When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Originally Posted by Nab Yags
@chevymans 77 Correct me if I'm wrong, but this is way I interpret it. When the balancer is at TDC, the number 1 cylinder is at max compression. If the timing is advanced, the cylinder would have already been lit and therefore the rotor should already be past the number 1 post. If the timing were retarded, you would still need more travel in the crank in order for the cylinder to fire, so the rotor would have be before the number 1 post.
Your correct in your thinking,
My post was to see if the rotor was actually set to the #1 post when the dist is indicating 60* timing, possible cross firing
I've ran into this a couple of times one caused by the incorrect timing cover for the engine I was working on and the other was from a balancer that was incorrectly marked, wrong timing tape used to index the dist.
Neal
Neal
Last edited by chevymans 77; Sep 19, 2021 at 06:50 PM.
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
when I look at the Cloyes install instructions for the 3 position set they show the mark at the teeth of the gear not down on the hub of the gear. Is it possible that the gear is on backwards as non of the pics in the instructions show the teeth misaligned between the crank and cam sprockets for a GM engine.
Thanks everyone for your input, it seems to be fixed! I don't know exactly what fixed it but just in case anyone else ever has a similar issue, I'll list exactly what I did to "fix" this. Unfortunately, the resolution isn't very satisfying and I'm convinced this motor just wants to make me look stupid. Michigan J. Frog comes to mind...
This is what I did to get it running good:
Adjusted idle mixture screws as @leigh1322 suggested
Plugged vacuum advance to manifold instead of ported vacuum
Set timing to around 12 degrees BTDC (where it should be)
Removed plug wires from the plug wire loom and separated them as much as possible in case the parallel routing of the plug wires was causing them to cross fire (not sure how much of an impact this actually had)
Waited for the car to warm up fully before putting any load on it. It seems like some of the exhaust gaskets are leaky and I've heard that that can sometimes cause a backfire in the exhaust. They tend to seal up as the car warms up.
Car now idles at around 20-30 degrees BTDC with the vac. advance but the mechanical advance takes over when the throttle is down. Engine goes from 12 degrees BTDC to 38 degrees BTDC at 3000 rpm.
It turns out the motor actually WAS running with initial timing of 60 degrees BTDC! I thought it wasn't possible but apparently it is. This could have been due to the combination of parts and the low compression ratio on this engine. I didn't really hear any knocking but it's good that I didn't drive it in that state. With the settings I described above, it ran the best it's ever run. Idled really good with the vacuum advance connected to full manifold vacuum and had good torque at low speed which improved drivability dramatically.
I guess the lesson here is to never try fixing a problem by adjusting the timing to some insane amount; and especially never try to adjust timing "by ear." The PO clearly did this because there was no timing tab... It can give you very misleading results about what your engine actually needs. The excessive timing I added was probably just masking some other issues like engine not running good when not up to temperature, exhaust leak, idle mixture screws not set properly or vacuum advance needing to be on manifold and not ported vacuum.
Hopefully this is not some sort of fluke and the engine will keep running this way. Thanks everyone for your help!
Last edited by Nab Yags; Sep 19, 2021 at 08:53 PM.
when I look at the Cloyes install instructions for the 3 position set they show the mark at the teeth of the gear not down on the hub of the gear. Is it possible that the gear is on backwards as non of the pics in the instructions show the teeth misaligned between the crank and cam sprockets for a GM engine.
Neal
I've always wondered about that, my Cloyes timing set is like the OP's, but I've seen other sets that has the dots on the teeth of both gears.
You pulled the plug wires; then you put them back correctly...and did NOT make the indexing mistake. That's the only possible answer.
I'm still waiting for my medal.....
P.S. For those of you who do not understand, the OP put his induction clip on the wire attached to the #1 cylinder. However, that wire DID NOT go to the proper location for the #1 socket on the distributor cap (for whatever reason). And, yes, with the timing light, it WOULD show 60+ degree ignition timing.
Last edited by 7T1vette; Sep 20, 2021 at 06:30 PM.
You pulled the plug wires; then you put them back correctly...and did NOT make the indexing mistake. That's the only possible answer.
I'm still waiting for my medal.....
P.S. For those of you who do not understand, the OP put his induction clip on the wire attached to the #1 cylinder. However, that wire DID NOT go to the proper location for the #1 socket on the distributor cap (for whatever reason). And, yes, with the timing light, it WOULD show 60+ degree ignition timing.
TLDR: None of the plug wires were removed from the distributor while doing this work, I only removed them from the loom...
I am a novice when it comes to working on cars and engines so for all I know, you could be right. I'll try explaining how I understand things and you can correct what I'm misunderstanding.
