distributor/intake interference question
 

I have had funky timing since I bought the truck and finally got around to following the instructions on this thread ( http://67-72chevytrucks.com/vboard/s...d.php?t=258643 ) and others to reset it. I started the truck and began to advance it from 0 degrees with a timing light. When I get to 7 degrees, the vacuum advance hits an intake runner and vacuum port and can move no further. Here is a picture of my setup with the areas that interfere circled in red. Have I put the distributor back in incorrectly? Do I need to change the vacuum advance?


http://www.myoldtruck.com/gallery/fi...istributor.jpg

Re: distributor/intake interference question
 

I'm thinking you might be off a tooth on the dizzy. Can't recall exactly what my timing is set at, but it's a bunch more than 7 degrees -- and I still have lots of clearance between the vacuum advance and the manifold. I'm running an Edelbrock 2101, but I think the runners are about the same.

Re: distributor/intake interference question
 

i dont see where its hitting an intake runner but with the clearance issue for the vaccume line just rebend reposition the tubing to get the clearance you need that tube doesnt need to be that specific shape or length to work properly

Re: distributor/intake interference question
 

you may have to pull the distributor & move it back one tooth so that you have the required "swing" to advance it enough.... This is an interesting problem - i've never heard of this before.

Re: distributor/intake interference question
 

your 1 tooth off on dist. install.

Re: distributor/intake interference question
 

I am quite good at creating interesting problems...keeps life interesting. Thinking it over, you guys are probably correct. I am off by a tooth or two. Thanks for the quick replies!!!

Re: distributor/intake interference question
 

I think that my timing is at about 12 degrees

Re: distributor/intake interference question
 

My timing is at 8 degrees BTDC (6 mechanical and 8 with vaccum), I had the same problem but the timing is dead on with about a two to three inch gap.

Re: distributor/intake interference question
 

I had that issue on my 6 cylinder - vacuum module was hitting the block before I could get the timing where I wanted it. I pulled dizzy, spun the body and put it back in (following all the other TDC, etc steps) - had a whole lot more swing and it didn't cost a thing... anywhoo....

Re: distributor/intake interference question
 

If it is starting okay, but you are just unable to set the timing I'd go with CDowns and move the offending fitting. It just may be that your are NOT off by a tooth, or two.

After I had a stroke, my Physician's Assistant brother-in-law said, "Don't look for a zebra, when you hear hoofbeats". I think moving the distributor, un-necessarily, is akin to a zebra. I'd try moving the vacuum part, just to be sure. If you have to reset the distributor afterwards, it won't hurt to have tried the other, first.

Re: distributor/intake interference question
 

Just move it one tooth and everything in will be fine.

Re: distributor/intake interference question
 

Been awhile since I've messed with my dizzy, but I'm pretty sure that vacuum advance gizmo was not agreeable to being moved...

Maybe I'm wrong though, just ask my wife.

Re: distributor/intake interference question
 

I was able to time the engine once I rotated the distributor two teeth further away from the intake runner(clockwise). However, I timed it to 10 degree BTDC and it ran horrible. I used my vacuum gauge to complete the timing since it was off the timing pointer at this point. By the time I had the highest vacuum(18) the mark on the balancer was almost straight up and under the waterpump. What could be wrong at this point? Looking for ideas at this point. Thanks for help so far!!!

Re: distributor/intake interference question
 

The outer ring on your balancer may have sliped at some point & thats screwing with your timing. July 07 Car Craft just had a good fix for a sliped balancer. PM me & i'll scan it for you if you want.

Re: distributor/intake interference question
 

A quick fix is to set the #1 cylinder at the top of the piston in the compression stroke (tdc). Here's what I do.

1. I remove the spark plugs to make it easier to rotate the crank.

2. I stick my finger in the spark plug hole while I move the crank with my 1/2 inch ratchet and socket on the crank bolt.

3. Once I feel pressure, I insert a screwdriver in the hole and watch it as the piston pushes it upwards to the exact top of it's travel.

4. At this time your harmonic balancer should also be at the tdc mark on the indicator. Place a white paint mark at that point and check your timing again.

All the above is if the balancer is not slipping or defective.

If you want to mark it permanently, use a small triangular file. I just clean it off real good with solvent and place a thin white paint mark using enamel paint I got from a hobby shop.

Re: distributor/intake interference question
 

68gmsee, those are exactly the instructions I followed last night. I had no problem getting the #1 to TDC and installing the distributor. However, the truck does not run properly until I have advanced the distributor from the stock 0 degrees mark on the timing tab to a point where the distributor mark is almost pointing straight up. Does that make sense...I had to reread what I just wrote so it made sense to me. To give you an idea of what it runs like at various timing points, it will start at 0 degrees but will stall within a few seconds. At 10 degrees it will run and idle but has NO power at all. From there I used a vacuum gauge to get it running "properly". What is confusing me is that TDC on #1 is also where the balancer mark lines up with the 0 degree timing tab mark. ???? Which leads me to believe the outer balancer ring has not slipped. Something else must be wrong. I have reached the extent of my knowledge at this point though.

