Have you considered a custom steel billet cam with a pressed on sleeve?

The problem is the limited choices from any of the cam manufacturers. So years ago I figured out how to order custom lobes.

http://www.compcams.com/Technical/Ca...obeCatalog.pdf

My 434 ci uses a altered firing order. Ford firing order runs smoother and has a different sound. From the lobe cat. I run big racing lobes.

But in you case. download this PDF and go to page 17 I would order something like 3119 I and 3111 E and use 1.5 Rockers 224/230 or even both 3119

check out the QXX line of lobes. my page numbers might be off, but I have had two motors that had ping at cruise with 91 octane. I tried everything and the fix both times was to add about 4 degrees at .050

You see that they also list the .200 duration numbers? 3110 has the same .050 224 degrees as the 3119, but at the higher .200 the 3119 gains and additional 8 degrees because of bigger lobes.

Or jump on down to page 19 and get the 3192 and 3194. Look at the .200 lift numbers on the extreme lobes. Mix and match to adjust your desires and lifts with even different rocker ratios between I&E

Then have them grind it on a 112 oe 113 because you have an auto tranny and 3.08


Even check out page 21 and the 3015 for intake and 13080 for exhaust. 13136,13137, 13138. Making your own cam can be fun.

 

BCould take me a few days to digest all this info. I'll comb through it see if I can understand what the numbers are telling me.

What kind of set up were those motors that pinged if you can recall the details. Ie roller or flat, CR and DCR, cam specs.

 

Look at the QXI HR lobes.

My first pining motor was a 355 ci with a crane 272 power max H-flat cam 114 LSA and 1.6 rockers. -7 or less flat tops two valve relief. 10.5 - 10.7 elevation 5000 feet. I tried everything. recourved dist. with high initial and slow advance to all in at 3200+ rpm. Octane booster. After a two year fight i installed the 278 power max. HF and it was a nice motor for many years.

383 with the best of everything. two valve relief .038 quench high 10 C/R custom cam 232/238 solid roller 112 It was right on the edge at 5000 feet Sea level I would use blended race fuels. The cure was to make another custom 236/242 112 custom SR cam

 

Increasing or decreasing rocker arm ratio will not affect cylinder pressure - the intake valve will still close at the exact same point regardless of rocker arm ratio. The cylinder will have a greater fill of air/fuel though with higher rocker arm ratios or higher lift cams. The cylinder pressure is dictated by the closing point of the intake valve - the later the IV closes (dictated by cam duration), the lower the cylinder pressure will be. I'm in the same boat as you right now in deciding on which HR cam I need for my setup.

 

I have some experience with pinging,
Cold air intake let me drop from 91 to 87. But, on a really hot day it had some ping. An engine builder suggested short-tip plugs. So i put them in the 3 hottest cyl's, and the ping was gone. At first i thought the short tip delayed the flame front. Now i think it could be the tip ran cooler and did not self-ignite. Not sure (did gkull try the coldest plugs available?)
If it won't stop pinging at cruise and it is self-ignition, the key could be turned off and it would keep going!
I did have that happen at the drags with a Mopar. throttle stuck WOT and i quickly shut it off, but the key had no effect! kept accelerating! Now THAT is some heavy duty self-ignition! That was a turbo car w/22 psi boost. When i shut the key off, i forgot that also shut off the water/methanol injection, so it instantly went from high octane to crap octane. And i don't recall hearing any pinging(but i was really concentrating on how i was going to stop)

 

So, if i ever had pinging that nothing worked on, i would try water injection since i know it works (just ask any turbo racers with high boost).
Non-turbo guys usually refuse to try it because it sounds too good to be true. And it is inconvenient having to add water. Quite a few turbo guys forgot to fill the tank and now they remember!
If all it needs is a cam change, that is a better long term solution for non-turbo cars. Water would be a temporary band-aid imo.

 

I ran the numbers for this one making some assumptions and come up with DCR of 7.37@5000 ft. If it had iron heads and hot intake air, inadequate cooling, or a lean mixture I could see it pinging. With aluminum heads, good cooling and timing it should run fine according to the numbers.

More reading today ( i usually have to read something 2 to 3 times to really absorb what I'm reading ) and I see that the rpm at which overlap no longer bleeds off pressure is referred to "full stroke capture" at this point SCR becomes the dominant factor in cylinder pressure not DCR. So DCR, like you said is a slippery thing, and only one of the many tools to determine power and min octane usage. It's primary usage for conditions prior to full capture.
I could see where full stroke capture could very well occur at cruising speeds on a shorter geared rear end and shorter cam duration and you end up in the perfect pinging range for the engine most of the time.

Also discovered VP index. Very interesting in comparing low rpm performance for various cam durations and intake valve closing points at different SCR's.
Altitude is definitely a large factor in performance. Not only altitude but density altitude. On an 85 degree day (typical late spring day) at 3000 feet elevation the density altitude has risen to just over 5000 feet. Even less cylinder pressure. So if you do not build in a little extra DCR or SCR to counter this reduction in air density your peppy cam can go from little hot rod to slow dog pretty quick. My typical driving conditions are in the 80* to 95* weather with 3000 being the lowest altitude. Of course the other side of the coin is hot air likes to detonate much easier than cool air.

