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bowtie44s 01-20-2013 12:34 PM

weird timing issue
 
Hey guys, I have been reading htis site for quite a while. It has been very helpful. I have a problem that i can't figure out and I was hoping someone on here could help.

I have built 2 engines, a 383 and a 454. They both run pretty good. I couldn't get the timing right on either one, so I timed them by ear. When I put the light on the timing is reading around 60 degrees.

I must be doing something wrong but have no idea what. I checked true TDC by using a piston stop and rotating clockwise, put a mark then ccw and put a mark and scribed the middle of the 2. One motor was right on, the other was 2* off. I have the firing order 18436572, have timing light on #1 plug wire, yes i'm on #1. I have tried 3 distributors on one motor and I tried 3 timing lights, 2 of the lights showed the same, one showed 3* different. If I put the light on cylinder 6 it shows the exact same thing.

If it really was 60* I don't see how it could actually run, let alone start. If I slow the timing down to where it should be it dies before I get there. What am I doing wrong?

I thought for sure it was me because it's 2 motors and 3 lights. I told a buddy that builds dirt track motors to set the time. He said why can't you, i said just see what you come up with. He did use one of my lights. He was under the hood for 15 minutes and he said I HAVE NO IDEA WHAT'S GOING ON.

Sorry for the length and thanks in advance.

MouseFink 01-20-2013 03:12 PM

Disconnect the vacuum advance hose and plug the vacuum source on the carburetor. Adjust the idle speed screw down as low as possible and check the timing. The initial timing advance should be 10 - 12 crank degrees BTDC at 650 - 800 RPM. After the initial timing is set, reconnect the vacuum advance hose and you are done.

The full timing advance is built into the distributor by the centrifugal (mechanical) advance mechanism and should be a total 34 - 36 degrees BTDC above 2000 RPM. The vacuum "advance" is actually a timing limiting device in order to prevent the mechanical advance from advancing too much or too fast. The amount of advance allowable by the vacuum advance device is stamped on the vacuum advance mounting plate and is 12 cam degrees. 12 cam degrees x 2 = 24 crank degrees mechanical advance. Therefore: 10 degrees initial advance + 24 degrees mechanical advance = 34 crank degrees total advance.

If you are seeing 60 crank degrees advance, with the vacuum advance mechanism is still connected to a vacuum source, the vacuum advance mechanism is bad, or the weight ring on the harmonic damper has slipped. I have worked on Chevy and Pontiac engines since 1962 and I have never seen a weight ring that has slipped. Just lucky or I don't abuse them.

bowtie44s 01-20-2013 03:32 PM

I had the vacuum advance unhooked and plugged, the idle speed was 750 rpm. I did find true tdc and the mark was right. When I rev it up the mechanical advance does work. I don't know how much full advance is because the mark goes clear out of sight.

RWENUTS 01-20-2013 03:56 PM

Are you using a dial back timing light?
What distributor?

MouseFink 01-20-2013 03:57 PM

In a GM distributor the mechanical advance pin is in elliptical hole in the weight plate and the amount of advance is limited by a rubber bushing. If the rubber busing has rotted and fell out, the distributor can be over-advancing. The pre-1967 distributors had a advance hole that is more elliptical than the hole in the weight plate of the 1967-up GM distributors. The 1967-up advance pin hole is nearly round which nearly totally limits the mechanical advance for low octane pump gas.

I am not confident this trick will help, but it can't hurt. You don't have to remove the distributor to do it. Use a hand mirror to see what is going on. If the advance pin bushing is missing, push a small piece of vacuum hose onto the advance pin in order to totally limit the mechanical advance.

lmsport 01-20-2013 04:24 PM

What ignition system are you using?

bowtie44s 01-20-2013 04:25 PM

On the engine I have been messing with the most recently I have a brand new MSD street fire. I also used a stock gm hei. The engine was throttle body but I converted to a carb (runs way better) so I had 2 stock tbi computer distributors so I guess I actually tried 4 distributors and they all did the same thing. I have used 2 different dial lights and one non dial. I am going to try a 4th light but I doubt it will be any different.

