[mchell]

Just out of curiosity, have you looked at your total timing with your vac advance hooked up?..... are you seeing the same total with and without?

[Schurkey]

Refresh my memory. WHAT are you using for an air intake system?

Specifically, is there a heated air intake that could be stuck in the "Hot" position? How about a stuck heat riser valve?

[400 Lemans]

Using your 406 center plate and 139 weights going by this chart gives 21 degrees. So add about 12 initial and you are in good shape with 33 total without vacuum advance.https://www.chevelles.com/forums/13-...ve-kits-2.html

[glhs#116]

Originally Posted by 400 Lemans

Using your 406 center plate and 139 weights going by this chart gives 21 degrees. So add about 12 initial and you are in good shape with 33 total without vacuum advance.https://www.chevelles.com/forums/13-...ve-kits-2.html

Yes. And I am pinging under full throttle at 22 degrees total.. How does that help?

Sam

[TAQuest]

What octane are you running? Sometimes the simple answers are the best. No amount of dicking with my distributor curve is going to make my engine not need better fuel that what my new cars can use. It is what it is.

[HWYSTR455]

I've never had good results grinding on the plates, and timing can become erratic. You certainly can expect to limit total by modifying the center cam. It will start adding more once you get over 5k rpm.

As cliff pointed out, you first start with initial, using as much as the engine likes without it having a hot start symptom/slow crank. Then you make sure total is where it needs to be, then rate (springs), and last, VA.

So one thing you need to have, is a consistent way of limiting total timing, as well as VA timing. Looks like you already have the VA limiting cam, so you just need to limit mech total. The most sure way is to limit travel of the plate via the pins that pass thru the plate, but that's hard to do consistently with an HEI.

IMO, quit messin with the ancient HEI and use a quality aftermarket unit. You will have full control over any advance you may need. (and you get a small body as an added benefit).


.

[glhs#116]

Originally Posted by TAQuest

What octane are you running? Sometimes the simple answers are the best. No amount of dicking with my distributor curve is going to make my engine not need better fuel that what my new cars can use. It is what it is.

The "super" here (which is what I run) is 95RON which seems to be equivalent (according to the internet) to around 91PON (US octane rating standard). So call it 91 octane..

Sam

[glhs#116]

So, very time limited as far as playing with this stuff. I managed to do the following at work today in the company parking garage with only one person asking me if I needed help (if the bonnet is up the car is broken, donchaknow):

1. Verified my current setup as 8 initial rising to 22 (adding 14) at 2500rpm (can't rev through the moon here) with the vac unplugged
2. Swapped the 139 weights for the 045 weights which seem lighter
3. Reset the base timing to 8
4 Verified now at 8 initial rising to 20(adding 12) at 2750rpm

So, I don't have the breakdown because I couldn't be so obnoxious in the work parking garage. Since I can't see the tach from the engine bay I basically have to rev twice for each RPM I want to record. Once in front of the car watching the light, second inside matching the RPM by pitch (I'm a musician, well, a bass player anyway) and recording the RPM from the tach. Of course I expect a very similar curve from same centre plate and same springs just slower. I will see on the drive home if this was an improvement.

Sam

[Jay S]

I would love to here your car rev’d up in a parking garage! That sounds quite entertaining.

I think your probably getting pretty limited on options with it only wanting 20 advance. You probably need to limit the advance and get the initial timing up and hold the full timing to 20. Then all you can do is run it with the cold plugs for a while and see how it fairs. If it does ok try colder plugs yet and work your way into more timing. Jay

[glhs#116]

Originally Posted by Jay S

I would love to here your car rev’d up in a parking garage! That sounds quite entertaining.

I think your probably getting pretty limited on options with it only wanting 20 advance. You probably need to limit the advance and get the initial timing up and hold the full timing to 20. Then all you can do is run it with the cold plugs for a while and see how it fairs. If it does ok try colder plugs yet and work your way into more timing. Jay

One thing scares me a little in that department. I don't see anyone listing anything colder than BKR9E. And I'm currently at BKR8E. (well, the Iridium ones. It seems the colder ones only get sold as Iridium).

Sam

[glhs#116]

Originally Posted by Schurkey

Refresh my memory. WHAT are you using for an air intake system?

Specifically, is there a heated air intake that could be stuck in the "Hot" position? How about a stuck heat riser valve?

It's a stock shaker air cleaner though clearly not the factory original since it has one snorkel instead of two plus the factory shaker which is completely open. There's no manifold hot air duct. Then again, Qatar is pretty much one big hot air duct in the summer..

