Workshop manual Ferrari 400GT

Simon,

I have done some work trying to remedy the problem.

1. Plugs are new and correct NGK
2. Compression test done before purchase - all good
3. Plug leads are a few years but seems ok. Could be fooled here...
4. Plug leads are numbered and in correct place. Will meassure them for correct resistance
5. Points removed. Replaced with Pertronix electronic ingition
6. Ignition timing will be checked again. There could be something here....
7. Air filters have not been replaced by me. Will have them replaced for next season
8. All 12 float valves are new this summer. They where long gone...
9. Float level is checked and seems equal enough. No major difference here
10. Carbs have been balanced using vacuum. They are not 100% and needs another go


Before I bought it the car had been sitting in a garage for several years,only short trips once in a while. All in all the car performs better now after the few things I've done but the irregular idle and difference in exhaust temp tells me there is something more. The idle problem could most likely be a tuning issue such as carb cleaning or new carb parts needed but I'm not so sure about the exhaust temp problem. It also has a annoying jerking behaviour at steady speed. Almost as if some of the sylinder cuts out. Could well be an ignition problem (leads,coils)?

 

So I've been told. They are apparently the longest chains ever fitted to a Ferrari and prone to stretching. The best thing to do is to have it checked at least.

Single chain ? Oil pump chain ?

 

I had a similar problem with my 400 when I first got it 2 years ago. The main problem was a fault with one of the distributors - I believe it was a loose base plate but wouldn't swear to this.

Personally I'd check the ignition system fully - you've already said that you intend to check the lead resistance etc but check the distributors carefully also.

 

How many miles are on the car? The good news about chains is that they do not deteriorate from sitting over time like rubber camshaft timing belts do. I have no personal experience with a timing chain that needed to be replaced but I have not heard a story of a chain with fewer than 60,000 miles (ca. 100,000 km) that needed to be replaced. Even then, I seem to recall a story on here a few years ago about an FChatter who changed his timing chain as a preventive measure and he found little to no stretch when he measured the old chain against the new chain.

There is an adjuster screw on the front of the engine that can be used to take up any slack in the chain. When there is no more adjustment possible, it is time to replace the chain.

 

John- At least one of our pros recommends changing the 365/400/412 DOHC engine chains every 25,000 miles due to the stretching problem. The 60,000 miles you refer to works fine for something like a Daytona or a Dino with short chains for each bank of cylinders or for the shorter single chain of the SOHC V12s.

 

I agree that your varied header temps are related to timing. I had similar symptoms and fixed the same items you did including the coils- I used Bosch reds. The steady throttle stumble was cured by going to 50f8 idle jets.

Can this be a sticky for the 400i WSM?
https://www.dropbox.com/s/5iizmnbfx6hnt0h/400i%20Workshop%20manual.pdf

 

Christian- Good idea.

 

The car has got 108,000 km on the clock. I do not know if the chain has been changed but I know the car has fully reworked heads done back in the late 90's. Probably the chain was changed then but this I would have to verify.

A quick check on the adjustment screw would reveal this. If it's no more play here then it's completely stretched and worn out. I suspect that this could be the case and that the loose chain causes the problem.

Time will show

 

Arvid

Do you have one pertronix in each distributor or two sensors in same distributor ?
If one in each? -may be worthwhile to check ignition advance curve to be equal in both.
Difference in ignition timing beween banks could maybe explain the temp-diff you are seeing ?

H

 

Ah, I'd start with this .......

Have you checked that the two distributors are correctly synchronized/timed. I would guess you have checked & set the timing using a strobe on plug #1 so that this distributor is set to produce a spark at the right time for plug #1 but what about the other distributor? I think you need to check that this is also set to spark at the right time. I can't check the procedure at the moment but from memory you need to check this by connecting the strobe to plug 7 and checking the timing in exactly the same way as you do with plug 1. It should spark at the same setting as plug #1 as I recall - perhaps someone else here can confirm this.

 

Harald and I are thinking the same way

 

I used strobe on lead 1 and 7 so the distributors should be equally set.

Simon - I had the temp problem before I changed to Pertronix. I noticed that the points had different gap and was worn. I convinced myself that a new maintenance free system should cure both exhaust temp issue and also further future adjusting of points.

Harald - This system has one sensor in each distributor. Part.nr.: MR-1121A. Fairly easy to install but the distributor has to be opened and dismanteled a bit.

Setting static to 11 dgr. was not all that easy mainly due to uneven idle. It will be checked and adjusted again now that the engine has a smoother idle. Maybe the problem lies here but I'm not convinced... The original points where unevenly adjusted with the right side out of sync. Now the ignition difference lies in the left side as this was the worst to set to 11 dgr. But still the right side is running colder than left......

 

The main indicator of chain stretch is a noisy chain. As I understand it, if it isn't noisy, it is adjusted correctly. Interesting about Tazandjan's comment that some of his pros recommend changing the chain around 25,000 miles as I had not heard of anyone who needed to do that but, sure enough, the workshop manual states that the chain should be changed at 50,000 km (31,000 miles) or if there is no further adjustment available. I stand (sit, actually) corrected!

