northiam

Looking for opinions from the learned gentlemen out there. I have been playing with the initial and total advance curves for some time now and to my bewilderment the Clevo likes 20 initial and 22 – 24 degrees mechanical advance (total 42 – 44 degrees). Before you right this post off as another d^”khead with ridiculous claims, read on. I’ve tried the 20 initial 12 mech, 12 int and 20 mech advance and many combinations in-between.
My engine specs are 351 + .020, 0 decked, ACL short flat tops, 302 closed 2V heads, 302 6.02” rods, F238 (21626) cam, 10.9:1 CR, tri-ys, 750DP, 3200 stall, 3.5 gears.
My hypothesis is, the engine likes the increased advance due to the longer piston dwell at TDC having the longer con rods. Secondly cooler combustion temps i.e.: quenching, polished chambers, 80C thermostat, shaker etc.
Note: The cam timing was set to zero with absolute precision! And the damper hasn’t slipped.

Racer

The more efficient the engine, the less timing required. 36-40 is about right for an old Clevo

brenx

XBWGN runs a similar setup but with 351 rods. It's got 12 initial and a total of 36-38 deg total. Which is the same as mine almost. I run 12 initial and 36 total. Mine didn't mind 38 but it detonated exactly twice during heavy load. So I went colder plugs and 2 deg less total timing.

Brenden

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XB Fairmont (street car) 11.07@123.02mph.

STROKEXD

northiam you're onto it! Through trial and error and some dyno work I've found that you can't have enough initial timing in a clevo. It seems this is a bit of a secret and the view of 6-12 degrees initial timing is old news.

I'm running 20 initial and 18 centrifigal to give me a total of 38. I'm a bit suprised you are able to run 44 without pinging in that set-up. It must come all in real late ie 4500rpm? Either way if it is not pinging you can't go wrong.

I'm considering experimenting with 25 initial next, but I can't modify my dizzy for anything less than 18 centrifigal ATM. Maybe going to buy a programmable timing computer in future.

What I've found is if you have a power producing cam and not a torque producing cam (like stock or near stock), running around 20 degrees initial timing restores a heap of low end torque.

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northiam

Total advance in by 3000 rpm, I'm now running hotter plugs NGK BPS5

4vxc

what are you using for fuel? hot plugs, 42 – 44 degrees, 10.9:1 CR, dosn't sound right to me.

northiam

Running PULP changed to hotter plug as I keep fouling the colder ones so far hotter are staying cleaner.

lowy

IC&E set up my distributor to suit my engine, they gave it 18 init with 20 deg advance.
No pinging problems with shell optimax and a bottle of wynns racing octane boost. I run 11.5:1 compression...

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85 XF 'S' Pack ute, lowered to the bejesus.
351 cleveland, 2800 stall, c10, 3.7:1 disc brake LSD nine inch, 750 double pumper, holley blue etc., 17 inch AU XR8 Wheels.