The V8 Owners Forum -

Those headers look pretty good to me.

You'll never get a properly tuned exhaust with a dual-plane crank V8 unless you bring the outer two from one bank and the inner two of the opposite bank into the same collector.

Chris.

That is what they do on the GT40 but there are very few other cars that can do this as the "cross over" section would be in the bulkhead of a normal front engined car.

It makes the exhaust note totally different.

AND the experts say when you do this the collectors should go in a circular fashion in the 4 into 1 but to help create swirl through the secondaries. (GT40 ran clockwise in 1 and anticlockwise in the other)
I.e on left bank primary top left , top right, bottom right, bottom left and then on right bank primaries top left, bottom left, bottom right, top right.

See for a discussion of this stuff

http://www.gt40s.com/forum/gt40-tech-en ... ring+order


Ian

It could be fitted to a regular car like mine for example if you were to bring the manifolds forwards then down and under like a tvr however that would take up alot of space.

I once offered up some tvr manifolds to my car and where they join into one came out infront of my radiator! Very long!

Hi Gavin
"I once offered up some tvr manifolds to my car and where they join into one came out infront of my radiator! Very long!"

Chrome them and stick a turbo on the end of each it would certainly be a talking point!!!
Mike

Its funny you should say that as that was the plan until i found out they had no chance of fitting!

Just cut a round hole in the radiator. that would work.

Formula 1 still hasnt got back to me yet....

Ian Anderson wrote:It makes the exhaust note totally different.

Wouldn't it make the engine sound like a 4cylinder??

Hi
Sounds like two 4cylinder engines perfectly syncronised (strangly).
As these exhausts are usually used on quilt highly tuned V8's (not worth the effort for a stock engine) and they are generally used with individual carbs or throttle bodies they sound lovely they are often used with a cam with quite narrow LSA as they are meant to bring the engine "on cam" sooner than the normal set up with a ballance pipe ,makes them sound even better at idle....
There are some US manufacturers that do them for front engine rear drive ford 302s and chevys (big and small block) a set of them would be really good on the pub tuning stakes
Mike

I'm definitely keen to try my hand at making my own exhausts. Got the cast manifolds at the moment (yuck) but trying to make 4 into 1 extractors at the right length will definitely be tough especially trying to keep them at the same lenght!

Is there a great deal of different between full length extractors when compared with something like a shorty manifold? Cause the construction would be far simpler!

There was an article on making your own headers in Carcraft a couple of years ago, explaine how to measure up and get them to fit, might be worth a look on Carcraft.com.
You can also buy kits of bits to build headers for specific engine/car combos from the US. I would think that if you can get access to a proper tube bender to make non squashed bends it would be lots cheeper.
Mike

How can you do a 180degree crossover set of pipes on a front engined car?

Primaries would be really long (goes against calculations for power) and the cross overs need to be under the car - not saying it can't be done but mid engine sure lends itself more to this treatment.

Blokes in the 40 club have looked at buying bends etc and making their own sets and then welding them up - ended up the bits to purchase for a 1 off would cost almost the same as haveing someone do the work with bends etc. (£800 for the bits (no silencers) and £1000 for the whole system from Tonly Law in Mild steel)

These things can EAT money

Ian

yes Ian they do make them (I will have another go at finding the site) they generally involve some horible routing around both ends of the sump and over the bell housing (and must make the bulkhead hot) but they make them, and yes they look a bit long.
The mid engined set up does lend itself very well to a cross over set up. Even here it is tricky to put it all in and get the lengths right.
Mike

I am toying with the idea of a track day only system on my MGB, of just having 8 primaries poking up through the bonnet. This is more for a laugh and photo shoot than a serious full time system. But there may be some use in this type of system if I can play with the primary they then. The primaries would end up at about 16 inches. But I suppose by fitting a slip coupling to each pipe, I could play with the tune of the engine.
An "expert" told me that doing this would burn my exhaust valves out in no time. But all the pro cars have open primaries. I want to do it just for the fun factor, but I dont want to damage my new engine.

Why would you think the exhaust valves would burn?

Think on a small aeroplane they are open pipes (normally very short) and not normally a problem

You may beed to remap fuelling / adjust carb as chances are you would end up at higher revs and could lean out - that would cause heat / burnt parts

IAn

Thats why I said "Expert" Ian.
I cant see any real engine problems from open primaries.
It will be an interesting project, and fun to hopefully see some flames.
I was contemplating slipping some copper pins through the pipes to turn the flames green for night racing.