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View Full Version : Carb conversion vs K-Jet ???? Is it Worth going Carbs:????



rtcraver
11-06-2016, 08:23 AM
How many have you converted to Carb and how satisfied overall with the results. Who/ Where did you get set up from?

Thanks

Tod #1815 Auto

Spittybug
11-06-2016, 08:57 AM
Consider all of your options first. Great success with EFI if you read the threads. Modern. Constantly improving.

Soundkillr
11-06-2016, 10:05 AM
Moved to carb section....

sdg3205
11-06-2016, 11:11 AM
What's the problem with your k-jet?

Andrew
11-08-2016, 01:02 AM
While I am not an expert, I have been a DeLorean owner for over 18 years and I have owned and driven K-Jet and carbed Deloreans. There are a number of advantages of carburation compared to K-jet or EFI:

1. Lower fuel pressures. Carburation requires approximately 1/10th the pressure of K-Jet

2. Less electrical components. With a carb conversion you can eliminate virtually every electrical aspect of the fuel system. This includes the RPM relay, the main fuel relay, the fuse 7 circuit, the lambda module and the idle ECU.

3. Mechanical fuel pump option: The DeLorean PRV has a mechanical fuel pump mounting location on the passenger side cylinder head. The cam is located under a blanking plate. (The pump is an Airtex 1436)

4. Ease of servicing and adjustment fuel system. An ear and a screwdriver is all that is necessary to adjust a carb. No need for computerized diagnostic equipment (EFI) or mason jars (K-Jet.)

5. Easier access to other components including but not limited to the water pump, clutch slave cylinder, distributor etc.

6. Lower cost than a K-Jet rebuild and a fraction of the cost of EFI. I was able to find two complete Peugeot 604 fuel systems for 250 each. With the fuel pump, K and N air filter, fuel lines and hoses my total cost expenditure was roughly 400. If you can't find a Peugeot system or if you don't want to deal with the Solex carbs, you can buy a carb kit. The last time I heard the kit in question was around 1100. A good chunk of the cost can be recouped by selling K-jet cores. I have a complete working K-jet system on my shelf. It will be included with 4194 if I ever sell it.

7. Time: A non running K-Jet car can be carbed in a day. Most of the time involved in the conversion is attributable to removing K-Jet and running fuel lines. In contrast EFI is a winter project!

8. 100 percent reversible: Depending on what carb you use, a modification to the throttle cable may be required, but NOS throttle cables are still available.

Personally I love my Peugeot 604 fuel systems. They provide very nice performance. The Peugeot single plane manifold really changes the DeLorean driving experience for the better. It should be noted that the dual Solex system and manifold are the same setup that Renault used on the Alpine, which is well respected on the other side of the Pond for it's performance.

If you are interested in a carb conversion, talk to other carbed owners to get their first-hand feedback.

Best of luck,

Andrew
4194
5052

DMCVegas
11-08-2016, 02:56 PM
Sorry, but I'm going to have to call out a few things here.


1. Lower fuel pressures. Carburation requires approximately 1/10th the pressure of K-Jet

Never mind that the math is off on that, exactly how is lower fuel pressure supposed to be a benefit? GDI systems can currently run up to around 2,900 PSI comparatively and there is no problem for gasoline to run at a higher pressure.



2. Less electrical components. With a carb conversion you can eliminate virtually every electrical aspect of the fuel system. This includes the RPM relay, the main fuel relay, the fuse 7 circuit, the lambda module and the idle ECU.

Yes, there are some fewer electrical components, but you will also have to graft in additional ones such as the Electric Choke. A better question however would be why anyone would believe that removing the fuel system relays is a good idea. In particular the RPM relay of all things. If you stall out or get into an accident, the safety systems of the DeLorean are designed to both stop the engine as well as the fuel pump. That way if you happened to have a severed fuel line, the car doesn't just continue to pump raw gasoline out to either help start, or continue to feed a fire to cause more damage and risk more lives.



4. Ease of servicing and adjustment fuel system. An ear and a screwdriver is all that is necessary to adjust a carb. No need for computerized diagnostic equipment (EFI) or mason jars (K-Jet.)

Now that is not correct at all. There is a reason that Exhaust Gas Analysers exist to tune engines. If they could be tuned soley by sound, then acoustic tools would have been introduced many, many years ago.

Furthermore, while K-Jetronic does require the proper use of an exhaust gas analyser, just like a carburetor engine, K-Jet is completely self-contained and needs only a single screwdriver to tune the engine at a single idle speed. Carburetors on the other hand must have the appropriate jets installed for the correct applications to start with. THEN you must tune for Idle, Fast Idle, and WOT independently. By contrast K-Jet's components are all pre-calibrated to take over those duties so that you never need to worry about them.

Certainly you can get a carbureted engine to run with a screwdriver and an ear, but you won't be able to properly tune it to run 100% correctly to pass emissions nor to avoid long-term internal damage.



7. Time: A non running K-Jet car can be carbed in a day. Most of the time involved in the conversion is attributable to removing K-Jet and running fuel lines. In contrast EFI is a winter project!

