dodger007

hello all, I have a 1968 442 basically stock. only modifications it has is Edelbrock manifold and Edelbrock carb. car was running great until I changed the spark plugs and wires. as I was replacing the wires on the cap, I noticed it moved, the whole distributor. the car has a very rough idle and backfires now. would the distributor being moved like that make all this happen? I'm sorry for the newb question, I've never really worked on cars this deep into it other than oil changes, brakes, straight forward thing like that. I really don't want to take it to the shop again if I can HOPEFULLY fix it myself. I figure I probably threw the timing off? if so, is it a easy thing to fix with a timing light (which I have to buy)? thanks in advance for the help

oldcutlass

Yes, your timing is off. You'll have to reset it.

dodger007

Ive been doing lots of reading and I have to confess, this timing thing is a little confusing. I'm going to give it a try though. I located the timing tab but they have no numbers. I searched the forum to see if anyone had posted what the numbers were but to my luck, pictures are gone! any idea what the numbers are on the tab?

Vintage Chief

You'll eventually get there - continue your reading - it will be difficult to develop a complete understanding in one or two days, hang in there. If you intend to learn how to do this & you intend to perform engine tune-ups on your vehicle while you own the car, you should own four items:
(a) Dwell Meter; (b) Timing Light; (c) Vacuum Gauge; (d) 1968 Oldsmobile Chassis Service Manual.

It is in your absolute best interest to purchase and own a 1968 Oldsmobile Chassis Service Manual (CSM). We cannot assume which engine is currently in your car. Nor do we know if your car has AC. We'll need to know if you have the original type OEM contact points distributor with contact points or an electronics points/ignition module installed or if you have a GM HEI distributor. Any chance you have a tune-up specifications label located on your fan shroud? It would be white/lack letters demonstrating the tune-up specifications.

Address these questions:
(a) Size of engine
(b) AC or no AC
(c) Type of distributor

There is only one sequence to tune-up an automotive engine:
(1) Set/Adjust dwell angle (dwell meter)
(2) Set/Adjust timing (timing light)
(3) Set/Adjust carburetor (vacuum gauge)

If the ONLY item which moved was the distributor, you might very well get by with ONLY having to reset your distributor, which as you stated you'll need a timing light. Tons of very knowledgeable members to assist you on this site; and, there are many threads regarding timing for which you can use the Search feature. Here is one such thread (below) there are many more.

https://classicoldsmobile.com/forums...-drive-134624/

dodger007

I will check to see if I have a tune up sticker on there somewhere when I get home. So, the car has original 400 engine, It does have original ac but not working at the moment (belt is connected to it) and as far as I know it also has original distributor. I bought this car from my uncle which he bought brand new in 1968, so I am second owner. everything was original in the car UNTIL my brother and I bought it. being young and dumb we wanted "name brand" things on it. Edelbrock manifold and Edelbrock carb are the only aftermarket upgrades we did to the engine. I recently (about 2 months ago) upgraded the front brakes to disk brakes. if that makes any difference. again thank you for all the help, I know these questions are easy to you veterans but I guess I should know how to work on my car if I want to have an "old skoo". thanks guys

p.s. I will be buying a timing light tonight after I get off work.

cfair

Timing is still hard for me and I've been doing this 35 years. At idle, cruise, and wide open throttle spark timing changes based on a combination of mechanical, vacauum and rpm values. And the key tool is the timing light.

We've probably all bumped our distributors here & there. But now you have to bump it back to where it was running better. If you have no timing light, you're flying blind, so best option there would be to go get a "dial back" timing light.

I like the Innova Pro 5668, but it's $100, so a cheaper one may be better for you now. The main reason to buy a dial-back light is that you can't tell timing at any speed other than idle without it. It only took me 30 years to learn that. Sooner or later you'll want to know spark timing at all rpm levels. So get a cheap one now to get the car running or get a good one now and keep it kind of thing. If you can swing it, get the good one, if you keep the car, you'll be adjusting timing occsionally for a very long time.

But for now let's assume you have the points (not HEI) distributor and you've knocked it and you want to get it back somewhere close to where it was. If you have a points distributor and didn't remove the cap, your dwell should be what it was with the old wires. It may be wrong, but shouldn't be different. I.e. save that problem for later.