The crank turns twice for every revolution of the cam (and distributor). That much we surely agree on. Timing is measured in crankshaft degrees and not camshaft degrees. Look at any balancer with timing marks and you'll see that the markings correspond to crankshaft rotation. All 8 cylinders must fire during 1 revolution of the distributor/cam. Therefore, each post on the distributor is 360/8=45 degrees apart. Since the crankshaft is spinning twice as fast, each cylinder fires 90 degrees apart with respect to it. By clocking all plug wires one index, you move them all 45 degrees in camshaft degrees, and 90 degrees in crankshaft degrees.
Let's say I did make a mistake and installed my plug wires one post off. My timing light was reading 60 degrees BTDC, so before I made the mistake, my initial timing must have been either 30 degrees retarded or 150 degrees advanced, both of which are far from ideal. However, the really important point is: the timing light does not know how a distributor works and it doesn't know or care which post you connect your number 1 plug wire to. It's a very simple device, it flashes when spark is supplied to the cylinder. If the timing light says you're running 60 degrees advanced on your number 1 cylinder, you are definitely running 60 degrees advanced on that cylinder, assuming of course the timing light is not defective and your TDC mark is correct. Furthermore, I could have corrected my mistake by rotating the distributor 45 degrees in the opposite direction to restore my original timing.
Another case would be the 1 and 2 wires or 1 and 8 wires swapped accidentally in the firing order. The amount of advance on the number 1 cylinder would no longer correspond to the amount of advance the rest of the cylinders are receiving. So the timing light might show 100 degrees on the number 1, while the rest of the engine is actually running at closer to 10 degrees. Let's assume that I did make this mistake. That means that the engine was running best with either 30 degrees of retarded timing or 150 degrees of advanced timing. This also doesn't make any sense. The engine should have ran best with something like 100 degrees of apparent advance on the number 1 cylinder.
This can all be summarized very simply as: the posts on a distributor cap are arbitrary and there is no designated post for your number 1 plug wire. By shifting them all, you advance or retard your timing by 90 degrees which your timing light will quickly tell you. You then simply turn your distributor body 45 degrees to correct the mistake. As far as I can tell, it's impossible for your timing light to give you incorrect readings based on how you've plugged your wires in.
Ultimately, I just want to learn and if you spot a mistake in my reasoning, please point it out. In any case, I appreciate your help in fixing this. - Nab
Out of interest, can you tell us how much you ended up readjusting your idle mixture screws.
Originally they were at a quarter turn, and I brought them out another quarter turn to make it a half turn. There is a better process for adjusting 4 corner idle like this but I haven't gotten around to it yet.
You had no clue what was going on with your car. Now, you know everything about it. I think that's all we need to know...........
Still can't be gracious enough to send me your 'promised' medal. You're welcome, whether you can muster a "Thank you", or not.
You had no clue what was going on with your car. Now, you know everything about it. I think that's all we need to know...........
Still can't be gracious enough to send me your 'promised' medal. You're welcome, whether you can muster a "Thank you", or not.
The difference is that you seem to be an *** on a regular basis to a lot of different people. I'm only a dick to you and only after you've been an ***. I'll say it again: If you are not here to help, STFU or GTFO. Your BS is getting old.
Allow me to introduce you to this little fellow: I've decided to name him ChuckFarley.
Originally they were at a quarter turn, and I brought them out another quarter turn to make it a half turn. There is a better process for adjusting 4 corner idle like this but I haven't gotten around to it yet.
Hmm, 1/4 turn out is hardly nothing. Initial starting point for these carbs is usually 1 1/2 turns out. I imagine you were running extremely lean at idle, thereby needing all that timing just to keep it running.
Hmm, 1/4 turn out is hardly nothing. Initial starting point for these carbs is usually 1 1/2 turns out. I imagine you were running extremely lean at idle, thereby needing all that timing just to keep it running.
good thought.
.
i've never used a 4 corner idle carb. my impression is that they worked well on single planes, where 1 corner had an odd behavior. or with huge cams that needed lots more gas, even just to idle.
on a dual plane, normal cam, i'd try turning in the rears closed, and just fine tune the front. they may not be equal after tuning for max speed/smooth idle. there is no "correct" turns.
good thought.
.
i've never used a 4 corner idle carb. my impression is that they worked well on single planes, where 1 corner had an odd behavior. or with huge cams that needed lots more gas, even just to idle.
on a dual plane, normal cam, i'd try turning in the rears closed, and just fine tune the front. they may not be equal after tuning for max speed/smooth idle. there is no "correct" turns.
I just did this on a Chrysler 340 with a Performer RPM dual plane and a hot cam with 10 inches of vacuum. The 750 Street Demon carb has four corner idle and it plain did not like having all four screws open......I was able to get another inch of vacuum by closing the rears and running solely off the fronts...adjusted of course. I usually try to figure out why this is but not this time....I put 20 road miles on it (Most fun I have had all year!) and shipped it.....my friend says it is fine to this day six months later.
I'm still waiting for my medal.....
