EXPERTS! 348 Timing Advance Specs?

Another thing you aren't taking into consideration is emissions. You can totally screw up the mixture by running too much over lap, or not enough.

Just set everything to what is recomended in the book.

The only real way you will be able to extract everything you can out of the engine playing with the timing is on an engine dyno. You would have to have the engine out of the car and on the dyno. That way any change you made to the timing you could see exactly what is does to the power. So unless you have access to an engine dyno, I think you're just shooting in the dark.

 

Now that I've thought about this a little more, this is sounding correct to my memory. I recall with clarity that the US 348 Challenge cam timing authorized modification is with the exhaust cam only (retard).

It will provide additional high rpm power... and a lumpier idle

I also recall FNA Technical Director Umberto Massoni (in the 90's) telling me that the timing specs are different due to US emissions regs and catalytic converter life (they were/are short lived anyway).

Same cams, different exhaust timing.

Don't have the specifications anymore though.

Best,
Rob

 

Fair point about Euro cams... I was only guessing the US got low lift ones, like 308,QV, 328 etc. Have never investigated 348 market differences.

I still say, if you're desperate for more power, get a local cam grinding specialist to remove a little base circle (need to check piston/valve clearance but I'd GUESS 0.5mm would be ok).

 

Intake would yield better return, but if budget allows, do both.... BUT CHECK PISTON/VALVE clearance AND VALVE/VALVE clearance. Also check spring retainer travel, to not foul oil seals.

Also, you'll need to use ~0.5mm (020") thicker shims, which are heavier of course, and need to be sourced... or use longer valves if you're making custom ones.

Engine mods are a specialised field, and each mod has many potential follow on problems...

Buy a Turbo Kit.... this can be removed and re-sold easily if you sell the car.

 

This is what I had in my notes...

European cars
Intake Opens 14 degrees before TDC and closes 53 degrees after BDC.
Exhaust Opens 53 degrees after BDC and closes 10 degrees after TDC.

US cars
Intake Opens 12 degrees before TDC and closes 56 degrees after BDC.
Exhaust Opens 54 degrees after BDC and closes 12 degrees after TDC.

Paul

 

Paul, the figures that you just quoted are exactly what shows in the timing diagram in the workshop manual, except for your last number. The manual shows that exhaust closes 10 degrees after TDC on both USA and European cars.

Note:The chart in the manual is not labeled "European cars" and "USA cars", it's labeled "Not catalyzed" and "catalyzed".

 

I certainly hope so!!

Jeff - They were figures that were posted on here some time ago - I did also look in 2 copies of the WSM manual that I have and they state the same as what you say.

Paul

 

For reference - From 348 WSM
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Here is what is says in my manual

No Cats

Intake:
Opens before TDC 14 deg
Closes after BDC 53 deg

Exhaust:
Opens before BDC 53 deg
Closes after TDC 10 deg

-----------------------------------------------------------

With Cats

Intake:
Opens before TDC 12 deg
Closes after BDC 56 deg

Exhaust:
Opens before BDC 54 deg
Closes after TDC 10 deg

-----------------------------------------------------------

All the above values are +/- 1 deg

 

No.

They all close at 10 deg, with or without the cat.

 

Erm - not quite

348 GTS/GTB
I -10/58
E -50/14
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If what has been discussed elsewhere, including the current thread discussing 308 2V, QV and 328 valve timing, compares equally with a 348, the guru's seem to be advising 100-110 degree lobe centers. Now I grew up with engines that had lots more duration and overlap than these newer cars, and I do know keeping overlap to a minimum helps with emissions, but it sure doesnt help HP very much. If it were me, I would advance the intake cam 10 degrees, to open around 20-24 BTDC, and retard the exhaust about the same amount, to close at about 20-24 degrees ATDC. This would give more overlap, but with such whimpy cams, its not a great deal, and should make the motor perform better. Perhaps someone with more experience dealing with the 348 could chime in with some better advice, or call Norwood.

 

Oh hardy, har, har, Mr.Smartypants.

I think the timing difference on the GTB/S version is different because of the slightly higher comp ratio.

How about for the Competizione while we're at it?

 

Actually let me change that. It looks more like all they are doing is moving it higher in the rpm range. The intake is still open 248 deg, and the exhaust 244 deg. They are just opening and closing later.

 

No it wasn't me, it was Phil

 

You know what, now that I think about it that sounds right. Since the GTB/S models are running 10.8:1 pistons it makes sence to retard the timing a bit. Other wise you may get some detonation going on.

 

Hahahahaa. You know what, you're right. Good grief what's wrong with me.

 

Top secret information so I am told

Tried looking in the GTC manual already but no joy - Malcolm??