I recently had my 74 E Type V12 tuned which included replacing the four carburetter diaphragms. Prior to the tune up, the car was lurching a bit and the exhaust was popping and chartering excessively. Immediately after the tune up, the car seemed to be much improved on both issues, but it only lasted several days of limited driving. Is the crackling and popping in the exhaust the result of the mufflers or could it be something else.

1974 E Type OTS
2000 XJ8 L

Submitted by dick@bartickfa… on Sun, 09/19/2004 - 14:49

The snap, crackle, and pop are totally gone and the E is running like new.
The fuel mixture was made much richer, a new set of plug wires and rotor cap, plugs re-gapped, and all four carbs balanced. An amazing difference.

Hopefully it will stay this way for a while. Thanks for your help.

Dick Bartick - Indianapolis

1974 E Type OTS
2000 XJ8 L

Submitted by NE52-32043 on Wed, 09/15/2004 - 13:08

I agree with Richard, especially with regard to the burbling sound. Loved to hear it on my old '72. As I mentioned, the gulp valve can be rebuilt, despite the way it looks. If you have trouble finding the article on how to fix it (it should be in the technical articles on this website), let me know and I"ll get the information for you.

Steve Weinstein

Submitted by dick@bartickfa… on Sat, 09/11/2004 - 08:47

Thanks Lenny,

Actually, the two center mufflers are not Jaguar. They were on the car when I bought it over 4 years ago, but the excessive crackling and popping has become louder in recent months. A little bit of this noise would be OK, but this is way too much. I believe the problem to be as you and Steve suggest and will let you know the out come when it is solved.

Dick Bartick - Indianapolis

1974 E Type OTS
2000 XJ8 L

Submitted by dick@bartickfa… on Fri, 09/10/2004 - 20:54

Thanks Steve for taking the time to carefully work through my problem. I have owned and driven Jaguars over for 30 years and while I know and understand them, I prefer not to work on the engines. I will do minor maintenance such as oil and coolant changes, but leave the other work for the experienced technicians.

I understand your thoughts and would agree with you on what should be done. I am going to schedule the car in for service and will have your comments in hand. I will let you know the outcome later next week. This car is currently in 3rd place nationally in class C19. It is mostly all original with 49k miles and in excellent condition. It is a driver, however, it seldom gets more than 2,000 miles a year. Thanks again.

Dick Bartick - Indianapolis

1974 E Type OTS
2000 XJ8 L

Submitted by NE52-32043 on Fri, 09/10/2004 - 10:27

Richard,

The popping usually means that you are running lean. However, before you go adjusting the carbs to make it richer, you need to do a bunch of routine maintenance. If you don't have the shop manual, you should get it, if you are going to do this yourself, so that you set everything up right.

First, check your spark plugs and "read" them. They should all have a nice light tannish color to them. If they are black and sooty, you are too rich. If they are white, too lean. Change the plugs and gap them all to .025". I personally used NGK plugs in my '72 and an '89 XJS that I owned and liked how they performed. If I recall right, the number is BP5ES, but double check. You can get them at most auto parts stores. Bosch's are good too. I'm not a fan of the Champions.

Next, check all of wires, distributor cap, rotor and trigger wheel in the distributor. The magnetic rods in the trigger wheel are notorious for falling out. Also, be careful of cheap, aftermarket cap and rotor. Spend the money and get the OEM replacements. With all the heat, the wires cook. Consider getting a set of 8mm Magnecor wires. Also, if the amplifier is still sitting down on the block in the V, consider moving it or raising it up to reduce the heat load on it.

Now, check ALL of the vacuum lines!! This is a major source of problems. Unless all of the vacuum connections are good and tight (and I mean ALL of the vacuum connections), the system cannot be properly balanced. Any question about the condition of the lines, replace them and make sure that they are all fitting snuggly. On the larger ones, you can use hose clamps to make sure they seal up tight. Also, check the glup valve, the check valve at the back of the engine to the air injection rail, the hose to the air pump and the air pump filter and belt. The diaphram in the gulp valve is notorious for failing. I believe that a repair procedure was posted in the tech forum on how to replace it (new gulp valves cost a small fortune).

Once you have done all that, then check the timing. As I recall, you should show 12 deg. BTDC with the vacuum line removed from the distributor (remember to plug the line while checking timing) at 700 rpm. To check the mechanical advance, simply increase the engine speed up to around 3000 rpm. You should see the timing advance up the scale as engine speed increases, to around 34 deg BTDC, as I recall. If it doesn't move, or only moves a little, your mechanical advance is not working or is gummed up. This is an often ignored maintenance item but crucial to proper running.

Now that you have all that done, follow the instructions in the shop manual for setting up the carbs. Balancing and setting the carbs is a real PITA job. To do it, you will need a "Unisyn" tool. It's a gauge that measures air flow through the carbs. You will also need the special tool for adjusting the needles in the carbs. Both are readily available and not expensive. I would not use the "hose to the ear" method, unless you are a piano tuner.

If you follow the instructions to the letter, and still have problems, you might consider having the carbs rebuilt by an expert like Joe Curto of College Point, NY (you can do it yourself, but the results will be much better if done by a pro like Joe). NAYYY. If they have not been rebuilt in 30 years, things like the shaft bushings (major source of vacuum leaks), the by-pass diaphram, etc. probably need replacing.

One other point -- Be sure to use 20W oil in the dash pots, filled only to 1/4" below top of the INNER tube. I personally liked ATF rather than 20W oil in mine, and use ATF in the SU's on my '70 FHC. DON'T use a heavier weight oil in the dash pots. You don't need to spend a lot for the "special" carb oil that some of the "usual suspects" sell IMHO.

Do all of this diligently and carefully, take your time, and you will be rewarded with a nicely running and more powerful car.

Regards,
Steve Weinstein, JTC-NJ
Former '72 E-type 2+2 and '89 XJS owner
'70 XKE FHC
'69 XKE OTS
'84 Ferrari Mondial QV

Submitted by LBR700527@netz… on Thu, 09/09/2004 - 21:00

Hi Richard! Just out of curiosity, it seems like you don't like that "crackling, popping sound" in addition to the exhaust tone. Obviously, it cannot be your mufflers because you did not mention doing any mods to them. I think when the carbs and rejuvenated and because sharper, crisper in bringing that stoichioic (sp?) ratio of air and fuel vapors, maybe the ignition could use either a check of the spark plugs, a check on the points, rotor and cap and wires. Maybe spark timing should be examined by rotating the distributor to see and hear any difference. I also thought that maybe check your exhaust pipes for any leaks or holes. Holes or leaks can introduce oxygenated air that would help burn off unburned fuel since these cars don't have catalytic converters. I know I may not be that much help but just offering a suggestion. I don't have that much experience with V-12's like my younger brother who has a 1989 XJ-S but theory of operation ought to be the same.

Lenny B. Ramjattan, N4WZQ
LBR700527atnetzero.net
1966 Jaguar Mk X, 1D76577BW
Pembroke Pines, Florida