 

I have read this also. I think it should state that "increasing rocker arm ratio will not affect cylinder pressure given that max flow from the valve seat design has been achieved" or something similar.
If I think about this for a bit, rocker arm ratio has to affect cylinder pressure just not as directly as intake valve closing point. Take it to the extreme and only open the valve .050". Intake valve closing point unchanged. Wouldn't that affect the volume of air allowed into the cylinder? Sure it would, unless .050" valve lift represented the same flow as .500" of valve lift. So the valve seat and valve design (size, shape etc) would seem to dictate how much valve lift represents the maximum flow for that valve event. If max flow is achieved at .045" then lifting it to .055" would gain nothing. However in my case if lifting the valve .049" represents more flow that .040" then lifting it to .040" would reduce the amount of cylinder filling since the valve closing event is the same and now the cylinder has to try to fill breathing through a much smaller hole in the same amount of time.
As I see it I just reduced my VE to something less than it was before at least at higher rpms where inertia becomes a significant factor for movement of air and the overlap is no longer a significant factor. I could achieve the same by reducing the amount of air I allow in the snorkle to the air cleaner. That's what GM did when they built this engine.
The Cold air intake on this L-48 was probably good enough for the low valve lift and restrictive exhaust that was on it stock. But I discovered that by just opening up the exhaust the intake was now the restriction in the system and I had to open it up too accommodate the increased flow out the exhaust.

Some really good reading here about DCR and SCR if you got time (took me a while to get it all)
http://victorylibrary.com/mopar/cam-tech-c.htm
Here is a VP calculator if you want to play around with that rather than slogging through all the calculations.
http://www.wallaceracing.com/dynamic-cr.php

My only experience with water injection is on turbine aircraft engines. It was used to increase mass flow through the engine to compensate for loss of performance due to altitude. The water reduced the engine temperature so dramatically that it was necessary to make it water/methanol injection to bring the combustion temps back up. So yes water injection cools the combustion greatly.
where do they inject the water in these cars. In the intake track after the fuel for carburated engines or is it through fuel injectors?

 

The above is why you leave a little play and don't push the envelope.

Building in a little extra DCR or SCR is a mistake on a street driven car. If you want a certain cam and operating range and your showing to high of DCR reduce compression instead of playing with fire. You will always cost yourself more power loss by cutting back advance curve or increasing A/F ratio to reduce ping than playing it safe to begin with. Gkull's combo is a prime example of a combo that theoretically works but don't in real world application. A full point of compression is about 2% in power. So on a 400 HP build it cost you about 8 HP to drop from 10.5 to 9.5 compression. This is barely ot not at all noticable in a street engine.

 

I always had aluminum heads, good cooling even high volume pumps.

Lean.......... I kind of doubt it they were good running motors with single plane and headers

 

I was just trying to figure out what may have been the cause that's all. No offense intended.

 

What happens to DCR if your cam is retarded 4 degrees? I spent allot of time doing dyno sims adjusting the valve event numbers before I ordered the cams.

 

Anyone not tuned for 87(85) needs a plan to deal with pinging.
.......what is your plan to deal with a gas station trying to make extra $$$ with LOW octane gas sold as HIGH? Hiring a lawyer and a lawsuit is not a viable plan
OEM's use a knock sensor and they cut back timing.

We have several options for manual control (under dash):
1. $3 solenoid valve reduces vacuum advance (cheap but only one stage per solenoid).
2. MSD timing control for HEI. (very precise, does not work with non-HEI, only sold used)
3. cable control to adjust dist. (crude but effective)
4. MSD timing retard module (expensive, stages).
5. (fill in latest gizmo)
So, for whatever reason, it starts to ping, reach under the dash and adjust the timing until it stops. I do use the solenoid sometimes on 40F mornings to lock in maximum advance as a cold engine wants lots MORE advance. Gives it the throttle response of a fully warm engine (no choke)
Another handy tool is a dist timing POINTER that eliminates the timing light during a low octane emergency. The pointer points to a scale with degrees marked on it. So u stop, loosen dist. turn to KNOWN timing marks without a timing light, and u tighten it quickly to the "cheap gas" setting. I have the pointer on my 72.

 

If I install the cam retarded 4* then the sea level DCR would be 8.39. I've read that you can be off as much as 4* on the cam timing and you won't really notice the difference. would you say that is accurate?

I would prefer to have a ping sensor with a light in the cab to let me know when detonation is occuring and then tune to eliminate it. This thing is loud with side pipes and all, and likely I will not hear the detonation until it is pretty severe at higher RPMs.
I used to have a Honda civic that had odd timing and I marked the dist. mounting plate with various marks for different timing settings, +10*, +6* etc and would adjust it accordingly if I wanted more performance or wanted more ping protection.
LOL of course I used to have to pull over on cooler foggy days and "deice" the carb when on a trip anywhere. The carb heating hose and shroud had been removed so ice had a tendency to build up if the humidity was high enough. I had to remove the air cleaner lid, pump the throttle to squirt fuel in the throat then ignite it and let the flames melt the ice giving it another pump occasionally to keep the flame going until the ice was melted out. Real safe huh?

