[glhs#116]

Originally Posted by Jay S

A couple of the plugs looked like they were burning hot, but not overly so. Just judging that by the white color showing up more down into the ceramic part of the electrode on a couple of them. But really the only thing they tell me is you have done a good job pulling your timing back to keep them running to hot.

Your compression test looked good. I recall you used a little bit undersized dingle ball hone to give 6 some extra clearance. It will probably take a little time to brake that in. Exactly like you mentioned.

There are not necessarily signs that you need a colder plug by reading them. If you just tune a car by ear there will almost never be a sign calling for a colder plug because you are pulling the timing out to manage the hot plugs. The sign is when you put a timing light on the engine, have it tuned by ear with no noticeable pinging, and are way down on your initial timing and the centrifugal timing. When you drop to the next range colder plug the colder heat range let’s you run more advance. Keep dropping the heat range on the plugs until you can get up above 32 full mech advance. Because heat ranges are broad on the hotter plugs you will find were your engine wants it’s full timing in at. If the plug is a bit cold it may want 38. To hot it may want 28. Once you get the heat range right then I would say it is time to start reading plugs and start focusing in on the AFR ratio.

So.. Interesting. I ordered BKR7E plugs and BKR8EIX (these are Iridium -- couldn't find copper plugs for the cooler ranges). Since my ignition is so retarded right now I went straight to the "8" plugs when I got them. I've been sick so this morning was my first chance to try them. I fully expected that these would be WAY too cold and I would have fouling issues. But.. Hmm.. Maybe I might even try "9"s if I can order some.

I haven't had much time at all to dial these in. Here's my notes from this morning:

1. Set idle advance from 3 without vac (25 with, can adding 22) to 12 without vac (34 with, can still adding 22). Happy idle but a little pingy if I rev it no load
2. One turn tighter (back off allen screw) on the vac can to where it adds 18 at idle in gear. Clean no load rev. Some slight ping on part throttle on test drive
3. One more turn out on vac can to where it adds 16 at idle in gear. Clean for entire drive to work. Some ping when I tried full throttle in 2nd and 3rd in midrange RPMs.

For this I will back off base timing to 10. But I'm sure I shouldn't have to if the plug isn't too hot. I will check it at home later if I get time to pull out the plugs.

Seems weird, right? Clearly the "6" plugs were too hot because this is a MUCH better result than before. Engine, of course, running cooler with the better advance curve. Car drives better cleaner and stronger. But a lot of other people on here saying that "6" is good for their combo and "7" is for turbo/supercharger. Well, I'm at "8" and it looks like I might be better off with "9". Could it be quench distance? My pistons are pretty much at zero deck and I'm with the .039" 1016 head gaskets. Of course it is hot and humid like hell here but I had a very normal advance curve on the old 197 heads and 068 cam in this climate..

Sam

[glhs#116]

OK. So, weirdly, my last post doesn't seem to show. Problems with the PY database again, I assume. Anyway, re-reading the comments it doesn't seem like "8" NGKs are a million miles off. I will try to order some "9"s when I can. I don't actually see anything colder offered. Can't even find a "BKR10E" of any kind listed..

I assume my "post 41" will be along some time when they sort out the software issues..

Sam

[Cliff R]

The more you do to increase combustion efficiency the LESS timing and fuel are needed. Certainly you do not need much over 10 degrees from the vacuum unit at cruise.

I've built a lot of engines very similar to yours. I set them up with around 10 initial, 10-14 vacuum advance, and 10 from the mechanical (20 at the crank). For your hotter climate and possible lower octane/quality fuel I'd probably even tighten up the mechanical a tad more to 9 or 18 at the crank.

I'd use a vacuum advance that starts around 8-9" vacuum and all in by 12" or so. This way you'd have the option to run it on MVA or ported. I seldom use a MVA on higher compression/efficient engines at idle with well chosen cams in them, they just don't need it in most cases.

You should not be experiencing heavy or WOT ping with 8-10 initial and 28-30 total, even with a pretty quick curve, but in any and all cases retard the timing for no ping at all as it will pound apart the best prepared engine.

Adding another 10-12 degrees from the VA for around 38-40 at cruise shouldn't ping either but still provide excellent efficiency, fuel economy, etc.......Cliff

[glhs#116]

I dialled it back to 10 initial. We'll see what the drive back from work is like. I think the vac advance is OK because the only ping I heard on the way in to work was the brief bit where I floored it. And that was pretty mild. I'll keep dialling it in and I will see if I get a chance to pull plugs and see what they look like..

Oh, took a 1/4 turn out of the idle mixture too.

Sam

[steve25]

You may want to play with the Carbs accelerator pump arm to check that the pump starts off as high in its Bore as it can yet still provide a quick enough pump shot to not have a off idle stumble take place.

Doing this will guarantee a long pump shot duration which may help to remove that cruse to full trottle ping that you have before the secondary's really start to flow well!

If the pump arm can't get the pump to sit higher in its Bore you can grind the pump shaft shorter.

