Just a question for a stroker, say a 500 or 511, if running a cam with 250ish degrees duration at .050, how much compression do you think would be safe for pump gas? And how much compression do you think it would take to give good results with a cam like that in the 500 cube stroker?

Looking for a cam that will work well with a stockish stall (2500) converter and 3.23 gears.

Assuming Aluminum heads & effective quench in the 10.5-10.8 range.. You really should look at dynamic C/R & shoot for a cylinder pressure around 155-160 psi...

im running just about the same thing except for i was useing 915 heads at about 70cc. right around 12.5 to 1 on 93 oct with a mopar .484 cam. and it was the limit i would say switching to eddys this year and hopeing to mill them .070 and run off pump again

11-11.5:1 with tight quench and AL heads, no problem on 93.

If you want to run a mild cam, I would keep comp around 10.5 and for sure under 11.

It would be using iron heads for the time being, aluminum when the budget allows.

You can go with more compression with aluminum up to 11.5 max and that is pushing it.

The iron heads much less. I would keep it at 10.5 max with the iron and again that's pushing it.

Keep an eye on your timing if you get any detonation, less is better with todays cruddy gas.

It's difficult for me to comment but I will. If you stay with iron heads, then I'd stick with anything under 11.0 on cr. Probably the most critical issue in your plan is quench. A .040 quench is optimal as it reduces detonation. This does however need flat-top pistons and a closed chamber head to be fully effective. Open chamber heads and dome postons can be made to quench but that normally results in a much higher compresion ratio. A cam that is at 250 @ 050 will work with good quench. If you build good cylinder pressure w/o quench, you may get a significant amount of detonation. Since I am at altitude, building cylinder pressure is much more difficult so my real would result's will not be the same as yours. I'll stop rambling. You really need good cylinder pressure and quench to go to the supposed limit of 11.0 cr on an iron headed motor. I'd welcome any rebuttal to this comment.

Wow, this is at least a full point more than I expected, with 500 cubes I figured 9.5:1 would be pushing it with iron heads and 93. Keep the comments coming, im trying to sqeak by with upper 9s or lower 10s with the irons so that I can be in the mid to upper 10s when I go aluminum.

And for the best quench, I guess the easiest way would be zero deck and .039 inch head gasket?

What if I do not have good quench and am, say, .020 in the hole to make things more realistic.

I did a 470" low deck.4.375 x 3.900, 6.760 rod. Right at 10.2:1. 84cc Eddys and a small dish(mirrors the chamber) w/.039 felpro's at 0 deck.I know I could have went higher,but I am unsure what pump swill will be available in a couple yrs. Has a 242/248@.050 solid roller,runs great on 93 and no ping on 89(that was an oops at the gas station ) This is a street only car.Hope that helps.

http://www.projectpontiac.com/ppsite/content/view/16/30/

Try this link, it works well and gives you a look at both CR and DCR. You will need the cam specs. I would say iron heads under 8.5:1 DCR.

i still think your all nuts just entered my specs and this is what i got

499.1 ci
8.18 lifter
13.76 to 1 static
10.46 to 1 dyna

off 93 oct, 34 deg timing and 915 heads

Did he say open chamber heads ?? I did not see which heads he said other then iron heads. That said I use 906 open chamber iron heads in the 440 in my 63. And I use the KB quench pad pistons. I had to work the pistons and chambers to get all my chambers in the .040 to .045 quench area and I got it to come out at 10.0 comp. I can run 38 total timing all in by 2000 rpm and I run 92 and 93 pump with no ping. I use the MP .557 cam with 296 advertised duration and it works nice with my combo. Ron

In part it depends on how you'll use it. Pushing compression up on a drag car which has a short run followed by cooldown is different than on a street driven car that will see traffic, high underhood temps and possible sustained hard running.

I guess I'm more conservative than many posters or perhaps its because its how I use my car. Your combo sounds like you plan to drive it based on cam and convertor choice. Also if you start with open chamber iron heads and convert later to aluminum, you won't be able to use quench dome pistons very well so the iron headed engine probably won't be a quench engine.

Assuming you are starting with open chamber iron heads, I'd shoot for mid to high 9's - say 9.7 - with a D dish piston at zero deck. When you put smaller chamber aluminum heads on that would get you in the low to mid 10's. You might be close on detonation with the iron heads but should be bulletproof with the aluminum heads and quench.

Sorry guys didnt specify, they are 516 closed chambers. I know I know, they wont work well but they have a fresh valve job and I cant see dropping the dough for machine work on a set of 906s and the price of cores for something that will get changed a year later.

Closed chambered 516's now and are you going to closed chambered alum ones when you switch(hope so) & if so are the cc's of the 2 close enough that you can get your CR where you want it now & have it pretty much the same when you switch to alum heads & you'll still have your quench(if you get it now) & if the cc's are radically different & you're switching in a year I'd get the CR where you want it based on the cc's of the upcoming swap