Zenith Stromberg 175CD vs. SU HIF44?

[Bret]

I’m sure most of you have seen the SU HIF44 advertised in Victoria British and the single carb conversion kit in the Moss Catalogs. Emissions issues aside for the moment - both are spouted as direct replacements for the Zenith Stromberg 175CD.

Question: Do any of you know if (aside from the choke, auto vs. manual) is there any other advantages or disadvantages? In other words is there any “performance gains” to be had by going this way without any other modifications to the otherwise stock engine?

Just curious, if anybody in our group has tried one of these.

Thanks,

[ 09-18-2003: Message edited by: Bret ]</p>

 

[tony barnhill]

Nope! A properly sorted out Zenith is as good as those carbs...it wasn't the carb that choked the engine!

 

[Baxter]

I disagree with Tony on whether the ZS is as good as an SU (and he knows that, we've flogged that old horse pretty hard). But Tony's right. There's no performance gain, as its the craptastic manifold that's the real problem. THe SU might be more reliable, maybe, and there were safety issues with the ZS setup on the B, But overall, the whole thing seems like a ploy to take advantage of the single-carb setup's poor reputation. Better to spend the money on a Weber or twin SU conversion, which WILL give more power, and just flat work better.

 

[Tom Bedenbaugh]

I agree with the above post. The only way your going to see any preformance improvement is to go Weber, or twin SU's. The Weber conversion is the easier of the two as there is a problem with clearence of the brake booster with the twin SU's. Also with the Weber it's normally a bolt on and go situation. With little if any maintanence.

 

[tony barnhill]

Baxter...I didn't say anything about dual carbs...I said the Zenith is as good as the other single carb setups he was talking about....
..I personally don't like Webers...when I change for performance, I use HIF-4's...
...that said, just switching out a carb & thinking there are gonna be loads of performance impprovements, is bogus also...
..Isn't it nice that Tom B, Baxter, & I agree & still disagree....I say a sorted out Zenith does what its designed to do...then, I say for performance beyond what the car had from the dealer, go with HIF-4's; Bax & Tom like Webers instead.....bet there's not a hill of beans difference is HIF-4's & Weber, performance-wise!

 

[Bret]

Speaking of the duel SU set-up. Do you guys have any comments on the duel SU HIF6 (1-3/4”) as an alternative to the normal HIF4s. VB claims +5HP in improved performance.

 

[Tom Bedenbaugh]

Unless you do some other things to increase the CFM's I wouldn't go to the 6's. They are too much carburator for a bone stock series B engine.
I would agree that the twin SU's and Webers are pretty much the same as far as improved preformance. What I said was the Weber is a far easier conversion, and relatively trouble free. I personally like the SU carbs. I like the way they look and if set up properly preform very well. I have the DCOE on both my cars because there wasn't a HS6 conversion avalible when I did my engines.

 

[Mark Beiser]

Another option that would provide LOTS more power, enhance the drivability of the car, massivly reduce the fuel system maintenance, and most importantly, put a smile on the face of your local Air Resorce Board burocratic peon, would be to install fuel injection.

Its a bit of a project, but with a no frills aftermarket engine management system that handles ignition through the distributor, its not incredibly expensive.

The major parts you would need:

Engine management system with ECU, wiring harness, and sensors. (Various manufacturers $500-$1500 depending on options. $500 systems work fine.)

Webber side draft or down draft manifold for MGB. (Not hard at all to find, and not expensive)

Throtle body with flanges to fit the manifold. (Large variety of manufacturers. $350 max for the best ones.)

A set of good headers that have the junction of all the pipes short enough that you have room to connect to your catalytic converter. (I think there are anti death penalty type people in CA that would kill you without blinking if you pulled the cat off. =x)


Most of the installation is just bolt on and wire it up. The hardest part is providing a safe way for fuel to return to the gas tank. Fuel injected cars have a constant flow of gass from the tanks, to the fuel rail and back to the tank, so you would have to plumb another fuel line and make a SAFE way for it to get back in the tank.
You would also have to fabricate connections for the oxygen sensor in the exhaust, water temperature sensors, etc. None of that is really hard.
You would have to get the engine mapping and such done on a dyno by someone that knows how. Since like 1/3 of the aftermarket engine management dealers in the USA are located in CA, I don't see that as a problem. =)

If you can do the installation work yourself, you could do the whole thing for ~$1200 +tuning for a fuel management only, or fuel+ignition management that fires through the distributor. Nearly double that if you want distributorless ignition, traction control, launch control, etc.

