Jeep Strokers

don't mean to beat a dead horse but I have looked all over and I have not found the answer to my question.
I am just about to put this thing together when I found out the compression ratio will be 9.8 to one. to me that is on the raged edge of using cheaper gas and having to use the premium gas. is 9.8 to one to high for the cheaper gas?

Possibly but it depends on a few other factors:

1. Are you using the stock iron head or the Edelbrock aluminium head? The latter will allow at least a half point more compression without detonation.

2. Did you smooth the combustion chambers and piston dishes to a near mirror finish?

3. What quench height did you end up with?

4. Which camshaft did you use? Use this site's dynamic compression calculator to find out where yours sits at.

5. Are you using colder spark plugs?

6. Did you upgrade the cooling system?

7. What's your ignition timing set at? Overadvanced timing will increase detonation risk.

8. Which injectors are you using? Running lean will increase detonation risk.

9. What elevation do you live at?

1. I am using a 331 hear that is polished and ported by russ.

2.yes, by russ

3. I not sure. had to deck the block .5000 off

4. a 12 weighted 4.2 crank from russ

5. did not know that made a difference. I was going to use what jeep said I should use.

6. yes. the block was dipped and cleaned. it is so clean I can eat off it. inside and out. Flex-A-lite with 3 electric fans

7. have not done the timing yet as it is not put together yet

8.24 lb 4 hole

9.I live in Omaha NE.

len1xj wrote: ↑June 8th, 2022, 2:03 pm don't mean to beat a dead horse but I have looked all over and I have not found the answer to my question.
I am just about to put this thing together when I found out the compression ratio will be 9.8 to one. to me that is on the raged edge of using cheaper gas and having to use the premium gas. is 9.8 to one to high for the cheaper gas?

You're spending all this time and $ on a motor just to run the lowest octane pump gas? Doesn't make any sense man. The stock 4.0L will perform identically to a low compression, poorly tuned, 87 octane stroker.

who said anything about being poorly tuned? at almost $6.00 a Galion is why I am wanting to go to a lower grade gas. why put all the time and money into something you cant even drive in fear of going broke. maybe you may not understand that but that is ok. Its my build and I know what I want and what this stroker will do no matter what fuel I use. all I wanted to know is this. at 9.8 compression do I have to use premium fuel, or can I use a lower grade with out the deadly pinging.
Thanks for your input.

I sympathize with your worry and possible frustration len1xj. This is a tough thing for anyone to answer confidently tho, as chermaniac is suggesting there are alot of variables. I think 9.8 Static is a good number for a strong street stroker, depending on cam and supporting mods, and where fuel cost is Not a concern. My 1st build was 9.6 static but i fully intended to run 93 just for assurance (in 2002 tho). If you were in the high-plains I'd wager you'd be very safe with 87 octane. Colorado offers even lower octane ratings but i don't recall what the price scaling looks like What does Russ have to say?? Not calling him out here at all, just that his opinion might serve you better than mine lol He may also be able to help you figure out the best way to dial things back to safely allow a lower octane fuel. Quite a few ways to achieve it & it Can be done, some are just more involved & maybe more permanent solutions to your build. They will just about ALL reduce the power levels you can achieve tho. Also depends on how you intend to run it. Are you wanting a horsepower monster or happy with just more torque across the middle? A good stroker build generally produces more torque at 2500rpm than the same 4.0 did @ PEAK. It's just a big flat curve. True horsepower gains are often less brag-worthy tho. Hopefully you were settled about the kind of engine you wanted to build when you worked w/ Russ to put it together. Less disappointment that way

len1xj wrote: ↑June 9th, 2022, 3:00 pm why put all the time and money into something you cant even drive in fear of going broke.

That extra $0.50/Gal is really gonna burn the checking account.

Thanks, working with russ was a joy. the machinist I have been working with just can't believe the quality of parts I got. after shaving off .5000 from the block he said I would be at 9.8 to one and he said I should reach 400 foot pounds of torque. Russ said 350. if everything goes right ( I know it will) torque starts at 800, peak around
2500 where it will flatten out to 5500. sounds like a dream to me. when I tune it I am shotting for the middle of the road between good gas mileage and power. it will be a daily driver, it will tow, trails, and some rocks. it will be a do all, everything jeep that will do everything well. the gas prices are a concern but it is not the main concern. getting the right is the main concern. I did not know there were so many factors involved on pinging on this compression issue. but that is why I ask here, to learn what I don't know.
Thank you

have you looked at gas prices. it is almost $6.00. so I am wandering why this is important to you. why do you want me to do this your way. anyway have a good life. peace and
+

len1xj wrote: ↑June 9th, 2022, 6:33 am 1. I am using a 331 hear that is polished and ported by russ.

2.yes, by russ

3. I not sure. had to deck the block .5000 off

4. a 12 weighted 4.2 crank from russ

5. did not know that made a difference. I was going to use what jeep said I should use.

6. yes. the block was dipped and cleaned. it is so clean I can eat off it. inside and out. Flex-A-lite with 3 electric fans

7. have not done the timing yet as it is not put together yet

8.24 lb 4 hole

9.I live in Omaha NE.

It sounds like your combo will be pretty well dialed in, so it's going to boil down to which camshaft you've chosen and where your dynamic compression ratio will be. In your answer to question number 4, you quoted the crankshaft by mistake.

oops comp 231

len1xj wrote: ↑June 9th, 2022, 8:09 pm after shaving off .5000 from the block he said I would be at 9.8 to one and he said I should reach 400 foot pounds of torque. Russ said 350.

They cut a half inch off of the deck? So it's an open deck block now? Do you mean .005"? Also, 24# injectors will not support 350-400 ft# of torque. There isn't a stock fuel pump that can support that either.

oops number 2, yes .005 easy to get a more powerful fuel pump that can handle this, but what about the injectors. if a 4 hole 24# injector will not handle this power then what will?

len1xj wrote: ↑June 10th, 2022, 12:15 pm oops number 2, yes .005 easy to get a more powerful fuel pump that can handle this, but what about the injectors. if a 4 hole 24# injector will not handle this power then what will?

Well the 231 cam wouldn't be enough for that power level anyway. That's not even a good NA cam. -12' of overlap? That's a low lift turbo cam. How much lift can your valve springs handle and are you using 1.6 or 1.7 rockers?

To make 400 Ft# NA you would need enough camshaft and cylinder head port cross section to support 400 HP. Basically, once you open the ports that much, you push the power higher in the RPM range and the engine will eventually make more HP than torque. You need a lot head work, more than .500" of valve lift and over 220' of duration, along with high compression, 93 octane and lots of fuel system. A 255 LPH pump, 40# injectors and the ability to tune with live data are all required for 400. 24# injectors are what I run on my stock Cherokee.

231 cam