Wedge TR7 Carbs

[Lawrenb]

Has anyone replaced the Zenith Stromberg 175 CDs with SUH6s? if so, did it improve engine performance?

 

[poolboy]

I can't think of a reason why they would..both those carbs have the same size "bore".
When I see a question like this, it's usually because some one has been unable to adjust out a problem that really can only be corrected with a complete or partial carb overhaul.

 

[tr8todd]

Yes, and yes. Especially if you add a performance cam and headers. Hard to find HS6s, so most TR7 guys source the SU knockoffs licensed and made by Hitachi that were found on the early 240Z. Later the 240Z got the bigger coffee can style Hitachi. You can find them if your patient on ebay for around $100.

 

[Lawrenb]

I have added a performance cam and headers. Also ported the head and increased the bore by 20 thou. I can get a set of reconditioned SUH6s for about $300. Maybe the SUs and a K&N air filter kit will give me the added boost I'm looking for. Your thoughts?

 

[poolboy]

The needles (B1DH) in the ZS carbs for a TR7 are fatter by comparison to the needles in the same ZS carb used on the TR6 engines.
If you think adding more fuel to the mix would help you could try the TR6 needles, B1AF.

 

[tr8todd]

The problem with the Zeniths is all the extra emission stuff. I use to have to keep the zeniths on the TR8 SCCA race car because of the rules. It took a lot of tinkering to get them to run as well as the SUs. It can be done, but its easier to just pop on the SUs. The 240Z ones are set for a 2.4L engine and I found them to be perfect for a TR7 with a warmed over engine right out of the box. While your at it, make yourself a cold air intake that gets the fresh air from the vent holes in the front of the engine compartment the way the TR8 does. You can bury a cone shaped K&N filter down inside the fender next to the headlight motor.

 

[poolboy]

...That sounds a lot like the scenario I described in my first post in this topic.
It's easy enough to disable the temperature compensators,the anti run-on feature and the throttle bypass valve on ZS carbs if you have difficulty adjusting them. Once you do that, they are pretty much equivalent to the SU's in terms of complexity.
Of course you do have to maintain an intact air valve diaphragm on a ZS carb, but they usually have a pretty long life span.

 

[Lawrenb]

90% of the pollution control equipment has been removed including the egr valve, anti run on device, air pump system etc. I've also removed the fan and viscous clutch assembly and installed an electric fan. So she's pretty well back to British spec. It's just the carburation that I have to improve on and both of you have given me excellent options to persue.
Thanks again to both of you.