M110 carby replacement and Holley quiz.

[craigb]

This is a bit of a non-benz quiz, although it is hanging off my Benz.  My 116 has a carby with Holley cast into it. It has 4 barrels and mechanically operated secondaries. The secondaries do not have their own pump jet. I had a mate looking at it on the weekend who has seen a few holleys in his day but didn't recognise this one.

Also I had this feeling that I had heard people say that a 350 Holley is better for the M110, with a 450 being overcarbied. It is replacing a 4bbl as standard isn't it? So maybe the choke size is just too big (not nice like some webber where you can change them). Not sure where to go with all this. Any suggestions on carbs to use?

[13B]

If it has mech secondaries then it must have twin accelerator pumps, these are known as a double pumper, and have float bowls shaped like an upside down V.

It more likely you have a 4160 "squarebore" with vac secondaries or maybe the carb has been modded to have mech secondaries but its not a good idea and shows poor planning for the use of the carby.

Best to look on the choke shround and tell me the list number, and I'll tell you tonight what its flow capacity is and how appropriate it is for an M110. 

Holley, generally by design, all look the same.  a squarebore 4160 looks much the same whether its a 390cfm or a 600cfm.  A double pumper looks much the same whether its a 600cfm or 850cfm...

A photo will also assist.

Ian.

[craigb]

Fantastic, thanks for that. There isn't always an answer available when you ask a question but great when you get a definitive one.

What you have said sounds similar to what my mate said except he didn't mention 4160. I reckon that is what one of the numbers was stamped near the fuel inlet. Will check and get the rest tonight and maybe a couple of pics. Definitely no vac secondaries, pretty sure not double pumper so as you say maybe converted.

If your busy maybe answer this after I get the other info but for me (and the record ie. others future info) what do you mean by not a good idea and poor planning. Sounds like there are applications where vac secondaries or mechanical is a better option

[craigb]

I knew I would have to work out how to insert a photo one day! Do i need to host it somewhere first?

[craigb]

Markings on the carb include:
Stamped-
7793MB
77933
L8517
3400
GR-5643B cast into it
and W21 handwritten.

Any of that mean anything to anyone?

[13B]

Does it look anything like this?



Thanks Oscar for the pic... thats a classic squarebore Holley.

7793MB - maybe an original dealer replacement for the dodgy solex?

Oscar has a tutorial somewhere on here about how to host pics, maybe look it up...

I.

[craigb]

Nope, nothing like that. Looks like photobucket is the go or gallery but that is getting all to late to think about.  Will have a go tomorrow but they are in a post on the ozbenz site, 116 under M110 carby

http://ozbenz.net/viewtopic.php?f=15&t=5739&p=36536#p36536

I wonder if that link will take you straight there?

[13B]

Can't see the pictures on OzBenz...not a member...

Anyway, I gave a pretty good write up on the Holley in this thread:

http://forum.w116.org/mechanicals/carby-questions/

From your description its probably a 4360-series "economaster" carby... just have to work out which one. 

Is this for your proposed track car?  If so I can give you a bit of background re. squarebore vs. economaster.

I.

[craigb]

OK I got as far as the gallery but now can see the bit about the URL but you should be able to see it there Ian.

[13B]

Ok, thats an Economaster carby, style number 4360.  They were sold in the late 1970s and 1980s by Holley in response to a market demand for a way to lift the economy up by 2mpg  on medium to large displacement V8 american cars.... by installing one of these on a 350 chev engine (the 8517 carb is rated at 450cfm) you lose a bit of top end performance at WOT, in exchange for better fuel atomisation and resultant better economy in the lower rev range.  (If you have a national speed limit of 55mph, what use is performance in the 100-120mph range? and in the aftermath of Energy Crisis II in 1974/5 (?) people happily exchanged top-end speed for lower speed economy - 2mpg is a good increase if your car returns 10mpg...)

That said, its not a performance carb... it probably fits where a 4160 carb would fit since they are meant as a downgrade to the gas-guzzling 4160s.

Again, this comes back to my question of whether this is the intended track car?  There's no reason why the 4360 wouldn't do an OK job with a standard engine, it wouldn't flow less than the solex, but the potential for tuning after modifying the engine is limited.  Higher compression, bored out pistons, and long duration camshafts, balancing and raised rev-limits will all require deeper breathing carbs and the 4360 isn't designed for that.

