Holley 94 Carb on 1937 248 engine(don't do it)

[Darius Stefan]

Hi!
I want to fit a Holley 94 carb on my 248ci Buick 8, however I'm facing difficulty in regards to the vacuum advance line. The threaded end is too small to fit in the vacuum port that the Holley has. Advice on where I can find an adapter? Sizes would be helpful too. Many thanks!

Edited September 16 by Darius Stefan
Obsolete modification (see edit history)

[Bloo]

Where is the port located? If it is an original 94 from the old days, the vacuum port is probably venturi vacuum, and completely useless for any sort of a normal distributor (like the one on a Buick). If it is a reproduction 94, you might have a useful port. I believe it would be down in the base if so, not way up on the carb like a typical 94.

[Darius Stefan]

Just now, Bloo said:

Where is the port located? If it is an original 94 from the old days, the vacuum port is probably venturi vacuum, and completely useless for any sort of a normal distributor (like the one on a Buick). If it is a reproduction 94, you might have a useful port. I believe it would be down in the base if so, not way up on the carb like a typical 94.

Hi Bloo! Thanks for the quick response! In the photo below you can spot the vacuum port blocked off with a brass screw cap in identical configuration next to my carb. IT IS a brand new repro Holley. The carb in the photo is not mine, but it's exactly the same.

[Bloo]

Could there be another port on the throttle body somewhere? That port looks to go to the venturi. If so, it won't do you any good. I have heard some of the reproductions have a "ported vacuum" port, which is what you want. Find the spot where the port comes out inside the bore. The port you need will be next to the edge of a throttle plate. It will be above the plate (atmospheric) with the throttle closed and idling, and below the plate (manifold vacuum) as soon as you crack the throttle open. You can probably see this on the Buick carb if the new 94 does not have it.

 

If there is no ported vacuum port, probably the best you can do is to hook the vacuum advance directly to manifold vacuum. In that case, there will be extra advance at idle when everything is set correctly. It usually works out OK on hotrodded engines. Sometimes it is OK on stock ones. It is better than running with no vacuum advance if you can get away with it.

 

My laptop battery is dying quick. I'll be back in a few minutes with come comments about possible threaded fittings.

 

Edited May 14, 2023 by Bloo (see edit history)

[Darius Stefan]

I will have to check up on those details. I plan to run it on a stock engine. Thanks again for the help, I will await your reply.

[Bloo]

Now about fittings. I am not sure what I am looking at there, as that plug looks like it might have a copper washer or something. I see you are in UK. In nearly any American carburetor, I would expect the fitting that screws into the carburetor casting to be NPT, and probably 1/16" NPT. 1/8" NPT might also be possible. NPT is the standard American pipe thread, it is tapered, so no copper washers or anything like that, and the thread diameter of a fitting is much larger than the numerical size.

 

On a vacuum advance, as late as the early 60s on some cars, the fitting that screws into the casting would most likely be 1/6" NPT to female "threaded sleeve". As near as I can tell, there is no better name for that fitting type than the somewhat ambiguous "threaded sleeve" here in the US. I learned on this forum that the Australians have a proper name for it but the name slips my mind at the moment. Threaded sleeve fittings are available in the US from Blackhawk Supply in Texas, and possibly some other outlets. I suspect threaded sleeve is what you will find on the Buick.

 

So, most likely on the Buick there is a 1/8" to female "threaded sleeve" brass fitting, and then a "threaded sleeve nut" on a piece of steel or copper tubing. It might have to be copper tubing today even if it was steel before. "Bundyflex" brake tubing is what was normally used when the line was steel, although I don't know offhand where to get any steel brake tubing as small as a vacuum advance line. Copper works fine too, and can be found.

 

After 1963 or so, vacuum advances used rubber vacuum hose. That's the easy way. You would just need an 1/8" NPT hose barb at the carburetor. Hose setups are kind of rubbish today because of the terrible quality of the hose, but they lasted a long time back in the day. At the distributor end, the Buick probably also used a "threaded sleeve" fitting, but the threaded sleeve nut probably connected directly to the advance unit without another fitting, so you would need to lash up a hose fitting somehow at the distributor end.

