Tuning a classic Ferrari

take it to the chassis dyno shop and go from there.

 

If the engine is in good condition, these are the basic steps to tuning it up:
Test drive car
Check/Adjust valve clearances
Check/adjust cam chain tension
Check/adjust cam timing
Replace/gap spark plugs (correct heat range)
Check distributor cap/rotor condition
Check resistance of spark plug wires
Remove/disassemble ignition distributors. Clean and lubricate advance mechanisms. Assemble with new points and condensors as necessary.
Run distributors on machine, checking dwell, points phasing, and advance curves. Make adjustments as needed.
Install distributors. Check static advance on both points sets and total advance (confirming advance function from the distributor machine)
Remove carb tops, check all jet sizes, clean jets. Check needle/seats, replace if needed. Set float heights. Reassemble carbs.
Syncronize carbs at idle and off idle. Adjust idle mixture screws.
Test drive car, It should run better than the first test drive. If it doesn't, then you did something wrong.

 

In my experience, the most common problems with older F-cars were:
1. Bad plugs. Before NGK's, it was difficult to find the proper heat range, and fouled plugs were common, hence the expression "Italian tune-up", meaning go drive it hard and hot in the hope of burning off some carbon or accumulated oil.
2. Bad plug wires. I discovered this one time while looking at the engine in the night, and seeing alll kinds of sparks in the plug wire looms.
3. Distributor problems, including broken point springs and mal-adjustment.
4. Carb mal-adjustments. Chinetti fostered the expression, "Keep your gold-plated screw-drivers away from the carbs", or something like that.

Of course, the other major bug-a-boo was excessive oil passing the valve guides, causing the dreaded smoke, but this hardly fits in the category of tune-up.

 

While not shown on a Ferrari, this is a set of manometers used to "balance" multiple Weber carb barrels, ideally getting the same volume of air through each.

Note that the engine is running in (both) these pictures, so the (fake__stainless steel rods) Mercury levels rise & fall with each cylinder's firing pulse.
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Hi Brian,

How do you guys synch the carbs at off idle? Thanks.

john

 

On the cable operated throttles you can wind out the threaded cable adjustment until the throttles are partially open. It does not require very high RPM. You really just need to get it a little off the stop screws. You want to confirm that the lever angles and rod lengths are correct and not causing a linkage geometry caused lack of syncronization and it helps to catch worn pieces like the ball or socket ends that might delay picking up one of the carbs. Also some of the carbs with parallel throttle shafts have an adjustable gear drive to assure both plates open in harmony.

 

Randy, thanks for those pics. I love the synchroniser in the first 2, and think a device of this kind is essential for successful tuning of Weber & Dell'orto carbs.

I had an Alfa Spider in the early eighties, and I used the device of the Alfa dealer (friend), same priciple but the dealers had a very large rolling board with large mercury columns for the purpose. Man did she run sweet after the proper carb tune-up.
The Alfa also had plugs in all exhaust-tracts to accommodate a CO2 sniffer, and together the 2 devices made for easy and extremely accurate tuning.

 

Assuming that you have good spark and the carbs are in good repair, with Weber carbs you are just setting the idle mixture and the linkage synchronization

For 4 cyl and 6 cyl cars, if you are good and have some practice you can do it by ear, never tried it on a 12 throat setup.......

I had a 4 cyl and later a 6 cyl BMW both with 45mm Webers (two on the 4 cyl and 3 on the 6 cyl) and got to the point where I could sync and set the idle mixture by ear.

I had a friend who said that was impossible, so I let him jack with all of the screws for the idle and throttle linkage to the point where it wouldn't run. I cranked it up and worked my way through the carbs setting mixture, then the throttle linkage, and watching and listening for the lope that get when the sync is off, and in about 5 minutes it was right. Then my friend put the instruments on the car and guess what, it was perfect....

