timing

[yoshi]

Originally Posted by enaberif

You would be better off just checking to see what maximum mechanical advance your distributor has at 3000 rpm.. You may find it has less or more than the 36 degrees.

how do I do that?

Originally Posted by 1project2many

I'd mark on the low side. The greater the distance, the more advance you're building in. And you really should measure across the balancer to get the actual diameter. If the balancer is smaller than 8" your mark will be too far advanced.

as I said receipt is for 8" but I will check, but being 23:10 here it won't be tonight!

[1project2many]

I realized the receipt says 8" but often times those numbers are generalized. 7.75" would qualify as an 8" balancer.

I can remember the days when I stayed awake too late, too many nights working on my truck. I used to take long road tests at work during the day so I could nap.

[enaberif]

Originally Posted by yoshi

how do I do that?

Watch your timing as you idle up the engine. At some point you will no longer gain any timing and when it stops going up that is your maximum. 3000 is the general area of most SBCs but many variables and differences can come into play.

[yoshi]

#17
02-01-2015, 10:29 AM
chevy49
Junior Member

Join Date: Jan 2015
Posts: 10

I Had another look at the truck today in between the snow showers. I fitted piston stop & turned the engine with a socket & ratchet. The engine came to a stop right at the end of the timing tab I would say 15deg BTDC. I then turned it the other way & it stopped 2 2/8" away from 0deg BTDC. Would that mean I have the wrong timing tab?

[OrrieG]

It should stop at the same place if you turn it one full turn each way. If you have that much variance your stop is off, probably too deep if you cannot turn the engine thru TDC. One you find the TDC you can make a mark on your balancer relative to 0 on the tab installed and proceed from there to check timing.

[1project2many]

Originally Posted by yoshi

I Had another look at the truck today in between the snow showers. I fitted piston stop & turned the engine with a socket & ratchet. The engine came to a stop right at the end of the timing tab I would say 15deg BTDC. I then turned it the other way & it stopped 2 2/8" away from 0deg BTDC. Would that mean I have the wrong timing tab?

It sounds like it. The balancer timing mark should stop BTDC (on the tab) when turning the engine clockwise and should stop ATDC when turning the engine counterclockwise. But you are not out of luck. Turn the engine clockwise until the crank stops then mark the balancer at 0 deg on the tab. Then turn the engine counterclockwise until it stops and mark the balancer again at 0 deg on the tab. Actual TDC is exactly halfway between these marks. Make a third mark at the correct location, remove the other two, and proceed to checking / setting timing with the light. If you later get the correct tab then you can remove the mark you just made.

[octanejunkie]

Originally Posted by 1project2many

It sounds like it. The balancer timing mark should stop BTDC (on the tab) when turning the engine clockwise and should stop ATDC when turning the engine counterclockwise. But you are not out of luck. Turn the engine clockwise until the crank stops then mark the balancer at 0 deg on the tab. Then turn the engine counterclockwise until it stops and mark the balancer again at 0 deg on the tab. Actual TDC is exactly halfway between these marks. Make a third mark at the correct location, remove the other two, and proceed to checking / setting timing with the light. If you later get the correct tab then you can remove the mark you just made.

This is the way to do it when using a stop. With the heads off you can get very accurate. I prefer a harmonic balancer cover printed with timing marks, you can set your 0 mark perfectly with an adjustable timing pointer vs. timing tabs.

[OrrieG]

1project, you are right, I was assuming he had it set for absolute TDC. It will stop short on either side the same distance from TDC so center in between is actual in relationship to balancer.

[yoshi]

I've remarked the balancer using the piston stop as you can see in the pic. I've also taken a pic of the distributer with a piece of alloy to show which way its pointing

[OrrieG]

Looks good to me.

[octanejunkie]

That's definitely in the ballpark.
The more accurate you are with TDC on #1, and timing your distributor, the easier ignition is to manage.

[yoshi]

I just hope my 8" balancer isn't on the move

[octanejunkie]

Originally Posted by yoshi

I just hope my 8" balancer isn't on the move

If you suspect your balancer is separating (outer ring coming loose) then replace it before it does. Sometime before it breaks free and grenades itself inside your engine bay (another reason I like balancer covers with timing marks printed on them) you will notice excessive and increasing vibration coming from the engine - this is your balancer deconstructing itself.

Otherwise, I don't know what you mean by "on the move"

[yoshi]

That's what I've been told is a possible reason for the TDC mark being where it is. Is it possible that a 305 8" balancer could've been fitted by mistake?

[yoshi]

Finally got some time on my truck, I couldn't start it so I decided to bite the bullet & fit the HEI distributer that I have sat in its box. It was too late last night to turn the key after fitting it. I made sure everything was ready then tonight I tried again, she started the instant I turned the key but only for a few seconds. A few tries again & it was running. The new mark that I'd made was too far after TDC but the original was at about 6 deg BTDC so I turned the dizzy to get 12deg. I then took it out for a short run. All seemed well at first then I noticed the smoke coming from the rear of the cab which turned out to be an oil leak from around the timing cover area & getting burnt on the headers. It also suddenly started making a noise inside the carb. Which seemed to stop just as I arrived home. Will have to check back on that one. After cleaning up & packing everything away I noticed the dial on the rear of the timing gun was on 33 so what I've done was wrong. I went to start the engine again but it seemed as if the battery was flat but when I checked I've got 12.6v. So I assume it's struggling to turn over due to timing.

[yoshi]

3100 v8 vacuum test:*http://youtu.be/jeezGuFLCF4
as you can see on tickover its jumping around, when i increase the rpms it settles down

[Irishbleueyes]

vacuum gauge jumping around at idle means the timing is to far advanced, back it off a bit

[yoshi]

At the moment I have the dial on my timing light set at 32, & I adjusted the timing till the mark on the balancer went to 0 deg. Should I set the dial to 30 then reset to 0 deg again?

[Irishbleueyes]

no, while the engine is runniung just back the timing down till the vacuum gauge stops jumping. that should put your timing at maximum at idle. now for full advance timing turn the timing dial till the balancer zeros while revving at 3000 rpm. that will tell you what your total timing is. should be about 32 to 34. if not, your distributor will need some recurve work.

[Irishbleueyes]

Oh wait, your vacuum gauge is jumping around at 3100 rpm?

[Irishbleueyes]

I mistook that gauge jumping around at idle.

[yoshi]

It's jumping around at tickover less than 1000 rpm

[Irishbleueyes]

Originally Posted by yoshi

3100 v8 vacuum test:*http://youtu.be/jeezGuFLCF4
as you can see on tickover its jumping around, when i increase the rpms it settles down

Google vacuum readings chart

[yoshi]

Seems like No.6

[Irishbleueyes]

Ok, jumping around at idle also means to much timing