 

Here is a threaded sleeve nut (male part of the fitting).

 

 

The nut bites into the tubing the first time it is tightened, and becomes part of the tubing. It can be disconnected from the female brass fitting as many times as you like, but can never be removed from the tubing.

 

So much for the fittings. It is all academic if you cannot find a ported vacuum port on that carburetor. Best of luck.

 

 

Edited May 14, 2023 by Bloo (see edit history)

[Darius Stefan]

Here you can see the exact threaded nut as the one you posted, must be a standard size across all series. NPT fittings are available to purchase in UK as well. 

So, to recap, at the carb end, the thread size is 1/8 NPT and the threaded vacuum line nut 1/6 NPT. To my understanding, I should search for a 1/8NPT to 1/6NPT female sleeved reducer/adapter.

[Bloo]

You should look for 1/8" NPT at the carb side. On a second look I think that's more likely than 1/16" NPT. You probably need Threaded Sleeve at the line side if you still have the Buick line. Threaded sleeve is not pipe thread, It is it's own thing with different threads and a conical (supposedly) or convex (more likely) seat inside to seal that fitting in the photo. Does the line look like the photo?

 

That is all academic if the only vacuum port on the 94 turns out to go to the venturi. If so it will be too weak to pull a vacuum advance, and if it did pull it, it would pull the wrong way.

 

Edited May 14, 2023 by Bloo (see edit history)

[Darius Stefan]

The photo I posted is the actual line on my engine and original. Should be 1/6npt in size, correct?. And yeah, threaded female sleeve is what I will need with the conical seat inside. I wouldn't want to give up the existing port on the intake for the wipers as I still use the original mechanism and at one point I plan to connect the vacuum pump in series to that, so yeah. I will try to look for both 1/8npt and 1/16npt to eliminate any error. Thanks for your help!

PS.: I do have a 40's style 248 replacement engine in it, hence the double action fuel pump.

 

 

Edited May 14, 2023 by Darius Stefan (see edit history)

[Bloo]

53 minutes ago, Darius Stefan said:

The photo I posted is the actual line on my engine and original. Should be 1/6npt in size, correct?.

The photo didn't come through. There is no 1/6" NPT. I think you meant 1/16"? 1/16" and 1/8" are the common small sizes. I was confused earlier in the thread, and I think 1/8" is the more common one.

 

Pipe thread stuff is measured by the hole in the middle of the pipe supposedly, but that can be dicey when you are looking at brass fittings. It is best to look up the OD of the size NPT you are interested in. Threaded sleeve stuff on the other hand is sold by the OD of the tubing the nuts fit.

 

EDIT: Here is the threaded sleeve stuff we can still readily get in the US without scrounging at swap meets.

 

https://blackhawksupply.com/collections/plumbing-brass-fittings-double-compression

 

Edited May 14, 2023 by Bloo (see edit history)

[Darius Stefan]

Thanks for the help. I will come back with an update once I get the parts I need. Hopefully this thread will be useful to someone else too one day.

 

[Bloo]

OOPS hang on...  I might be wrong about the threads in the 94. Just a moment...... Is that the only port?

[Darius Stefan]

Yes, it's the only port that I can see. 

[Bloo]

I am getting conflicting information about those threads. Here is an article showing how to convert an original 94 to ported vacuum. That port in the picture is not used.

 

https://www.eatonbalancing.com/2010/02/07/modifying-the-holley-94-two-barrel-for-late-model-distributors/

 

You can consider any Buick distributor "late model" for the purposes of that article. Fords had distributors called "Loadomatic" for a few years. Those were an oddity, and were what used venturi vacuum.

 

Also, that article may not be the last word. It may put you on the right track. The article appears incomplete to me, though it has been a while since I looked at a 94. The bottom line is the vacuum for any normal distributor needs to come from a hole just above the throttle plate (idle) and just below it (throttle cracked). A direct connection to manifold vacuum is the second best option.

 

I have heard of modern reproductions being built with the modern style vacuum port. By "modern" I mean "for everything except loadomatic". It's a pity if they didn't build yours that way.