[Cliff R]

Set the total timing for no ping at all. If you end up dialing back the initial further than desired shorten up the mechanical curve so you can put some back in it.

There is no need for much more that 10 degrees additional timing from the VA for you current set-up. I've never built or tuned a 455 with aluminum heads, mid 10 to 1 for compression ratio, tight squish and 230 something @.050" camshaft that needed it. Matter of fact I've only built/tuned a couple that we used MVA on, and one of those was an "odd" combo that was originally going to use #12 head but they ended up being cracked to they ordered small chamber ported KRE's from Dave at SD instead, and his OF camshaft. The pistons had the HUGE dish in them. It idled OK with about 12 degrees initial, but enjoyed another 10 or so degrees from the VA due to the low static compression ratio and pretty "hefty" camshaft.......Cliff

[glhs#116]

OK. I'm reading this again and I feel it gels with what I'm seeing driving the car. It definitely wants a shorter mechanical advance curve. I need more initial timing for a good cool idle without getting too much total when it revs up.

The two problems I currently have are:
1. It comes in too fast. I know this because when I dial the ping out of most places I still have it in the 2500-3200 or so range

My notes look like:
8 @ 1500
12 @ 2000
13 @ 2500
14 @ 3000

2. It comes in too much. And according to my notes I'm only adding around 14 mechanical. But I am at my limit as far as stiffest springs and best combo of factory weights and centre cam (I think 139 weights and 394 centre numbers down as correct for CCW distributor). I think I can see how I might be able to slow and limit that by carefully grinding the centre cam but I hate to chew up good factory parts and I'm pretty sure it needs to be done really slowly and carefully. I can't weld and I'm not sure what else to make a decent stop with..

Sam

[HWYSTR455]

One thing I will mention with adjustable vac cans is that once you turn the set screw all the way out, no way will you get it back in, and the adjust is gone after that.

I cut a crane open a long time ago and counted the turns, there's a thread hear on that with the results, including the total number of turns it takes to make it fall out.

A hand held vacuum pump with a gauge is a great, inexpensive tool. Once you get past a certain number of turns, and the can sees X inches of vacuum, it jumps a number of degrees at once. You can unplug the can, use the vacuum pump, with a timing light on it, you can go inch by inch of vacuum and plot the can's advance-to-inches rate.

Anyway, I'm on the side that thinks it's a lean spot in the carb.


.

[Jay S]

Am I following correctly? It is adding 14 degrees total mechanical advance, all in by 3000? That should be closer to 22. It sounds to me like your having to advance your initial timing to make up for the lack of mechanical advance? I think if your still able to adjust the vacuum canister it is probably ok and not the issue.

Sounds like your looking in the right area Sam if I understand correctly.. For some reason the dizzy is giving you not enough mech advance, and it should not be all in by 3000 either. That number appears to low too.

Would really be nice to have someone check that out on a distributer machine. Or have another dizzy done and swap it out. Or maybe one of the distributer guru’s can point you in the right direction. Jay

[glhs#116]

Jay, maybe not. I am currently at 6 degrees initial with 16 vac.

So at idle I'd be 6 without vac or 22 with vac.
My mechanical adds 14 (actually my notes here are saying 16) so that's 22 at 3000+rpm under load.

On my deal that 22degrees total seems too much (ping under load). On the other hand the 6 initial is barely enough. I also can't seem to take more than 16 degrees of vac for part throttle (or I get ping light and trailing throttle).

So, I need less mecahnical advance at the top end AND more initial advance at the low end. In other words, I need the cretrifugal to add less. Also, I need it to come in a bit slower / later.

Sam

[TAQuest]

https://www.youtube.com/watch?v=pQicdbn_ZPE

[Jay S]

I follow you better I think. Your right the 6 initial is not enough. Then it sounds like the vac is adding 16 for a total of 22. Ideally the initial should closer to 10 or 12. Then the mech advance should put in around 22. For 32 to 34 full advance. You should not need to be more than 30-32.. Then the vac should bring it up to 40-50, or add 8 to 18. You sound like your on the high side for the vacuum advance, and the low side on the mech advance. It still describes one thing trying to compensate for another. Or basically your trying to tune the vac advance and making it compensate for the lack of mechanical advance, which will not give you enough advance full throttle (mechanicals job) but to much partial throttle (vacuums job) It sounds like you have a combination of problems to work out there.

[Jay S]

Is it pinging full throttle at 22 mechanical then and 6 initial with the vac advance unplugged to?

[glhs#116]

Yes. That’s the deal. I am on the bkr8e plugs and it still doesn’t want more than 22 degrees total.

Sam

[glhs#116]

See, this, to me is the puzzler. I was thinking about it. Actually, the fact that the engine seems to want the centrifugal curve shortened goes hand-in-hand with it wanting only around 20 total. Both point to a really quick burn. However, the fact that this result is over 10 degrees out from what is expected from other almost identical combos makes me think something is wrong. I would suspect the balancer mark but that's verified. I would suspect the cam timing but not only is that verified from the timing chain marks, I also am getting compression readings that match very closely with what a compression calculator tells me I should get with that engine and cam and cam timing.

