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Seeking HIF4 gurus - need help!

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RickB

RickB

Yoda
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You can see my post over here, read all the sordid details.
https://www.britishcarforum.com/bcforum/u...e_Ne#Post688274

Basically I've got a pair of HIF4 carbs now attached to the Datsun 1500 motor in my Midget.
The reason I'm posting here is that I figure more MGB owners are used to having to deal with the HIF4 than Midget owners.

Any help at all will be greatly appreciated.

Basically I've bolted a pair of HIF4 carbs to a dual intake manifold connected to a high performance GX cylinder head.

The carbs don't want to run right, symptoms include running very rich to the point of smoking up the neighborhood, not running at all, running but wanting to race away up to 4k - 5k rpm, sometimes idling properly, most of the time not. I had a higher pressure fuel pump, we swapped it out to one that does only about 2 psi.

I will be going out to work on it again today, it would be great to get this problem solved - again any help at all would be great!
 
I just went out and turned the key on, gas started coming out the front carb overflow.

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Hi RickB, I went through a nightmare scenario with my HIF4's on my '74B.I bought new needles and seats,disassembled and cleaned the carbs and replaced the parts,Then set the float level according to John Twists tutorial on you tube concerning the float levels etc.
Fuel came out the vents on the carbs so I assumed that I had the float level wrong as there is only a few millimeters leeway in the float level adgustment.
Off with the carbs and reset,back on , same thing happened again. After 4 or 5 times I rethought things and put the old seats back in and Bingo,everything fine. Faulty new seats!One good thing about this though...I can now re and re the carbs in about 10 minutes lol.
I seriously recommend John Twists video as a prerequisite because he explains the float level setting procedure very well along with a lot of other stuff about those HIF4's and it helped me tremendously.
Watch out for those cheap repro parts too. Hope this helps...Mark
 
Thanks Mark, I will look up those vids and watch asap.
Right now I'm installing a regulator to make sure I am not over pressuring the carbs.
 
Notice there is a fuel feed hose that loops around to the back carb?
I'm looking and looking and looking and not seeing it until just now, the things have a hose that goes between the two carbs at the front, supposedly to feed fuel from the front to the back carb.
So why does this fuel line from the pump go to both carbs I was wondering?
I look and look at the diagram in the book and it just hits me - there's a fuel feed hose to the front carb but the back only has "breather pipe" and "vent hose" connections on the right side - no fuel feed in over there as the fuel feed in is on the left side of that carb!!

So - what happens when you feed fuel into the carb via the 'vent tube' or the 'breather pipe'?
Whatever it is, I will bet it isn't good!!!

Going out to make it look like the book right now. Will report soon.
 
So as you might imagine hooking up the fuel so it only goes where it should and doesn't backfeed into the VENT made everything way way better.

A little adjusting and OFF TO THE RACES!!!

Wow - the GX head and a pair of 1.5 inch carbs is WAY freaking better performance than the econo head and the little hitachi downdraft.

I take off from the line now like amazing and it just pulls and pulls and pulls.

This is nothing short of amazing!!

So - to summarize...

Datsun A15 motor with a GX performance head and a pair of SU's in an MG Midget = AWESOME!!!

Add a 5 speed and maybe I'll just have to feel like I've died & gone to heaven.

Yeah, it's just that good!
 
I'm not going to get too involved in this, but it looks to me like you have it plumbed wrong! Here's a photo of the wifes 72 engine bay, take note of the carb plumbing. This is a factory setup. The fuel goes into the front carb and to the back carb via a short connecting hose between them. I can't figure out your set up, as I've never seen B carbs set up that way before.
<span style="font-weight: bold"><span style="font-size: 9pt">OOPs! Sorry, didn't read the last post! Hope all's well. PJ</span>
</span>
72ENG2.jpg
 
Thanks Paul,

One more question - where is the vacuum advance connected?
In your picture it loos like that's it behind the throttle cable on the manifold?
 
On the intake manifold for the HIF4 set up. Look at Paul's above picture, see the small black hose kinda hiding behind the blue throttle cable, that is his vacuum advance hose, it is routed behind the cylinder head over to the vacuum advance unit on the distributor. Hope this helps.
 
Ok - so manifold vacuum looks like the ticket.
I'll see if the manifold I've got has anything like that.

I have a problem, developed yesterday after running fine the first day.

Gas leaking out the overflow tube on the front carb.
I pulled the carb, turned it over, unscrewed the bottom and pulled the float out.
Things looked "ok". If I push the float valve in the fuel inlet closes.
I put it back together and attached a hose to the fuel inlet and blew in, with the float down air moves in, with the float up it stops.

This is the most rudimentary test, but I'm not sure where to go from here.
Gas still comes out the overflow when the engine is running.
Just on the front, the back is working fine.
Could be the valve tip is worn to far?
Maybe the float is sticking?

If I could run down to NAPA and pick up a new float & valve I would... maybe I'll just give them a call. Not sure what to ask for though.
 
Thanks!
Good videos, good too see how it supposed to be done!
I will go ahead and replace those float valves and adjust the floats and see how it goes.
 
Yeah, they have a metal tang, so it can tweaked to set the float level. Rick, ok you shocked me a bit by telling me NAPA has SU carb parts, but that doesn't mean they have good SU carb parts, in fact not many of the British car part vendors have good SU carbs parts, so I say this again, www.joecurto.com take this from a guy who builds SU carbs for living. The kit you show is a minor kit, no needle, no jet, no shaft, no throttle plate screws. I support Joe Curto, because he forgotten more about SU carbs than most will ever know, and if you get in jam, well you're talking to guy who has literally built thousands of theses carbs you are working on, and knows every trick in the book, you won't get that type of servce from your local NAPA store. I'm a strong supporter of the cottage industries that keep the hobby alive.

For example when it comes to needle and seat valves, an item that seem to give alot of trouble, three are some very questionable needle and seat valves out there, that are junk, like Grose jets, the viton tipped needle and seat valve is what you want. Call me crazy but I'm a parts snob, I like the buying the best parts and never looking back, I don't like fixing things twice :smile:
 
:iagree:

Hap said:
For example when it comes to needle and seat valves, an item that seem to give alot of trouble, three are some very questionable needle and seat valves out there, that are junk, like Grose jets, the viton tipped needle and seat valve is what you want. Call me crazy but I'm a parts snob, I like the buying the best parts and never looking back, <span style="font-weight: bold">I don't like fixing things twice</span> :smile:
Click to expand...

Call it what it is: <span style="font-weight: bold">"come-backs SUCK!"</span> :wink:

As for those "Two balls do the trick" thingies, we had a jar full of 'em on the front counter. All replaced with Viton tipped ones. Some folks seem to have no issue with 'em but AFAIC they're scrap right outta the box.
 
I really hear you guys - but I have an immediate need to get this thing fixed today. If the part I can get from Napa this morning doesn't work they will hear about it. When I order a full kit it will be from Joe.
 
yep, Doc, comebacks can be a nighmare for me, especially if it's lump we're talking about. Yep one thing building a engine to put in your car at the other end of the garage, it's entirely different matter when you're shipping a engine aross the country to someone, I'm anal out of necessity :smile:
 
It PAYS to be "fussy". :wink: Your reputation is counting on it.

Of the few crate engines we ever dealt with, a BMW 2002 was the least painful. With the Ferrari, Jag and Porsche clients I would take NOTHING for granted and do them in-house. The machine shop we used was akin to a hospital ER, with very good machinists.
 
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