Timing issue on a 350
 

This is my first time messing with timing, so Im just trying to figure out what I am doing wrong. The engine is a pretty stock 350. My problem is, my timing is about 40°BTDC at idle, with the vaccuum advance capped. Is this normal? The sticker on my engine bay says 4°, so why is it around 40°?

I put a new balancer on (so i had all the marks). Verified that 0 on the balancer is at tdc. I put the dist in so that the button was right before the #1 on the cap. Wouldn't start. It sputtered if i turned the dist all the way counter clockwise, so i took the dist out and moved it back a tooth. It now runs decently. With the vac advance capped, it is around 38-40°BTDC at about 700RPM. Pushing on the throttle will advance it to around 50°BTDC

I guess im just wondering if this sounds right. Im no expert but the advance just seems like a lot. I think the engine runs alright (im still adjusting the dist every time i drive it because it will either kick back or ping, so i ever so slightly turn the dist appropriately when it happens). I also think it might lack power under load, but that could also be the 35" mud tires and 3.73 gears...


Thanks for the help.

Re: Timing issue on a 350
 

How did you determine that zero on the balancer is at tdc?

Re: Timing issue on a 350
 

You could have got the wrong balancer. I'm going to assume you have a 350 in a 67-72 truck with a short water pump. Timing tab was at the 2 o'clock position off of the timing chain cover. 1973 when things were switched over to long water pumps the timing marks moved to the 12 o'clock position. You would look behind the water pump and look at the timing tab tack welded to the timing chain cover.

That being said... if you got a later model (12 o'clock mark) balancer and put it on an earlier model (2 o'clock mark) engine... and only lined up the timing mark on the balancer to the ZERO on the timing tab... your timing will be way off. A lot way off... just like you have now.

Gary

Re: Timing issue on a 350
 

Ok, so the truck is a 1986 K20 with a 1989 350 (carbeurated). The engine originally had the timing mark at 12 oclock. I started having trouble with timing when the chrome dist hold down clip started not holding the dist in place. I thought there was something wrong with the 40°BTDC so I got a summit balancer with all the marks on it, designed for the 2 o clock position, and put a timing tab off the side of the timing chain cover (also at the 2 oclock position), hoping this might explain the problem.
I took the cap off the dist, pulled #1 spark plug, and took drivers side valve cover off. I had someone turn the crank from the bolt inside the crank pulley as I watched the dist. It was 180 out (which I already knew), so when the button got to about 9 o clock on the distributor, I started feeling in the spark plug hole with a dowel rod, and could feel the piston coming up. Once it stopped and started going back down, I turned the crank the opposite direction until I felt it was at the top. The timing tab lined up almost perfectly with 0 on the balancer. I verified that both valves were closed on #1, so I knew it was on the compression stroke.
At this point, I took the dist out, marked the dist base with the cap for #1, and put the dist back in the engine so that the button pointed right before (counter clock wise of) the (real) #1 mark. Then it wouldn’t fire at all. This is when I started moving the dist a tooth and finally got it to fire again.
Timing light is reading 40 at about 700 rpm with vac advance plugged.

Thanks.

Re: Timing issue on a 350
 

THose calibrated dowel rods, pencils, pieces of wire or pinky fingers are notorious for being 20 to 30 degrees out to lunch!
How many degrees of crank rotation are there during dwell time when the piston just gets to tdc and the lag before it starts to go back down?
You need a piston stop.
You need to be accurate or you're wasting your time.
A link for you.
http://www.crankshaftcoalition.com/w...op_dead_center

Re: Timing issue on a 350
 

You're sure all the wires are in the right places on the cap? It's easy to eff them up when you're tired, frustrated, working on a hot motor or all the above.

Plug wires? Yes, I'm positive they are right. The engine runs good (just bogs down a bit going up hill, but that could be a timing thing). The only way I've been timing this engine is to manually turn the dist and then drive it, so it's not that accurate.

I did notice last night that one of the wires that run from the dist to the cap was stripped, not sure how good of a connection its getting, but I'm going to swap the distributor with a different one later today.

I'll try to get my hands on a piston stop. I know my method with the stick in the spark plug hole is not extremely accurate, but when the timing mark was so close, it just made sense that the timing mark actually does line up with tdc, so I went off of that. I mean 30 degrees on the balancer is quite a distance off...
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Re: Timing issue on a 350
 

Make a piston stop from a sparkplug. Knock the guts out and tap the inside for a bolt or piece of ready rod. Taper the end of the rod. Put a locknut on it. Have at it.
Check for tdc by turning the motor by hand. Unplug the battery too.

Re: Timing issue on a 350
 

just to put some numbers to what geezer said: at 5° btdc (and atdc) a piston in a 350 sbc is .001 in. down in the bore
at 10° it is .003 in. (roughly 1/32 in.). meaning your balancer travels a full 20° (10° either side of TDC) and the piston only moves 1/32 in.
20° is over 1 1/8 inches on a 6.75 balancer

that is what makes any thing other than a piston stop guesswork.
http://www.wallaceracing.com/stroke-piston-travel.php

I got something like this (http://www.summitracing.com/parts/sum-900189/overview/) which as you can see is the same as what geezer is saying you can easily make yourself