Distributors in these years were held into the block with a hold down clamp and a 9/16's bolt. You should see the bolt at the back of the block below the distributor cap on the driver's side. It's probably loose which is why the distributor moved when you bumped it. Snugged down properly with the bolt into the block, the distributor shoud not rotate with a bump.

Dirt can be your friend: There may be a pattern to the dirt & grime on the base of the distributor giving you a clue which direction & how far you knocked it. If so, just turn it back until you see a consistent pattern in the dirt on the outsides of the hold down clamp. The idea here is that if there's a light area of the distributor base with less dirt or no dirt, that's probably where the clamp was covering the base of the distributor. Move it back to where it was and you may get where you need to go. But there is no precision here at all and the engine may run like crap.

You may have a timing tab is marked ||A. |||| O. ||||R.||. With these, I was told that each line=2 degrees. Therefore: A=+8 degrees, 0 is 0 (Top Dead Center), R=-8 degrees. Once you have a light you can see where the #1 plug is firing relative to TDC and you're off to the races. With the engine idling at 800-900 rpm, your timing (without vacuum attached) should be in the neighborhood of 12-14 degrees as a starting point. You'll find 12 degrees BTDC at the "top" of the timing tab if yours is like mine.

I can't remember if backfires indicate that you advanced the distributor too far or retarded it too far. Maybe someone else can comment on that.

Others here know a helluva a lot more than me and can probably give better advice.

Good luck and expect to spend a couple of hours getting it back in shape. You'll set the timing, get it running, then test drive. Then rinse and repeat until you're happy.

Chris

Sugar Bear

Were the plug wires changed one at a time?

Is the cap properly seated on the distributor? There is a notch in the distributor and a spot on the inside bottom of the cap, they have to seat together.

Good luck!!!

BangScreech4-4-2

This may be the key question right now -- you may not have moved the distributor at all. If the hold down bolt had been loose all along, I'd think your timing would have been all over the map prior to this incident.

dodger007

that's what I thought too but it actually does move, not loosely but it does move. wiggling the cap around to install it that's when I noticed it move because I moved it

so I bought a timing light today and this is where my timing is. like I stated in my previous post, I have no idea what degree that is

Vintage Chief

This is why you need a CSM - I strongly suggest you buy one. I do not have a 1968 CSM. I believe the image (below) is the timing pad you have posted in your image. The punched holes represent the 10° and 0° (BTDC) marks. Did you look for the tune-up label on the fan shroud? It will indicate what your timing is supposed to be @ idle (etc., etc.). From your image it appears the timing is set to 10° BTDC - which is probably what it is supposed to be set to - perhaps 12° BTDC; but, again I do not own a 1968 CSM.

Are you sure you have the correct spark plugs and did you gap your spark plugs correctly? Did you remove the distributor cap and perhaps move the points or loosen the points in any possible manner?

You need to be more specific. Moved is a meaningless term. How far does it move and what moves? The top of the distributor as in specifically the distributor cap moves? How far does it move? Does it turn 1°, 5°, 10° or 1/4", 1/2", 3/4".

The distributor cap should be tight and it should not move. If it does, something is broken or not clamped correctly. The distributor lock-down tab should be secure and not allow the distributor to move "at all".

dodger007

yes I looked around and couldn't find anything with tune specs. when I say moved, I mean the whole distributor, not just the cap part but the whole thing. as far as how much does it move, as much as I want it to move either way, just afraid of turning it too much. yes I did replace the cap, so you might be right, maybe I messed up the points. I gapped the spark plugs to .035. I will be ordering a CSM as you recommend.

Vintage Chief

If your entire (whole) distributor is moving that may be your issue. And, you will not have to re-adjust your dwell (hopefully). The distributor is "locked" into place to the top of the engine. There is a lock-down plate at the bottom of the distributor where the distributor is inserted. There should be a single bolt running through the lock-down plate and that single bolt should be tight enough to hold and maintain the distributor from not moving. The distributor cannot and should not move "at all". Double check the lock-down plate on your distributor and make certain it is locked down adequately. If you find the lock-down plate is not "securely" fastened, then we'll just need to reset your distributor - hopefully. This is basically re-establishing your timing. As I mentioned in my previous post, there is only one manner to tune an engine: (1) Dwell>(2)Timing>(3)A/F Mixture (Vacuum).

