Zenith 175s on 4.6.Jets

nickm · Post by **nickm** » Wed Mar 02, 2011 4:52 pm

I have a 4.6 with John Eales big valve/ported heads 10:1CR and Piper 270 cam.It was intended for a Westfield but a change of plan means it is now destined for a 1972 Range Rover.I want to fit the RR Zenith 175 carbs/inlet manifold to keep costs down.Can anyone tell me which jets might be suitable for this and where I can get them from?Also,might it be better to fit standard cam from a 3.9?Wonder if the 270 might be a bit peaky[and thirsty!] for the RR.Thanks,Nick

ChrisJC · Post by **ChrisJC** » Wed Mar 02, 2011 6:06 pm

I run a 4.6 with a piper 270 on 2" SU's in a Land Rover (with auto transmission), about 10.5:1 comp and ported heads, and can confirm that power delivery is perfectly satisfactory!

There are more options for tuning SU's than Zenith 175's, not sure how much joy you'll get.

Chris.

kiwicar · Post by **kiwicar** » Thu Mar 03, 2011 11:36 am

I would go to the effort of finding a set of SU's , 2" preferably the SU is a much better made carb and quite honestly any Zeneth/ stromberg is going to be well past it's "use by date", for very moderate cost you will have a much better set up. Also the 2" is a very under rated carb and not much sought after as about the only thing they apear on is the straight 6 jag engine during the '60s '70s and early '80s there must be loads of the things in scrap yards.
Best regards
Mike

nickm · Post by **nickm** » Thu Mar 03, 2011 4:01 pm

Thanks for the advice.Would 2"SUs fit on the same manifold as the Zeniths and are the linkages easy enough to set up?

kiwicar · Post by **kiwicar** » Thu Mar 03, 2011 4:22 pm

Hi
The 2" sus go on the same bolt fixings, you have to open up the hole in the manifold, it is a good idea to do some basic gas-flowing and port matching of the manifold while you are at it. The basic linkage should be able to be adapted from the one you have using bits from the Zenith carbs if necessary but will be dependent on SU vintage as to exactly what has to be done. It has been done loads of times.
Best regards
Mike

ChrisJC · Post by **ChrisJC** » Thu Mar 03, 2011 4:34 pm

You also need to tilt the carb slightly as it will foul on the rocker cover on one side of the engine.

How to tilt the carbs...:

Chris.

CastleMGBV8 · Post by **CastleMGBV8** » Thu Mar 03, 2011 6:41 pm

Chris,

Remind me, most HD8 SU's are side draft can you still get the adaptor pieces to realign the float chambers for semi downdraft use?

I'm asking as I have a pair lying around somewhere!

Kevin.

kiwicar · Post by **kiwicar** » Thu Mar 03, 2011 7:48 pm

Hi Kevin
certainly on the 1 1/4 and 1 1/2 SU where the float bowl is side mounted it can be turned so that it is upright even when the venturi of the carb is angled down to about 30 degrees Further the carbs will tollerate the float bowl being about 10 degrees off horizontal if you adjust the float height. You could mount 4X HS1s in a row straight on the aldon 8 port mini heads (45 degree down draught ports) with a simple 15 degree wedge and a mounting plate to bring the bowles horizontal used to look wicked

I would think you can do the same on the 2" Su
Best regards
Mike

ChrisJC · Post by **ChrisJC** » Thu Mar 03, 2011 9:09 pm

CastleMGBV8 wrote:Chris,

Remind me, most HD8 SU's are side draft can you still get the adaptor pieces to realign the float chambers for semi downdraft use?

I'm asking as I have a pair lying around somewhere!

Kevin.

I just modified what I had, I don't recall there being any issues with that part.

The hardest part was sorting out the linkages.

Chris.

CastleMGBV8 · Post by **CastleMGBV8** » Thu Mar 03, 2011 11:27 pm

Thanks guys, i seem to remember that there was a flexible piece with a lug to control the float angle and presumable they just fitted one which angled the float for the particular application.

Kevin.