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SU spacer on twin cam
Posted: Sun Jul 22, 2018 1:18 pm
by 1970 cortina GT
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.
Re: SU spacer on twin cam
Posted: Mon Jul 23, 2018 11:22 am
by Sideways
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.
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.
Posted: Wed Jul 25, 2018 11:01 am
by s2europa
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.
Posted: Wed Jul 25, 2018 11:09 am
by s2europa
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
Posted: Wed Jul 25, 2018 12:36 pm
by 1970 cortina GT
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.
Posted: Tue Sep 04, 2018 8:57 pm
by 1970 cortina GT
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😉.