Air cleaner (it's a K&N washable filter)


Open shaker


As installed


Sam

[TAQuest]

Originally Posted by glhs#116

The "super" here (which is what I run) is 95RON which seems to be equivalent (according to the internet) to around 91PON (US octane rating standard). So call it 91 octane..

Sam

A bottle of octane booster opens up your options and gets you out of the ditch you are in.
Then you can use an out of the box HEI. Set your timing for optimum performance. So simple and easy.

[Cliff R]

That engine combo should be fine with more than 22 degrees total timing no matter how quick it comes in.

I suspect a fundamental issue, maybe something as simple as the actual octane of the fuel being used is about 10 points lower than the estimates.

I will have tuned more of these engines than most who will read this, and even when the engine builder makes horrible choices for cam/compression we are in most cases still able to get them to stop pinging by pulling out a little timing less than optimum, and using the highest octane pump gas available.

Thinking back the WORST 455 I ever had brought up here for detonation was around 9.5 to 1 with a Comp XR276HR cam in it. I had to reduce total timing to 26 degrees to get it to stop pounding like SLEDGEHAMMER in the mid-range (3200-3600) and use 93 octane fuel. It would only take about 6 degrees from the VA or it would ping at part throttle as well. So 32 at cruise was all she wanted.

It was also a gutless "pig" for a 455. Sounded pretty bad-ars at idle speed, nice lope in the exhaust and very "aggressive" sounding thru the mufflers when you revved it up.

Your set-up should be fine on pump gas, even 89-90 octane with around 30 degrees total timing in it. I've been around enough of them. A couple of "flags" go up with your set-up. One is idle quality. It should only be making around 11-12" vacuum at idle speed with about 10 degrees initial timing in it, and cranking pressure should be around 175-180psi. The idle should have a noticeable "lope", not dead smooth.

The idle being smooth tells me that the ignition timing is advanced some, the cam is smaller than advertised, or the compression a point or so higher than you think it is.........Cliff

[glhs#116]

Originally Posted by Cliff R

That engine combo should be fine with more than 22 degrees total timing no matter how quick it comes in.

I suspect a fundamental issue, maybe something as simple as the actual octane of the fuel being used is about 10 points lower than the estimates.

I will have tuned more of these engines than most who will read this, and even when the engine builder makes horrible choices for cam/compression we are in most cases still able to get them to stop pinging by pulling out a little timing less than optimum, and using the highest octane pump gas available.

Thinking back the WORST 455 I ever had brought up here for detonation was around 9.5 to 1 with a Comp XR276HR cam in it. I had to reduce total timing to 26 degrees to get it to stop pounding like SLEDGEHAMMER in the mid-range (3200-3600) and use 93 octane fuel. It would only take about 6 degrees from the VA or it would ping at part throttle as well. So 32 at cruise was all she wanted.

It was also a gutless "pig" for a 455. Sounded pretty bad-ars at idle speed, nice lope in the exhaust and very "aggressive" sounding thru the mufflers when you revved it up.

Your set-up should be fine on pump gas, even 89-90 octane with around 30 degrees total timing in it. I've been around enough of them. A couple of "flags" go up with your set-up. One is idle quality. It should only be making around 11-12" vacuum at idle speed with about 10 degrees initial timing in it, and cranking pressure should be around 175-180psi. The idle should have a noticeable "lope", not dead smooth.

The idle being smooth tells me that the ignition timing is advanced some, the cam is smaller than advertised, or the compression a point or so higher than you think it is.........Cliff

Cliff,

You are correct about the idle. That's with 20degrees that it is smooth warm (still fairly lumpy on cold start). 8 initial, 12 from can. Cranking pressure is indeed right where it should be as I think I shared in some other thread. That's the funny part. It suggests the cam is installed where it should be..

Actually, the car drives really nicely, pulls well too. Just starts audibly pinging with more than 22degrees total or so at full throttle. I wouldn't say "sledgehammers" or anything. It's not dramatic. It's audible but it's something that, say, the passenger might not notice.

By the way, with the lighter 045 weights things are a lot better. Pretty much only pinging now under full throttle over 3200ish RPM. I'm wondering if I shouldn't try to rig some kind of "pre" stop so that the advance I get I get nice and late.

Sam

Sam

[TAQuest]

Originally Posted by glhs#116

Cliff,

You are correct about the idle. That's with 20degrees that it is smooth warm (still fairly lumpy on cold start). 8 initial, 12 from can. Cranking pressure is indeed right where it should be as I think I shared in some other thread. That's the funny part. It suggests the cam is installed where it should be..