Again, the distributor DOES NOT move. The distributor must be securely locked into place with the lock-down plate. Check it and let us know.

Vintage Chief

Your best purchase is an original paperback edition of the factory CSM. Don't buy a digital CD/DVD which you have to view form a PC while working on your car - they're worthless. You need a good paperback edition and you should get an original. Many of the reproductions lack clarity, the print gets washed out, the images are poor, etc. The CSM is the most definitive and authoritative piece of literature you need for your car. Additionally, you'll get the original wiring diagram.

https://www.ebay.com/itm/1968-OLDSMO...MAAOSwFLRepfTO

dodger007

ok so I checked the lock down plate with the bolt and it was loose enough to let the distributor move. I was able to tighten the bolt and sure enough the distributor doesn't move anymore.

Vintage Chief

OK That is very likely your issue - your distributor was slipping. We'll get you through this.

Vintage Chief

The distributor lock-down plate bolt was most likely tight "enough" to maintain "some" hold-down pressure onto the lock-down plate but it wasn't tightened down thoroughly. During your adjustments, you managed to turn the distributor to one side or the other just enough to offset your timing. You might get away with simply tightening down your lock-down plate at the correct timing and be done with it (best case scenario). However, if when you removed the distributor cap and if you did make any adjustments or moved the contact points, you might need to re-establish your dwell. What I'm "thinking" at this point is the possibility your distributor is offset just enough that it's more or less wobbling from the position it should be at when locked down. If it's moving (turning) while you're driving and idling, the timing is going to be uneven and rough. Again, I'm not certain exactly what you touched - if you bumped, nudged, or made any adjustments to the contact points you'll need to re-establish the dwell and then adjust your timing again. But, for now you might just get by with re-establishing your timing and locking down that lock-down plate securely so the distributor does not move.

dodger007

I appreciate all the help fellas, thanks!
I guess my next question is the million dollar question. at this point, should I invest in a HEI system? if I'm already messing around with the distributor

Vintage Chief

I am not certain what the dwell and/or timing should be on your 425 and at what RPM. If you can find those numbers, you should be good-to-go.

Here is how to tune-up your engine. Remember: Dwell>Timing>A/F Mixture (Vacuum). Don't forget to unhook the vacuum advance and then hook it back up after establishing timing.

NOTE: This is from my 1971 CSM. The timing mark/pad will look different and maybe a couple other pictures or whatever, but the process is the same regardless.

dodger007

this is great!!! thank you

Vintage Chief

Just remember at this point, if you're going to simply attempt to readjust your timing - my suggestion to you; you MUST disconnect the vacuum advance before adjusting your timing and then reconnect the vacuum advance. This is done at a specific RPM - generally about 1100 RPM or thereabouts. If you're idling a little high after you adjust timing, you can re-adjust your slow idle screw on the driver side of the carburetor.

Vintage Chief

You're opening a can of worms asking that question.
Don't consider the installation of an HEI system to be some mysterious upgrade to the OEM contact points system. Your issue was/is not an inefficient or poorly designed feature. Your issue was simply one single bolt was not properly tightened. These cars run flawlessly and efficiently on contact points as they were designed to perform. There are benefits to a GM HEI system. I would suggest you learn the ins and outs of your current system (changing out rotors, distributor caps, contact points, learning about dwell, A/F mixture and vacuum) then after some time make a more educated decision if you want to move over to an HEI system.

matt69olds

Exactly what he said! If your not having problems with the points system, there is no benefit to converting to HEI. The biggest advantage of HEI is the timing doesn’t change. With ignition points the timing changes as things wear. Considering most people drive these cars on a limited basis, dwell and timing adjustments are needed every couple years.

