1968ragtop

I have a rebuilt 455 in my car havn't started it yet. Just wondering what the timing should be set at once running?

455...
9.5 comp
comp cam xe 262H
performer intake
442 ex manifolds
HEI ignition
C heads

442much

My 455 has 100 miles on it and I'm still trying to work a few things out before the Oldsmobile Show in Olds next Saturday.

I've been told.....

"all in @ 2800
initial should be 4 to 6 and it has 14 in it
As for vacuum advance that varies with the amount of vacuum and isn't adjustable on yours"

Right now mine is about 10* (with the vacuum advanced blocked) because it runs like crap at 4-6*. The HEI is non adjustible, so I'm told, and the RPM should be around 2800 with total timing all in. Mine is running about 34* total. I'm still working on it but have to borrow a timing light from Canadian Tire to check it again. No point in owning equipment if you don't know how to use it.

Right now, I can drive it and the temp is good as is the oil pressure. No issues there. Vacuum lines were set up as they were before the rebuild.

After it gets warm it wants to stall. I'm being told that because the engine is tight (and 10.3 CR) it will do that for a while, "it's normal". I don't know if I am fully convinced of that. The distributor has been recurved and carb rebuilt. If it was normal, it should start even after it's warm. It doesn't overheat.

Anyway, I'm still learning about timing so better take advice from someone who knows better than me. Just wanted to let you know what I've been told and the results. Good luck with the start up and if all goes good, bring it to Olds next Saturday. You're pretty close as it is.

coltsneckbob

Wow 4-6 BTDC? I run mine at 12 degrees advanced. Though I also use a blend of 110 leaded and Sunoco street Ultra unleaded which is 93. I figure I average out at around 99 to 101 octane rating - though to be honest I don't know if a simple average is the correct computation.

Are you serious a 2800 idle rpm? And stalling when it gets warm......sorry but to me that doesn't sound right at all.

TripDeuces

Here's a simple way to do it for non-stock set ups. I usually start at 10' BTDC. If it starts easy I bump it two more degrees until it wants to start hard then back it off two degrees. I like a lot of initial because it makes the car more responsive. From there you have to adjust the distributor degrees to get your total timing whatever that may be. I usually ran between 34-38 degrees total. Have it all in between 2800-3200 and you'll be fine.

1968ragtop

442much, I am trying to get it ready for the olds show and I'm getting pretty close to starting the motor.
As for timing this motor was a 75 smog motor with the factory 75 HEI ignition. Its not a smogger any more though, but this distributor hasn't been touched, which might cause me problems. I have the vacum advance blocked off. When I used to play with these cars years ago, if I remember right I was setting total timing advance at 36 and not worrying about the timing at idle, does that sound right?

442much

My car has the factory 76 distributor and it was just recurved for this build. I'm running total timing at about 34* and will play with it a bit. I'm going to try TripDeuces' suggestion and see how that effects driveability. I am really new at this timing thing and learning as I go.

My car idles at about 750 in park (dang Hurst digital tack jumps between 07 and 08). So, I suppose I should make it 700 in drive and about 1000-1100 in park. That might cure the "wanting to stall" issues. I'm going to try that also.

Thanks for the suggestion TripDeuces.

1968ragtop

I think the smoggers from the factory were set up differnt for emissions. I'd throw away any factory timing numbers. I beleive the HEI vacum advance module can be changed mine says 18 degrees, I was told a module with 10 degrees will work better, but I have mine blocked off so it doesn't matter right now.
442much, do you have a crazy cam in that car? Most hydraulic cams, the motor should idle at 750 rpm no problem. If it needs to be over 1000 rpm to idle, sounds like another issue, maybe a vaccum leak?

TripDeuces

I believe HEI's come with 20-22' built into the distributor. Which means you'll need 14-16 on the balancer at idle to get your total of 36'. Vacuum advance is for part throttle driveability and economy. All that vacuum advance comes out of the equation at WOT and you're left with pure mechanical advance. Unless you're talking about CCI/CCC stuff but since this is a 68 I'll disregard that.

442much

Not a radical cam, and it doesn't need to be 1000+, I'm just experimenting and will see if that is where it should be. If not, I'll set it where it sounds and drives the best. I'm just trying to see where it should be.

Bill in NC

For a street car, this is a great starting point, and will probably be all that you need. Good luck and let us know how it runs.