If your busy maybe answer this after I get the other info but for me (and the record ie. others future info) what do you mean by not a good idea and poor planning.

Vac secondaries, even on race engines, open slowly, compared to how quickly mechanical secondaries can be opened with your foot (which is almost instantaneously).  Stand on the accelerator on a double pumper and as the secondary butterflies are quickly opened, a large shot of petrol from the second accelerator pump makes sure you don't get a high speed lean-out.

When you modify a Vac secondary carby to mech secondaries, when you floor it the secondaries open instantaneously, but with no secondary accelerator pump you have a momentary lean-out, and depending on your engine revs and load, you could have a cough, backfire, or melted piston.

When a vac sec carb is floored the primaries open to WOT (with the accompanying shot of petrol from the accelerator pump to avoid the lean out) but the secondaries remain shut.  Vacuum drops to a couple of inches, and as the engine revs build up this vacuum increases.  At a certain vacuum level the secondaries will open, referenced to vacuum (and the tension in a spring in the vacuum diaphragm), slowly, so an accelerator pump isn't needed. 

Holley sells a kit (20-13), which allows you to change the spring to one of the different tension, thus alterning the opening characteristics of the secondary barrels.  Most people don't know about it and if they do have no idea how to use it, so they just bodge the carb to make the secondaries mechanical with varying levels of success...

I. 

[craigb]

Thanks heaps for all your info.

My first point is that for all those numbers on the carb you reckon one of them would say the model hey!

and asking the straight forward questions first, what is the flow (cfm)/ choke size of this carb compared to the original? You mentioned earlier you had some reference and it could be 390 to 600 if a 4160, which you state is a gas guzzler. Is 4360 the same sort of cfm range and hopefully some of those numbers stamped on it will give a hint as to exactly how much?

Answering your question in short, it isn't intended as a "track car" but will be used on the track. To try and explain that takes a bit longer so if you are short on time skip the rest of this paragraph! Years ago I rallied a Mk 2 Escort and on a young guys wage it basically sent me broke or used up all my spare cash. Then a mate did supersprints in an Alfa and I found that by buying a standard car I could sprint on Sunday and drive to work on Monday and have enough money left over to save for a house and still have fun! I have got to drive competition prepared cars, yes they are more fun but bang for your buck sprinting in the right standard car is pretty good. Now I am an old fart with young kids and financially it doesn't make sense to pour thousands into a car for a few days of my pleasure a year. I know sprinting can be done on a budget and I am hoping that if I show to other club members I am doing it cheaply then I will get a few more of them out there and maybe we will hang on to a few younger members that will have something to hold their interest.

So, I have a standard engine with good and even compression. Unless the carby is unworkable, I would prefer to make it work best it can and I am guessing a dyno to get the optimum jetting in there is the best move. On the street, the secondaries won't see a lot of work and on the track they will be constantly open except when it is all closed, so maybe the mechanical conversion is not such a big deal? Anyway, thanks for your description about the role of the vac vs mechanical, that all makes sense.

Off this topic but the car has excellent standard suspension with new sachs shocks and I will get a set of those comp 3 pads to slip in for track days. Apart from that I intend to keep everything just as it is. I wouldn't expect a buzzbox to stand up to this, but like my Alfa, I reckon my Benz will stand up to the occasional punishment and if not it might need more upgrading. The beauty of sprinting is that you are racing the clock and not other cars so you don't need to keep chasing performance, just your own skills and times. If I won the lottery I can think of all sorts of things to do...... but then I reckon I would get an open wheeler!

[13B]

Ok so yours is a List-8517 rated at 450cfm.  Its mechanical secondaries from the factory, and it can get away with this because the accelerator pump is so designed to give a decent shot of petrol when the secondaries are opened.

I don't know what the solex flow rate is but I do know it has small primary barrels and large secondary barrels, and that the reviewers of the car when it was new even said that sudden flooring of the car while cold would cause it to bog down, indicating that even the Solex isn't the optimum size for the engine.  However if they'd put a smaller carb on then the car would likely be out of puff by 80mph... 

CFM rating is hard to apply to a carb as a general rule.  Webers sizing related to throttle plate size (a 40mm DCOE has two butterflies that are 40mm in diameter) flow capcaity relates to the chokes installed... restrictive chokes may have the weber down as low as 250cfm, and very large chokes might have the flow up over 500cfm.  Likewise Holley knows that changing booster venturis changes flow capacity so a carb with the same butterflies and choke sizes but different booster venturies have different cfm values, so its dumb to mark on the carb as XXX cfm.  Far better to give it a unique number identifying what was in it as it left the Holley factory so anyone can look up Holley reference charts to determine what has to be changed  / has been changed.

