Prsabordo

Hey everyone, just swapped secondary rods on my dads 1970 delta 88. It runs awesome (thanks jensenracing77). However, i think the timing is a little off because when i checked for carb vaccum it read 15, which said late ignition timing. Does anyone know what the timing should be on the crank for a 455? Also what should the dwell be set to? What order do i do these in, should i do timing light, then dwell, then carb vacuum? Thanks for the help.

svnt442

Timing is 8° BTDC @ 1100 RPM with the vacuum advance disconnected and capped. Dwell is 30° +/- 2°.

Prsabordo

How can you tell what rpm? Our car doesn't have tachometer. Where is vacuum advance located? So do timing at the crank first then dwell?

joe_padavano

You need one of these:



Timing adjustments won't change the dwell, but dwell adjustments CAN change the timing, so you need to set the dwell first, then adjust the timing.

Prsabordo

Ok, so dwell first, then timing, then carb vacuum? Can carb vacuum affect timing or dwell? So to set timing at 8 degress BTDC @ 1100 RPM do you have to have someone keep that RPM by pressing the accelerator or holding the throttle on the carb while timing it? Or is that what the RPM should be at idle? If so, do you change idle by idle adjustment screw on carb?

joe_padavano

Yes.

No, but adjusting the mixture screws will affect idle speed, so you need to reset the idle speed after adjusting the mixture, or else THAT will affect the timing.

I usually work the throttle lever on the carb with one hand while holding the timing light in the other. If it's easier, you can temporarily adjust the idle speed screw, since you will likely be adjusting it after the idle mixture adjustment anyway.

Prsabordo

So just to clarify, the idle speed is Not 1100 RPM? The idle SHOULD be 1100 RPM when timing is 8 degress BTDC, correct? What is the recommended idle?

MDchanic

At this juncture, please allow me to ask this question:

Do you have a shop manual?

If not, then you should get one. They are not expensive on eBay, or from other sources.
Get a beat-up one - you'll beat it up anyway.

In the meantime, the manual for your car is available here, and the specific section you need for tune-up info is here.

You really should read the manual first if you haven't done this stuff before - it isn't hard to do, but it will go much better after reading the instructions.

Sorry if I sound terse, but this seems to come up a lot.

- Eric