Ferrari Forums banner
1 - 18 of 18 Posts
G

·
Discussion Starter · #1 ·
I would like to check the timi

I would like to check the timing and carburation of my 512BB. The operating manual says to check through the slit of the flywheel housing that the satic ignition advance is 5 deg at 900rpm and 16 deg at 3200rpm and that the advance should be 35 deg at 5000rpm.

Where is the slit on the flywheel?

I understand how the advance should be 5 deg at 900 rpm and 16 deg at 3200rpm. I do not understand the reference to 35 deg since the advance curve is flat after 3200rpm/16 deg.

Second, I read the proceedure for balancing Daytona carbes that JVR wrote in the Tech Section. I purchased an old Haynes workbook manual on Webers and the Pat Braden book on Webers that covers IDA3C carbs. I assume the 40IDF3C's are similar. Would the same proceedure apply. That is using the color-tune and the manometer to set the boxer carbs.

May be over my head here but would like to learn without messing anything up.

Drew Altemara
 
G

·
Discussion Starter · #2 ·
Drew,
There's a fair amou


Drew,
There's a fair amount of ground to cover here...so let's start with the ignition timing. The 365 is essentially the same setup, though the total advance is slightly different.

Most importantly, you should be concerned with the total (maximum) advance, which is the AF 36 (365BB)or AF 35(512BB/) mark on the edge of the flywheel. This is measured at 5000 rpm with a timing light. The manual is some what confusing in their nomenclature, in this regard. So, where does the number come from...Good question. Here's the math:

Static: 5 deg. engine advance
Distributor: 16 deg advance-Since the distributor turns at half the speed of the engine...the actual engine advance is 32 degrees.

Total advance=Static + engine advance, hence 5+ (16x2)=37 degrees total advance.

If the max advance is set at the AF 35/36 mark, in theory, the idle advance should be correct. As max advance is more important than idle, that's what I shoot for...and the idle advance is usually within a degree or so...

If the idle advance is way off, likely there's a problem with the advance plate in the distributor sticking,,,which is very common on the BBs.

How to check:
Right side of engine: Small plate about 1" x 2.5"-Remove plate....you'll set a pointer. That is the reference point. There are three marks on the flywheel...1)
PM 1/6=TDC
AF 18=3200 rpm mark per your manual (365BB different)
AF 37??=max advance at 5000 rpm

Hope this helps to get you started.


Regards,
David

 
G

·
Discussion Starter · #3 ·
A few notes....beyond Davids a

A few notes....beyond Davids accurate comments.

Distrib timing is set at the flywheel thru the hole in the clutch Bellhousing by removing the small aluminum cover held on with 2 6mm nuts on the left side, rear. It is helpful to mark the flywheel with Red/White/Green/Yellow paint for easy fast viewing especially at the high rpms.

Check & set idle timing first ...blip throttle a few times carefully and watch timing mark action ...to get a feel for advance mech operation & condition. Have helper then carefully rev to 5K rpms for check of Total advance. And try to do make the check quickly. Then let off the throttle and check idle timing again.

As David mentions, poorly working advance mechanisms is very common on Boxers.

If the Distrib Test & Set fails...forget about trying to set the carbs properly until the issue is resolved.

If the distrib test & set passes...then you can clean & gap (or replace) the plugs & move on to Carb Setting as outlined in the Daytona procedures. First the Air Balance, Linkage Check & Set, then proceding on to the mixture check and set.

*note: leave the idle high if it climbs with carb adjustment until all mixture is set, then go back & check/set the timing lower if neccesary one more time, then back to carbs for final idle air/rpm set. I know this is a PITB, however as you get the carbs leaned down & balanced the idle rpm & timing have a tendency to creep up...so it's important to get all cylinders helping each other (working in harmony) before making final rpm/timing checks/adjustments.

HTH's

ps: David, thanks for the help & tips....with such high quality posters here the Ferrari-Talk boys will have the finest running Ferraris around!! {
}
 
G

·
Discussion Starter · #4 ·
JRV,
Let's take this dist


JRV,
Let's take this distributor issue a bit further...
Mine has seized through the years of limited activity...I've been through it a couple of times, freeing up the weight plates, etc. From time to time, I do have problems with the timing not retuning to the base setting, or not advancing properly...I've always had some concerns about the advance springs...do they fatigue? Are they installed correctly?