I'll get back to you later with carby stats for your carb.

Whens all said and done your Economaster carb will be suitable for daily driving and basic sprint work.  Maybe, like the others have said put the car on a dyno and make sure the mixtures are within spec for your engine, but it should run as good as a Solex on your engine.

IF however you planned on modifying the engine you'd want to run a 4160 Holley, and this is especially so if you are looking into blow-thru-carby turbo charging.  You can also get Holley float bowls for 4160s (standard on 4150s) "race float bowl kit" part 134-108 which gives much better fuel control thru left-to-right-to-left etc. transitions (ie. esses) and I fit them to any holley I set up for the track.  I can't comment on the fuel bowl characteristics of the Economaster.

I bet Oscar would be keen to hear how the Economaster runs as some time a go we had a discussion about the suitability of the 4160 390 and 465cfm carbs to the M110 engine.  His was being a little eccentric at times.  Oscar?  You still around and having troubles with your 280S carb?  Or did we decide it was your piston#6 compression??

I.

[craigb]

Do I start a new topic or continue......anyway

Not that I didn't believe you Ian, but when 2 knowledgeable people tell you exactly the same thing it does add weight. I rang West Torrens Dyno who are a long term reputable place and the guy said that the 4360 was not ideal due to the mechanical secondaries and no pump (sound familiar), so he said by the time you compensate for that you end up losing a lot of economy and I may end up having to put another carb on it. He still reckoned it was worth having a go... standard fee of $300 and that usually sorts stuff.

So I am thinking maybe just get a better carb but then that is getting away from my intent of keeping costs down. So to do a total backflip, and something hinted at here somewhere or ozbenz, what about turning it into a set of butterflies and go to dedicated gas? Probably cheaper with the rebate in the long run. Done sensitively the car should be able to be returned to original if anyone has the urge to do so in the future. I have what is now a very rusty  108 250s on gas and that goes very well and had done so for a very long time. It did have twin gas outlets into each of the Zenith carbs and I often wonder if that is why it works so well. Did any of the carb M110's have a twin carby manifold and does anyone think that would make a difference with gas?

[oscar]

Hey fellas, been away for work in Wagga, or still am till Friday.  I've borrowed a laptop so I'm online tonight at least.

Re my 280S and the holley, I'm still at where we left it last time 13B.  Just too many other commitments culminating in this week.  So hopefully, back into it soon.   I think my carb is as good as I can get it for the moment.  I haven't even tested with a vac gauge on the manifold yet but the engine needs dismantling first.   6th cylinder at best needs new rings.  My mech is where I'm staying at the moment so I talked to him today who reckoned the same.  Plus there's the headgasket and I'd be mad not to get the bores evaluated plus head tested.   So, looks like a while before it's up and racing i mean driving.  

Ha seriously, if GrantV can race a finnie and you get your 280S sprinting Craigb, maybe I'll ditch my plans for a 450 and have the 280S racing.  Oh yes, the bug has bitten.

I can't really add any advice, 13B's got the goods and I was going to post the same link.  I haven't tackled the carby for so long that all the figures and terminology has escaped me once again so when I do get into it, I'll have to relearn what I knew beforehand.  And yeah, I do agree and wish Holley had a simpler numbering system.

But here's some thoughts, bahnstormer has a Solex carb for sale on ebay for $5.  He says pick up only but you could ask for post and see.  However whether the Solex is your preferred carb for your part-time track plans, I don't know.  Plus you need to have the original electrical connections for the shut off solenoids too which may have been removed when your Holley was put on.  I'll be interested to see how you go. 

Re the twin manifolds - I'll have to check my manual when I get home.  I'm sure they didn't but will check on the weekend.  Don't know about gas??  Is it worth it??

[13B]

On a different note, just thought I'd give you guys a heads up if you want to experiment with carbys on your 280Ss...

You need one of these in order to put a Holley 350 2bbl carb on a car designed for a 4 barrel:

Carb adaptor

If you are shopping for a 350 Holley for track car you need one with centre pivot (race type) float bowl, like this one:

350 Holley

Ian.