 

Edited May 14, 2023 by Bloo (see edit history)

[Darius Stefan]

Son of a...biscuit.. okay, so this raises the concern that I may have the wrong carb that WON'T be a plug and play type of deal. Dammit. You learn something new every day. 

[Bloo]

https://www.jalopyjournal.com/forum/threads/holley-94s-can-i-add-vacuum-port.193993/

 

Bruce Lancaster's posts in that thread are the interesting ones. Some of the other folks are confused. The version he speaks of has both venturi vacuum and ported vacuum plumbed together to the external port, and only needs a passage to the venturi tapped and plugged. Maybe it is that simple.

 

[Darius Stefan]

I will have to check the specs again with the seller I guess.

[Darius Stefan]

On 5/14/2023 at 9:37 PM, Bloo said:

Could there be another port on the throttle body somewhere? That port looks to go to the venturi. If so, it won't do you any good. I have heard some of the reproductions have a "ported vacuum" port, which is what you want. Find the spot where the port comes out inside the bore. The port you need will be next to the edge of a throttle plate. It will be above the plate (atmospheric) with the throttle closed and idling, and below the plate (manifold vacuum) as soon as you crack the throttle open. You can probably see this on the Buick carb if the new 94 does not have it.

 

If there is no ported vacuum port, probably the best you can do is to hook the vacuum advance directly to manifold vacuum. In that case, there will be extra advance at idle when everything is set correctly. It usually works out OK on hotrodded engines. Sometimes it is OK on stock ones. It is better than running with no vacuum advance if you can get away with it.

 

My laptop battery is dying quick. I'll be back in a few minutes with come comments about possible threaded fittings.

 

Quoting on this one where you recommend checking where the ports come out into the bore; 

 

I checked and here are some photos, one port is close to the venturi and one is next to the throttle butterfly. I highlighted the port near the venturi with a red dot. The port next to the throttle butterfly is, as you indicated, above at idle and underneath when cracking open the throttle. It seems to be connected to the factory port on the outside. 

Edited May 16, 2023 by Darius Stefan (see edit history)

[Bloo]

7 hours ago, Darius Stefan said:

The port next to the throttle butterfly is, as you indicated, above at idle and underneath when cracking open the throttle. It seems to be connected to the factory port on the outside. 

Excellent. That's what you want.

 

7 hours ago, Darius Stefan said:

one port is close to the venturi and one is next to the throttle butterfly. I highlighted the port near the venturi with a red dot.

It sounds like you have the setup Bruce Lancaster was referring to. If the venturi port is also connected to the factory port, you need to plug the venturi port somehow.

 

[Darius Stefan]

1 hour ago, Bloo said:

Excellent. That's what you want.

 

It sounds like you have the setup Bruce Lancaster was referring to. If the venturi port is also connected to the factory port, you need to plug the venturi port somehow.

 

So they are not meant to run in series if I want to use the carb with my 248 straight 8.

[Bloo]

Yes. Ported vacuum *only* (or manifold vacuum) for any normal car including the Buick.

 

1949-56-ish Fords with the original Loadomatic distributor are one of a very few rare exceptions. There is also something odd about the pre-1949 Ford V8s. The details have slipped my mind. Those did have a centrifugal advance mechanism, but used something called a "vacuum break" instead of a normal vacuum advance to compensate for load.

 

Edited May 16, 2023 by Bloo (see edit history)

[EmTee]

7 hours ago, Bloo said:

...you need to plug the venturi port somehow.

So, are both of those orifices connected to the external vacuum port?  To make the vacuum interface function as a 'ported' vacuum can the venturi orifice be plugged with a dab of epoxy?  I just want to make sure I understand the situation...

[Bloo]

Yes. I believe people have been taping and plugging ports with set screws. I'm not too hot on the idea of epoxy around gas, but its just a vacuum port so it might be ok.

