SBC Timing - 2 timing marks on damper

[jonbillings]

Hi – now the answer may seem blindingly obvious to the experts, but I am confused (and not too shy to ask)…………….

The problem – timing marks - Harmonic damper with grooved timing mark and another one hand painted on.

The engine – 350 SBC, flowed heads, Comp Cams 286 Hydraulic Camshaft, Rhoads Hi Rev lifters, Mallory Mech Adv Dizzy, Edelbrock Performer Manifold, 750 cfm Holley Vac Secondary - all assembled by someone else (so I have an excuse at least).

When I find TDC - #1 on compression (both valves closed – feeler in the spark plug hole to feel piston), the grooved timing mark in the damper and the tab line up, I rotate the dizzy so that lead to #1 is lined up with the rotor arm ……and it won’t start!!
If I then fiddle with the dizzy (rotating it a large amount) I can get it to start – but when checking the timing with a light it lines up with the other mark on the damper (it runs pretty well with 10 degrees advance against this mark)
The “second” mark is some 70-80 degrees in front the “proper mark” in relation to the direction of turn.

The question being - what’s going on?? (I could time the car off the mark there is – if after all runs fine and performance seems pretty good, but the cause is nagging me).

Is the dizzy gear drive meshed a cog or two out or is it something else blindingly obvious??

When I set the rest up I am looking for a dwell of 26 degrees (or point gap of .020), is 10 BTDC best or is there an optimum setting for a set up like mine??

Thanks for advice in advance.

Jon


"I'm growing older but not up
My metabolic rate is pleasantly stuck
So let the winds of change blow over my head
I'd rather die while I'm living than live while I'm dead"

[callum]

When aligned with the rotor arm is the HT lead going to No 1 cylinder? Or are your leads 'one along' in rotation?

[JIM]

If your Crank Damper is a few years old and seen a bit of use then it is possible that the outer ring (The inertia ring with the timing mark on it) has slipped relative to the hub , thus the timing mark is angularly now in the wrong position. This is fairly common particularly on old dampers where the rubber between the inertia ring and the hub starts to perish and shrink allowing the outer ring to spin realative to the hub. On my own SBC the ring had slipped some 60 degrees !!! The paint mark was probabally somebody finding the true TDC Position and marking it , but dont forget that the ring could have slipped again since it was last marked. I have seem some books that tell you what the angular position of the timing mark should be realative to the hub keyway, matbe you could check thru this.

Jim

[dave]

Just a thought, If the ring flies off at 6000RPM it will not stop to go around your bodywork, it will fly straight through it and possibly through your floor pan.............This could hurt a little.



Take care.

[TINKA]

Dave, what position are you mounting your engines, as I would have thought the front of the engine was quite a bit in front of the floor pan.x( x( x( x(

Martin :tu :tu

[dave]

Hi Tinka
My engines go in the middle of their allocated hole unlike some peoples rear wheels!!!!!!!!!!

Can i have a caucer of milk please.

Seriously though, it would bounce about under the car if you were driving along and it would come through the floor of your car easier than it would go through the surface of the road.
Scary stuff.

:tu

[jonbillings]

Thanks for thoughts - cannot rember where arm was in relation to No1, as for damper - I thought it was fairly new when I got the engine - but maybe it had been cleaned up. I purchased the engine som7 years ago and it has only been running for 3 and done about 1500 miles. If I get a new one - I presume it has a key to line up from installation? I guess I will need a hub puller to get it off as well.
I suppose as long as I can get it running fairly well there is no problem, but do not want to lose a few horses somewhere if I can avoid it!

Jon

I'm growing older but not up
My metabolic rate is pleasantly stuck
So let the winds of change blow over my head
I'd rather die while I'm living than live while I'm dead

[TINKA]

OW!! x( x( Bring your own BBQ stuff next time :f :f :f :f :f

Or tools to rectify my wheel problem {-} {-} {-} {-}

Martin :tu :tu

[dave]

:7 :7 :7 :7 :7 :7 :7 :7

[jonbillings]

Now the bickering has died down............

What damper do you all recommend - I guess fitting a new one is a start, is it cheaper to get a decent US damper sent over or just go with a Real Steel one - advice appreciated?
...........and any installtion tips appreciated?.

Thanks - Jon

I'm growing older but not up
My metabolic rate is pleasantly stuck
So let the winds of change blow over my head
I'd rather die while I'm living than live while I'm dead:tu