So...
In the constant quest for (sincerely) the "finest" running Ferrari, do I a) Replace the distributor with a brand new unit....or b) Send it to ????. My understanding is that, other than the bearings, there are no rebuild/replacement parts available.

Regards,
David
 
G

·
Discussion Starter · #5 ·
David, all the Lay Down Marrel

David, all the Lay Down Marrelli Distribs suffer the premature failure issue.

They can be rebuilt and yes it is neccesary for them to work freely and well in order to tune properly and "hold the tune" after servicing.

Don Rudd, good friend and son of very old timer Bill Rudd, of Bill Rudd Motors of Van Nuys fame, (a true expert and entusiast in every sense of the meaning)can rebuild the distribs to perfection on his Distrib Machine and he has new or machined parts to fix any and all ills.

Don was working for the Nethercut Collection last we spoak, and doing Distribs in his spare time for guys like me. Don't have his numbers handy here at home, I'll look them up at work and post them.


With your compression ratio you could possibly get him to recurve slightly to help the bottom & mid range without excessive advance to avoid detonation at max advance?

His prices are Very reasonable.

Regards, JRV
 
G

·
Discussion Starter · #6 ·
OK, thanks a lot guys.

The


OK, thanks a lot guys.

The timing and carbs were set by Terri Gerome about 2 years ago when the belts, waterpump, distributor mechanism, etc was done. Everything still runs great. I just would like to check and learn what is in my limited ability.

As for checking the timing. I understand that the marks should line up with the AF16 deg at 3200rpm and AF35 at 5000rpm. Is this right?

If so, where is the reference point to set the static timing? And is it this what I first line up at 900rpm by turning the distributor? Once this set I can move on?

I'm going to try/check this first before I move onto checking the carbs.

Thanks again. Your site is great JVR. I still can't believe how much time and information you put into it.

Drew Altemara
 
G

·
Discussion Starter · #7 ·
>>I just would like to

>>I just would like to check and learn what is in my limited ability.<<

Outstanding idea on these cars and with a little proper guidance not that hard in many cases..

>>where is the reference point to set the static timing? And is it this what I first line up at 900rpm by turning the distributor? Once this set I can move on? <<

Ok, after hooking up the timing light and getting ready, start the engine and let idle, shine the timing light into the hole at the pointer/flywheel...you should see a P/M 1-6 mark and in front of it to the left an A/F 5-6 degree static setting mark. If for some reason you can't see either of the marks, shut off engine and with a screwdriver, (wile shining a good flashlight into the hole) start rotating the engine with the screwdriver until the PM 1-6 mark i visible, now paint this PM1-6 mark, now look left about 3/4's of an inch for the AF 5-6 degree mark, continue to rotate and mark 16 & 35-36 marks.

Restart engine and check again. Adjust Distrib if necc to align correct marks at idle and proceed with all the checks. Done.


>> I still can't believe how much time and information you put into it. <,

Drew, thanks, and truly I can't believe the quality of guys that want to use FT and the depth & wealth of experience everyone is bringing to the table. Helping others as you can see let's me dig deep about problems I don't see everyday and helps keep me at the top of my game and this type of knowledge and experience sharing is going to where it does the most good, owners. Truly if everything I've learned over the last 30 yrs had no where to go it would be useless, a forum like this gives all our knowledge and experiences VALUE that would otherwise be lost.

Good Luck, Best Regards, JRV
 
G

·
Discussion Starter · #8 ·
I feel good today and its all

I feel good today and its all because of you guys. I followed JRV's directions.

I painted the PM1-6 (TDC) red, the AF (5 deg dist, 10 deg engine) which was about 3/4 of an inch to the left green, another mark AA (32deg engine) which was a couple more inches left white and another mark also AA (35 deg engine) a half an inch further left yellow. Warmed up the car.

