Zetec Powered MGB Build Thread

[mikebontoft]

Again, excellent work guys. These are my favorite kind of threads

It's pretty cool that you're working on something together. I've tried to get my dad to work on cars together with me but I know he would just do it to make me happy.

[79mgb]

Tomorrow my dad and I are going to a local junkyard to hopefully find a decent engine. In the meantime, I hope you guys don't mind me posting some photos I took earlier tonight. I was able to take much better photos of the cylinder head using ambient lighting and a tripod. I can't wait to get this engine built and get the zx9r carbs on there.

[mikebontoft]

wow. cool photography too

[sleepyboy]

Very nice, I hope your not planning on using that factory exhaust manifold are you? It'd be best that you get a long tube and chop it up to fit the RWD chassis or make your own header. That stock one flows like poo.

[79mgb]

Originally Posted by sleepyboy

Very nice, I hope your not planning on using that factory exhaust manifold are you? It'd be best that you get a long tube and chop it up to fit the RWD chassis or make your own header. That stock one flows like poo.

I'm not 100% sure what the plan is for the header/exhaust. I'll probably use the stock manifold to connect to the existing exhaust when we initially fit the engine in the MGB. The OD of the stock exhaust tubing on the MGB is a whopping 1.75". The build would still benefit from a better exhaust system.

We actually found that we could probably adapt a 1.8L Miata header if we really wanted to to go with a long tube header. (This is a photo of a cheap-o OBX header).

The spacing between ports should almost be the same. I don't think it would outflow the stock exhaust.

I've also considered installing an aftermarket shorty header and pairing it with a better exhaust.


Home made headers are also something we considered but we'll just have to wait until we get to that point of the install. Anyways, I hope this made sense. I've been pretty sleep deprived lately.

[Mustangsix]

Originally Posted by sleepyboy

Very nice, I hope your not planning on using that factory exhaust manifold are you? It'd be best that you get a long tube and chop it up to fit the RWD chassis or make your own header. That stock one flows like poo.

Within the performance and rpm envelope we're working in, there's probably not 5 hp difference between a stock header and an aftermarket shorty. Eventually we'll probably make our own or make an adapter for the 1.8 Miata header. The bigger gains will probably come from selecting good mufflers and pipes.

There are also some British RWD headers available but shipping is really a deal killer. The design we'll follow is tri-y with 1-4 and 2-3 each paired, then those will feed another merge under the car. Similar to the obx above as well as the SVT headers.

But the stock ones will be easy to work with for now and should provide good enough performance.

[sleepyboy]

Go long tube if you can, it's where most of the gains come from in a zetec. Shorties only give low end power but the long tubes give all the low end gains that a shorty does but also gives top end power which the zetec needs. You'll be really choking that motor down with the stock or shorty header when you throw that head and cams on there. Not that it'll be a turd though in that light MG lol

[whynotthinkwhynot]

I'd think you'd have to go custom on the exhaust manifold, but good luck!

[Mustangsix]

Port spacing on the 1.8 miata is only 1mm different than the zetec. Looking at exhaust, but the MG is tight.

[my_beautious_ZX3]

nice!!!! you certainly win the prize for "Coolest dining room table centerpiece".

Originally Posted by sleepyboy

I hope your not planning on using that factory exhaust manifold are you?

that's what I was thinking too. You're trading a 1x67mm throttle body for 4x40mm (?) carbs; I would think you'd want higher throughput on the other side of the head as well.