A brief comment on the Pertronix, that is an electric eye replacement for conventional points, is that not? If so, my understanding is that they either work or they don't, there is no middle ground of bad performance for misadjustment or wear like there is with conventional points. I found this out the hard way in my vintage race car when I replaced the points with an electric eye and it left me stranded on the back side of the race track when it failed one time. One second I was hammering along the short straight heading into West Bend at Lime Rock and the next second my engine shut down completely and I coasted off to the side to watch the rest of the race from there. With points you have at least a chance of limping home to the pits.

 

Can't say the chain is noisy but then again I have no other Colombo V12 to compare it to around here. I reckon it should be quite noisy or just a rattle ??

Pertronix leaves you stranded for sure if it fails. The earlier versions 10 years ago had this problem but resent models are of assertive better quality. Since there's two seperate systems,and if one fails,you could always limp a bit further on 6 sylinders (not recomended though....) The only thing to criticize so far with the Pertronix is the mounting plate with the capacitive sensor. This ought to be adjustable but is not. This means the distributor must be rotaded further to get the correct static advance,maybe further that it allows with original holes.

 

Arvid- The adjustment procedure on the chain for the 365-412 series of engines is to tighten down the chain until it gets noisy and then back off slightly. On my Daytona, when you tightened the chains, there was a definite whistling sound, after which you would back off until the whistle went away. No whistle, chain too stretched and needed to be replaced.

The chains on the 365-412 engines were a continuing problem area and the chain tensioning interval went down to 6500 miles for the 412 in the OM, with the 400i WSM actually calling for tensioning every 3250 miles with a chain change at 30,000 miles. If you make a mistake in design, preventative maintenance can often make up for it.

Brian Crall, IIRC, said a stretched chain caused timing problems on the left bank of cylinders more than on the right. That sounds like some of the symptoms you are seeing.

Just in case, though, I would check the distributors by checking timing at 5000 rpm. Or did you say the Petronix system eliminated the advance mechanism? Still worth checking.

 

Terry - Whistle as in chain rubbing against the tensioner ? What Brian Crall describes seems about the same as my problem accept on opposite side. Could be the same though...

Pertronix rules out the advance at 5000,yes. But will have it checked along with the rest of the timing/valvejob.

Great This discussion really boils down to a few things. Either :

-incorrect timing due to worn or loose chain
-incorrect ignition timing due to improper adjustment
-problem with a distributor (bearings,rotor,cap)
-coil (have new ones,still to be mounted)

Sound about right ?

 

Arvid- I thought the whistle came from the chain itself, but could be wrong on that one. It was a fairly high pitched sound and easy to recognize. Guess it could have been rubbing on the tensioner too much and causing the whistle.

 

I don't think so. Pertronix is only an electronic triggering device to fire the spark -- the advance is still done by the stock mechanical gizmology...

 

Hi Arvid
On the chain its unlikely that it has stretched if it is the original Renold chain as I replaced mine after 30 000 miles and measured the new and old exactly the same length no stretch in 30 000 miles! however the tensioner has a pad which will wear and the bushings for the pulleys will wear over time hence the need for adjustment.
Adjustment chain is correct if there is a 20 kilo weight placed between the 2 pulleys there is a deflection of 1 mm.

Cam timing remove the covers, engine at TDC, there are marks on the cam front ends and on the caps make sure they line up 1 mm out is ok more needs adjustment (I got mine to right in the middle of the marks which ime proud of, bang on as they say)there is a trick to this as the springs are so aggressive the cams tend to move ever so slightly after you think you have got them right on the marks so what to do is take an old business card and put it between the cap and the cam preventing the cam turning then you can make up all the other caps. I can run you through the procedure once you get there call me if you need. Its reasonably straightforward.
Regards
Alastair

 

I agree with that statement, would suspect incorrect camtiming by previousowner before suspecting chain stretch

If I understand your description above correct -your timing marks are "all over the the place" at idle ?
Then you need to sort the sentrifugal mechanism in the distributors !
With pertronix and the HT leads sorted, the timing marks should be fairly stable.

H

 

Harald - I will have another go at the distributors along with new coils. Maybe the mechanism is the problem although it looked and felt ok.

I have a long list of things to check when I get some spare time. All I want for christmas is 48 hour days....;-)

 

Pulled of the front cam covers today to check the timing of the cams and condition of chain. Can't find reference marks anywhere in there... I am using the WSM for 400i and fig.32 on B35 clearly shows the marks.

Why is there none on my 400GT ? Has this model marks under the main cam covers ?

 

Yes the 400GT markings are as shown in fig. 32 and are under the main cam covers.

 

Simon : fig.32 show the markings under the front covers,not under main covers. Is there different markings for GT than GTi ? What does the 365 GT4 2+2 WSM say ?

Also fig.54 states that there should be a tension of 20kg/pr.mm play in the chain between cam pulleys. Clearly I have to tension the chain cause I have several mm play here...

Maybe the suspected timing issue is to be found here ?

 

Apologies Arvid, I meant to write front covers and not main covers.

Have you checked the engine is at TDC 1/6 when the marks line up?