 

i had icing here in FLa winters. cure was to pull a tiny bit of heat off the header attached to air cleaner base. just an empty 26oz food can cut to fit header with 1/2" pipe. i never thought of setting it on fire

 

Finally the holidays are over and I can get some answers from manufacturers.
Ideally to reduce my SCR a bit I would like the 10cc pistons. But 10cc pistons for a 4.00" bore do not come in a 1.56" compression height, only 1.54". I couldn't confirm this until this morning. Sooo my next best option is a 12cc piston.
This comes in a 1.561" CH and would lower my SCR to 9.8:1 and my DCR to 8.64 @ sea level.
This would be a 7.56 DCR at 3000 ft. and a VP index number of 126.
7.56 is a number that is comfortably below problems with detonation with 91 octane.
I ran the numbers for a 280/280 cam on a 110 and 7cc pistons just for comparison and it comes out to DCR of 8.21 @ sea level or 7.61 at 3000 ft. with a VP index of 120.
This would seem to indicate that at altitude the 270/270 on a 108 would have similar torque characteristics as that of the 280/280 on a 110 at least at lower RPMs and maintains this similarity as altitude climbs.
I think with the extra valve lift, and the roller cam combo I could see too much cylinder filling to be combined with the 7cc pistons and 61cc heads. I could chance it and probably be fighting detonation when the conditions were wrong but that sounds like it could get old real quick. I know Mako63 has been trying to pound this into my thick skull, but I like to explore all possible options before making a final decision. In this case availabilty of components and painting myself into a corner made the decision for me really. It just took me some time to figure that out.
Thanks for every ones input so far. I'm sure I'll have more questions that make no sense. I'm learning something new on this stuff all the time.

 

I did fabricate something later on similar to what you describe once I had a couple bucks to do so.

 

Crane cams are ground typically 4 degrees retarded when compared to a similar cam from say Comp cams. So my customs also got the 4 degree retard. You end up with less reversion and a smoother idle.

The reason my high DCR motors would ping at cruise:

You have several principles going on in a cylinder. Have you ever heard that in higher VE motors that they take out timing as rpm rises? *** bikes and race engines do this. The reason is the higher the atomization of the fuel the faster it burns. In an efficient high swirl chamber with good quench and spark placement the ignition timing is less that older heads

Now as rpm increases in intake velocity is approaching the speed of sound flame travel speed in the chamber increases because of the total atomization of the fuel. It doesn't have time to form a foggy denser large droplet mix.

Now at cruise speed in the cams efficiency range. You are at very high vacuum and the throttle blades barely open. It is probably the warmer time of the year, so engine temp is up. Also speeding flame travel. Your A/F mixture is probably the leanest. You have additional vacuum advance and boom you are into knock. Modern knock sensors pull timing out to avoid the death rattle.

I used Crane adjustable vac advance cans turned down to only an additional 4 -8 degrees. You fire before TDC so the piston is starting to build pressure just before swinging over the top. The knock is if the piston is experiencing to much pressure before TDC.

On the other side of light throttle cruising is WOT. Where you have enriching circuits bring the A/F ratio down. Slowing flame travel down. Loss of vacuum causes retarding of the timing.

 

throwing a switch under the dash to bleed off the vacuum advance would be the 1st thing i'd try if there is sometimes too much cruise advance. like in the desert it could be what, 115F on a hot day?

The bigger cam, what does it do? Does it lower cylinder pressure? Not at cruise. How can it? At cruise it takes X HP. HP is made with cylinder pressure. The throttle is barely open. For X HP it requires the SAME cylinder pressure big or small cam to make X cruise HP. There may be slight changes in throttle position to maintain cyl pressure. The thing that is different is the amount of exhaust sucked in during overlap, which increases with the larger cam. This exhaust slows the burn as exhaust introduced into the combustion process makes the mixture burn slower, and stops pinging just like reducing timing. There is usually more than 1 way to solve a problem. I start tuning with the easy things first, like switching off the vacuum advance or other adjustments.

 

I believe this would depend on how big the cam is and at what RPM you cruise.
If the cam is say a 300/300 on a 109 LSA with 82* of overlap it will require much higher rpms before reversion effectively stops than say a 260/260 on a 112 LSA which has 36* of overlap. The 260 might cease reversion at 3000 rpms. If your cruise RPM is 3300 due to gearing then there is minimal or no loss of cylinder pressure due to overlap.
With the 320 cam it's point of no reversion (full capture) might be more like 5500 RPM. It's unlikely that gearing in a street car is going to give you 5500 RPMs at cruise. So this cam would still be allowing cylinder pressure to bleed off in the form of some of the intake charge exiting the exhaust valve as well as some contamination of the fresh charge during the overlap period.
So I would say that this cam is in fact lowering cylinder pressure by virtue of the large overlap at cruise.
To recover that loss of HP required for steady state cruise it would then require a larger deflection of the throttle blades and more fuel to off set any power below that required for cruise.


So when you say ground without the 4* advance does that include all valve events, or just the intake valve closing point, or just specific valve events?