850 spider upgrades?

Chaostoy said:
I snapped two rocker rods! The first broke when the studs somehow came up out of the head. I took the head to a shop and had it fixed, then later a second snapped as well. I replaced the head.
Click to expand...
pulling these rocker studs or them breaking under racing conditions isn't that uncommon, and one of the things you address when building these engines. Studs snapping off will be fatigue related, usually seen when the head has been skimmed too far and the rocker posts need to be shimmed up to achieve any valve lash, it introduces a stress point right at the base of the stud if the shim isnt absolutely ground flat and parallel both sides.

Studs pulling out is common on high mileage engines too, they even make over sized studs for this application, i.e. larger on the threaded portion (next size up in thread, I think it's M12) that goes into the head... especially needed when anything heavier than standard in the valve spring department is used.

the DCNF manifolds I've seen only suit a vertical engine application though, and the 850 tilts to the left (viewed from behind the car - front of engine) so this will lean the carby over unless you modify it....fine for a 600 as that stands up straight from memory.

SteveC
 
fiatfactory said:
the DCNF manifolds I've seen only suit a vertical engine application though, and the 850 tilts to the left (viewed from behind the car - front of engine) so this will lean the carby over unless you modify it....fine for a 600 as that stands up straight from memory.

SteveC
Click to expand...
Yep
 

Attachments

  • 20200821_104217.jpg
    20200821_104217.jpg
    213.8 KB · Views: 10
I like the DCNF caby, has loads of flow potential and is nice and compact, still available new in the USA - spanish made genuine Weber, maybe 400$usd each I think I paid the last ones I bought, which really sin't that bad for a brand new piece of precision equipment. Mounted the way you have it seems to work OK with the float pin to the front too - even though technically it's orientation is "incorrect" .... but it is really well oriented for the air flow path thru the engine like this... much better flow path than with the DCD style orientation, and the lnkage hookup and fuel hookup is clean / neat too like this.

getting the tilt out isn't too hard ... but I guess that depends if you're finding it affects the tune / setup / float level... one thing Eduardo does say in his tuning bible is downdraft carbs should be mounted vertical... as float level definitely affects the tune. Lots of flow for just 903cc capacity tho, but if your racing and in the top of the rev range all day, (and depends what choke sizes) not a bad choice size wise for a vintage / hstoric racer engine.

Back to the O.P. just one thing really I would add to Jeff's advice / logc path ... when you set the ignition timing, set the points gap using a dwell meter.... it's the only way I've had really good success in setting timing well in the OHV's, YMMV but I guess it's best practice anyway, makes them easier to start when the dwell is right and the static timing is correct.

If you havent put a new set of points into it, do that too, plus a new condensor... some fresh plugs too or at least give them a wire brush and blow out with air to make sure they are OK / gapped... inspect the cap and rotor , make sure the carbon brush and spring is inside the cap...don't assume. Start from square one... I find it's the quickest path most times.

SteveC
 
fiatfactory said:
set the points gap using a dwell meter
Click to expand...
I only have basic tools. Test light, feeler gauge, ect.
I did get new plugs, condensor, cap and rotor.
Ebay is a bit hit or miss when I search. Where is a good place to find a new DCNF?
I did just find some nice looking Ruote Borrani wire wheels but they are in Croatia.
 
I think it was top end performance in the US I bought from... and Pierce manifolds probably have them too.

a 40 would be BIG for a stock engine tho... too big

maniffold I've seen some CNC made ones on ebay, I wonder if they could CNC one with a tilt for 850?

SteveC
 
You must log in or register to reply here.
Back
Top