HS4 vs HIF4

I'm looking to replace the Zenith/Stromberg on my '76 B and have been searching e-bay for carbs. I'd like to know what the pros and cons are on the different SU carbs. Any advice is appreciated.

I have my 76 B apart now installing a pair of HIF4’s I bought off of eBay and sent to Jimmy Hilton for refurbishing. If I had it to do over again I would skip the eBay thing and contact Jimmy directly for a pair of carbs. He has been an incredible asset and resorce. You would be well served to just do as he suggests.

If you want to be pure to SU carbs then please ignore my post, but if you are looking for a better general carb compared to the ZS then you might consider a weber DGV. From my understanding, the twin SU setup is "more pure" and can provide a little more low end power, but also requires a little more maintenance and fiddling than the weber.

If you are in the market to buy, then post on the trader forum, there are always carbs for sale there.

There are other issues to consider as well, if you pull the ZS. You will probably have to replace the intake manifold and maybe the exhaust manifold as well depending on what option you choose.

The HIFs are a more sophisticated carb than the HS-4s, mostly because they had to be to meet increasingly stringent emissions standards in the 1970s. That means that you benefit by their better overall performance.

If you have been watching the forum here recently and read some of just the gas mileage reports folks have given, it becomes pretty obvious that the HIFs deliver better gas mileage. And to do that, their contribution has to be better performance overall. JMO

Although I have a DGV and love it, this forum is full of advocates for both HS and HIF. In either case, you will need an older exhaust and intake manifold, both of which are available. Please do a search and you will find more than you bargained for. Enjoy! :)

I personally have the HIFs. From a conversion standpoint they work better on the ZS equipped cars:
1) The PCV system easily adapts to the HIFs. Take the tappet breather, add the Y and connect to the take offs on the HIFs.
2) The manifold vacuum works correctly with the distributor that you already have.
3) The later intake manifold has a provision for the vacuum servo check valve.
4) HIFs used biased needles. There are hundreds of needle profiles to fit your needs, although they do wear since they are constantly in contact with the jet tube.
5) The anti-runon system can be left in place just run the overflow to the carbon cannister(s).

I did the HIF conversion on my '79 and am quite pleased with the results. However, having picked up a '69 with HF's I'm not quite sure the later carb's are better. The Seat-o-Meter says the '79 has better acceleration but worse mileage than the '69. Granted, there are other factors but both sets of carb's have been professionally rebuilt by the same person so should be of equal qualiity. One problem that has arisen with the HIF's is higher temperature idle change. When the car gets hot (just above normal operating temp) the idle drops down to around 400 rpm or just quits running. So far, the problem has not occured with the HF's. The mileage issue is probably relates more to tune than inherent differences.

I guess if I really wanted to know, I would rebuild the spare HIF's on the shelf and put them on the '69. Nah.

Kevin Mott
,79 B HIF's, Pertronix, Jeff's rebuild 45d, Z car wheels
'69 B GT HF's, Pertronix, 45D, 15" wire wheels
OKC OK

At the meet in Hiawasse, GA there was a B with a side draft weber that is a bolt on for your carb. No changes to the manifods are required. I do not have the owners nam, but it looked preety good. I think he said he got it from Weber Direct onthe web.
Good Kuck
Steve

IF you decide to go the Weber route make sure you purchase from a vendor that will work with you on the jetting.

Search is your friend!
Here's some more info.

http://www.mgexperience.net/phorum/read.php?1,589414,590025#msg-590025

ClayJ Wrote:

losmorob Wrote:

Hap would know, and I can say from personal experience that his rebuilds are the best. I've got HIF's rebuilt by him and I couldn't be happier with the result.

R.

Another bolt-on possibility is the HIF44 that's on my car. I purchased it new from Moss. While it probably doesn't give as much horsepower, for the type of driving I do it's a reliable alternative, and I'm getting about 30 miles to the gallon. I had a Zenith before, so anything would have been better, but the HIF44 coupled with my rebuilt distributor from Jeff has made all the difference in drivability and reliability.

Given my choice of what to run, HS4's would win 99 times out of 100 (other than for originality). To rebuild, HIF's are a bit simpler if you know exactly what you are doing.

I would be willing to wager that I can get better mileage, better performance, and more reliability out of an HS4 over an HIF. And would also bet on that against a downdraft Weber.

set float levels on both types and see which you prefer!

golf Wrote:

BTW, when I said that HIFs have better performance than HS type carbs, I meant as relates to their own performance as carburettors, NOT the performance of the engine or the car. Hap and others who have knowledge about which provide best seat of the pants performance can give guidance about which will give you your best joy ride. However, the HIFs have some modifications missing on the HS units which made them better able to deliver the type of carburettor performance needed to more tightly rein in emissions than the HS series and it is very likely that those same modifications may well have made them less adept at producing the type of engine and vehicle performance necessary for all out HP gains.

I'm getting 32 MPG on a cammed up twin HS4 engine. I think either carb will net you good peformance and good gas mileage, if you get the fuel mixture spot on and everything operating correctly. And Bob in theory, there's no reason whatsoever why you couldn't take a HIF4, for racing go hog wild with it, thru boring and such and probably equal the performance of it to be just as good as a HS carb, I think for the most part, racers don't go this route due to servicabilty of the float chamber, the HS series is just more user friendly in this area, but the HIF is a very good carb in it's own right.

Paul, you can't really go wrong, which ever way you choose, I think you are making the right choice though, the twin carb set up will net you the best performance, and if you study thie twin carb set-up. As much as SUs seem to puzzle people, it's fairly straight forward and a very simple design, you have to look long and hard to find a simplier designed carb than a SU, with as few of parts.

WOW! I'm overwhelmed by the information and advice on such a "tepid" topic such as carbs! I'll certainly be in contact with the carb experts quoted within this thread before purchasing anything. Y'all have alot to say and I wonder if you ever break away from this website to do any work! Much appreciated from this newbie B owner!The carb work will come after the front end mods and brake work. No sense putting more horses under the hood until handling and braking is improved. Thanks to all for your help.

This is almost as good as a Weber vs SU thread!