MGB 80 MGB carb conversion to twin SU's

[karls59tr]

Hello MG afficianadoes. I visiting from the Triumph forum so B's are not specialty. My brother owns an MGB that has all the pollution control devices on it and I read somewhere that this totally robs the car of the HP it originally had in earlier years. How much trouble would it be to convert the car to a dual carb setup to regain some of the lost power? What would a used manifold and carb setup cost?(I dont mind rebuilding the carbs with a kit).Linkage mods? Ignition and timing issues? Anybody been there and done that? Karl TR3A

 

[tony barnhill]

Can't use HS4's because of the power brake assembly - have to use HIF-4's.

 

[rick_ingram]

Can't use HS4's because of the power brake assembly - have to use HIF-4's.

I have HS4's on my 1978 MGB.

I did have to use a pancake style air filter, though.

UPDATE: Rick informed me (Basil) that he has since upgraded to the K&N Filters discussed herein.

 

[tony barnhill]

Yep, & those pancakes keep your carbs from operating at their optimum thus not allowing your car to fully use its power, IMO only!

& you have to have almost brand new engine mounts!

 

[karls59tr]

Why would the pancake air filters prevent carbs from operating at there optimum?

 

[rick_ingram]

Why would the pancake air filters prevent carbs from operating at there optimum?

There can be a restriction of airflow. These filters are obviously not the best choice....but the original filter assembly will not fit...and it would be hard to use a K&N filter without some serious adaptation to the rear filter.

But....it is indeed possible to use HS4s on a boosted MGB.....and it runs a (edited by rick because of undocumented censoring)a lot better than with the ZS (or for that matter, the single HIF6 that I had on it for about 6 years).

 

[AlanT]

I use HIF-4's for converting power brake MGB's to dual SU's. I cut one of the carb spacers in half for more clearance. K&N did make a tapered air filter for the rear carb or a Unipart # GFE1063 Dolomite filter can be used.

Alan T

 

[JM1NA]

I have twin HS4's on my '80 with a set of moon type filters. Works fine for me and I didn't replace the motor mounts. I just put a slight dent into the filter mesh to clear the booster.
I'm now replacing the rear carb with a carb ported HS4 so that I can run carb port vacuum to my new distributor as opposed to the old manifold vacuum port advance. Should give me a little more throttle response.
I've been very happy with the conversion and along with lowering the car it's quite fun to drive.

 

[ICESWH]

I also have a set of HS4's on my '80 B. I have the K&N cone filters ass'bly's. It's works fine. No problems.

 

[rick_ingram]

I also have a set of HS4's on my '80 B. I have the K&N cone filters ass'bly's. It's works fine. No problems.

Got a picture you can post?

 

[terriphill]

Spent today removing the old carbs, manifold and exhaust off of the 80 B. I have been following this post with interest because we have a set of HIF-4s we are planning to install. We want to add a header and entire new exhaust. Any suggestions?

 

[fogliner]

Hi terriphill and everyone.
It would probably be easier to just put a stock intake and exhaust manifold pair from an earlier MGB on it then you can use stock parts right back to the rear of the car and just put them together yourself on the weekend. The earlier exhaust manifolds are basically a header anyway and you won't haave to worry about spacing the header to the same thickness as the intake manifold to bolt it together.
Careful of the thickness of the mounting ears on the manifolds to make sure they are close,a matched pair is best. Good luck from North west BC.

 

[Scott_Hower]

Hi terriphill and everyone.
It would probably be easier to just put a stock intake and exhaust manifold pair from an earlier MGB on it then you can use stock parts right back to the rear of the car and just put them together yourself on the weekend. The earlier exhaust manifolds are basically a header anyway and you won't haave to worry about spacing the header to the same thickness as the intake manifold to bolt it together.
Careful of the thickness of the mounting ears on the manifolds to make sure they are close,a matched pair is best. Good luck from North west BC.

There are two different CBB exh mainfolds. Just make sure you get the intake to match and you'll be fine.

 

[JM1NA]

Hey fogliner,
My wife and family are from Terrace. She still has a brother who lives there. Jon Hughes. They also have a house out a Calem lake(sp?) Know of them?

In regards to the exhaust system. I went with an original manifold and a bolt up mild steel exhaust system. They can be a real challenge to bolt up, but I got lucky and everything lined up to the hangers with a little help from a floor jack. I think the mild steel factory exhausts sound the best. Not tinny at all like the stainless versions. But if the car is exposed to lot's of water then I can understand the use of SS setup.
The original manifold is as good as a header and sometimes better when compared to the cheapy headers. I wouldn't bother with using a bigger exhaust setup unless you were running a hotter cam and uprated head.

cheers

Ron

 

[fogliner]

Hi Ron..Can't say as i do but i am terrible putting faces to names so its possible i might recognize them.I have been to kalum lake a few times over the years though.
Sounds like you did great on the exhaust.My exhaust does seem to sound tinny now that you mention it...it has stock exhaust (not SS)also but i was thinking a loose baffle in the muffler or something.
I have been picking up all kinds of hints and tricks off of youtube and "university motors" video's that John Twist does, its great to see someone doing that, if you haven't seen them its worth it. Great Driving

mark

 

[Tom Mueller]

How much is the two pipe exhaust manifold, intake manifold and carbs from a 1973 MGB worth. Have the complete engine, clutch, transmission.

 

[JPSmit]

How much is the two pipe exhaust manifold, intake manifold and carbs from a 1973 MGB worth. Have the complete engine, clutch, transmission.

Hey Tom, not sure you will get a helpful answer - you're picking up a thread that is 13 years old.