Keep in mind that a non-running K-Jetronic engine can also be brought back to live within the span of a day as well when you're just swapping out parts.


Now I have nothing against Carbs. If it gets another DeLorean back on the road, I'm all for it. I just want to see it all done the correct way in a safe manner, and that people can make a properly informed decision. Because yes, there are indeed several advantages to carbs, just as there are some disadvantages.

What I personally am curious about is if anyone has ever mated a carburetor with a set of Performance Cams, higher compression, better ignition, and a proper dual exhaust system.

Andrew
11-09-2016, 05:29 PM
Sorry, but I'm going to have to call out a few things here.



Never mind that the math is off on that, exactly how is lower fuel pressure supposed to be a benefit? GDI systems can currently run up to around 2,900 PSI comparatively and there is no problem for gasoline to run at a higher pressure.


If I were to have a fuel leak I would much rather have a low pressure leak 50 plus PSI...but that's just me.




Yes, there are some fewer electrical components, but you will also have to graft in additional ones such as the Electric Choke. A better question however would be why anyone would believe that removing the fuel system relays is a good idea. In particular the RPM relay of all things. If you stall out or get into an accident, the safety systems of the DeLorean are designed to both stop the engine as well as the fuel pump. That way if you happened to have a severed fuel line, the car doesn't just continue to pump raw gasoline out to either help start, or continue to feed a fire to cause more damage and risk more lives.





Now that is not correct at all. There is a reason that Exhaust Gas Analysers exist to tune engines. If they could be tuned soley by sound, then acoustic tools would have been introduced many, many years ago.

Furthermore, while K-Jetronic does require the proper use of an exhaust gas analyser, just like a carburetor engine, K-Jet is completely self-contained and needs only a single screwdriver to tune the engine at a single idle speed. Carburetors on the other hand must have the appropriate jets installed for the correct applications to start with. THEN you must tune for Idle, Fast Idle, and WOT independently. By contrast K-Jet's components are all pre-calibrated to take over those duties so that you never need to worry about them.

Certainly you can get a carbureted engine to run with a screwdriver and an ear, but you won't be able to properly tune it to run 100% correctly to pass emissions nor to avoid long-term internal damage.




Keep in mind that a non-running K-Jetronic engine can also be brought back to live within the span of a day as well when you're just swapping out parts.


Now I have nothing against Carbs. If it gets another DeLorean back on the road, I'm all for it. I just want to see it all done the correct way in a safe manner, and that people can make a properly informed decision. Because yes, there are indeed several advantages to carbs, just as there are some disadvantages.

What I personally am curious about is if anyone has ever mated a carburetor with a set of Performance Cams, higher compression, better ignition, and a proper dual exhaust system.


If I were to have a fuel leak I would much rather have a pressure leak at 5 PSI than 50 plus PSI...but that's just me. Can I get an Amen from anyone who has ever lost an accumulator hose while driving? I have! Furthermore, with K-jet even with the fuel pump off, the fuel will continue to flow through a leak until the system depressurizes. This is a result of the accumulator.


Less electrical / electronic components = Less potential items to fail. In my years of dealing with K-jet, I've had fuse 7 blow while driving, I've also had an RPM relay fail once. Finally, I had 4 K-jet pumps fail within a matter of years. In contrast, in 20 years I had one mechanical fuel pump fail and that was on a 25 year old junk yard motor with unknown mileage.

With regard to the stalling concern, since a mechanical pump driven via a cam lobe, it will stop pumping if the engine stalls.

I've been driving carbed cars for the past 20 years. Never once have I used a gas analyzer. My 72 Rivera has over 200K on the original engine and my daily driver 85 Toronado has 212K. The 72 Riv actually gets around 15 MPG, which is pretty good for a 455 V8. Ironically, when I lived in an emissions testing state, the only car I ever had difficulty with at testing time was the DeLorean (I was running k-jet at the time.)

With regard to performance mods, I am not sure if anyone is running a carb with performance cams. If I ever need to take the heads off 5052's engine, I will strongly consider adding them. I'm running HEI on both 4194 and 5052, but it's really difficult to ascertain any real difference in performance with the HEI alone. However, 5052 is running a set of Hervey headers with custom bent pipes and a Magnaflow Tru-X muffler. I've been very happy with the sound and the performance improvement of that system.

While I don't have an exact number, I think there are a few dozen documented carbed DeLoreans in existence. And if I recall correctly, only one owner was not happy with the results (but I don't know whether or not that owner went back to K-jet.)

SamHill
11-10-2016, 10:52 PM
Anyone truly interested in the comparison can read one of many threads already in existence.

Honestly I don't know why after liberating your non restricted exhaust and a properly set up carb you would need to mess with cams. The car will be demonstrably faster, fast enough to get you in trouble in a curve and cause you to back off if you know what's good for you.

Bob635
11-11-2016, 11:24 AM
Tod,

I too am interested in the "how to" of carberator conversion. Carberated engine's are simpler to maintain and depending on the choice of parts considerably cheaper than FI.

