42 DCNF's on a Mopar 440

[Grant007]

Harry .. I know it was so strange that we both mentioned it within a matter of hours after all this time!
Thank you for your reply Harry, yes.. you are the carb man, and a very clever one too, for that please accept one of these >>>
I do have in stock and will be using a set of Stainless Headers anyway Harry yes, and, I was aware that each header pipe would need a port for a Lamba sensor if we were going down the EFI route, but to be honest Harry I would be just as Happy with 44 DCNFs, but I have had a search out for a set for 2 years now, well since you gave me that Chevy IR inlet Manifold, nothing has ever appeared on Ebay, well, not a matching set anyway, I do know of a place that I think may have a set but it would be a visit rather than an online thing. I'll give them a whirl I think, it is a cheaper option that's for sure, and a simpler affair generally. The only other advantage of the Jenvy throttle bodies is that I believe they are slightly lower are they not Harry?
Thank you as always Harry... Grant

[JACB]

One question regarding your overdrive unit. You mention an 'interring switch'. I am assuming that to be what we here would term a 'kill switch' that would be used to cut power to the overdrive solenoid when you are running with OD locked out?

I will be running an overdrive transmission in my own car and am always interested in how others approach such adaptions.

Hi Harry

Sorry "interring switch" is predictive text for "Interesting switch". Bruce came up with a way to use the gearshift detent (top of slap-Shift) to turn the GVO on/off.

Re the GVO I would avoid the auto sequencer they made that should have allowed automatic split shifts. Ie 1, 1+OD, 2, 2+OD, 3, 3+OD effectively turning a three speed transmission into a six speed transmission. It was full of issues … One guy in NZ did make it work and his story can be seen here http://www.cuda-challenger.com/cc/index ... ic=23610.0



Gear Vendors Standard AutoDrive Electronics had the AutoLaunch feature and you can read about that here https://www.gearvendors.com/operationtips.html

If you like paddle shifting I note that the master shift will work with the GVO … much like the Auto Sequencer … 3 becomes 6. More can be seen here https://ls1tech.com/forums/automatic-tr ... ndors.html & here https://www.mastershift.com/

[JACB]

… the ultra rare Inglese casting originally intended for small block Chevy...... Mounted on your 400 (or 440) engine …

As for fitting the prototype DNCF intake to your MOPAR engine, that will involve splitting the intake on a bandsaw, making it 2 individual pieces much as the Aston Martin intake casting. This will allow alignment front to rear with the MOPAR intake runners.

Then you will need to make up some aluminum head plates (adapters/spacers) to go between the intake and heads. These will be much as the plates that allow 383/400 low deck intake to be used on 413/440 raised deck blocks except they will be a bit thicker. Then, with a bit of creative hand fitting, machining and drilling/tapping you will have a 1 of 1 IR type EFI intake for your 400 or 440 engine.

Harry

That is quite a thought if Small Block/Big Block Chevy intake manifolds could be converted to Mopar big block heads … what a huge supply of "New" Manifolds we would have to consider!? I have no idea about the various dimensions …. but surely this must be a mammoth undertaking?

[Grant007]

but surely this must be a mammoth undertaking?

James.. well I guess everything is a lot of work, but the basics are to cut the chevy manifold across the middle from left to right , then the front and back will be parted and line up the ports in the heads luckily, then you make spacer plates that fit between the heads and the manifold, the same design as you can get from summit racing that will make a 383 manifold fit a 440, but the plates need to be made out of a slightly thicker material to take up the difference to allow the chevy one to be the correct fit .. that's the basically it

[enigma57]

Hi, Grant! The vision of a one off IR induction setup sitting atop your MOPAR engine in the Jensen Interceptor brings a smile to my face. I know it can be done and I know you can do it.

I suppose the most compelling decision priour to proceeding will be whether to run carburettors or convert to EFI. As you know, I'm a carb guy and have a deep affinity for Weber carbs, most especially the DCNF series. And the visualization of 2 brace of them in a row atop your engine brings a huge smile to my face. Nonetheless, I will do my best to be fair and look at both scenarios as dispassionately as I can.

With an individual runner design, sufficient flow through the carburettor(s) or ITB(s) is key. Runner cross section in the Inglese casting is generous, so that is not an issue. And should you elect to convert to EFI by way of utilizing Jenvey TBI(s), the 45mm version should be more than adequate even for a 'built' 440 engine.

