4.6 Stroker Compression Ratio for pump gas

[Cody Brought]

I am gathering parts to build a stroker with a 1999 block from a wrangler. I dont care much for top end power; I want to bring my torque peak lower in the rpm range. My question is can my build(how I have it currently planned out) run on either 87 or 91 octane gas safely.

Im using 4.0 rods, hyper pistons with a 21cc dish and 1.353 compression height, .043 head gasket, and a stock cam.

I plan to deck the block .030 to give me a -.003 deck height, and it will be overbored by .030.

The pistons are a reverse mirror of the combustion chamber, and I plan to polish all surfaces seeing combustion.

static cr: 9.76
dynamic cr: 8.42
quench: .040
Sea level, highest temperatures seen are around 93 F

I know there are no rules of thumb in regards to compression ratio vs what octane gas I can use, but if anyone has experience or knowledge that can pick my build apart and give me a thumbs up or criticism, it would be greatly appreciated.

[Cheromaniac]

With your specified SCR & DCR, I think you'll need at least 91 octane to avoid detonation especially close to sea level.

[GASnBRASS]

With your specified SCR & DCR, I think you'll need at least 91 octane to avoid detonation especially close to sea level.

In your experience what's the upper DCR limit for 91 pump gas with iron head vs aluminum head?

[Cody Brought]

With your specified SCR & DCR, I think you'll need at least 91 octane to avoid detonation especially close to sea level.

From what I read that sounds about right. I have 91 or 93 octane available everywhere around me, and if im doing all these modifications id like some good compression.

I was going to look into cold spark plugs too, to give me a better safety factor for pinging

Thank you for the response!

[Cheromaniac]

In your experience what's the upper DCR limit for 91 pump gas with iron head vs aluminum head?

There are multiple variables that can affect an engine's tolerance of 91 octane gas but an aluminium head will allow at least a half point more compression.
For example, my Mustang 4.6 3V all-aluminum engine has a 9.8 SCR, 8.5 DCR, and is tuned for 91 octane with 30 degrees maximum ignition timing advance.
As you add more static compression you'll need to use colder spark plugs and back off the timing. Alternatively you can add a camshaft with a later closing intake valve event to reduce dynamic compression.

[mpgMike]

My 4.6 is running a static CR of 10.2:1. With the stock '95 ZJ PCM it would ping on 91 octane (highest I can find around here). I installed a stand-alone (www.rusEFI.com - UAEFI model) so I can control ignition timing and -- I got rid of the pinging on 91 AND picked up all sorts of power! Next fill-up I'm going to add 87 octane. My goal is to run 87, even with the high CR.

Side bar, I'm running Comp Cams' Rock Crawler Cam, which means I have an extremely high dynamic CR (haven't checked the online calculator in awhile, so I forget the exact numbers). A stand-alone was the magic bullet for me.