If you think you are going to run 11:1 and that cam and pull at very low RPM, you are in for a bad revelation!!!
I see this all the time and your best solution is to change PISTONS. Having said that, your initial timing is the biggest issue here and stronger advance springs or any other patch up is not going to solve the problem.
Try lowering the initial timing until the pinging stops. It will help.
You should manually, if necessary, downshift or unlock the converter below 2000 when doing any acceleration.

 

Everyone is saying a higher duration cam that will lower the dynamic compression would help. You're saying only changing pistons would help? Now I'm a little in the air about which to believe.

 

I would think that "3 in the hole" would be .003" and that "30 in the hole" would be .030"
If it is indeed .030 in the hole that means the block was not decked at all and that could be the source of lousy quench (for that compression ratio) and therefore "abnormal combustion" including ping.
.003 sounds to me that it was decked and the ping is from that compression ratio with that cam. 11 to 1 is high for pump gas even with aluminum heads and a really efficient combustion chamber. A longer duration cam might be fun for you but I would swap out the high compression slugs.

 

Both are true. A cam with higher duration won't affect static compression at all but it will lower the dynamic compression because of the overlap. Changing the pistons will lower BOTH the static and dynamic compression because you are essentially making the combustion chamber bigger.

The cam is easier to swap out than pistons. With a piston head change you have to pull the engine and pull the rods and pistons out of the block. If you do this, you'll be better off turning the crank and installing new bearings and rings.

Changing the cam requires the radiator to come out or be angled forward, removing the accessories int eh front and the water pump and oil pan and timing cover at the very minimum. The intake will need to come off and if you are changing the cam you should also change the lifters. Finally, IF you need new springs, you can do this with the heads on the engine in the car.

 

When changing a cam, it's better to pull the engine. 45 minute job.

 

Hrm. Well I don't think pistons are something I could do myself. I could change out the cam with help but that would be about my limit. How much would it probably run me to have a shop swap pistons? I know that's a lot of work.

 

I'm sure it would a little........depends on what the end use of the car is. With the high CR he has now, I bet he'd never know the difference for a street car. If it's used for racing/competition then maybe not a good idea.

I did it once on a motor and couldn't tell the difference but it was a street car. Just an idea.

 

With shop labor and no parts or fluids or disposals, you'd be looking at around $3600. Add $200 for pistons, and machine work on the crank, and price for new bearings, rings, gaskets, and fluids.

 

Larger cam will lower the dynamic CR and help. Now it won't go at all below the 2000 or maybe greater RPM range.
Anything you do except change the compression ratio is just a patch or crutch on the street with pump gas.
You can lower the CR with heads and that is what I would do in your situation. 72cc or larger combustion chambers will get you into a drivable CR.
Another option is go to E-85. That really works and you can probably change over for less than any other option.
Another option is higher octane gas. 100+ octane will solve your problem.
I see this every day and every time it is the same: somebody decided 11:1 was good and the new cars can do it so I should be able to do it too.
WRONG!!! New cars have combustion chamber designs and COMPUTER CONTROLS to make them work, and then they are on the ragged edge for pump gas.
Until you do something to lower the MECHANICAL CR to maybe 10:1 or less OR you increase the octane of your fuel, you are in trouble

 

maybe gkull will chime in again since his combos r exceptional.
george
could u tool around at 1200-2000 in lockup and not ping? that is joshs' goal.

 

Alright well I really appreciate the help. I wish I could do more to just easily fix it, unfortunately when I bought the car I didn't know I was going to have all these problems and I'm left a bit in the hole trying to figure out how to fix it with the money I have.

Again my goal is just to have a drivable car on 93 octane at this point in time. I just have to try and find some way to get there for the money I have, and unfortunately $4000 in work for pistons isn't in that range.

Again thanks for the help guys

 

Can you not do the work yourself? If you can get some friends, and pull your engine out, you can do the piston change for around $350 or so give or take gaskets and fluids. Friends usually work for beer. Heck, if you were closer I would do it for a few cold ones and some BBQ.

 

Amen. Now's the time to learn this stuff. The cost of garage labor is mostly why I do my own stuff.

 

I don't know how to change pistons honestly, I'd be afraid to screw something up. On top of that, none of my friends really know how to work on cars that much The one thing I DO have is the facilities to do it, but not the labor

 

neuroclast

I have been following this thread and there is alot of good sound advice being given on possible courses of action. I am by no means even a novice as I have just built my first stroker and I went through many mind numbing calculations to make sure I was buying the parts for the build I wanted, ....and I still got some wrong. (with the grace of God and a lot of help from this forum my engine is complete) I would just add, to take a step back and gather up as much information on the engine build that you have. See what the numbers give you. You may have play in the quench numbers, hell you quench could be way off and could lower the CR with a gasket swap. It might be a timing issue or a cam swap but I think you need to do the number crunching to see where you might be able to make improvments. IMHO at 11:1 you are on the fence with obvious detonation issues. I would find out exactly what your both dynamic and static CR and quench is, what head gasket you are using and the compressed thickness, what the cc's of your heads, whether the block or heads have been decked/milled, piston and cam spec's and do some serious number crunching. Double check the heat specs of the spark plugs you are using as well. When you get the numbers I think it will be clearer on the best course of action. At least you will know what you can change. Good luck and I hope this helps a bit.