Actually, the car drives really nicely, pulls well too. Just starts audibly pinging with more than 22degrees total or so at full throttle. I wouldn't say "sledgehammers" or anything. It's not dramatic. It's audible but it's something that, say, the passenger might not notice.

By the way, with the lighter 045 weights things are a lot better. Pretty much only pinging now under full throttle over 3200ish RPM. I'm wondering if I shouldn't try to rig some kind of "pre" stop so that the advance I get I get nice and late.

Sam

Sam

When you have audible pinging at 3200 rpm you also have inaudible below that causing damage.

[Cliff R]

Retard the timing till it quits pinging at heavy and full throttle. It will pound the rod bearings to the copper and destroy your engine, and pretty quickly.

Slowing up the curve has zero effect on that deal as cylinder pressure will be highest at peak VE which is going to be well past where your distributor is reaching total advance. Most of those builds will make peak torque around 3700-3900rpm's.

I suspect you are dealing with a combination of extreme heat and piss-poor fuel quality.

I didn't realize you were use MVA and 20 degrees timing at idle. It should idle pretty decent with 20 degrees timing in it at idle speed, probably making around 14-15" vacuum or so at 700-750rpm's. With 10 degrees timing you should start to hear the cam a bit, but still relatively smooth and making at least 11-12" vacuum, maybe a little more depending on the exact compression ratio and intake lobe centerline.........IMHO......Cliff

[Schurkey]

You answered my question about the heated air intake. How about the heat riser valve? Disabled/removed? Heat crossover in the manifold blocked? An excessively-warm intake manifold will make for detonation.

Originally Posted by glhs#116

The "super" here (which is what I run) is 95RON which seems to be equivalent (according to the internet) to around 91PON (US octane rating standard). So call it 91 octane..

Originally Posted by Cliff R

I suspect you are dealing with a combination of extreme heat and piss-poor fuel quality.

I think you're wrong about your guesstimated octane. 95 RON would be "approximately" equal to 89--91 Pump (or "Posted") Octane in the USA and Canada. Wikipedia says there's a 4--6 number spread, between RON and MON, and I bet it's more like six (or more) than four where you are.

https://en.wikipedia.org/wiki/Octane_rating

Five gallons of Toluene might tell an interesting tale when added to a half-tank of gasoline.

[Jay S]

Originally Posted by glhs#116

One thing scares me a little in that department. I don't see anyone listing anything colder than BKR9E. And I'm currently at BKR8E. (well, the Iridium ones. It seems the colder ones only get sold as Iridium).

Sam

If you end up trying something colder I think you will be better off switching to the NGK race series. We run the race type plugs but we do not put tons of miles on any of our old cars. IRC, the numbers start with R5671-X, number after the dash is the heat range. I know it seems strange to go that cold, but back here we are not tuning the engine in Qatar like you are. Your apparently fighting some different challenges. Your probably not going to fowl plugs out until you start getting the timing up past 30 with no detionation.Guys run COLD COLD spark plugs in boosted and NOS street engines, we run tons of timing normal when not on boost to keep them hot enough to not fowl , then pull the timing back out on with progressive controllers on boost or NOS.

Blocking the exh cross over would help too.

Btw. As smooth as the idle is it sounds like the cam could have been ground a bit small. The compression and engine size changes the idle, but I have measured one 60919 that had 308* at .006 on ALL the exh lobes and 242 at .050 (very rough idle). Then seen a couple hover around lower 290s at .006 and 237-238 at .050 (fair to smooth idle). I know of one guy checking one said it was the lower the 280s at .006 and lower 230s at .050 on the exhuast, it was a pretty smooth idle. Have seen and intake at 283@.006 and 228 at .050, one at 285@.006 and 227 at .050. I think PMD400 has one on here in the 286/294 range too. LOL. All on the 60919!. The Mellings, comps, UD, cranes and OEMs I check are ussually almost spot on. I have checked a ton of cams. It makes it a little difficult to to build a pump gas engine pushing compression when the cams specs are that random, it forced me to check them.

[Schurkey]

Originally Posted by Schurkey

Wikipedia says there's a 4--6 number spread, between RON and MON, and I bet it's more like six (or more) than four where you are.

OOoops. Should have said 4--6 number spread between RON and PON, but it's too late to edit the original post.

[Cliff R]

I know what it's supposed to be and what they are telling him it is. The symptoms all indicate that the octane is much lower than advertised, or his timing marks have slipped about 8-10 degrees.

NOTHING about the issues make sense for the combination of parts being used. Not being able to run more than 22 degrees total timing tells me something in this deal is fundamentally wrong.

Right to start with what method is being used to determine total timing, an indexed balancer, measuring and making a mark at 22 degrees, dial back timing light?........Cliff