Standard 850 Exhaust with twin HS2..

[gs.davies]

Thinking about fitting my 295 to the 850 along with the twin HS2 and 997 manifold I have.

What options are there for retaining the standard exhaust? Is it possible to cut the inlet off the standard one piece manifold and use that? Or is there a better solution?

[gs.davies]

Ah yeah. But I like the 850 sound and the way it clears the solenoid...

[iain1967s]

yes, you can carefully slice the cast iron manifold in half, to separate the inlet from the exhaust.
[ I did it the other way around, to use the cast inlet manifold with an LCB some years ago ]

Another option would be to use something like an MG1100 exhaust manifold, and join that to the 850 downpipe.
There are a few on eBay:
https://www.ebay.co.uk/itm/143942658210
https://www.ebay.co.uk/itm/143942652918
https://www.ebay.co.uk/itm/133659040684
https://www.ebay.co.uk/itm/143941604364
https://www.ebay.co.uk/itm/203256694056

But as noted, the 850 'pea shooter' exhaust will be restrictive to the flow unless you change the whole system for a larger bore.

[gs.davies]

yes, you can carefully slice the cast iron manifold in half, to separate the inlet from the exhaust.
[ I did it the other way around, to use the cast inlet manifold with an LCB some years ago ]

Another option would be to use something like an MG1100 exhaust manifold, and join that to the 850 downpipe.
There are a few on eBay:
https://www.ebay.co.uk/itm/143942658210
https://www.ebay.co.uk/itm/143942652918
https://www.ebay.co.uk/itm/133659040684
https://www.ebay.co.uk/itm/143941604364
https://www.ebay.co.uk/itm/203256694056

But as noted, the 850 'pea shooter' exhaust will be restrictive to the flow unless you change the whole system for a larger bore.

Ah, forgot, I have one of those knocking about. How do I join it to a standard exhaust though?

[gs.davies]

I did once read that the standard exhaust was good for 50hp or so before it became a problem

[gs.davies]

The Aussie sports 850 and the inno 850 had a 295 head. Should be ok. Wonder what exhausts those cars had?

[gs.davies]

I’ve wondered what they did about the CR too. My guess is that Inno used the Automatic piston (which I presume was taller as the Autos had a higher CR at 8.91:1). The Aussie Sport 850, probably left it as was as these were dealer conversions.

I’m sure someone with actual knowledge of this will eb along to fill the gaps in my knowledge though.

[imack]

My dad used an Austin A30/35 exhaust manifold with twin hs2's and a Downton head on his 850 traveller in the late 60's

[Minigman]

I pushed 48bhp through my single box 850 exhaust with the 1132cc engine. I was running a single HS2 also. Neil Slark did say it was costing me a lot of power by retaining it.

[winabbey]

The Aussie sports 850 and the inno 850 had a 295 head. Should be ok. Wonder what exhausts those cars had?

Pretty sure the Aussie Sports 850 retained the standard head. The only mechanical change was the twin carbies, manifold and exhaust exiting in the middle rather than side.

[greyghost]

The Aussie sports 850 and the inno 850 had a 295 head. Should be ok. Wonder what exhausts those cars had?

Pretty sure the Aussie Sports 850 retained the standard head. The only mechanical change was the twin carbies, manifold and exhaust exiting in the middle rather than side.

im sure they had a standard head too, or they would have been way faster than they are
the whole conversion was essentially a bolt on kit, with a few optional stripes


OP, you'll find the exhaust really restricts the car, and worsens the fuel economy too (simply cause you drive everywhere with your foot to the boards)

[gs.davies]

The Aussie sports 850 and the inno 850 had a 295 head. Should be ok. Wonder what exhausts those cars had?

Pretty sure the Aussie Sports 850 retained the standard head. The only mechanical change was the twin carbies, manifold and exhaust exiting in the middle rather than side.

im sure they had a standard head too, or they would have been way faster than they are
the whole conversion was essentially a bolt on kit, with a few optional stripes


OP, you'll find the exhaust really restricts the car, and worsens the fuel economy too (simply cause you drive everywhere with your foot to the boards)

So what exhaust manifold did the sports 850 use?

[iain1967s]

So what exhaust manifold did the sports 850 use?

From http://mk1-forum.net/viewtopic.php?f=5&t=12630

The original manifold was cut to leave the just the exhaust part, a free flow system was then connected to it.

[CooperTune]

In high school I worked two part time jobs to build my 850. I had cam bearings 2 and 3 line bored and installed. Bored block .060 with Power Max pistons. Cooper S camshaft, 295 head with std size valves and surfaced .125. Cooper S exhaust manifold larger pipe custom bent to clear push button starter to Cherry Bomb and out center. Cooper S intake and HS2s and S dizzy. I feel a standard exhaust would have choked the very nice little engine. Steve (CTR)