[Darius Stefan]

A year later, comin back to this topic...I got the carb finally fitted on the Buick today. It idles like a sewing machine but revving up.. doesn't like it, sputters back at me. Ignition and timing is fine, I been driving the car with the Stromberg AAV-167 that the engine came with with nearly no issues. Definitely the H94 is still sending the wrong vacuum signal somehow. I checked out a thread on Eaton Balancing about this specific topic but they have an H94 version with an economizer thingy in the base plate that mine doesn't have and it left me with questions on what other mods I need to make to get this thing to work right on the 248.

[EmTee]

It does sound like the vacuum advance isn't working - have you verified that diagnosis with a timing light?

[Darius Stefan]

1 minute ago, EmTee said:

It does sound like the vacuum advance isn't working - have you verified that diagnosis with a timing light?

I haven't yet, I'll do some more troubleshooting in the following days, pretty sure that my vacuum advance is also meant to be in good working order, considering I've been driving the car rather often for the past week. The only reason I'm going through all this trouble really is because this Stromberg AAV-167 is really worn, throttle shaft is loose, leaking gas out of the bowl, main body cast is cracked and has an old JBWeld repair on it, there's questionable jets inside, the list can go on, I really doubt this core is rebuildable at this point, it's just done with life.

[Bloo]

This picture from the Eaton link shows the meat of the vacuum advance issue.

 

 

We are looking at this from the top with the throttle shut. The port is open to the atmosphere. but as soon as the throttle is cracked, that port is below the throttle plate and receives full manifold vacuum. What you need is for your distributor to be connected to this port and ONLY this port. How you accomplish it is up to you. Ford probably had that port teed into venturi vacuum or something, and that won't do.

 

I have no idea what else you might have to do to it for non-distributor issues. If I remember correctly, these take standard Holley power valves. They are available for various vacuum levels. The valve is selected so that it is closed at all times except hard pulls or hard acceleration. Vacuum is low in those instances and the valve should open.

 

The port feeding vacuum to the power valve is the one directly above the "e" in the first instance of the word "hole" in the pic above. It probably leads down to the intake manifold through a hole in the gasket I guess. It needs to go directly to manifold vacuum, no exceptions or any funny business.

 

Main jets are selected for light throttle cruise operation. The power valve just adds more fuel for high load.

 

The accelerator pump must start to squirt instantly with any slight movement of the throttle. No delay is acceptable. Keep working with it until it does.

 

This is not an exhaustive list, but just the first and most important things. Good luck.

 

Edited September 15 by Bloo (see edit history)

[Darius Stefan]

As you pointed out Bloo, I triple checked the throttle body and the port for conventional vacuum as we all know it is there and only goes straight down where you see me pointing.

 

Therefore it's not necessary for me to drill down vertically as pointed out in the article by Eaton Balancing.

Edited September 15 by Darius Stefan (see edit history)

[Darius Stefan]

Additionally, I blocked off the venturi vacuum port as pointed out by me in the images which in turn allows me to use the diagonal plug-in for the distributor vacuum line.

[Bloo]

That oughta do it.

[Darius Stefan]

1 minute ago, Bloo said:

That oughta do it.

Indeed, I checked for other ports that might suck up the wrong vacuum but found none others....I guess I should triple check how good of a seal the vacuum truly has. I'm definitely certain that the vacuum chamber on the distributor is good, it proved so while driving.

[Darius Stefan]

Test fitted the H94 again today...backed the timing a bit too thinking it might be too advanced..to no avail. Feels a bit hopeless which is a damn shame considering how nice it idles compared to the Stromberg AAV-167... I'm thinking that this new carb is just not sending the correct vacuum signal, I get ignition before the intake valves close. I even made sure that the vacuum advance line is sealing properly by applying some pipe sealing tape on the adapter, didn't help. I'll upload a link to a video showing the symptoms shortly.

[Matt Harwood]

You seem pretty far down this road, but Stromberg AAV-16 carburetors are relatively inexpensive and plentiful on eBay. I realize you're overseas, but getting one of them shouldn't be difficult. Why reinvent the wheel with the Holley? A good Stromberg is easy to tune and will make the car run properly while saving you a ton of time and headaches along the way.

 

Just a thought.