Considdering that a side draft webber conversion, headers, etc.. would total out to $800+, basic fuel injection is a reasonable alternative.

Its something to considder for a non concourse car anyway. Your car would start right up every time, cold or hot, have fantasic throtle response, pass emissions(even in CA, CARB smiles on FI conversions), and no pesky air pump cluttering things up under the hood. Oh, and you would be getting more power out of the engine than any dimigod of engine tuning could ever get out of the same engine with any type of carburetor. And great fuel economy!

You can get really wild with it. The setup I'm going with on the TR7 Sprint conversion I'm building is gona set me back nearly $3000. Plus the engine!
Sometime after I complete the TR7, I want to get another MGB. MGB's were my first love, but I want to build a turbo charged fuel injected motor with distributorless ignition and one of those cross flow heads I have seen for the B.

[ 09-18-2003: Message edited by: Mark Beiser ]</p>

 

[Bret]

<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Mark Beiser:
<<SNIP>>

Its something to considder for a non concourse car anyway. Your car would start right up every time, cold or hot, have fantasic throtle response, pass emissions(even in CA, CARB smiles on FI conversions), and no pesky air pump cluttering things up under the hood. Oh, and you would be getting more power out of the engine than any dimigod of engine tuning could ever get out of the same engine with any type of carburetor. And great fuel economy!

<<SNIP>>
<hr></blockquote>

Hey Mark,

Interesting idea, its been brought up in past treads but I never really gave it too much thought. I guess I’ll have to look into the EFI possibility a little more. Just so you know out here in California – the smog Nazis (CARB) have some pretty strict rules on what you can & can’t do when it comes to transplanting power plants. While they might like the idea of citizens converting to EFI, I don’t want to invest too much time and effort in trying to make the conversion to my B without knowing all the facts first.

As previously discussed in other related threads, out here in la la land – the emissions laws require that all vehicles retain “all” of their original emissions equipment. In the case of the MGBs’ 1800 Engine this means that you must keep the EGR valve, Catalytic Converter and the Smog Pump intact and operational. While this isn’t such a big deal if your car is exempt from testing if your vehicle is above 30 years of age. But for folks like me, who’s vehicles are still required to be taken in for a smog test every two years – nothing can be changed under the bonnet.

Except for the your suggestion of going with EFI in the 1800, I’ve actually researched just about every aspect of squeezing out as much performance as possible and still passing the strict emissions test. Wouldn’t want to upset all of those over zealous tree huggers & environmentalist storm troopers.

Some of the ideas I’ve had involved – retaining the smog pump & going with a header exhaust system and an aftermarket free flowing Cat located just down stream. But what keeps tripping me up is how to deal with the single intake/exhaust manifold with it’s built in EGR valve. Back in the days when the EGRs where adopted – many manufactures incorporated them into the cylinder head & intake manifold. But in the case of the B’s engine there wasn’t any room. Thus with no place else to put it we are left with the restrictive 75-80 duel purpose intake/exhaust manifold.

That said I wonder if there is a single throttle body out there I could use in place of the Zenith Stromberg 175CD. I seem to recall somebody talking about this at one time in this forum. I’ll look back through the previous threads.

[ 09-18-2003: Message edited by: Bret ]</p>

 

[Mark Beiser]

Not being from CA, I have never had to deal with the details of the regulations there. I do recall seing quite a few articles where people have talked about getting some sort of exemption from the CARB though. If I'm remembering correctly, the exhaust had to pass a test that is more strict than the one for the model year of car they had.