It is very important to note that the early version of the PRV engine was carberated. I have seen a totally stock carberated engine and it had some unique parts that probably increased its volumetric efficiency aka performance.

I know Bill Robertson was doing some conversions and was working on a new intake manifold, but that project did not seem to evolve.

I have heard that Dave Baurle is doing conversion with some machining of the stock FI manifold and a carberator adapter plate. these changes remove about 20 lbs of parts from the car and make the engine bay much more servicable.

Ironically, today's automechanic students learn NOTHING about carberators. Worse yet, all they learn is too plug in a diagnostic port and ASSUME that this will fix the engine. AND when it doesn't your screwed.

K Jet fortunately is not a complicated, BUT there is NO UPDATED diagnostic flow sheet based on over 30 years of diagnostics and repair. Without this UPDATED information this "black box" will remain a mystery to repair to most owners.
For these people a simple carberated system is a possible alternative.

Look at the CARBERATED crate engines that you can buy from GM and Ford. These are great inexpensive engines that bolt into old cars with more HP and performance.

What the D community needs is choice.

Bob

Andrew
11-11-2016, 11:54 AM
Tod,

I too am interested in the "how to" of carberator conversion. Carberated engine's are simpler to maintain and depending on the choice of parts considerably cheaper than FI.

It is very important to note that the early version of the PRV engine was carberated. I have seen a totally stock carberated engine and it had some unique parts that probably increased its volumetric efficiency aka performance.

I know Bill Robertson was doing some conversions and was working on a new intake manifold, but that project did not seem to evolve.

I have heard that Dave Baurle is doing conversion with some machining of the stock FI manifold and a carberator adapter plate. these changes remove about 20 lbs of parts from the car and make the engine bay much more servicable.



You are correct regarding the original design of the PRV engine. Early versions of the PRV used various carb setups. The most common is the dual Solax setup which can be found on the Renault Alpine, Renault R30 and the Peugeot 604 and 504. To the best of my knowledge, only the Peugeots were imported to the US / Canada. Renault also used a twin triple bbl Webber and a triple two bbl Webber setup on some models. Volvo used a single bbl carb on a 1970s PRV, but again to the best of my knowledge, those manifolds are virtually extinct.

The Peugeot / Alpine manifolds seem to be the most common carbed PRV manifolds available. While they aren't easy to find, it's not impossible either. In fact I know of a few owners who have had manifolds shipped from Australia where the Peugeots were more common.

The common practice is to replace the 2bbl solex carb with an Autolite 2100 fitted with a custom adapter plate, the single bbl solex is replaced with an adapter plate. However a few of us are actually running the Solex carbs.

Bill successfully carbed in excess of 2 dozen DeLoreans. He offered either a Peugeot manifold or a custom fabricated dual plane manifold. Last I heard he had a number of people on a waiting list, but I don't know the status of that.

It would be great to see what Dave is developing. It certainly sounds like a promissing option.

opethmike
11-11-2016, 03:19 PM
I have to giggle whenever I see the word 'performance' regarding DMCs.

MountainGoat
11-13-2016, 08:58 PM
For what it's worth, I have a D where the previous owner had let bad gas fester in there (2 - 5 year old gas), and worse ran the engine with that gas in, so the whole fuel system was a mess.

If you have a fuel system problem, I think the carb option is at the very least the *cheapest* option. You can do carb for about the price of a rebuilt fuel distributor + new fuel pump + new K-Jet injectors, which is sort of the very minimum of what you'll need to fix your K-Jet. You'll probably need new fuel injector lines, maybe a new cold start. Oh, and the fuel accumulator -- replacing that is a special nightmare of an ordeal in addition to being an additional expense.

I spent all the money on K-Jet and still couldn't get it to work :) Some kind of pressure problem, still, and now there's some $250.00 tool I need to get to diagnose it. Starting to feel like good money after bad at this point ...

And yeah, I'm a novice, arguably in over my head, and there are people on this board who could probably fix my car. BUT... it's my car and I have to deal with it, not theirs. The carb setup is simple enough that I can understand it, cheap enough that I don't feel like I'm throwing good money after bad, and I bought my setup from Bill who has been really great about support and answering questions.

So in the end, I think it was the right decision *for me*.

For you? If your D doesn't have fuel problems, I'd say don't worry about it. If your D does have fuel problems, then carb is a valid route to getting it to work and I'm hoping to get my car running shortly. (... sadly, my conversion has been slowed down by life and *other* problems I've found like coolant in my valley. Argh!)


.... Edit .....
OH -- and EFI. I considered that, too, but damn is that expensive! With my own careful study, I decided EFI seemed like it was going to be complex, difficult to tune, super expensive and entirely over my head. It wasn't the right thing for me. I think its another valid route if you have the confidence you can deal with the extra complexity :)

Rich_NYS
11-19-2016, 06:21 PM
I drove Bill Robertson's carbed 5-speed and a stock 5-speed on the same day. Bill's car felt like it had a lot more horsepower.