[Darius Stefan]

I'm on the hunt for one of those too as I go, only reason I went for a Holley is I was excited for the manual choke and the simpler design, automatic ones are a pet peeve peeve of mine, but the more I go into this the more I realize it's really not worth it and should trust automatic chokes; quit fearing of the increased component count in a Stromberg.

[Darius Stefan]

I've got my eyes on a Carter WCD 663S too and upon an initial search I stand better chances of finding rebuild kits for that. My 248 is built somewhere in the late 40s, 48/49 most likely. Thoughts?

[Matt Harwood]

Carters are somewhat more complex than Strombergs and more challenging to tune, but they do seem to work better--the Carters give a smoother idle. Performance is about the same between the two. Parts are plentiful for both and rebuild kits are available from a variety of sources (I prefer Jon, @carbking here on the AACA forum).

[carbking]

A few thoughts:

 

As Matt stated, both Strombergs and Carters are available.

 

We make rebuilding kits for both, no problem.

 

As far as the automatic chokes on the later carbs, this link to my website should help:

 

Heat stove fabrication

 

As far as 1937 and 1938 carbs in general, this link may help you understand:

 

1937 and 1938 Buick carburetors

 

There are more parts in the Carters than in the Strombergs. If you order a rebuilding kit from us for either, ask for a factory specification sheet; as tuning information will be helpful. Many of the Carters REQUIRE a special metering rod tool to set the metering rods; we have these tools available as well as the kits. Not all Carters require the tool, ask when you order the kit, and I will look. The post-WWII Carters are as easy to work on as the Strombergs.

 

I personally think you will be MUCH happier with either a Carter or a Stromberg designed for a Buick than the imitation Holley currently being sold. Even an original Holley found at the bottom of a well, with 500,000 miles, and then rebuilt would be better than the modern imitations. But even with an original, you would still have the distributor vacuum issue.

[Bloo]

Automatic chokes are totally fine on American cars, with only a few exceptions. My Pontiac, a 36 does just fine. Despite the fact that it's choke does not seem to operate on the same strategy as later ones, and the fast idle is not quite completely automatic, it is trouble free.

 

On a 37 or 38 Buick though, the original Delco choke was troublesome even when new. Despite that, @EmTee managed to rebuild his Delco choke and make it work properly. A choke on a Carter carburetor will "just work" when adjusted to it's published settings. All you have to do is arrange a way to feed it clean air through it's little tube that has been heated by the exhaust manifold.

 

1 hour ago, Darius Stefan said:

I've got my eyes on a Carter WCD 663S too and upon an initial search I stand better chances of finding rebuild kits for that. My 248 is built somewhere in the late 40s, 48/49 most likely. Thoughts?

The WCD is a complex but great carb, and it probably has a Carter automatic choke. I don't know the number 663s. Regardless, I would encourage you to get one that was intended for a 248 Buick.

 

2 hours ago, Darius Stefan said:

I'm thinking that this new carb is just not sending the correct vacuum signal,

The signal for the Buick is not complex like the Ford. It's on or off and the engine does the rest. Once the throttle is cracked, the carb is completely out of the process. You verified that you are connected to the correct port, and you plugged the extra port. How could it be wrong? Hook a vacuum gauge to the distributor port. At idle you should have nothing. Crack the throttle slightly and you should have manifold vacuum. That's all there is to it.

 

Edited September 16 by Bloo (see edit history)

[Darius Stefan]

Thanks everyone for all the help so far. I'll follow up with an update at some point. 

[carbking]

7 minutes ago, Bloo said:

On a 37 or 38 Buick though, the original Delco choke was troublesome even when new.

Stating that the Delco choke was troublesome is like stating that the Pacific ocean contains some water

 

Most 1937 and 1938 Buick owners with the Delco choke adjust the choke so it is wide open when the engine is at normal operating temperature. If it actually partially closes on a cold engine, great, but don't expect it to do so. When starting the engine, pump the accelerator several times, and when the engine fires, hold it at a fast idle until the engine is warm.

 

To be perfectly fair, the Delco choke actually does work fairly well.................................at an ambient temperature of 105 degrees F.

 

Jon