exhaust manifold size?

Post Mon Jul 10, 2006 9:32 pm

What's the ideal pipe diameter for an M20 exhaust manifold?

Post Mon Jul 10, 2006 9:38 pm

I'd say go for whatever the port diameter is.

The S50B32 primaries are only 1 1/4" and that's not too much bigger than the port dia of the M20B25.

Think if you have a google search there are some calculators on the web which help in calculating primary and secondary lengths and also diameters

Post Mon Jul 10, 2006 9:40 pm

Cool thanks

Here's a few piccys of the progress at the exhaust place. Its just someone commented that the pipes were a bit small. These are just a mockup at the moment though:

Post Mon Jul 10, 2006 9:55 pm

Bloody hell, you having six massive long primaries at that diameter?

Would've thought a 6-2 with crossover or 6-2-1 would be more conventional.

Oh yeah, and the first person to mention 'back pressure' as being necessary without understanding why or what they're talking about gets to slap themself with a tin of wet tuna!

Post Mon Jul 10, 2006 10:00 pm

Yeah its more of style over substance exhaust... going for a classic 1930's race car look

The side pipe will come quite a bit further forward than pictured, pretty much to the scuttle panel.

Will see what its like, if worst comes to worst I could always get my hands on a 6 branch and do an under floor exhaust, but that wont look as nice.

Post Mon Jul 10, 2006 10:01 pm

How cool is that going to look with 6 primaries running down the side??
More importantly, how cool is it going to sound?

Really wish Id gone for the M20 powered Westfield idea I had now

Post Mon Jul 10, 2006 10:13 pm

Be very interested to hear it actually! Are the pipes going to meet at any point or just all do their own thing?

Post Mon Jul 10, 2006 10:16 pm

Turbo-Brown wrote:Be very interested to hear it actually! Are the pipes going to meet at any point or just all do their own thing?

They will merge into the bottom pipe, I'll drop by some of the E30Zone meets when it's finished

Post Fri Jul 14, 2006 9:30 pm

Well its been someone of a disappoint end to the day. We went down to look at the progress today to find nothing done at all. He showed up 5 very poor quality bent pipes that were the wrong length and still hasnt given us a price on the side pipe. The bends came from custom chrome and again its custom chrome that seem to be dragging their heels with the side pipe price.

The manifold plate - again was told the custom chrome one didnt fit so he got a local company to make one. This is "out for polishing" so we couldnt see it.

We're going back Wednesday - im going give him a call tomorrow and say if we dont see any progress we're pulling the plug and taking the car home again. The really is very far from what i would call good service!

Looks like i may end up getting a 6 branch / under floor exhaust the way its going at the moment!

Post Fri Jul 14, 2006 9:37 pm

Is it a company or someone private doing the exhaust?
Sounds like someone who doesnt really know what they are doing

JazzMan wrote: Looks like i may end up getting a 6 branch / under floor exhaust the way its going at the moment!

You cant do that - the side pipe with 6 primaries will look

Its got to be worth getting it done properly.

Post Fri Jul 14, 2006 9:40 pm

Its a custom chrome authorised dealer thats doing the work.

I may go under floor and then when the cars on the road i can drive to somewhere like blue flame and get it done properly.

Post Fri Jul 14, 2006 9:42 pm

Noooooooooooo.

An underfloor system will look so wrong, even as a temp measure!

Get it trailered to Blueflame or BTB and get it done right first time mate. think of the cost of a 6 branch and system, its cheaper to get it trailered

Post Fri Jul 14, 2006 9:43 pm

If i were to go under floor first then change later i would use the stock manifold and chop the middle part down a bit

I would go 6 branch and then change as you've said due to the cost.

Post Fri Jul 14, 2006 9:49 pm

At least you have the option of using the standard manifold as a temp measure. (I assume it will fit)

The 6 branch and side pipe is a must to finish the car off

Post Fri Jul 14, 2006 9:51 pm

yeah your right, going to give the guy and ultimatum tomorrow and see what happens!

Post Fri Jul 14, 2006 11:18 pm

Think if it were me I'd make sure I was there and in a position to take the car away immediately if I was gonna start giving ultimatums. Never know what they might get up to otherwise!

Post Fri Jul 14, 2006 11:27 pm

Also a good point, migh have to see how it goes this week then - what a mess ! If you can do yourself you buggered everytime!

No doubt I'll sort it in the end though!

Post Sat Jul 15, 2006 6:12 pm

Well we pulled the plug today. Going to pick the car up begnining of the week. We're going to under body it to start with using as many donor parts as possible, get through the SVA and then go see specialists elsewhere! Oh well you live and learn. Don't worry though - in the end it will be

Post Sun Jul 16, 2006 3:53 am

I have been fallowing your progress and i must say bravo very nice job. Im glad to see that you will be taking it to someone that will do it right.

Post Sun Jul 16, 2006 1:34 pm

bottlecapE30 wrote:I have been fallowing your progress and i must say bravo very nice job. Im glad to see that you will be taking it to someone that will do it right.

Thanks

Its been a lot of work so far, still have the body work to do & now the exhaust again before we can SVA it and get it on the road

not long now I hope! We'll about the side pipes, custom chrome head office has offered to do it there but once the car is on the road the options you have increase a lot as its just so much easier to move the car!