4 branch exhaust manifold

[Gaz1300SR]

Just wondering if a 4 branch aftermarket exhaust manifold from a 1.2 will be the same as a 1.3 Sr? Anyone point in fitting it or will it be a different bore size?

Thanks

[Gaz1300SR]

Any ideas?

[Gaz1300SR]

Any ideas?

[swedge]

It will fit but you might need a different centre section as the flanges might be different

[mowgli]

it will fit, but a 4-1 is only useful if you have raised the rev range with a big cam & head job etc.....

[Gaz1300SR]

I have a cam kit to go on and, when I can get hold of a set for sensible money, a set of webers. Would it be worry getting the head ported and polished at the same time? No idea where yours these things mind you.

[swedge]

port and polish is always a good thing if you can afford it

[mowgli]

port polishing is a bit 1970's now.... they realised that if the port wall is slightly rough, the turbulence helps keep the fuel mixed, apparently, if it is polished, the air can travel too fast & the fuel gets left behind..
so i'm led to believe.... waits for mk999;)

[swedge]

ive done a bit of reading about p&p

the inlet has to be a bit rough so the air and fuel mix better but it seems the exhaust ports are better smooth with a small step down onto the manifold

[Gaz1300SR]

Interesting stuff, thanks for the info.

[Gaz1300SR]

port polishing is a bit 1970's now.... they realised that if the port wall is slightly rough, the turbulence helps keep the fuel mixed, apparently, if it is polished, the air can travel too fast & the fuel gets left behind..
so i'm led to believe.... waits for mk999;)

Owe you +1, apparently I must spread some around first!

[C612DNM]

Unless your cam kit is a solid lifter cam kit, and the 4:1 is a BTB one, put the one you have in the skip. They only really show benefit above 7000rpm - which is solid lifter territory. Then you will kiss goodbye some some low to mid-range power. Only the BTB manifold (in my many hours of dyno time) shows literally no loss compared to factory (port matched) at low/medium revs (3-6000) and a small (4-6) HP increase over 7000 compared to a port matched iron one.

Get the standard 1.3 cast iron manifold, a set of genuine Vauxhall downpipes, and port match it to the gasket - it'll be about 8hp better than the scrap that comes out of some big name 4-branch manifold manufacturers (often mentioned on here) when used with twin 40's in a race setup.

The only thing a 4:1 does do is make it quieter than the 4:2:1 setup which are inherently raspy.

Been there. done that. Got the silverware to prove it.

[Novasport]

What about the E16SE GTE manifold? It looks a better designed manifold but would it mate to the 13SB downpipes and/or centre section?

[mowgli]

What about the E16SE GTE manifold? It looks a better designed manifold but would it mate to the 13SB downpipes and/or centre section?
they are a different design. the 13sb type is very good as std

[Gaz1300SR]

After what people have said I think I am sticking with the standard manifold, at least for now.