I6 Timing and Advance

[BMERDOC]

Does anyone have any good timing references for the inlines? The only one I've been able to scrounge up so far is 10* initial, 24* mechanical and 6* vac., all in by 3000. But 40 total sounds a little high to me. 10 degrees initial seems a little high with 8* being as high I as I can imagine (4* is text book).

[70cst]

Don't know if this helps but maybe this will be of some help till others chime in ...


http://www.67-72chevytrucks.com/vboa...d.php?t=288938

[camrycurt]

Well, I don't know that I'm a particularly good reference but I can tell you what I did. I've got a 230 with HEI mated to an SM465, so I needed all the help I could get as soon as I could get it. I also wasn't really looking for performance, just trying to match the stock specs as much as I could.

For the mechanical I bought the Moroso 72300 curve kit and used the lightest springs, which provide 23* by 2500.

And for the vacuum advance, I put in a NAPA VC1828 can because it was the closest match for the stock points can specs that I could find in an HEI can. That can provides 10* of advance. Here's a link to the specs for all of the different GM vacuum cans: http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf

On the intial, I actually don't know what it's set at. I've heard that the timing mark on most of the inlines is way off by now because of slippage over the years so it's best to just time the initial by ear, and my truck seems to run fine where it's at so I didn't want to mess with it.

But I can say that the new vac can and advance springs really helped my truck.

Hope that helps.

[BMERDOC]

Thanks guys! hmm, balancer slippage...looks like I've got another thing to add to the list to check.

[68 IRON]

Timing mark slippage? What signs would you look for if this is happening? The only way that I know would be comparing it to a serviceable balancer...or picking it up off the ground. Is the key way clocked to the same position as the timing mark? I know, I know soooo many questions.....

[camrycurt]

I'm only smart enough to know that I need to rely on people much smarter than me to fix most things, so I'm simply repeating what I've seen Tx Firefighter and the other real gurus say on the board: http://67-72chevytrucks.com/vboard/s...1&postcount=14

Most of them just say that the balancer slips as the rubber wears out and it's best to time inlines by ear, feel, rpms, using a glass of water, etc.

Someday I hope to know as much as them, but I'm not holding my breath.

[geezer#99]

To check for slipped balancer you need to find top dead centre on #1 on compression stroke. DISCONNECT BATTERY!!! Pull all the plugs. Buy a piston stop that screws into #1 sparkplug hole. Crank motor over by hand slowly till the piston hits the stop. Mark your balancer at the zero mark on your timing tab. A jiffy marker or white-out works for a mark. Now hand crank the other way till you hit the piston stop. Another mark on the balancer. Tdc is exactly dead centre between the 2 marks. If the line on your balancer is exactly between the lines then it hasn't slipped. If line is off centre mark a new one or scratch it with a file. Use the new mark or line to set your timing with.
The reason to pull all the plugs is to make it easier to hand crank.
Easy Peazy!!

[BMERDOC]

I've been thinking of how to check it with a dial indicator without removing the cylinder head. After much thought I suddenly realized I wouldn't give myself scrap price for the POS powering my truck. That is to say, If I know I can manually find what I think is TDC (there is a bit of dwell when the piston travels over center) then that should be good enough. If I did want to get a little more scientific about it I could find max lift on the lifter (side cover removed) and call that TDC. It is equipped with a timing gear and not a chain so I'm not worried about chain slop making the cam timing "slow" or "retarded". Once TDC is established I can compare it to the balancer reading and correct.
There is also the option of replacing the balancer because they are somewhere between $50 and $75.
I'm big on numbers. I like vacuum gauges and timing lights. Tuning with water isn't for me but I hear its good for detecting dinosaurs (Jurasic Park joke, sorry). As long as I establish a baseline I know my numbers and can make adjustment for improvement. Tuning be ear would be fine if I was just establishing initial timing but I wanna tinker a little and recurve the distributor for best performance.

[BMERDOC]

Thanks Geezer, forgot the piston stop method!!

[geezer#99]

And you can make a piston stop out of an old sparkplug too! Break the porcelain out of the middle and screw a fine thread bolt insde. Taper the end of the bolt. The fine threaded bolt will cut it's own threads. Cheap and easy.

[RichardJ]

>> the balancer slips as the rubber wears out and it's best to time inlines by ear, feel, <<
>>because of slippage over the years<<

That is not a reason to not use a timing light. Any engine made with a harmonic balancer that has rubber under the outer ring can come loose. Ford, SBC, anything.
There is one difference in that most engines have the pulleys in front of the HB outer ring and are bolted to the hub. That traps the ring so that it cannot fly off.
I dropped one on my 292 at 65 mph. Bang, gone. Years later, the new(used) HB dropped to the ground when I started the engine.
My solution at the time was to bolt a pulley on the front to keep it from flying off. That pulley is now used for the AC. I painted a line across the outer pulley, across the HB and the timing mark. If it slips I will see it right away.
My experience with any of them, I6 or V8 is that once they break loose, they will get much looser in a very short time.
Paint a white line from the hub out onto the outer ring. If the ring has come loose the white line will tell you.
Corvair uses the HB outer ring to drive the fan/gen belt just like a I6. For some reason they cut two hash marks so that the HB could be checked very easily. On this rebuilt Corvair HB I have painted a line on the hash marks and the timing mark.


If you don't want to set the timing at factory specs, that is fine, but it is not a reason to not use a timing light. Instead of the factory you want to add 2 deg, then 2 more. The timing light tells you where you are. You add 2 more deg and it pings. You use the timing light to drop back 2 deg and you like it there.
You take that reading and write it in your book or on the wall or in the glove box. The next tune up you look at what you wrote and set the timing there. Done.

[68 IRON]

I agree with the ear/ feel technique. When I installe the HEI, I didn't have a light to use. Just put it in the "groove" where it really hummed (made music) to me I am gonna keep an eye on that balancer though

[BMERDOC]

In the end as long as it sings its good I like to have charts and graphs...numbers. I wanna log where I've been so I know where I'm going. I wouldn't hesitate, in the end, to time an engine by ear if it were an emergency or just neccessary but if I'm baselining everything I wanna know where I started.