Re: distributor/intake interference question
 

I have a couple of (misguided?) thoughts on this. It seems that you have done everything right and without offending you, have you made sure that you are on the #1 plug wire with the timing light. It looks like you have an HEI distributer in there. I have seen a point dizzy with a loose cam gear (slipping on the shaft) causing the timing to change every time it was started.
Has the engine been rebuilt recently? If it has, it may have been assembled a tooth off on the cam gear of the timing chain. I've also seen aftermarket cams that have the dowel pin off by as much as 12 degrees. This will make you set your ignition timing off to compensate for the valves not closing at the right time and also rob you of HP.

Things that make you go Hmmmmmmmm?

Re: distributor/intake interference question
 

Yes. I am positive I have the #1 cylinder correct. No. You have not offended me. I think the top end of the engine was rebuilt in the late 90's. Could the valve timing be off? I would not even know the symptoms of that.

Re: distributor/intake interference question
 

Mine is nearly stright up too when timed to idle well.I figured it was the old balancer outer ring slipping on the rubber layer,causing the index line for TDC to travel to that position.I just run it as-is.

Re: distributor/intake interference question
 

Not sure what you mean by "the truck does not run properly until I have advanced the distributor from the stock 0 degrees mark on the timing tab to a point where the distributor mark is almost pointing straight up."

You may just have to adjust the distributor timing until your truck runs good. These trucks have been changed from stock in so many ways these days, that you can't go by the book anymore. Move the distributor until your truck runs to your satisfaction for now.

I've heard that some guys adjust it to 12 degrees tdc and some even higher just to get their trucks to run good. Play around with it and see what you can do.

Also, re: valve timing. If your timing chain is worn and/or your cam worn flat from many miles of use, it definitely will affect the performance of the engine.

It would require you to remove the timing cover to check the condition of the chain.

Re: distributor/intake interference question
 

Valve timing being off a few degrees can show up as you described. By that I mean, having to time by vacuum. Being off as a result of improper installation of timing chain, I don't know. Only timing chain experience is when they have jumped teeth and wouldn't run properly or at all.
Before getting into anything major, have you checked the voltage to your coil? Should be 12V.
Hope I haven't led you on a goose chase.

Re: distributor/intake interference question
 

68gmsee, I don't doubt that I need to adjust the timing more than what is normal(8-12 degrees) but I must be MUCH higher than that to be vertical. I might take a look under the timing cover if I find some time. I do have a new engine to put in but that is a couple of months off.

sixlug, I do have 12V. I rewired it a couple of years ago to provide more voltage than was going there. Don't worry about the goose chase. I am learning something everytime I touch the truck.

WorkinLonghorn, I think I have discounted a slipped outer balancer ring in my case since #1 TDC is at 0 degrees.

Having timed it using a vacuum gauge, where should I go from here to fine tune the timing? I have never been overly pleased with the performance of the 350 with 3.73 gears.

Re: distributor/intake interference question
 

Alex, forgive me but you did disconnect and plug the vacumn hose going to the vacumn advance when timing it right?

Re: distributor/intake interference question
 

Yes. I did unplug the vacuum advance. That does bring to mind a question from me. When timing by vacuum gauge, should I have the vacuum advance unplugged? Or does it matter at that point since at idle there is no vacuum?

Re: distributor/intake interference question
 

I am thinking that at one point the small block balancer timing tab was straight up. I am a little foggy on this but it rings a bell. Maybe it is not an original balancer

Re: distributor/intake interference question
 

If it's on ported vacumn it won't make any difference at idle speed.
I 'd say adjust your timing by the vacumn gauge to get the best idle and clamp er down. Then drive it and seen how it performs. If hard starts show up back it down in approximately 2* increments until it starts good again hot.

You know tuning the engine to achieve best idle somehow doesn't make good sense to me since we don't drive down the road at idle speed. :rolleyes:

Re: distributor/intake interference question
 

Long Roof, I think I have heard about timing tabs that were straight up. I don't think my engine is one of them though, as the water pump would completely cover it up. You could be right about the balancer not being stock. I will continue to fiddle with the timing and see how it turns out. This is REAL incentive to get my new engine finished and in my truck. THANK YOU EVERYONE for all of the ideas and help!!!!!!

Re: distributor/intake interference question
 

I found the problem. The mechanical advance was frozen. THANKS sixlug! I was able to loosen it and time it correctly. I had limited experience with the internals of a distributor and did not know how it should behave if working correctly.

Re: distributor/intake interference question
 

Boy, that'll sure do it alright. Been there. Mine got so sluggish it wouldn't pull itself on level ground. lol