Single HS4 on a 1500

[bigjones]

Hi folks,

I've been following this thread on the conversion but have some questions:
https://tinyurl.com/ygoj9o6

Do you elongate the holes in the carb to make it fit the existing stud pattern on the manifold? I just want to double check before I take a file to a brand new carb!

Also, on my engine at least, it is necessary to use carb vacuum to suck on that hose coming off the valve cover, otherwise there is big oil leaks. Has anybody figured this out on the HS4 - there is a tiny pipe but that must be for the vacuum advance. There is a larger hole but that has been shut off at the factory with a plug. Should I try and remove this plug and fashion some sort of pipe?

Cheers

 

[dklawson]

Hey Adrian! I've been wondering where you were!

I modified the manifold on my Triumph 1300 (same basic manifold) to move the studs and not have to file the HS4. However, by all accounts of those who have done this, the easier method is to elongate the HS4 mounting holes into slots. If you are worried about messing up that new carb... and can come up with a spare manifold to modify, I can move the studs for your setup also. Remember, I'm only over in Durham.

I eventually fitted the ABD MGB needle to my HS4 and I switched to a thicker dashpot oil. The engine ran better with that arrangement. However, I learned today that the other "sick engine" symptoms I've been experiencing and blaming on the carb were a failing head gasket and some leaky intake valves. In short, I'm still a long way from being on the road!

 

[bigjones]

Doug!
Many thanks for the post.
Yeah, I have not been on the forum for a while - the MG is running very nicely with no problems. Apart from the poor gas mileage (22 mpg). Hence the interest in the HS4.
I picked one up from Burlen in the UK almost a year ago - I have put off installing it because it is a thing of beauty. Now and again I take it out of the box and fondle it lovingly.

Thanks for the clarification on the mounting holes and your kind offer to move the bolts. Let me ponder that awhile.

This carb has a standard needle - I would be very surprised if it does not require some modification. But that is in the future - right now I'm trying to figure out just attaching the carb to the manifold!

Like yourself, I think I'll use a heat shield between carb and manifold and use that to attach the accelerator and choke cables - I have a beat up 1275 heat shield that I'll try to modify.

Would be nice to get it operational before the car show!

Sorry to learn of the head gasket problem - I've replaced those on the 1275 and the Triumph - takes a while but its not high tech! Best of luck!

Cheers,
Adrian

 

[JPSmit]

Adrian - I'm the one with the HS4 and I elongated the holes. Looking at your carb I can understand why it would hurt to hurt it. Looking at the carb you will also have to make a decision about your float. It will need to hang vertically when the carb is mounted. If you talk to Joe Curto he can tell you what float to use and will sell you one for about $45. Or, you can adapt your existing float. First off, the bolt holding the float to the carb body is not in any way connected to the fuel system, so, anything you do at that end will not make it leak. I foolishly ground the flange off the body of the carb, rotated the float vertically and tightened the bolt - still worked fine though. However, I am having the carb rebuilt even as we speak and the guy doing the work will pin it properly. What I should have done was adapt the "washer" on the float that "keys" to the flange on the body. (it will make sense when you have the float off). The only other issue was the fuel line from the float to the carb - it should be shortened slightly but I tried it and ended up with a leak so, second time I just left it and it worked fine. I love the HS4 though and would be happy to post pics when it comes back.

 

[Hap Waldrop]

The float bowl assembly itself is not what sets the angle of the float bowl, it's the float bowl grommet that sandwiches itself between the float bowl and carb body, Curto will have the correct grommet to correct the float bowl angle, and they a fairly inexpensive. So no need to replace the float bowl, just the grommet.

 

[bigjones]

JP and Hap,

Thanks for the info on the flange - I was just going to grind it off but getting the correct grommet would be preferable! I'll get in touch with Joe.

I'm pondering now on how to attach the choke cable - the carb has a hole in the body, below which is the choke mechanism. VB sells a "trunnion" - is that a little cup that fits in the hole and holds the outer sheath of the cable?

Cheers

 

[bigjones]

Hmm,

May have that wrong on the choke cable mechanism.

Anybody know offhand how the outer choke cable is secured on a 1960's MGB?

Cheers

 

[dklawson]

I don't know how they ran the choke cable on an MGB. I didn't use the boss on the carb body for the choke when I fitted the HS4 to the 1300. I made a clamping block and ran the throttle cable and choke cable parallel to each other. I can take a picture of it if you want but it may not be much help.

 

[DrEntropy]

On the B there's an "arm" as part of the air cleaner retaining bracket with a hole for the inner cable to be secured, via a clamping bolt. The sheath does the moving of the choke mechanism (from a "socket" on the cross-linkage).

With a single carb you'll need to MacGyver up your own device, methinks.

 

[bigjones]

DrEntropy,

Oh, OK. Back to the drawing board.

(Hmmm, kippers! I'm getting hungry!!)

 

[DrEntropy]

:lol:

I'll try and post a photo or two of the relevant MGB parts. It appears you have a right side (rear) B carb... the "arm" I referred to mounts on a front one but with pix you may find a way to fettle one to work.

'smits (SWMBO) has the camera just now so it may be tomorrow before I can post anything enlightening.

 

[Billm]

Here are some photos of the hole modification that I did to put an HS4 on my 1500:

BillM

 

[JPSmit]

I just got a call tonight that my carb is ready - will likely pick it up on Wednesday and will post pics of the choke ASAP

 

[dklawson]

I just got a call tonight that my carb is ready - will likely pick it up on Wednesday and will post pics of the choke ASAP

??? I thought you already had the carb. Were you having it professionally rebuilt? If so (out or curiosity) by whom?

 

[JPSmit]

I just got a call tonight that my carb is ready - will likely pick it up on Wednesday and will post pics of the choke ASAP

??? I thought you already had the carb. Were you having it professionally rebuilt? If so (out or curiosity) by whom?

Rebuilt - Blane Hughes here in Toronto - everyone says he is the guy to go to. will let you know

 

[bigjones]

BillM,

Thanks for the good photos.

Looks like you drilled out the holes instead of filing, is that right?

Does your accelerator cable pull downwards?

How did you hook up your choke cable?

Cheers

 

[Billm]

Actually I used my mill and a 3/8" mill cutter, made it much easier.
Bill

 

[bigjones]

Hmm, Ok then.

 

[dklawson]

Remember Adrian... I do have a mill. We'd just need to make a fixture to bolt the intake side to to hold it in the vise.

 

[bigjones]

Doug,
Many thanks for the offer - I'll probably just go ahead and file elongations to make it fit on the studs.
Do you think we will need the MBG spacer block?
(I'm getting up a list of things)
Cheers!
Adrian