SU spacer on twin cam

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1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

SU spacer on twin cam

Post by 1970 cortina GT » Sun Jul 22, 2018 1:18 pm

I’m toying with the idea of removing the coolant spacer thingy between the head and the SU carbs on my twin cam. Looks like the bolt pattern will match by putting the carbs straight on the inlet manifold casting of the head. My concern is that I won’t have the ‘ soft mounting ‘ with the Thackeray washers, I would appreciate any thoughts. Thanks.Image
Life isn't complete until you have a pair of twin cams in the garage...

Sideways
Posts: 462
Joined: Mon Oct 03, 2011 12:58 pm
Location: Delta BC Canada

Re: SU spacer on twin cam

Post by Sideways » Mon Jul 23, 2018 11:22 am

1970 cortina GT wrote:I’m toying with the idea of removing the coolant spacer thingy between the head and the SU carbs on my twin cam. Looks like the bolt pattern will match by putting the carbs straight on the inlet manifold casting of the head. My concern is that I won’t have the ‘ soft mounting ‘ with the Thackeray washers, I would appreciate any thoughts. Thanks.Image
Correct, it won't have the soft mounting which it certainly needs with Webers but with SUs... I dunno?

Try it and see, I suppose.

s2europa
Posts: 142
Joined: Wed May 30, 2007 11:54 pm
Location: Seattle

Post by s2europa » Wed Jul 25, 2018 11:01 am

That spacer acts as a balance tube between the carbs. It has to do with unequal
firing that helps balance out the pulses. It won't run correctly without it. There is a European version that looks better and has a balance tube at the top so the fuel doesn't pool.

s2europa
Posts: 142
Joined: Wed May 30, 2007 11:54 pm
Location: Seattle

Post by s2europa » Wed Jul 25, 2018 11:09 am

Scroll down to the high balance manifold. This is a custom made one, but gives you the idea.

http://www.lotus-europa.com/forsale.html

1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Wed Jul 25, 2018 12:36 pm

Good information thanks. I don’t know if there is anything in the carbs I can change , just doesn’t seem to have much power when I compare it to my Weber twin cam in the MK2. Difficult to get a spec for the SU set up I guess.
Life isn't complete until you have a pair of twin cams in the garage...

1970 cortina GT
Posts: 343
Joined: Thu Dec 05, 2013 7:19 pm
Location: Saskatoon, Saskatchewan

Post by 1970 cortina GT » Tue Sep 04, 2018 8:57 pm

Just an update to anyone that is interested. I removed the section between the carbs and the head and the difference is black and white. The increase in power is quite something. I have adjusted the timing and now I have it running at about 14 BTDC. The idle is not as smooth but I can probably get some improvement by changing the needles. Somehow I also notice a difference in the revs, they are now lower than before, no idea how this works.......
I realize I don’t have the soft mounts anymore but if the carbs snap off next week it will have been worth having that extra power for a few days😉.Image
Life isn't complete until you have a pair of twin cams in the garage...

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