3 replies to this topic

[Scruffs]

Evening all, anybody have a clue on the below problem?

Engine is a 998 A plus with a Stage 1 (engine#99HB81). Has not been run properly for ages, is a replacement for my last engine. Only carry over parts were carb (fully rebuilt), dizzy (Lucas 59D4 41882 w/magnetronic) and stage 1 kit. Have been trying to get it running today…all went fine until I tried to give it some revs!

Timing initially set to 8deg BTDC (vac pipe plugged, connected to carb still) @1500 rpm as per Haynes then colourtuned to a reasonable flame on cyl 1. Idle a bit lumpy but throttle response rubbish, massive hesitation to the point of stalling if I don’t release throttle.

Playing around with dizzy appeared to affect it so I kept advancing…advancing…advancing until throttle response was acceptable.

I then plugged vac pipe again and strobe showed 30-35ish degrees of advance @1500 rpm. !!! With vacuum that has to be a MASSIVE amount of advance, should this engine even run like this?! There is no sign of detonation/pinking etc when it’s idling or being revved.

Vac advance appears to be functioning (sucking on the pipe, watching it all move), also when vac is connected can see the spark retarding and advancing cleanly. Carb-wise dashpot full and piston is moving smoothly. Colourtune shows richening of mixture on transient as you’d expect. Coil brand new. Compression good and vacuum steady. TDC on #1 corresponds to marks on timing cover/pulley so they’re on correctly.…oh and #1 is radiator end

Thinking back, this used to happen on my old engine, I just threw caution to the wind and left it at 30-35 BTDC or thereabouts and drove it like that . However I’m trying to get this engine set up as close to spot on as I can in my garage. Do not want to RR this engine as within a few months I would like to be using it as a test bed for this ECU plan I have.

I’m flummoxed on this, the ONLY thing that is clearly wrong is a small capacitor (what I assume to be a capacitor anyway) connected to the coil, which I’ve just pulled the lead clean out of like it was never connected anyway…About penny sized in diameter, 20mm ish long…This component is not on the wiring diagram, is it critical for lowering some spikes off the LT voltage or something, radio interference?

Anyway, apologies for another marathon problem post, I generally try and solve them but when it goes wrong it leaves me with more to write!!

Thanks in advance! (boom boom…)

Al

[twiglett]

sorry to not have any info but this exactly what my 998 did.
around 3200 revs it would make a loud induction noise and the revs would drop unless the throttle was released.
i have only just managed to get mine running at an acceptable level by adjusting valve clearances and timing, ( it is seeeriously advanced with the vac advance connected)
so if you manage to cure it could you let me know how.

[lrostoke]

Just had a very similar situation..

We timed my bro in laws up with strobe and although running felt under powered, so we timed it using the vacuum gauge method.. After doing this the car ran great, but timing was no where near any standard settings, we've left it, no overheating, plugs burning nice colour. Been like that about 3 week now

One your gauge is connected and seen to be registering a vacuum you can begin the tuning process

(normal vacuum at idle should be about 18-22In (4 Cyl), 19-21In (6 Cyl) or 15-18In on low compression engines (In is an abbreviation which stands for inches of mercury))

Start by first warming the engine and note the idle vacuum reading
Adjust the mixture on your carburetor to obtain the highest steady vacuum reading.
Richen the mixture setting until the needle begins to fall. This will give you the correct mixture setting for maximum power.
Slacken the distributor clamp bolt, and with the engine still at idle advance or retard the ignition until the highest steady vacuum reading is obtained.
Retard the timing until the vacuum gauge reading drops slightly (½In).
Your engine should now be tuned to perfection. Tuning with the engine running compensates for wear in the timing gear and therefore will provide better results than the manufacturers ignition settings.

Edited by lrostoke, 24 November 2008 - 08:15 PM.

[Scruffs]

Thanks for the replies chaps

Somewhat comforting to know other people are having the same problem...I have never used the vacuum method but as I have recently duct taped a vac gauge into the car it would be a shame not to use it! I will give this a go.

As I said before, with any luck this will not be running mech ignition for long, I just want a useable grunt with good economy for the moment.

I will post back up if I find anything more but don't hold your breath, I'll probably just mess about with it until it drives right, after I get it thru MOT

Any ideas on this capacitor thing?

Thanks again

Al