So the question as to functionality becomes...... Will DCNF carburettors on IR intake provide sufficient flow for an engine of 400 or 440 cu. inch displacement? This, with the understanding that this is not a max effort race engine, but a large displacement engine in a mild state of tune which will power a road car of 3,500 - 3,600 lb. curb weight. As such, an engine which will likely not be revved in excess of 5,000 - 5,500 RPMs.

I believe they will...... If taken to their limit as regards choke and throttle bore size. In choosing a Weber carburettor, the first consideration is usually choke (main venturi) size. Weber's recommended choke to throttle bore sizing is 1.25:1 and you can usually go one step (2mm) up or 1 step down in choke size with good results when it comes to tuning.

The largest choke size I have seen on DCNF carbs relative to throttle bore on an OEM installation is the mid-'70s Series 3 Aston Martin. 5.3 litre V8 redlined at 6,000 RPMs. These ran 42 DCNF carbs on IR intake with 36mm chokes...... A ratio of 1.166:1. If you increase throttle bore to 44mm, this ratio would give you a choke size of 37.7mm and if you increase throttle bore to 45mm, the equivalent choke size would be 38.57mm.

So let's take a look at the Aston Martin 5.3 litre (325 cu. in.) engine with respect to induction flow requirements. If we assume same percentage of volumetric efficiency (or state of tune, if you will)...... A 325 cu. in. engine at 6,000 RPMs requires the same induction air flow as a 400 cu. in. engine turning 4,900 RPMs. So hypothetically, we can assume 42 DCNF carbs running 36mm chokes on each of these engines should support both engines to those engine speeds....... Rough rule of thumb. And if we further increase throttle bore and choke size, the DCNF should allow the 400 engine to rev even more freely.

I looked around e-Bay last night, Grant. There were several 44 DCNF carbs there. Most of them look to be original to the Ducati Paso motorcycle. These typically run 36mm chokes and #10 accelerator pump cams. Not sure whether all had matching Weber part numbers though, as there were several carburettor part numbers used on both the Paso 750 and 906 Ducati over the years.

Now granted, a matched set of (4) Weber 44 DCNF carbs will not be easy to find, as they were much less used than the smaller versions of DCNF (36, 40, and 42). And prices range from $400 - $500 apiece and up for used examples in rebuildable condition. Still less expensive that converting to EFI with all the ancillaries involved, though. And if fitted with 37mm or 38mm chokes, they would certainly fill the bill.

So here is an idea...... Just something to consider...... The gnarly looking set of 42 DCNF carb bodies I sent along a while back which were original to a '74 Aston Martin...... Need to be rebuilt and the throttle bores cleaned up anyway. Why not have the throttle bores honed larger and fit them with 44 DCNF throttle blades when rebuilding? The 36mm choke tubes can be honed out to 37.5mm, as well.

As far as that goes...... If you have a 42 DCNF carb body that is too far gone to save...... Try boring the throttle body (below the lower land the choke tubes fit into) to 45mm. If there is sufficient material in the aluminum casting to safely increase throttle bore to 45mm...... You can fit throttle blades from 45 DCOE and hone choke tubes out to 38.5mm .

The compact DCNF carb has close coupled throttle bores (48mm center to center). So 44mm throttle bores would have 4mm between them and 45mm throttle bores would have only 3mm separating them if bores are increased to 45mm in diameter.

Jenvey have a nice dimensional diagram for their DCNF EFI throttle bodies which shows the DCNF carb mounting pattern and is a good guide when laying out your carb mounting holes for drilling/tapping......

https://store.jenvey.co.uk/pub/media/do ... B_ISS1.pdf

https://store.jenvey.co.uk/throttle-bod ... il-tc40-45

As you noted...... The Jenvey ITBs are shorter in height than are DCNF carburettors. If you make allowances for the Bosch injectors, an air box similar to that used by Aston Martin with their carburetted Lagonda engine can be fitted along with DCNF contoured air entry bellmouths.

In either case...... Whether you decide to fit DCNF carburettors or Jenvey ITBs...... You will have a unique and well performing induction system, Grant. Just let me know which way you elect to go with this and I will do all I can to help you make it a reality.

Best regards,

Harry

[enigma57]

… the ultra rare Inglese casting originally intended for small block Chevy...... Mounted on your 400 (or 440) engine …

As for fitting the prototype DNCF intake to your MOPAR engine, that will involve splitting the intake on a bandsaw, making it 2 individual pieces much as the Aston Martin intake casting. This will allow alignment front to rear with the MOPAR intake runners.

Then you will need to make up some aluminum head plates (adapters/spacers) to go between the intake and heads. These will be much as the plates that allow 383/400 low deck intake to be used on 413/440 raised deck blocks except they will be a bit thicker. Then, with a bit of creative hand fitting, machining and drilling/tapping you will have a 1 of 1 IR type EFI intake for your 400 or 440 engine.

