Carburetion

[mgtildth]

I've posted here before regarding my dismay of the HIF4 SU's. They suck. First of all, the enrichment screw on the rear carburator is a bitch to get to, and when you do get there, I can't even get a stubby in there to turn it. So, do I get a 32/36 weber and be done with it, or get a 45 DCOE? I'm thinking the 32/36 might be a waste of money because if I ever get the motor rebuilt I will need different carburetion for performance applications.
Anyone interested in the carbs and K&N's, let me know.

cheers /ubbthreads/images/graemlins/thirsty.gif

 

[John Moore]

Personally, I'm a fan of SU's. I rebuilt my HS4's use AAA needles with K&N's and it runs like a top. They are perfectly matched to the motor. They are extremely simple carbs once you set them up. But if they are worn, you will have a bear of a time. Others are fans of the Weber. It really depends on what you want out of the car. I think the weber makes it look like tractor motor. A 45 DCOE is too much carb, unless you've ported and polished the head. Maybe you should consider the 38 Outlaw Weber, offered by Brit Tek.

Sure drop me a line, I will take them off your hands!

 

[mgtildth]

I like SU's, just hate the HIF4's, they're crap. I have a perfect pair on my convertible and they're great. Very easy to tune, unlike the HIF4's. From what I've read the 45 DCOE will work fine on a stock motor if you get the jetting right. I know a guy who loves 'em and has one on his car. Supposedly once they're dialed in they're good to go. The reason I'm leaning towards this carb is it will be good when the time for a motor rebuild comes around. Otherwise I'd probably need to invest in different carburetion.

K

 

[John Moore]

Well the good thing about a DCOE 45 is that they are infinitley changable, the bad thing about a DCOE is that they are infinitley changable! lol! It's a nice carb, it will just take a ton of tweaking, and yes you're right, if you plan on modding the engine, it's a great carb to have.

 

[Banjo]

Be aware that the Tweaking of the Weber DCOEs is accomplished by changing out parts, not turning screws. if you don't order them pre set up for exactly what you have then it can be very costly and frustrating, unless you know exactly what you're doing.
Also DCOEs are an awsome carb, but they have crude street manners. I have seen more than one person switch back to SUs because of how choppy they are in city traffic. But that probably has a lot to do with people not knowing exactly what they're doing, as I said before.

P.S. if John dosen't take those carbs, let me know. I'd love to have an extra set. /ubbthreads/images/graemlins/grin.gif

 

[Guest]

Buy me a plane ticket and I'll have your HIFs working great! When I need to adjust the rear carb a 5" long screw driver works fine for me.

I really hate to hear people say they've given up on their SUs when they are the simplest carburetors made.

I can walk you through your problems if you would like to explain them in detail on here.

 

[Guest]

I agree with John about the DCOE not being a great choice unless you want to spend lots of money setting it up. If you want to get the Jets perfect that means spending money on Dyno runs at your local speedshop. They can cost close to $100 for two runs and they might not let you tune (switch jets) between runs.

SUs are great because their design is the closest a carburetor will ever come to the efficiency of Fuel Injection. A stock pair of HS4 or HIF4 SUs with richer needles and K&Ns are good till about 130 hp at the flywheel, which is 100 horsepower at the wheels. Getting to 100 hp at the wheels will cost serious $$$$.

 

[mgtildth]

Last night my neighbor and I had a go with them. He's got a '72 midget with a Fiat motor in it. Were I get hung up on the HIF4's is setting the mixture. I had the front carb pretty much sorted. When I'd lift the piston the rpm's would rise a little then go down. The rear carb was a bitch. When I'd lift the piston it would want to die. It runs good now, I'll have to have a look at the plugs to see what's going on. They were black, which was probably due to being way too rich at idle. I will report back on the condition of tune when I can take it for a spin. It's pissing down rain here, Southern Ca. Cheers, K

 

[703MGB]

I just read this tread while investigating needles for HIF4's.
The SU caburettors are extremely good and very easy to maintain. Usually folks having problems with them are because they are either very old (loose parts) or very dirty.
Peter Burguess which is the absolute expert in tuning MGB's has written a book (How to Power Tune an MGB) and this book is a must for anyone around MGB's.
Anyhow here my tricks for good working HIF4:

- Everything must be clean and up to specs.
- Make sure you are running the proper needles and that the jets are ok.
- Make sure the float is not all dirty, setup to the proper level and that the needle to close the incoming fuel sits properly.
- Make sure that your fuel pressure does not exceed 1.5 to 2 pounds. If you are not sure put a fuel regulator like I did.
- Make sure the mechanism between the 2 carbs open together without delays.
- follow the instructions for tuning from a good Haynes book and synchronize your carb that's a big key.

Now about those DCOE they are a very bad idea for your none race car MG. DCOE couls give your more HP at very high RPM with a huge sacrifice at low RPM.

Also note that DCOE have NO provision for vacuum advance which means you will have to change your distributor for a mechanical advance one only.

Finally if you wish to avoid the repairing of old broken down SU's there are pretty good suppliers out there selling brand new SU's (make sure to select the right one, you cannot swap HIF4 for HS4 without making changes the vaccum advance valve and pick-up point)

Happing motoring!