If its not possible to get an exemption, that would be a real shame, and kind of stupid on the part of CARB. An engine with propperly set up fuel injection, electronic ignition and a 3 way cat produces FAR less harmfull emissions than the stock carbureted engine when it was brand new.
A good 3 way cat would remove the entire reason the smog pump and EGR valve even exist, thats why new cars don't have those parts...

I'm curious, how do they handle kit cars in CA when it comes to emissions testing? Maybe you could get it classified as a kit car for emissions testing.

 

[Bret]

Again, I haven’t looked into this yet, so I could be wrong. But it would be reasonable to assume that if you did opt for EFI on an older car, that the rules would be similar process wise to what you’d have to do when performing an engine swap. Currently the way this is done here in California is that you need to take your vehicle down to be inspected by a CARB certified “referee” to make sure that you did the job correctly. As I understand this would involve a smog check in addition to making sure that you have all the right equipment.

As for Kit cars? I don’t know for sure, but it has always been my understanding that because of the small production runs involved they would be exempt from testing. I remember reading that someone actually took a late model MGB (75-80) and bought a Cal-Ace (poor mans AC) body kit. Upon completion he either registered it as a kit car or an earlier year of manufacture that is now exempt from testing. Anyway I’m not sure how he went about doing this without getting into trouble, but it seems feasible. Perhaps the inspectors of the DMV or the CARB where fooled because of the different body allowed him to pull this off. Regardless doing a full body kit wasn’t part of my plan for my 78B.

 

[Baxter]

EFI on the B is VERY intriguing, but it's also pretty much a no-go on the stock head. A-series guys are in the same boat: The siamesed intakes totally freak out the computer and it doesn't know when to pulse the injectors.

Throttle-body injection MIGHT work. Maybe -- if you sorted out a plenum just right, didn't have the fuel drop out of mix, and if you got lucky and the mixture across the cylinders worked out.

Other than that, forget about it. Just not gonna fly on an MG engine without a crossflow head.. now THAT is an intriguing proposition.

 

[Mark Beiser]

I don't follow how having siamesed intake ports would have any affect on any of the systems I have been looking at. The systems I have looked at seem more than capable of being configured to handle any sort of intake arangement, even the budget oriented systems. They can handle supercharged engines that mix all of the fuel/air charge before the compressor.

I can see your point if it was tried with a dual Weber DCOE manifold where you could have some problems caused by 4 throttle body boars feeding into 2 intake ports, that would cause some serious issues with mixture control. I'm envisioning use of a single DCOE manafold though. Each intake port would have its own intake runner and throttle body bore. Most of the DCOE flanged throttle bodies I have looked at even have provisions for 2 injectors per bore.

I agree about the crossflow cylinder head, it presents some fantastic oportunities. Whenever I look at one, all I can think about is TURBO. There is all the room in the world for the turbo plumbing over on the exhaust side. The parts to build a strong bottom end for a B engine are easy to get hold of too.

I'm no expert though, and admittedly, my research into it so far has been with the aim to fuel inject a 16 valve Sprint motor for my TR7.

 

[Baxter]

I've looked into it, and they all shy away from siamesed. There's a page on the web somewhere detailing efforts to inject an A-series, and the guy went into some detail over WHY it wouldn't work.

Supposedly the Megasquirt guys figured out how to make it work, but everything I've seen suggest otherwise, and I've never been able to find any info on how they did it, if they in fact did.
The problem is that you've got injectors pulsing at certain times and valves opening at certain times, and with the siamesed ports you get one cylinder stealing from the other. With carbs it's not such an issue, because you're constantly refreshing the charge, rather than pulsing it in.
At least, that's if I understand the problem correctly. FWIW, a K-jet (CIS) injection system should overcome the problem nicely, since it doesn't use pulsed injectors and is a constant-flow system, but everyone hates K-jet. And there's a lot of good reasons to hate K-jet.


Now this is all just saying multi-point injection is not gonna fly. Single point (Throttle body) probably would, but you gotta ask if it's worth the effort. However, TBI with turbo? Solve the blow-through carb pressurization problem, and could be very sweet.

At any rate, it should be a relative cakewalk on a TR7 motor. heck, a Saab 900 would probably have eveyrthing you need and be relatively easy to convert over.