Fix what’s wrong, then as your knowledge and comfort with these cars improve you will be in a better position to make those kinds of decisions

dodger007

yeah you are right, should fix it and learn it. That way i know what the hell is going on for future problems. Thanks for all the help! Guess i have to look for a dwell meter

dodger007

yeah i guess i was trying to get an “easy” way out. But you guys are right, better to learn it

RetroRanger

Your pic of the timing tab points to about 10*. If your vacuum advance was still attached that might be way off. As chief noted disconnect and plug vac advance line, then check the timing. Usually 12-14* is a good base setting for points ignition. If it pings when you punch it youll need to turn it back a little. This will get you going until you get a dwell meter.

the hei is fine and will get away from setting points and dwell, but youll need new wires, and the timeing curve is generally different than the OE curve which is taylored for your engine.

ie the hei just opens up another can of worms.

there are distributors like the MSD ready to run, that replace points and allow you to taylor the advance curve easier than the hei. Unfortunetly those start at about $400, and are likly to cause you to spend more money on accesories etc.

probably noneof the above options will alter performance significantly over the points system.

cfair

I asked myself the exact same question about HEI decades ago. Seemed simpler. Seemed like an advancement. I'm using them now, and probably won't go back but they're not the clear advantage I thought they'd be. Combined with a later model internally regulated alternator, I've found the upgrades a good solution. GM got better at making systems as they gained experience, but their design goals changed along the way too.

The upside of HEI is they solve the problem of mechanical points that degrade over time and eliminate the need to set dwell. They're also one unit instead of coil, and distributor as 2 separate pieces. Cleaner look in the engine and less to mess with. But you have to remove the factory resistance wire (pink in my case) and put in full keyswitched 12v to the HEI to have it work right. Cool if you're into wiring, less so if not.

The downside is HEI's were designed & implemented during the 70's smog era. The advance and dwell they have built in adheres more to smog standards than the late 60's performance era. Those settings are built in to the HEI module which is not adjustable. These modules are mostly reliable, but I carry a spare in the glove box just in case I need to change it by the side of the road, plus tools to open the HEI cap to change it. Failure hasn't happened often, maybe 4 or 5 times in 25 years across 2 cars, but HEI modules either work or they don't. They just stop working, they don't degrade like points which give you warning that they're needing replacement. On my mechanic's advice, I use AC/Delco modules in hopes that they're more reliable.

I've also found that HEI's have a lot more advance built in, so I get pinging (knock) at part and full throttle on my 455's unless I turn the timing back (retard). This makes the engine run hotter and causes some power loss. My latest solution is to have a Cadillac vacuum advance that seems to have solved the knock problem instead of the Olds 1975 vacuum pot or the aftermarket adjustable ones. I'm not sure it's exactly right, but I'm getting there with a good deal of trial and error. But hey, trial & error includes test driving, i.e. enjoying the car!

The other downside is you'll have to figure out your tuneup specs from other-than-the-68-CSM. It's not real hard, but it means that whole section on dwell angle and points is irrelevant. HEI has its fans. When you can't sleep google up HEI modifications, HEI tuning and so on, you'll find site after site of devotees and people who love them.

Way out at the weird edge, if a nuclear blast nearby causes and electromagnetic pulse with your HEI in range, it probably won't work afterward. Points will. I watched "Independence Day" last night with the family and the old Dodge truck (presumable with points, not HEI) got the characters to safety.

Hope that helps
Chris

matt69olds

If ignition points really are too much hassle, get a electronic conversion for the point style distributor. You won’t have to mess with new plug wires, ignition coil, recurving the HEI distributor, etc. Pull out the points, swap in the conversion kit, reset the timing and forget about it.

oldcutlass

A nearby nuclear explosion will be more devastating than the EMP it produces and your ignition system will be the least of your worries. With all that said yes, there is really nothing more reliable than points. Points and HEI can be used equally in most stock or performance settings. Both distributors need advance settings compatable with the engine they are installed on.

Stock tuneup setting are for reference not gospel. They can be fine tuned for better performance.

Fun71

Sorry in advance for the thread derail but I wanted to address some of Chris's comments.

The HEI has less mechanical advance, so in order to achieve the same amount of total advance, the initial has to be set higher. During my extensive work with distributor timing for my car, I found that the Moroso HEI Advance Curve Kit has a center bar and weights that mimic the mechanical advance that my points distributor has, with 24º of mechanical advance. This kit allowed me to set the initial timing to 10º which was the same as the points distributor. So if you want your HEI to mimic the points distributor, that would be a good kit to use.

If you like tinkering and building/modifying things, this is something to consider. I followed Schurkey's instructions and turned the factory 24º vacuum canister into an adjustable unit. This allowed me to limit the vacuum advance to whatever I want, which is currently around 10º.

cfair

It may be derailing a bit, but I’m glad to see others chime in and teach me more about HEI.

Genuine thanks from me.

Chris