Rods 'n' Sods - UK Hot Rod & Street Rod Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
211 Posts
Discussion Starter · #1 ·
To all you chevy experts out there, I have a head scratcher!

Before changing my 327 to a 350 I've always set my initial timing up by the balancer groove and timing tab. I have since set up my 350 the same way and had it running fine! I ended up pulling the motor to replace the rings and brgs and again set up initial timing same way as always. Motor ran fine, even raced at Shakey.
Now I have changed my intake for twin 4 high rise and all set up ready to go, I spent 2 days cranking the motor trying to get it to fire, with no joy! Double checked dizzy wasn't 180 out etc. Now with more hands on deck, billy 4 speed came along and had it up and running in 20 mins! He decided to find tdc compression stroke using the good old 'hold your finger in the plug hole' technique rather than go by balancer marks and valves. Once tdc was confirmed, checked dizzy rotor... Totally off lead 1. Checked balancer pulley groove and it was at the bottom of the balancer..??? We marked the balancer where it was against the timing tab and she fired straight up!

How this engine has ran before is beyond me, but does anyone know of timing tabs that are located underneath the motor? Or of a balancer like this? Also if I was to buy a new 8" balancer would this correct the timing marks?

Cheers!
Kurtus
 

·
Registered
Joined
·
211 Posts
Discussion Starter · #2 ·
Is it possible for the outer ring on the balancer to move from the inner ring with age and high revving?
 

·
Premium Member
Joined
·
1,798 Posts
Is it possible for the outer ring on the balancer to move from the inner ring with age and high revving?
Harmonic balancers are normally located on the crank by a dowel off the crank nose so one position only and the outer and inner bit are connected by rubber so if it slips the rubbers gone and it isn't balancing anymore.

I found this from an Internet search. "Just pull the balancer if all is installed right with the ignition rotor pionted pretty close to number 1 cyl ( number 1 cylinder being at top dead center) the key way on the crankshaft should be between 1 o'clock and 2 o'clock posistion....if it is.... the inertia ring is slipped.....which is very common in sbc's especially if revved passed 6,000rpm" a number of sites mentioned the outer ring can slip on 350's and a lot of people report being 180 deg out but I can't see the outer ring moving that amount. Lots of results with this search: https://www.google.co.uk/search?q=harmonic+damper+180+degree+out

It sounds like it may have slipped but how was it running before hand if all you changed was the inlet? Strange! Hasn't Billy got any ideas?
 

·
Registered
Joined
·
211 Posts
Discussion Starter · #4 ·
Nice one!
Sounds like the most plausible of explanations with the outer ring slipping.
I guess maybe the initial set up was when the balancer was 'almost accurate' and since I've been running it, that's when it's slipped so setting it back up with initial timing after the change in intake is probably why it wasn't accurate any more? Billy thought maybe there was a timing tab that was located underneath the balancer rather than the 2oclock position... He is a Ford man after all so just his first thought.
I will have a look at the balancer with the pulley off and see what the key way is against the putter ring... I'm pretty sure now that the balancer has had it's day!
 

·
Rust buster...
Joined
·
602 Posts
It is possible for the outer ring to slip on the inner hub if they come unstuck, which they do when they get old - one of the good reasons to run a decent aftermarket damper on a high revving engine.

There's 2 key way positions on SBC dampers in relation to the timing marks - so make sure you get the right one.

The damper used from 1969 to about 1984 has the TDC line at the 2 o'clock position- or 10º before the keyway. You'll find that aftermarket dampers are the 10º type, as are the bolt-on tabs sold by the aftermarket, unless they're adjustable.
Warning Note: This includes the SBC 400, although the 400 damper is counterweighted because the engine is externally balanced, and the 1985-present 4.3L V6 with its respective 6.75" damper (raised outer lip) that has both a 2 o'clock and a 4 o'clock position (for some vans eg. G-series, Express, and Astro/Safari). Do not mix and match internal and external balanced dampers!

An alternative timing mark was used from (some) 1978 to about 1995, and nearly all 1984-1995 (exc for 1985-present 4.3L V6 and van applications). It is at the 12 o'clock position- or 40º before the keyway. This damper uses a timing cover that has the tab welded on at about the 12 o'clock position - the timing covers with this setup had either the 6.75" (305 and pre-1985 90 degree V6) or 8" (350/5.7 only). Professional Products lists the years for this type damper line as being 1984-1995 and is a 6-3/4" diameter damper.
 

·
Registered
Joined
·
211 Posts
Discussion Starter · #7 ·
Great stuff guys nice one. I think I'll invest in a decent balancer before the Hot Rod Drags... Would rather not cause a mess down the strip!
 
1 - 7 of 7 Posts
Top