I was hoping you guys could let me know what you think about this recipe for a stroker running on 87 octane.
98 4.0 block
.020 bored over
.0 deck
.043 head gasket
18.8cc piston area (I obtained that using the 802cp with including the gain from the ring depth as was posted on the linked stroker build http://www.fourwheeler.com/techarticles ... index.html)
5.875 cast 707 connecting rods
250 intake duration
113 cam lobe seperation angle
3 degree advance
#24 Ford injectors
this gave me a 8.49 DCR and a 9.88 SCR and a quench of .043
Would I have problems running 87 octane and should I run a cooler thermostat?
A 180* t'stat, cooler plugs, and polishing the combusion chambers/piston dishes would help but with a CR that high (both static and dynamic), you're still not going to run 87 octane without pinging. Realistically you'll need at least 91 octane and you'd have to drop the CR by at least 1/2 a point to have any chance of running 87 octane.
Cheromaniac wrote:A 180* t'stat, cooler plugs, and polishing the combusion chambers/piston dishes would help but with a CR that high (both static and dynamic), you're still not going to run 87 octane without pinging. Realistically you'll need at least 91 octane and you'd have to drop the CR by at least 1/2 a point to have any chance of running 87 octane.
My stroker has higher static and dynamic then Dino`s disaster recipe. One guy who built one engine and is now the know it all of Jeep strokers. Trust me, you can do much better then Dino`s opinions. He is a legend in his own mind.
Run 87 with no problem.
Factory plug heat range is fine.
What cam are you getting numbers from ?
Forget the 180 stat. Strokers like heat. Run the 195.
Comp Cam 68-232-4. I am really trying to run 87 in this machine If there is anything that I should do before building it and it is cost effective I am going to be sure to do it. You guys are the authority in this and I am doing my best to learn as much as I can before I complete this project.
jsawduste wrote:
My stroker has higher static and dynamic then Dino`s disaster recipe. One guy who built one engine and is now the know it all of Jeep strokers. Trust me, you can do much better then Dino`s opinions. He is a legend in his own mind.
As for my el cheapo "disaster recipe", it's still running great after 57k miles and it's a joy to drive so that's a disaster I'm very happy to own.
Actually I've built three engines, not one. I also helped a friend build a carbon copy of my stroker out of my old 4.0L engine which he's very happy with, and I also rebuilt the 5.0L engine in my Mustang 2 years ago.
jsawduste wrote:
Run 87 with no problem. With a 9.9:1 SCR, 8.5:1 DCR, and an iron head? I doubt it.
Factory plug heat range is fine. A very big maybe.
What cam are you getting numbers from ? CompCams 68-232-4
Forget the 180 stat. Strokers like heat. Run the 195. Agree if it has the Hesco aluminium head, otherwise 180 for the stock iron head. Heat + high cylinder pressures + 87 octane + stock plugs = ping city
I wish I knew what the max DCR would be to run 87 octane. I can't find that info anywhere. I can only tell you that I run 87 octane with no ping problems at all. My DCR is 7.75 and SCR is 9.25 with a zero deck, .043 MP head gasket, and 180 thermostat. With my build I was shooting for an 8.0 DCR. After all my calculations, and head cc's being bigger after the SBC valve install, I fell a little short. How much HP and torque did I loose by the .25 lower compression? I don't know. And like I have posted before, I put almost 100 miles per day on my stroker, so I am not worried about a little lost HP. I would rather be able to run 87 octane.
Maybe others can chime in on what the minimum octane they can run, and what thier DCR is. Then just maybe we could get a better handle on this.
To answer you question, what can you do to better your chances of running 87 octane gas? Well if you want to lower your SCR and DCR you can increase your head combustion chamber, and/or piston head cc's, keep the quench tight and cylinder head temps low.
I cleaned this thread up as best as I could, which I should have done earlier. Play nice and keep it civil.
As for on topic, my stroker has 9.5:1 static and 8.29:1 dynamic, .048" quench. Running the Comp Cam 68-231-4 I was able to run midgrade (didn't get around to try 87), but the AFRs in WOT were very rich, around 10-11:1, far from where they should be for optimum power. It did not ping in WOT with that AFR. Still running midgrade I started to pull fuel out where necessary to get it closer to 12.5-13:1. When I was right around 12.5:1 it started to ping. Filled up with premium and brought it closer to 12.5-13:1 with out ping.
To sum up, I was able to run midgrade with a very rich AFR.
dwg86 wrote:Maybe others can chime in on what the minimum octane they can run, and what their DCR is. Then just maybe we could get a better handle on this.
Here in the UAE there are 3 grades of fuel available: 91 RON E-Plus (87 US Octane), 95 RON Special (91 US Octane), and 98 RON Super (94 US Octane). My stroker has a SCR of 9.25:1. When I had the Crane 753905 cam, the DCR was 7.86:1 and I ran Special year round. Swapping the stock cam in dropped the DCR to 7.36:1 and I can run E-Plus during the cooler months when daytime temps. are not higher than 85*F. I'm running the stock computer, stock Champion RC12LYC plugs, a Robertshaw 180* t'stat, 3-core radiator, and a Flowkooler water pump.
On the dyno my A/F started at ~14:1 at 1500rpm, gradually decreasing to ~13:1 at 4000rpm, ~12.5:1 at 4500rpm, and ~11.5:1 at 5000rpm. I've got my MAP adjuster set at 5.2v and the A/F ratios at idle/cruise are stoichiometric.
dwg86 wrote:Maybe others can chime in on what the minimum octane they can run, and what their DCR is. Then just maybe we could get a better handle on this.
Here in the UAE there are 3 grades of fuel available: 91 RON E-Plus (87 US Octane), 95 RON Special (91 US Octane), and 98 RON Super (94 US Octane). My stroker has a SCR of 9.25:1. When I had the Crane 753905 cam, the DCR was 7.86:1 and I ran Special year round. Swapping the stock cam in dropped the DCR to 7.36:1 and I can run E-Plus during the cooler months when daytime temps. are not higher than 85*F. I'm running the stock computer, stock Champion RC12LYC plugs, a Robertshaw 180* t'stat, 3-core radiator, and a Flowkooler water pump.
On the dyno my A/F started at ~14:1 at 1500rpm, gradually decreasing to ~13:1 at 4000rpm, ~12.5:1 at 4500rpm, and ~11.5:1 at 5000rpm. I've got my MAP adjuster set at 5.2v and the A/F ratios at idle/cruise are stoichiometric.
SilverXJ wrote:I cleaned this thread up as best as I could, which I should have done earlier. Play nice and keep it civil.
As for on topic, my stroker has 9.5:1 static and 8.29:1 dynamic, .048" quench. Running the Comp Cam 68-231-4 I was able to run midgrade (didn't get around to try 87), but the AFRs in WOT were very rich, around 10-11:1, far from where they should be for optimum power. It did not ping in WOT with that AFR. Still running midgrade I started to pull fuel out where necessary to get it closer to 12.5-13:1. When I was right around 12.5:1 it started to ping. Filled up with premium and brought it closer to 12.5-13:1 with out ping.
To sum up, I was able to run midgrade with a very rich AFR.
Lets get back on topic.
To the OP. As you can see there are many variables to consider when building an engine. Not just a stroker.
Could you share some of the vehicle specfics, locale, driving style, tuning method, electrical system type, intake and exhaust plans, cat convertor or not. Do you know if your local fuel is blended with MTBE or ethanol ? With this we maybe able to offer some advice.
