Tom's most recent blog

[Steve Meltzer]

I found this post and problem to be just fascinating, as I continue to srtuggle with a "soft popping" or almost cough like hiccup on my GTC. It has been present for several years and is quite annoying. Like your conundrum, it occurs at about 3K RPMs or slightly higher. Worse when the engine is cold and sometimes nearly gone when fully warmed up. Cannot be replicated unless the car is under load...can't reproduce it in the garage.

Initially, I thought this was a carb issue, tho' I put in new plugs. Carbs are as well tuned as I can get them (sl larger idle jets), under the guidance of Dyke Ridgley, who has worked really hard to help me solve this dilemma. I'm confident they're not the issue. I had a couple of exhaust leaks, and they've been fixed. I've passed the propane torch multiple times to be certain there's no vacuum leak, and there's none. I too, spoke with Mike Pierce about this, and he didn't think it was the a carb issue either. Fuel pressure is correct at about 4.5 PSI.

I'm replacing the ignition wires at this point; playing off the pun, the points look good and have only about 3K miles on them. New coils, both sides. I'm hoping that the new wires will solve this weirdness, and if not, I plan to pull the distributors to check the advance and phasing. We'll soon see, as I'm also trying hard to get the Daytona running, as noted on other posts. Thanx for the interesting blog. steve

[afwrench]

Hi Steve, I cured a similar issue on my car by cleaning and tightening the connections on the external resistors.Afterwards both showed proper OHM value and a crisper running motor. Good luck, Mike PS after 40+ years of pulling wrenches I have found the majority of carb problems are ignition related

[Steve Meltzer]

HI Mike, thanx for the info. The new coils have built in resistors, so we'll X that off the list. I've heard other experienced mechanics voice the same belief..."carburetors get blamed for everything". s

[zac]

One thing I learned early on as a mechanic is never apply one diagnosis to another car even if the symptoms sound the same. Always start with a clean sheet of paper and eliminate the basics. A great ignition and proper timing is essential on a car with two seperate distributors, make sure the ignitions are in syc and check timing on both 1&6 and 7&12 to be certain. I know both C4s and Daytonas love a nice fresh MSD and a good hot spark. A good hot ignition lets you run the car a little richer to eliminate lean issues. Problem is you just never know what the last 40+ years worth of hands have done in there so it's always best to get everything back to square one and start from there.

Zac

[tyang]

Hi Steve,

I always go with the adage of "easy things first." Most times, we can find the root of the problem with a few checks, but this one car nearly beat us! Hopefully you'll find your "smoking gun!"

Tom

[Steve Meltzer]

I'll keep you posted, tho' it may take awhile to get to it completely. A little bit here and little bit there....runnin' as fast as i can. s

[tyang]

Hi Steve,

When you get a chance, tell me what the specs are on the carbs. ie, main jet size, idle jets, and emulsion tubes. We surveyed three 330GTCs and one 330GTS and found some discrepancy on what was used. It would be interesting to know what you have in your carbs.

Tom

[Steve Meltzer]

HI Tom, The carbs in your blog look like DFIs. Yes? Mine are DCZs, and here are the numbers on mine.

Main jets=130, and that's spec
Idle jets =65, spec is 60
pump jets=60, and that's spec
Don't think I looked at the idle speed correction jet
To my knowledge that carb has no emulsifiers.

steve

[John Vardanian]

Hi Zac, if the distributors are dialed in on a Sun first, is there a real need to check timing on 1 as well as 6 (or 7 as well as 12)? I am asking because I just set iming on 1 and 12 (at 5000RPM only) and that's it. Thanks.

john

[zac]

John,

On the three lobe distributors each set of points fires 3 cylinders so setting timing on 1/6 and 7/12 sets timing on all 4 sets of points.

Like Tom touched on in his post when you are checking/setting cam timing you check it on at least 1/6 and 7/12 which allows you to not only double check you work but it also allows you to see if the cam has twisted. Because of the length of the hollow cam, spring pressure and aluminum heads/blocks tendency to move around these cams have a tendency to twist. If the cam has twisted it will cause all the cylinders on that bank to run a little different depending on how severe, the only fix is to either replace/regrind or set the cam timing in the middle to compensate. It's not that these motors are any more complicated that a Chevy V8 its just that on a V8 all the parts are readily available so just about every servicable part is replaced each time the engine is gone through not to mention the cast iron block and heads are pretty stable. On the Ferraris parts tend to be very expensive and people tend to cut corners to save money, since these cars are 40+ years old there is no way of knowing just how many corners have been previously cut.

I think starting with some fresh clean fuel, filters, proper plugs, new or tested plug wires, properly set up distributors and coils that are not cooked is a good place to start. Tune ups used to be a standard practice that was done on a car bi-anually or at least anually which kept things in good runing condition. These days a "tune up" consits of replacing a few parts and pluging in a computer to reset the service light, the cars on board computers do the rest and make constant adjusments. This is a huge problem in my profession where most mechanics are genrally just parts changers and computer technicians.

zac

[John Vardanian]

Thanks Zac, cam twist is something I hadn't thought of. It makes sense now.

john

[Steve Meltzer]

ooops! I goofed. Of course the 40 DCZ has emulsifiers (X2) I just never removed them for cleaning. Sorry 'bout that chief. s

[tyang]

ooops! I goofed. Of course the 40 DCZ has emulsifiers (X2) I just never removed them for cleaning. Sorry 'bout that chief. s

You have to clean EVERYTHING in order to make sure you haven't missed a small piece of trash fouling up the works!

Tom

[Steve Meltzer]

Well, if the car doesn't run well after I've replaced the plug wires, I'll go back and start over, including the emulsifiers and probably check the distributors' advance curves. %^$#&%^*&*&*( s

[tyang]

Well, if the car doesn't run well after I've replaced the plug wires, I'll go back and start over, including the emulsifiers and probably check the distributors' advance curves. %^$#&%^*&*&*( s

Hi Steve,

When you cleaned out your carbs, how did you do it? There are several ways to do it from soaking them in a paint can of carb cleaning solution, to sitting them an ultrasonic cleaner. After either method, they need to be thoroughly rinsed. There are a bunch of little passageways that can trap dirt and debris, and you'll have to remove all the jets, needles, and emulsion tubes to wash out the internals. If you're worried about assembling things correctly, disassemble two at a time, and leave one assembled to see how it goes back together. The good thing about Webers is they make different sized threads for the different pieces so they rarely go in a different hole.

Look on the bright side, no one is paying your hourly rate to do this!

Tom