If you had a 12 throat setup you might need a Unisyn (a little flow meter that you put on each velocity stack) to get the linkage synched right, but really setting the idle mixture and getting the carbs synchronized isn't that big a deal. Most mechanics who tuned these cars a long time ago just had a Unisyn and their ear and they did just fine, but also having a "good" mechanic and tuner was a prized thing back then too... If you didn't have a Unisyn. the mechanic would hold a length of hose to his ear and hold the other end on the edge of the velocity stack, and then listen to the hose, he could tell by the sound what the relative flow was... As an aside, watch the movie "The last run" with George C Scott and you will see him doing this in the beginning of the movie setting up his carbs.....

Nowadays we tend to rely on technology to do things. Back when these cars were designed, the technology wasn't very advanced, but you made up for it with skill and talent....

 

Indeed. Another modern tip is using an infrared temperature probe on the exhaust tubes right at the head; real easy to find the "cold"cylinder getting too much fuel or the "hot" one not getting enough.

Also, the availability of handheld wide-band O2 sensors is a godsend. Again, making up for a lack of talent (yes, I have one, shown here being used to verify the tune on a modern BMW__M RDSTR__after being fitted with a supercharger).
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Hi, I found that in the extremes of a salt water marine enviroment the NKG plugs worked by far the best and would recommend them over all othere. just one man's opinion tongascrew

 

+1 on the NGK's, they work far better than the others.

NGK developed their plug technology for rotary engines in the early 80's, they have a broader heat range and don't foul as easily. I was living in Toledo (home of Champion at the time) and had a couple of friends that worked there. They were giving me plugs for my two RX7's (one on the track and the other on the street). The rotaries needed a plug that could stay clean with the additional oil in the mixture, as well as had a broad heat range, since the rotary never got much plug cooling from the incoming charge. The guys at Champion couldn't get it right, nothing they did would last more than a couple of weeks on the street before they started to misfire. I was afraid I was going to wear out the threads on the Wankel, as many times as I had to try a new "tweak" that the Champion guys came up with. NGK's were the only thing that worked.

 

Randy,

What brand probe thermometer do you use? I got a pretty nice one from McMaster Carr that had a max of 1000F, but the moment I would touch the probe to the exhaust headers the car's ignition would interfere with the unit, making it useless. Thanks.

john

 

Thanks Brian. This car has pull and push rods for the throttle. When I took my truck for smog check the fellow used a gadget that went between the steering wheel and the throttle pedal. He was able to ratchet the thing to change idle speed. I have to ask him where he got that.

john

 

No one else uses a Colortune to set the idle and Weber synchrometer (much better than a Unisyn) to balance the secondaries ? O2 sensors and temperature probes seem too high tech for me. Good idea to verify the throttle geometry.

 

If you want to do this work yourself, and there's no reason you can't w/ simple tools and a synchrometer from Pierce (or others), you should pick up:
Ferrari Guide to Performance by Allen Bishop

and

Ferrari Tuning Tips and Maintenance Techniques by Gerald Roush

 

Bryan, you're a man after my own heart. We need to meet to talk about tuning. I've never needed to use an exhaust temperature probe, a leakdown tester, an exhaust gas analyser, or mercury manometer to tune a pre-closed-loop-engine to run well. Making a modern engine meet the EPA's emission laws is another matter. Many of those things didn't exist when these vintage engines were designed.

I use a compression test (wet and dry) to determine the state of the valves and rings, a vintage Uni-syn to synchronize the carburetors (with my own homemade adapter), a feeler gage for the points, the owner's manual for distributor timing (point opening and 10AF flywheel mark- no timing light), and a little card that I made with the correct valve adjusting screw "back-off" angles for setting the lash. 0.010 inch clearance = 91 degrees back-off of the lash adjusting screw from a zero clearance condition and 0.008 inches = 73 degrees back-off angle. For lash adjustment, I find that the feeler gages are too difficult to use and not accurate enough with the valve tips recessed into the spring retainer, like they are on the 365 GT 2+2.

When I do it like that, I can almost feel Gioacchino Colombo smiling while looking over my shoulder and saying "Molto buono, thatsa my boy."