When I applied the strobe light it was pointing to just past the red line (TDC) but closer to TDC than the 10 deg static advance mark. At 5000RPM it would not get to the white yet alone yellow 5000RPM/35 deg line. Rotated the distributor (actually took a couple of tries to get it perfect). Now it idles at the correct static green mark and pulls past the white mark almost to the yellow 35 deg mark. Its so close to the yellow, maybe a degree or so, I'm going to call it a success.

Man, even for 5 seconds with your head under the hood at 5000RPM it scares the poop out of you.

The other interesting thing that happened was that the car had been idling low (maybe 800) Now it's just above 900.

It's Labor Day, I know where the speed traps are, I'm going for a drive.

Thanks again, next the carbs.

Drew Altemara
 
G

·
Discussion Starter · #9 ·
JRV,
Please clarify, based on


JRV,
Please clarify, based on your experiences, the base idle setting for the 365BB carbs. I have always used 3.5 turns out on the idle mixture screws as my baseline starting point. Seems the +/- .25 to .5 turns either way seems to be optimum. Yet, today I read that if the base setting for the idle screw is more than .75 turns out, the idle jets have been selected incorrectly.

I am using the factory reccomended jets, per the WSM...which I have confirmed have not been drilled larger...For a point of reference, the air corrector screws are out from 0 to 1.5 "turns" (the max, being on the vacuum brake pick-up port on #1 cylinder.)

And...Turning "in" on the mixture screw leans and turning "out" richens the mixture..Correct?

I guess reading this article today made me question what I have been doing over the last 20 years with this car...

Appreciate your input.

Regards,
David
 
G

·
Discussion Starter · #10 ·
>>I have always used 3

>>I have always used 3.5 turns out on the idle mixture screws as my baseline starting point.<<

I use 1 1/2 -2 1/2 myself, after a carb overhaul for example.

>>Yet, today I read that if the base setting for the idle screw is more than .75 turns out, the idle jets have been selected incorrectly. <<

Well, I think 1 1/2 is a more realistic number of turns, however I wouldn't call the 3/4 exactly wrong, just maybe optimistic. With the potential for wear, corrosion, deformation, and air leaks on these Old Carbs I never jump to Jet conclusions. However, all things being equal if the mixtere screw has to be out to far "it could" indicate a jet 1 size too small. But, it also depends on the size & condition of the idle air bleed.

>>And...Turning "in" on the mixture screw leans and turning "out" richens the mixture..Correct?<<

correct.

Not to take away from the article or critasize it, since I don't know what it says or who wrote it, however, if the article doesn't go into theory and malfunctions it does a small diservice to those reading it by trying to give absolutes (if in fact that's what it did) without explaining the many variables and why absolutes don't always exist.

Regards, JRV
 
G

·
Discussion Starter · #11 ·
Ok, on to carb setting.

I o


Ok, on to carb setting.

I ordered a STE SK Synchrometer and color tune today. I re-read the Haynes and Braden manual on setting webber carburetors along with JRV's Daytona writeup.

I believe the distributor to be in good condition since the timing and advance appear to be dead on. Will install new plugs. Here is what I believe is the proceedure:

1) Set air bleed of each carb to get equal reading on all 3 throats.

2) Adjust idle screw to get all four carbs to read same air flow. Pick middle flow rate carb and adjust others up and down using idle setting.

3) Use colortune and set idle mixtures.

4) Reset timing

5) Go back and do it again.

Did I get it right?

A couple of questions?

First where do I start with the air bleed screws. The Haynes manual recommends all the way in? Also as I turn "out" the screw it lets more air bypass the throttle plate so the air flow goes down? I' not sure of this one?

Second, once the throats of an individual carb are flowing the same amount of air I have to make sure all four carbs match. I do this by adjusting the idle screws of the carbs that are higher and lower. OK, fine. But what insures that as I adjust the idle screw that the throttle will be in correct allignment with the idle jet hole so that the progressing phase comes on smoothly? Is there a reference to start from that insures this or do I have my logic wrong?

At this point I am more interested in understanding "how this works" than a regimented proceedure.

Any help without giving away trade secrets appreciated.

Drew Altemara
 
G

·
Discussion Starter · #12 ·
Drew,

I'd leave the air


Drew,

I'd leave the air bleeds alone until you've balanced the 2 primary ports and 2 secondary ports.