Harry

That is quite a thought if Small Block/Big Block Chevy intake manifolds could be converted to Mopar big block heads … what a huge supply of "New" Manifolds we would have to consider!? I have no idea about the various dimensions …. but surely this must be a mammoth undertaking?

James, thanks for your explanation of the interring switch. I must come up with something similar when working up a reverse gear lockout to ensure overdrive is disengaged when shifting into reverse.

Yes, with considerable effort, such intake manifold adaptions are possible. Is it worth doing? After all, there are many fine intake manifolds available for the MOPAR engines, including the early 1960s long runner crossram dual quad......



All depends on whether the end result is what you are after. I would say a unique intake such as Grant is considering would be worth the effort, as is the EFI conversion of the vintage low profile Offenhauser you will be doing.

My first such effort was whilst I was stationed aboard a sub tender in the 1970s. I had a 500 cu. inch Cadillac engine and there being no aftermarket intakes made for them back then...... I located an aluminum tri-power intake for a big block Ford which had very nearly an identical port layout. I trimmed off the water jackets, head flange mounts and unneeded pieces. Made 3/8" thick aluminum flanges to fit the pared down Ford intake to the Cadillac heads (by hand, the hard way). Then with the help of a friend, welded the tripower intake to the new head flanges that fit it up to the Cadillac engine. Took many, many hours of welding on our off hours whilst at sea. Worked beautifully fitted with Holley tri-power carbs, though.

Good luck with your project. Please keep us informed of your progress.

Best regards,

Harry

[Geoff2]

Harry.

On the 440, redline was 6000 rpm. On the 455, redline was 5500. The 48 IDFs come with 40mm chokes, which I used on both. On the 455, I tried 43mm custom chokes from TopEnd Perf in Calif. Terrible. I was expecting improved top end with the bigger chokes, but it was worse everywhere...
As you know, these carbs were never designed for such larger cyl volume. I found I had to use very large air corrector jets, 250, & extra holes in the E tubes to cure off idle richness.

[enigma57]

I hear ya, Geoff! Although we were reconfiguring DCNF carbs for plenum intake rather than IR, we ran into similar tuning issues. I am not sure what motor fuel formulation you have there, but here in Texas in counties neighbouring the cities, we are pretty well stuck with 10% ethanol for pump gas. No access to pure gasoline unless you have friends at a small or private airport which serves primarily piston engined planes, who will look the other way and sell you some avgas for your car. Even the white gas we used to be able to get at the lakes for small boat engines has become scarce as hen's teeth in recent years.

Did you experiment with increasing the size of your idle air bleeds? That is one of the things we have looked at with the DCNF carbs.

At times, tuning Webers seems rather counter intuitive. What we finally ended up with was a combination of larger diameter (lean) emulsion tubes, larger main, idle (slow running) and accelerator pump jets, smaller main air correctors and larger idle air bleeds. Seems to be working well. Next challenge will be to address vapour lock, heat soak and fuel percolation by venting off underhood heat, adding a fuel return line and insulating exposed fuel lines in the Saab 96 engine compartment. Its been over 100 degrees Fahrenheit here the past 10 days and underhood heat seems to wreak havoc with the newer, more volatile reformulated ethanol fuels.

Whilst we are awaiting delivery of the fuel line insulation, I have talked Mark into running wooden clothes pins on his underhood metal fuel line spaced at 1-1/2" intervals and wrapping the spaces between them with 3 wraps of aluminum foil as a stop gap measure. Not very high tech, but it works. Mark hates the look of it, though. So I told him how neat it would be to get some photos of his engine and embellish his low tech clothes pin installation by hanging a couple socks from them.

Best regards,

Harry

[Geoff2]

Harry.

No didn't change IABs. They are fixed on IDFs. My theory is that if changeable air bleeds were necessary, they carb would be made that way. I have never had a flat spot or stumble going from idle to cruise with just light throttle opening. It is exceptionally smooth actually. The problem I was getting was at larger throttle openings getting into the main system.

I am in Australia & we have a choice of E10, 91, 95 & 98 octane. E85 is also available at some outlets. It is claimed that our octane #s are 4-5 points higher than yours. When I had used 4 bbls, I had to use 98 to prevent pinging & also had to be careful with the ignition curve. 9.8:1 CR with factory iron heads. With no other change than swapping to Webers, I can now use 91 octane, never pings even on 44*c days; plus, I can [ & do! ] run with a locked dist at 35*. I will not use E10. I left a cupful in a container on the bench overnight. Next morning, there globules of water floating in the bottom...