Anyway, yeah. Seems to want a curve that will only give me about ten degrees on the mechanical. That would let me get the low rpm timing in that it wants and avoid over 20 degrees under load at higher rpm which it seems to not want. I'm really scratching my head what can be so different in my combo.

For running temperature: I don't buy it. Engine has never been much more or less ping sensitive based on whether water was hot or cool and it still isn't
For carb mixture: I don't buy it. I have long observed that if I run out of fuel (like vapour lock) the car will sag but not ping. I actually went to richer secondary rods a few days ago. The car liked it (it hadn't liked those richer rods with the old combo) but although the car had more power it didn't have more or less ping under load with the same advance
For plug temperature: I could believe it. However, I'm apparently already on cooler plugs than many with this combo

Anyway, I suppose at some point the mystery will be solved..

Sam

[Cliff R]

The correct steps for distributor tuning and setting the timing are as follows.

Set the total timing until it quits pinging under load. Don't worry about where it ends up at for initial timing till later in the process.

Modify (or adjust if it has that feature) the VA until it doesn't ping under light throttle/normal driving and gives you the best light throttle response, power and fuel efficiency.

Not where the initial timing is at and if it idles fine and doesn't "buck" the starter fully heat soaked on re-starts leave it alone.

If you find you need more initial timing shorten up the advance curve by adding a positive stop for the advance internally.

The mechanical advance curve can also be fine tuned by changing springs, but in your case it sounds like it doesn't want, need, or respond to a quick curve so I'd use the heaviest springs that you have available provided they still allow the timing curve to start right off idle.

I've ran into a few Pontiac 455's that were difficult to tune and pinged easily if you tried to put much timing to them. All of them were coincidentally using either the Comp XE268 cam or it's roller cousin the XR276HR cam. I really helped one of those engines by installing high ratio rockers on it, telling me the cam was just too small for the CID and static compression ratio.

I also played around with carb tuning thinking I could add more fuel to help the situation and found myself going right back to where I started with that deal, as fogging the motor with a bunch of fuel is NOT the correct course of action to reduce detonation. It needs to correct A/F ratios for best efficiency......Cliff

[glhs#116]

Yeah, it also idles really smoothly when warm. I know that Jay was saying that the Crower 60919 is one of the "smaller" 041 cam clones and that it may have faster more "modern" lobes than, say, the Melling. And I think it is ground on a narrower LSA than some of the other 041 clones. Honestly, it really wasn't my first choice but it was the one that was "ready to ship" when I needed to order. And I do have 1.5 rockers, 10.2:1 compression and 462 cubic inches. Maybe it is just acting a little "small".

I'd try bigger ratio rockers but I'm told that the Edelbrock heads won't take that without pushrod hole enlargement. Seems silly that they don't just give you more clearance there (it IS an aftermarket head) but anyway, there it is.. I've been trying my hand at reshaping a centre cam for less advance. Hopefully I will get to try that out sometime soon.

Sam

[TAQuest]

Originally Posted by glhs#116

Yes. That’s the deal. I am on the bkr8e plugs and it still doesn’t want more than 22 degrees total.

Sam

It may want more octane. Try some octane booster. I use it in ever tankful and don't get any ping with high compression. Without it I get some ping when I set the timing for best performance.

[Jay S]

It sounds like you have painted yourself into a corner now on the tuning and are looking for a way to get the initial timing up and limit the total to mech advance to 20. Your 393 center plate then appears to be putting in 14-16 advance in just over 3000 rpm. I noticed earlier you had a 345 and a 406 center plate. That 406 with your weights should be about 21 mech advance and be all in at about 3700 rpm with medium springs. IRC, a 398 has 19 with medium springs and is all in by 3500. The heavier springs should lower the advance a bit and raise the curve some to a higher rpm. I wonder if you would be better off with the 406 center with the heavy springs. It does put in more advance but it should put it in at a higher rpm. Maybe that would get you past your problem area. The plates that limit the advance to 15 or so can put the advance in early, or sometimes done early rpm wise. I think there are a couple center plates the limit the advance to 6 or 7. IRC 393, maybe a 365 if you can find one.

How is your engine doing with the 8 plugs? Have you noticed it being harder to start since you have some miles on them?

[glhs#116]

Jay,

I was sure the 8s would be too cold and start loading up or whatever. They've been great. No hint of trouble so far. Haven't had much time to pull them out and look at them, though. I'm using the heaviest (old, stock, from junkyard distributors) orneriest springs I can find. I'm on the 139 weights (I recall) though. I think I have 041 and 045 weights. They look like they are smaller so I was wondering if they might slow the curve..

The cam I've been grinding on (haven't tried it yet -- haven't had time) is something like 368 but the number has missing bits so it's hard to be sure. I do have a 346, the 406 and a 366. The cam in the distributor now is 394. With the 139 weights and heavy old stock springs.



Sam