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What would be the ideal timing setting?

Scramblin_Jim

Scramblin_Jim

Legacy Registered User
City
Goodyear
State
AZ
I looked thru the history and didn't see this exact topic discussed. If it is there please excuse me and point to it, otherwise . .

After installing the Howell TBI and a hotter coil/wires and bigger distributor cap on my '83 with a 258, all these sources recommend a timing setting of 6 to 8 BTDC. I had found mine at 12 or 13 BTDC before I readjusted it to their recommendation.

What is the harm in having the timing at 4 or at 15 BTDC?

What is the ideal setting and doesn't it matter as to if you are running an automatic transmission -vs- manual, California emissions -vs- elsewhere?

Thanks in advance for your input.
 
Ditto

I have had the fate of waking up last week to find my Scrambler didn't start. Worked fine the day before. I was planning in the very near future to do the same swap (HEI and TBI, or MC2100) because I didn't want this to happen away from home. I don't think the carb just crapped overnight- but its a rebuilt Carter so that may be an issue. Checking the timing was my next concern
As far as timing I have tried to beef up on reading and research reading and I have the manuals but cannot find anything describing in good detail about timing "how to's" and trouble shooting. I'll be looking this up to catch what I can and hope you get it right.
 
There is no 'ideal' timing position for all engines of one particular type, simply because as they wear, they're going to run differently. This one may have loose valves and runs rich, that one has a cylinder running under-pressure and has EFI. Too many variables to have to account for. That said, I run my 258 (bored .040 8 years ago, Comp Cam, no emissions garbage, Carter BBD, HEI/TFI, 2.5" exhaust with 400CFM cat and cherry bomb) at 8* BTDC. I could probably go higher, but I haven't played with it yet. My wife's 258 (stock high-altitude engine, with Weber 32/36 carb, no emissions) runs at 12* BTDC.
I think the best way to determine where your timing NEEDS to be is to do it the old fashioned way: vacuum. Hook up a vacuum gauge to a manifold vacuum port (has strong vacuum at idle), disconnect and plug the vac line going to the distributor, and see where the gauge reads with the engine idling. Now, loosen the distributor clamp and slowly rotate the distributor first one way, then the other, while watching the vac gauge. The vac level of a healthy engine should be 17-23 inHg (inches of mercury, the original method of checking vacuum used liquid-filled tubes. Mercury works best because it's heavier than most other liquids, so you don't need really long tubes to read it).
The point at which the gauge reads highest is your best baseline timing, but may impart a bit of 'ping' on acceleration, so back off 1-2 inHg. Tighten the distributor clamp to fix it at that position, disconnect the gauge, reconnect the distributor vac line, and go for a drive. If it 'pings' on acceleration, back it off another touch until it stops.
 
Timing is relative to max torque output without high levels of NOx. If you have too low timing, it will not produce good torque. If it's too high, it'll detonate and also lose torque.
 
Ping method for me

This is what I do...

I warm up the engine and loosen up the distributer just enough so that you have to put some effort into turning it. Then I go out for a ride.

I pop it in 5th gear and lug it. If it pings, I back off a bit and try again. If no ping, I'll advance a bit. I'll do this until i find a setting that does not ping under load and is at maximum advance.

Now, this is under ideal street conditions. My timing right now is 16 btdc. As long as you are not pinging, you are in good shape IMO. But with your new setup, I probably wouldn't go less than 10 unless you are pinging. Oh...and I always run middle grade gas.
 
I had an MSD unit on my '83 with a timing control. I adjusted my baseline per Nick's method (best one, so far) at dial zero, then I could adjust 7.5 degrees in either direction. Reason was, I lived at 7500 ft and had to come down into town, which was at 4950 ft. I could "tune" as necessary. It was pretty handy, and worked well.
Paul
 
Sorry for the long delay, I just 're-found' this thread. 1-2 inHg, NOT degrees. It may only be a fraction of a degree change, but it's enough to keep you right on the ragged edge of power before you ping. As others have said, take it out and lug it, and if it pings, back it off a touch.
 
I tried the timing light for the first time and found that by manually adjusting- putting a screw diver down the #1 and turning the fan by hand to reach *6 worked best for me. Mind you it was the first time I used a timing light, but I really couldn't get as good a setting as with the ol' fashioned hand method.
Runs great, but now I have to adjust the carb a little to get right "bang" for the buck

Your definately correct, the manual says to contact the dealer(?), like that'll help. :banghead:
 
Check this out...

Maybe this can shed some "light"- no pun intended...Well look at the newer thread regarding "Jet Install" that has a few PDF's that you may be able to use.:cheers:
Duff
 
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