Cheers & keep Webering.

[Grant007]

Hi, Grant! The vision of a one off IR induction setup sitting atop your MOPAR engine in the Jensen Interceptor brings a smile to my face. I know it can be done and I know you can do it.

I suppose the most compelling decision priour to proceeding will be whether to run carburettors or convert to EFI. As you know, I'm a carb guy and have a deep affinity for Weber carbs, most especially the DCNF series. And the visualization of 2 brace of them in a row atop your engine brings a huge smile to my face. Nonetheless, I will do my best to be fair and look at both scenarios as dispassionately as I can.

With an individual runner design, sufficient flow through the carburettor(s) or ITB(s) is key. Runner cross section in the Inglese casting is generous, so that is not an issue. And should you elect to convert to EFI by way of utilizing Jenvey TBI(s), the 45mm version should be more than adequate even for a 'built' 440 engine.

So the question as to functionality becomes...... Will DCNF carburettors on IR intake provide sufficient flow for an engine of 400 or 440 cu. inch displacement? This, with the understanding that this is not a max effort race engine, but a large displacement engine in a mild state of tune which will power a road car of 3,500 - 3,600 lb. curb weight. As such, an engine which will likely not be revved in excess of 5,000 - 5,500 RPMs.

I believe they will...... If taken to their limit as regards choke and throttle bore size. In choosing a Weber carburettor, the first consideration is usually choke (main venturi) size. Weber's recommended choke to throttle bore sizing is 1.25:1 and you can usually go one step (2mm) up or 1 step down in choke size with good results when it comes to tuning.

The largest choke size I have seen on DCNF carbs relative to throttle bore on an OEM installation is the mid-'70s Series 3 Aston Martin. 5.3 litre V8 redlined at 6,000 RPMs. These ran 42 DCNF carbs on IR intake with 36mm chokes...... A ratio of 1.166:1. If you increase throttle bore to 44mm, this ratio would give you a choke size of 37.7mm and if you increase throttle bore to 45mm, the equivalent choke size would be 38.57mm.

So let's take a look at the Aston Martin 5.3 litre (325 cu. in.) engine with respect to induction flow requirements. If we assume same percentage of volumetric efficiency (or state of tune, if you will)...... A 325 cu. in. engine at 6,000 RPMs requires the same induction air flow as a 400 cu. in. engine turning 4,900 RPMs. So hypothetically, we can assume 42 DCNF carbs running 36mm chokes on each of these engines should support both engines to those engine speeds....... Rough rule of thumb. And if we further increase throttle bore and choke size, the DCNF should allow the 400 engine to rev even more freely.

I looked around e-Bay last night, Grant. There were several 44 DCNF carbs there. Most of them look to be original to the Ducati Paso motorcycle. These typically run 36mm chokes and #10 accelerator pump cams. Not sure whether all had matching Weber part numbers though, as there were several carburettor part numbers used on both the Paso 750 and 906 Ducati over the years.

Now granted, a matched set of (4) Weber 44 DCNF carbs will not be easy to find, as they were much less used than the smaller versions of DCNF (36, 40, and 42). And prices range from $400 - $500 apiece and up for used examples in rebuildable condition. Still less expensive that converting to EFI with all the ancillaries involved, though. And if fitted with 37mm or 38mm chokes, they would certainly fill the bill.

So here is an idea...... Just something to consider...... The gnarly looking set of 42 DCNF carb bodies I sent along a while back which were original to a '74 Aston Martin...... Need to be rebuilt and the throttle bores cleaned up anyway. Why not have the throttle bores honed larger and fit them with 44 DCNF throttle blades when rebuilding? The 36mm choke tubes can be honed out to 37.5mm, as well.

As far as that goes...... If you have a 42 DCNF carb body that is too far gone to save...... Try boring the throttle body (below the lower land the choke tubes fit into) to 45mm. If there is sufficient material in the aluminum casting to safely increase throttle bore to 45mm...... You can fit throttle blades from 45 DCOE and hone choke tubes out to 38.5mm .

The compact DCNF carb has close coupled throttle bores (48mm center to center). So 44mm throttle bores would have 4mm between them and 45mm throttle bores would have only 3mm separating them if bores are increased to 45mm in diameter.