Tom Kizer

 

My experience is that you MUST use the machine as described by Motob above:

''Run distributors on machine, checking dwell, points phasing, and advance curves. Make adjustments as needed.''

Without this you could be doing better....

 

246tasman, I agree with you 100% if the objective is to make the engine run as well and as powerfully as it can possibly run. However, the original premise was, to excerpt from the original question of enzo thecat:
---------------------------------
"Say you want to take your 250 GTO out for a spin and the engine is running ruff.

What are the COMMON variables that need to be tuned and tweaked to these classic engines? I know that there are old timers out there that can do it by touch and sound. But what exactly are they adjusting on those older engines when they tune them? Rich/Lean? What else?

P.S. Just for clarification, I'm asking about the adjustments that the mechanics do while the engine is running...ie without disassembling the engine".
---------------------------------
I really enjoy working on old engines with old technology and old tools, or at least, old-fashioned tools. To me vintage cars are time machines, and I get less satisfaction out of using new technology to work on them (unless of course it's safety related).

I guess if my vintage car starts quickly and runs well, I don't car if I could have gotten a few more hp out of it. To each his own. But we can probably all agree that these old cars are fun, especially if they run well.

Cheers,

Tom Kizer

 

Tom,

If your car runs well, as intended, the specs have to be spot on. Old cars are fun, but only if they run well, which I immediately connect with reliability as well. Not running well or less than perfect means that there is room for improvement, and therefor room for more enjoyment/less worry and headache.

Of course this can be achieved with old fashioned tools, I'd even say that there are relatively few modern tools that find use on the old engines. That said you need to bear in mind that a vintage Ferrari also in its' time was a very sophisticated machine, and needed more than just the average toolkit to perform well. Synchronising carbs can be done by ear by a well trained hand, but real precision comes from accurate measurements, hence the mercury columns. A distributor only performs well if all checks out, and that includes the often forgotten advance curve. You need a machine to check that properly.

Besides the obvious advantages of getting it all right, there is also the matter of avoided risk. Pinging destroys pistons, and a lean running throat destroys valves. Things that can be avoided with doing things properly, 90% won't cut it.

Further I much agree with you that working on old cars with old-fashioned tools is a real joy; instant gratification comes to mind (with instant being somewhat relative when adjusting valves on some models)

 

The reason so many 250s and 275s were dead in some guys carriage house was that the local "sports car" garage had "tuned" up the Ferrari for only 200.00!
A feeler guage is a back yarders best attempt....more damage was done by guys with just enough understanding to get themselves and the cars into real trouble down the road. The next wave of catastrophic failures resulted in dropped valves-a direct correlation to bogus ignition advance curves and inferior phasing of points.
LOF, change the plugs, what a deal!

The criticality if ignition is best remebered by the fact that the difference in the force exerted on the upper ring lands and top ring due to detonation is 30X more violent/shocking/forceful...than is the pressures which are generated by the gaseous propogation of it's ignition/intake charge.
30 x.....Check with the Society of Automotiuve Engineers Web site for archives and articles...they go back decades.
Carb adjustment is vastly overrated and over feared, as so many are incapable of getting the more basic-and more critical-issues done PRIOR to fooling around with fuel.
What sets the Weber apart from all others is the progression circuit to around 3200ish RPMs....it is the closest you could get to fuel injecction in those days.
Apart from the transient surging fuel spike on a driving trace due to the accel pump jets squirting, a BB will., largely be drawing a flat line under steady cruise in the FTP-75! Fuel control, webers are GOOD, injection is better. spark control is as, if not MORE, critical...you shouldn't denegrate the topic if you do not understand how critical it really is...
I'm harping on all of this because there is an absurd supposition all through out this thread-that a "GTO" and "vintage old Ferraris" are all "sunday" cruisers...
Ridiculous-these were, and still are RACING CARS.
There is not much "hopping in" and tooling around for a spin...that entire line of thought is akin to us standing around the bar with Brandy snifters and telling lies to each other about "the good ole days..."