4 Webers is slightly different procedurally than 6 webers.
 
G

·
Discussion Starter · #13 ·
OK, you got me? What are the

OK, you got me? What are the 2 primary ports and the two secondary ports? Now I'm really in the dark.

Drew
 
G

·
Discussion Starter · #14 ·
sorry.

Two of the carbs le


sorry.

Two of the carbs lead and the other two follow by way of the linkage arrangement. The two carbs that are hard linked are the primarary, the two carbs that operate off those by spring loaded linkage pieces with the setting screw are the secondary...if you are familiar with carbed 308's Boxer carbs are linked in the same basic manner.

Because of this arrangement the Two Cylinders on the Idle speed adjustment screw side of the Carbs are set first to each other, cross bank, then the two secondary carbs are balanced to them. So in the first phase, Air Readings are only taken off 4 cylinders not all 12, and only the 4 on the linkage endof each carb.

We together on this so far?
 
G

·
Discussion Starter · #15 ·
Got the first part, primary an

Got the first part, primary and secondary.

Had to read the second part a couple of times but I believe I understand.

You set up one cylinder of each carb cross bank, and those cylinders are the ones with the idle speed adjustment screws which I believe are the foward throat of the LR and the forward throat of the RR.

Then move to the secondary and set what would be the rear throat of the LF and the rear throat of the RF. Correct?

To do the above am I using the idle adjustment screws or the air bypass adjustment?
 
G

·
Discussion Starter · #16 ·
Just answered my own question

Just answered my own question on prior post. Idle adjustment screw.
 
G

·
Discussion Starter · #17 ·
Interresting discussions guys.

Interresting discussions guys. This is my first post here so here goes.

I recently purchased a near complete set of new 40DCNF45/45/46/48 carbs for my 308. Well of course I had to tear them apart to confirm how they were setup. All the interchangeable stuff was as advertised. I still would like to find a new lever arm to convert one of the /45's to a /47 (left rear) carb. Anybody have a new one of these lever arms (has ball stud and a fork with an adjuster screw and spring fitted)?

Some observations:

1. The idle mixture screws were all 2-2.5 turns open. I set them all to 2.5 turns open.

2. One balance screw in each carb was closed. The other was open between 2-4 flats, then locked. This seems to imply that they may have been flowed on a bench during manufacture to ensure interbarrel balance.

3. The float levels were set to between 47-49 mm. Spec for this series of carb is 50 mm, so I reset them to that. Float droop for all was much less then spec for these carbs. The GT-4 WSM cites a stroke of 10.5 mm while my Haynes Weber manual specifies a stroke of 8.5 mm. I reset them to 8.5 mm as the sin here is to allow too much droop where they may hang up and not shut down the fuel flow when necessary.

Does anyone have a trick to negate the sloppy threads on the push rod end fittings? When I adjust these things the desired amount by twisting the rod ends, the adustment changes when I lock them with the lock nut. One thought is to try some teflon tape, swage the end fittings down a touch, or replace them.
 
G

·
Discussion Starter · #18 ·
Welcome aboard.

>>A


Welcome aboard.

>>Anybody have a new one of these lever arms (has ball stud and a fork with an adjuster screw and spring fitted)? <<

I'll look around.

On the linkage...the lock nuts actually don't need to be very tight, after 20-30 years they will feel tighter than the gates of hell to the next guy {
}.....

Is this your question?
All linkage is/should be adjusted after the carbs are set & finished imo. Both nuts are loosened and the rod turned to get a nice but not real tight fit (yes it sometimes requires more than one try), then nuts tightened and the minute final adjustment made with the ball capture screws that locks with the cotter keys. It's important to check the rod lenghts at half & full throttle (engine Not running) also to insure they are the same lenght and provide equal travel. Also, after adjustment but before final tighten one must gently pull throttle cable while very carefully obseving both lead carbs to insure both lead levers start moving at the exact same time. Once one has carefully viewed every different portion of operations you will see any tiny tweeks you need to make and how to go about them.

HTH's
 
1 - 18 of 18 Posts
Top