1098 Manifold Swap

[Bigrob]

Morning all.

I'm going to be taking the engine out in the coming weeks to start the refurb, along side welding the body, all between refurbishing my Bongo!


I've got the intention of fitting a larger carb and inlet manifold.

Which leaves the exhaust manifold.

I don't want to buy the maniflow manifold as it'll be a total waste on my 1098.

I do have an old 12g787 (mini) manifold kicking around, which I can remove the inlet side and open out the exhaust side. I'm trying to upload a photo but it wont work again.

So here's a link to the same type:
https://www.google.com/search?q=12g787& ... yQnnW-02LM


Would this be an adequate change?

[philthehill]

Why split the manifold?
Vizard is complementary about the manifold in his book Tuning The A Series in that it has good flow in and out.
I would just bolt it on with the larger carb. No need to make yourself extra work.

[Bigrob]

Why split the manifold?
Vizard is complementary about the manifold in his book Tuning The A Series in that it has good flow in and out.
I would just bolt it on with the larger carb. No need to make yourself extra work.

I intend to purchase the H4 you posted yesterday, which wouldn't fit the mini manifold.

Or would I be better to use the mini manifold as is and buy a hs4 instead?

[ampwhu]

i use a 12G3538 manifold with a hif38 carb on my 1098. I had a larger bore exhaust system made to the same as a standard system. works very well.

[philthehill]

Bigrob
Personally I would use the manifold you have and purchase a HS4. Change the HS4 wax stat jet to a normal (red) jet.
Phil

[Bigrob]

i use a 12G3538 manifold with a hif38 carb on my 1098. I had a larger bore exhaust system made to the same as a standard system. works very well.

Trouble is getting hold of one!

Bigrob
Personally I would use the manifold you have and purchase a HS4. Change the HS4 wax stat jet to a normal (red) jet.
Phil

Cheaper too! I will eventually be changing the head for a 940, as and when I can get one which is silly money! So the HS4 will cope with that too

[liammonty]

I think I've got a 12G3538 (exhaust section) kicking around - I'll look it out if you're after one.

HIF 38s are easy to come by - there was one on here for sale a week or 2 ago for a pretty low price.

i use a 12G3538 manifold with a hif38 carb on my 1098. I had a larger bore exhaust system made to the same as a standard system. works very well.

Trouble is getting hold of one!

Bigrob
Personally I would use the manifold you have and purchase a HS4. Change the HS4 wax stat jet to a normal (red) jet.
Phil

Cheaper too! I will eventually be changing the head for a 940, as and when I can get one which is silly money! So the HS4 will cope with that too

[Bigrob]

I think I've got a 12G3538 (exhaust section) kicking around - I'll look it out if you're after one.

HIF 38s are easy to come by - there was one on here for sale a week or 2 ago for a pretty low price.

If you would Liam that would be brilliant thank you. What do you want for it?


I've settled on a hif38 with decent inlet manifold. One came up at a very good price locally so I grabbed it

[Sleeper]

Bigrob
Personally I would use the manifold you have and purchase a HS4. Change the HS4 wax stat jet to a normal (red) jet.
Phil

Phil
Being a complete novice , relatively , could you expand a little re wax jet / red jet?

Thanks
John

[Bigrob]

From the little i know, waxstat for economy, waxjet for stable performance.


I'm probably way off the mark, and have no idea how each is achieved

[liammonty]

I think I've got a 12G3538 (exhaust section) kicking around - I'll look it out if you're after one.

HIF 38s are easy to come by - there was one on here for sale a week or 2 ago for a pretty low price.

If you would Liam that would be brilliant thank you. What do you want for it?


I've settled on a hif38 with decent inlet manifold. One came up at a very good price locally so I grabbed it

Hi Rob,
Thanks ve been out and had a look for the manifold, but I think that lockdown might be driving me mad as I can’t find it. I’ve got a sneaking suspicion I may have passed it on to someone already and forgotten... I’m really sorry - if it transpires it is in the garage I’ll let you know!

[Bigrob]

Hi Rob,
Thanks ve been out and had a look for the manifold, but I think that lockdown might be driving me mad as I can’t find it. I’ve got a sneaking suspicion I may have passed it on to someone already and forgotten... I’m really sorry - if it transpires it is in the garage I’ll let you know!

No worries at all, thank you none the less for looking!

[ampwhu]

All is not lost I think. You can use a 12G787 manifold (on ebay at the moment) and secure the Hif38 carb with an easily made adaptor plate or just the 2 bolts. I'm sure I've seen it done.

[Bigrob]

All is not lost I think. You can use a 12G787 manifold (on ebay at the moment) and secure the Hif38 carb with an easily made adaptor plate or just the 2 bolts. I'm sure I've seen it done.

Yeah I'm pretty sure you can mount it with the diagonals.

The carb I've bought has a good manifold attached to it. So I may still chop up the 12g787, I'll see how I get on