Jenvey have a nice dimensional diagram for their DCNF EFI throttle bodies which shows the DCNF carb mounting pattern and is a good guide when laying out your carb mounting holes for drilling/tapping......

https://store.jenvey.co.uk/pub/media/do ... B_ISS1.pdf

https://store.jenvey.co.uk/throttle-bod ... il-tc40-45

As you noted...... The Jenvey ITBs are shorter in height than are DCNF carburettors. If you make allowances for the Bosch injectors, an air box similar to that used by Aston Martin with their carburetted Lagonda engine can be fitted along with DCNF contoured air entry bellmouths.

In either case...... Whether you decide to fit DCNF carburettors or Jenvey ITBs...... You will have a unique and well performing induction system, Grant. Just let me know which way you elect to go with this and I will do all I can to help you make it a reality.

Best regards,

Harry

Your such a Chap Harry and that is why we love you!!.. I've sent you an email Harry with some technicalities.. Thank you again Harry for your help as always

[enigma57]

You are most welcome, Grant! I look forward to helping with your project in any way that I can. Really enjoy one off induction systems. Lots of fun!

Best regards,

Harry

[enigma57]

Harry.

No didn't change IABs. They are fixed on IDFs. My theory is that if changeable air bleeds were necessary, the carb would be made that way. I have never had a flat spot or stumble going from idle to cruise with just light throttle opening. It is exceptionally smooth actually. The problem I was getting was at larger throttle openings getting into the main system.

I am in Australia & we have a choice of E10, 91, 95 & 98 octane. E85 is also available at some outlets. It is claimed that our octane #s are 4-5 points higher than yours. When I had used 4 bbls, I had to use 98 to prevent pinging & also had to be careful with the ignition curve. 9.8:1 CR with factory iron heads. With no other change than swapping to Webers, I can now use 91 octane, never pings even on 44*c days; plus, I can [ & do! ] run with a locked dist at 35*. I will not use E10. I left a cupful in a container on the bench overnight. Next morning, there globules of water floating in the bottom...

Cheers & keep Webering.

Sounds like you have your IDFs dialed in very well, Geoff! Idle air bleeds on our DCNF carb are fixed brass bushing, as well. They vary in size depending on original fitment of carbs. Anywhere from 1.1 to 1.35 . I usually leave them be for the same reasons you stated. But if need be, will drill them oversize. DCNF and IDF use same idle (slow running) jets, so figured idle air bushes were similar as well.

Ethanol (even 10%) is really bad stuff. Not only did 10% drop our mileage on ourdaily drivers from 30 MPG down to 27...... Its highly corrosive. If we could get straight gasoline here, that's all I would run. As you noted, ethanol picks up moisture like a sponge. Even condensation that forms on the inside of fuel tank above liquid level. Which is why I keep the fuel tanks on our daily drivers as full as possible. On my Chevy, I will be running carbs. Webers. So I will add a drain plug to bottom of fuel tank and have picked up a good marine type fuel filter having provision to drain off any moisture collected from fuel.

I have a friend in NSW. Met her when she and others from her school visited Texas as they were traveling across the US. We have kept in touch since 1964. I was pretty crazy about her when I was a teenager. Even considered shipping myself 'down under' in a wooden crate at one point. Had it all figured out and a couple of friends were going to drop me off at the airport, but then I heard about a couple of instances where guys froze to death doing that and realized that (in those days), there was no way to know whether I'd end up on a prop job or a jet. If it was a jet they flew higher and would very likely end up freezing to death in an unpressurized cargo compartment. So I signed up for the Marines and Uncle Sam treated me to an all expense paid vacation to Quang Tri Province, RVN. Anyway, we both married others and raised families and remain friends to this day. Reckon that's how it was meant to be.

Best regards,

Harry

[enigma57]

Grant, I found these photos in a magazine article this morning. This is a Lincoln Y-block engine fitted with a Chevrolet intake manifold.

Note thick aluminum spacer / adapter plates between Chevy intake and Lincoln heads. This is the same method of adaption I suggested for mounting your prototype Chevy DCNF intake to your 400 Chrysler engine.

Only you will have an advantage, as your intake is undrilled, so after trimming the unneeded water jacketing and distributor mounting areas from your prototype intake, you may drill your holes in intake and adapter plates wherever you need them. For most, you will be able to drill so as to use a long bolt or stud that passes through both intake and adapter plate, lining up with existing tapped bolt holes in Chrysler heads below. For the few intake bolts which won't line up and must be relocated, you can counter-sink a bolt holding adapter plate to head flange, then drill another hole that aligns better with the intake and drill / tap the adapter plate to accept it.

To magnify images, either click on link to original article below...... Or click on individual images to enlarge them.

Best regards,

Harry

https://www.hotrod.com/articles/a-rare- ... y-block-01