Please recommend an appropriate stroker recipe for my needs.

[cb3]

How about midgrade gas? What, if any, is the gain from building an engine with CR for that? What would be the ideal CR for midgrade gas?

[dwg86]

You can run a higher compression with a tight quench,.040 to .050. How much compression? I don't know. I have heard some running 9.5:1 with a tight quench and no pinging. The cam you use will also play a part in it. How much valve overlap and intake valve closing will affect dynamic compression ratio(DCR). Your DCR has the final say on what octane you can run.

For example, I have a 401 in my CJ5. It has 10.5:1 compression, but a bigger cam. It doesn't detonate on 93 octane. I haven't tried any lower octane(affraid to). Its just a toy so I can afford to fill up with 93 a few times a year.

Maybe some who have completed thier strokers can chime in on what combo they are running and what they have experienced with the different octane fuels.(static comp, dynamic comp, cam, and Quench).

[eliv1]

Im running a 4.5L stroker, with a 1:9.7 DCR, and a 68-231-4 compcam's cam, on 95 octane RON rating (eqiuvilent to 91 in the U.S) with no pinging what so ever. the chambers are polished for reducing Pinging, so maybe this helped too.

[Mgardiner1]

Surely you mean a 9.7 STATIC compression ratio......

I've run 93 and 91 on my 8.25 DCR/.057 quench/30AB cam stroker with no issues

[eliv1]

Ops , ofcourse you are right , i meant an SCR of 1:9.7...

[cb3]

I probably should have been more specific about gasoline grades in my local area and what that means in regard to octane. It seems like maybe it varies from my local area to where some of you are located? Maybe so.

In my local area:

Low grade E10 gas has 87 octane. My stock engine pinged on that while going up hills.

Midgrade E10 gas has 89 octane. My stock engine likes it and never pinged on it.

Highgrade/premium E10 gas has 92 octane. Never used it.

My mixture I now run of 40% lowgrade E10 gas (87 octane) with 60% E85 (105 octane). My stock engine likes this mixture and never pings on it.

So when I said I'd like to build (or consider building) for midgrade gas, I meant 89 octane. What compression ratio and pistions would be best for that?

That would allow me to run a mix (gas/E85) locally. When traveling out of town and if can't find an E85 pump, I could run midgrade gas. I think having a higher CR would be helpful when running the mix, but want to keep the CR low enough to run midgrade gas when I can't find E85 to mix.