[Carbo]

Hey guys, need some help. I have a 408 sbc with an MSD 6al box, petronix distributor and msd coil. I've always had timing issues with the car where it won't hold the timing I've set. According to the engine builder, the timing is to be set at 10-11 degrees initial and 34 degrees at 4000 rpm. When I set the timing at the initial setting it will lose degrees over time....i.e down to 7* after a few hundred miles. Also, the most advanced I have ever gotten at 4000 is around 24-25*. I've played with the weights in the distributor, wd40 on them and made sure they weren't frozen..no luck. Any suggestions?

[Steptoe]

the timing is to be set at 10-11 degrees initial and 34 degrees at 4000

4000 is way to high..ball park 3000/3200
As to the creeping.....do u have a std factory GM tie down for the dizzy or an aftermarket fancy chrome tie down?
replace thefancy one with a good old crappy factory one.

[cnorton7311]

Originally Posted by Carbo

Hey guys, need some help. I have a 408 sbc with an MSD 6al box, petronix distributor and msd coil. I've always had timing issues with the car where it won't hold the timing I've set.

If you continue to experience "creep" after replacing the hold-down, remove the cap and pull upward on the rotor. There should be a small amount of vertical play in the rotor shaft when the distributor is locked down. Some rebuilt engines have had the end rails of the block trimmed so far that the distributor bottoms out in the oil pump drive. When that happens, the extra force you apply to the hold-down is transmitted directly into the oil pump instead of to the distributor flange at the manifold. Result? The distributor tends to "walk" with the rotation of the motor and retards itself and the extra pressure applied to the oil pump rotor isn't good either. Correct the condition by adding a couple of extra gaskets between the manifold and the distributor.

[dawg]

either the hold down isnt working or your harmonic balancer is seperating and moving.
400s do not like alot of advance unlike the smaller sbc engines.
everything should be all in by 3000 rpm not 4000!
put the original springs and weights back in.

[Carbo]

Originally Posted by Steptoe

4000 is way to high..ball park 3000/3200
As to the creeping.....do u have a std factory GM tie down for the dizzy or an aftermarket fancy chrome tie down?
replace thefancy one with a good old crappy factory one.

The 4000 rpm at 32* was suggested by the engine builder. I don't have an original GM tie down but I'm going to get one from summit racing.

Originally Posted by cnorton7311

If you continue to experience "creep" after replacing the hold-down, remove the cap and pull upward on the rotor. There should be a small amount of vertical play in the rotor shaft when the distributor is locked down. Some rebuilt engines have had the end rails of the block trimmed so far that the distributor bottoms out in the oil pump drive. When that happens, the extra force you apply to the hold-down is transmitted directly into the oil pump instead of to the distributor flange at the manifold. Result? The distributor tends to "walk" with the rotation of the motor and retards itself and the extra pressure applied to the oil pump rotor isn't good either. Correct the condition by adding a couple of extra gaskets between the manifold and the distributor.

I'll check the vertical play anyway just out of curiosity.

Originally Posted by dawg

either the hold down isnt working or your harmonic balancer is seperating and moving.
400s do not like alot of advance unlike the smaller sbc engines.
everything should be all in by 3000 rpm not 4000!
put the original springs and weights back in.

The engine is a 350 block bored and stroked. It was built by the late T&L Engines. They recommended the timing at the particular rpm ranges.

I don't have any original springs and weights but I can get a pertronix set from summit when I order an OEM clamp.

Thanks for all of the suggestions guys. I'll keep you posted.

[Steptoe]

The 4000 rpm at 32* was suggested by the engine builder.

Read Johns timing 101...take particular note of his comment, which is basically the same as mine and others who have specialised in this arwa for many decades...MOST mechanics engine builders etc have no idea the actual requirements the whys blah blah of timing on the street..cent timing.
Now go back ask your builder
1/ Why is a particular engine has a given timing curve..what is the piont of advancing.
2/If an engine is rebored does the timing change?

I don't have an original GM tie down but I'm going to get one from summit racing.

Dont have a wrecking yard near by?...to source an actual genuine GM tie down.

[Carbo]

Originally Posted by Steptoe

Read Johns timing 101...take particular note of his comment, which is basically the same as mine and others who have specialised in this arwa for many decades...MOST mechanics engine builders etc have no idea the actual requirements the whys blah blah of timing on the street..cent timing.
Now go back ask your builder
1/ Why is a particular engine has a given timing curve..what is the piont of advancing.
2/If an engine is rebored does the timing change?

Unfortunately, T&L engines built mine and they are out of business so there is no going back to ask questions. Thank god for this forum. I don't need to call them anyway. I get better answers here anyway.

[Everett#2390]

You can check for dist creep by marking the dist and manifold with a marker.
Mark, drive, check later for alignment of mark.
If the clamp bolt is screwed into an alum manifold, dab some antiseize onto the threads preventing seizure.
Better choice is using a stud and a nut - finger tighten the stud into the manifold, use antiseize again, then the clamp, thick flat washer, and nut.

[Steptoe]

You can check for dist creep by marking the dist and manifold with a marker.
Mark, drive, check later for alignment of mark.

Once engine dialed in , tuning specs established I use a punch...clamp the dizzy down then on the edge between the valley cover and dizzy punch a mark....this is a useful reference point later on replacing dizzies etc.

Better choice is using a stud and a nut - finger tighten the stud into the manifold

I have abstactly thought about so many times over the yrs...one of those 'should do' things. A tiny drop of silicone on the tread of the stud near the top ...is enought to stop the stud moving but weak enough if wish to pull at a later date.....also for places like carb mounting studs, air cleaner stud etc.

[Carbo]

Just recieved the new dizzy and weights and springs. I'm going to play with it today and hopefully have it all figured out by tonight. I'll let you know when I finish.