406 bug 01-20-2013 04:37 PM

Quote:

Originally Posted by bowtie44s (Post 1636939)
Hey guys, I have been reading htis site for quite a while. It has been very helpful. I have a problem that i can't figure out and I was hoping someone on here could help.

I have built 2 engines, a 383 and a 454. They both run pretty good. I couldn't get the timing right on either one, so I timed them by ear. When I put the light on the timing is reading around 60 degrees.

I must be doing something wrong but have no idea what. I checked true TDC by using a piston stop and rotating clockwise, put a mark then ccw and put a mark and scribed the middle of the 2. One motor was right on, the other was 2* off. I have the firing order 18436572, have timing light on #1 plug wire, yes i'm on #1. I have tried 3 distributors on one motor and I tried 3 timing lights, 2 of the lights showed the same, one showed 3* different. If I put the light on cylinder 6 it shows the exact same thing.

If it really was 60* I don't see how it could actually run, let alone start. If I slow the timing down to where it should be it dies before I get there. What am I doing wrong?

I thought for sure it was me because it's 2 motors and 3 lights. I told a buddy that builds dirt track motors to set the time. He said why can't you, i said just see what you come up with. He did use one of my lights. He was under the hood for 15 minutes and he said I HAVE NO IDEA WHAT'S GOING ON.

Sorry for the length and thanks in advance.


Check for correct timing tab and or loc of tab. recheck tdc and make sure dist. is on #1 when piston at tdc.

bowtie44s 01-20-2013 05:47 PM

Quote:

Originally Posted by 406 bug (Post 1637016)
Check for correct timing tab and or loc of tab. recheck tdc and make sure dist. is on #1 when piston at tdc.

I stated in my first post how i did that. Piston stop, rotate clock wise, mark balancer, rotate ccw mark balancer and went to the center of these 2 marks. I have my light on the very front cylinder on the crank (driver side front) #6 (next to last on pass side) shows the same thing. When I am at tdc, I take the cap off, the rotor is a good bit ahead of the #1 plug wire. I never did see if it was clear up to 8 but I can check that. Correct me if I'm thinking wrong, but 60* crank rotation is 30* cam and distrubotor rotation. There is 45* distributor rotation between cylinders so the rotor should be almost to the #8 plug.

Maybe I'm thinking too deep into this but I have been fighting this for a year and am out of ideas. I have just been living with it but i'd really like to set my timing at 34*-36* I am going to try my 4th timing light next weekend. I'm out of ideas.

68NovaSS 01-20-2013 07:04 PM

I read in several threads here that some timing lights aren't compatible with MSD ignitions, check it out. MSD reps on another forum say digital and dial back lights aren't accurate with multiple spark ignitions. If using a dial back light, is it zeroed?

bowtie44s 01-20-2013 07:43 PM

Quote:

Originally Posted by 68NovaSS (Post 1637061)
I read in several threads here that some timing lights aren't compatible with MSD ignitions, check it out. MSD reps on another forum say digital and dial back lights aren't accurate with multiple spark ignitions. If using a dial back light, is it zeroed?

I have read they have trouble reading the multiple sparks of a msd box, but all i have is the msd street fire hei. I also used a stock gm hei off of like a 85 chevy truck or something like that with the same results.

With the dial back lights, I set them on 0 and used the tape I put on the balancer and I set it to 60 and got the same thing. I think actually what i'm running now is 56 at idle with vac unhooked and plugged. My uncle has a regular non dial light that i am going to borrow next weekend. I just don't see 3 lights all being off that far and by the same amount.

jaw22w 01-21-2013 08:13 AM

After you checked for TDC and marked the balancer, did you set the #1 piston at TDC and check to see if it lined up with the tming tab mark? It sounds to me like the timing tab is not in the right place. I would suggest putting a timing tape on your balancer.

cdminter59 01-21-2013 08:54 AM

weird timing issue
 
If you are standing in front the vehicle. Looking at the timing chain cover and the top of the crankshaft, where is the timing scale located. Use the postion of the hands on a clock. Is it at 12:00 or at 2:30?

bowtie44s 01-21-2013 11:07 AM

I have timing tape on my 8" balancer and the mark lines up at tdc. The pointer is at around 2 oclock. I checked the mark so it's right.

lmsport 01-21-2013 11:16 AM

How much compression and what are the cam specs.


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