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Standard 850 Exhaust with twin HS2..
Posted: Fri Feb 12, 2021 5:39 pm
by 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?
Re: Standard 850 Exhaust with twin HS2..
Posted: Fri Feb 12, 2021 7:32 pm
by gs.davies
Ah yeah. But I like the 850 sound and the way it clears the solenoid...
Re: Standard 850 Exhaust with twin HS2..
Posted: Fri Feb 12, 2021 8:00 pm
by 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.
Re: Standard 850 Exhaust with twin HS2..
Posted: Fri Feb 12, 2021 8:18 pm
by gs.davies
Ah, forgot, I have one of those knocking about. How do I join it to a standard exhaust though?
Re: Standard 850 Exhaust with twin HS2..
Posted: Fri Feb 12, 2021 8:21 pm
by gs.davies
I did once read that the standard exhaust was good for 50hp or so before it became a problem
Re: Standard 850 Exhaust with twin HS2..
Posted: Fri Feb 12, 2021 11:39 pm
by gs.davies
The Aussie sports 850 and the inno 850 had a 295 head. Should be ok. Wonder what exhausts those cars had?
Re: Standard 850 Exhaust with twin HS2..
Posted: Sat Feb 13, 2021 11:35 am
by 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.
Re: Standard 850 Exhaust with twin HS2..
Posted: Sat Feb 13, 2021 12:29 pm
by 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
Re: Standard 850 Exhaust with twin HS2..
Posted: Sat Feb 13, 2021 1:12 pm
by 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.
Re: Standard 850 Exhaust with twin HS2..
Posted: Sun Feb 14, 2021 2:33 am
by winabbey
gs.davies wrote: ↑Fri Feb 12, 2021 11:39 pm
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.
Re: Standard 850 Exhaust with twin HS2..
Posted: Sun Feb 14, 2021 5:35 am
by greyghost
winabbey wrote: ↑Sun Feb 14, 2021 2:33 am
gs.davies wrote: ↑Fri Feb 12, 2021 11:39 pm
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)
Re: Standard 850 Exhaust with twin HS2..
Posted: Sun Feb 14, 2021 2:34 pm
by gs.davies
greyghost wrote: ↑Sun Feb 14, 2021 5:35 am
winabbey wrote: ↑Sun Feb 14, 2021 2:33 am
gs.davies wrote: ↑Fri Feb 12, 2021 11:39 pm
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?
Re: Standard 850 Exhaust with twin HS2..
Posted: Sun Feb 14, 2021 2:53 pm
by iain1967s
gs.davies wrote: ↑Sun Feb 14, 2021 2:34 pmSo 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.
Re: Standard 850 Exhaust with twin HS2..
Posted: Sun Feb 14, 2021 3:44 pm
by 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)