Stroker plans for a HO

[3XJFamily]

I've got a 91 HO that is getting tired, and needs to be replaced, also facing emissions testing starting here. Working with a friend who suggested we rebuild, and do a few performance modifications to the 4.0 My objectives for this Daily Driver: Dependability and reliability, I do not want to spend a bunch of time and $ getting an engine dialed in and running properly. MUST run regular 87 octane fuel.

I'm thinking about using Dino's 4.6L Low-buck, low 8.8 CR "rockcrawler" recipe

Or going with the "kit" from speed-o-motive with 9.0 CR special cast pistons
http://www.speedomotive.com/jeep_4.htm

I know there are a lot more issues with pre-detonation than compression ratio - Is running regular fuel possible on a stroker? Especially with a HO engine? Anyone with experience?

 

[Dr. Dyno]

I know there are a lot more issues with pre-detonation than compression ratio - Is running regular fuel possible on a stroker? Especially with a HO engine? Anyone with experience?

I don't have any experience running 87 or 89 octane because where I live, there's only 91 octane available. Nevertheless, my stroker doesn't ping on 91 and this is the time of year (mid-summer, 115*F outside) when it would be most likely to, so if you copy my stroker you should at least be able to run 89.
___________________________
Dino's "Mean Green Machine"
1992 XJ Laredo 4-dr - 13k miles on 4.6L HO Stroker AX15, NP231, D35c, D30

265hp@4900/325lbft@3500, 1/4 mile = [email protected], 0-60 = 5.5secs
Websites - Jeep 4.0 Performance, 4.6L Stroker Build-Up, Dino's Jeep Tricks

 

[MrShoeBoy]

If you want to run on pump gas get a set of custom pistons to keep the CR ratio under 9.0:1. I have a 9.5cr ratio in my stroker and I can get away with 89 octane but I have an Apexi SAFC that allows me to adjust the fuel curve to adjust for the cheaper fuel. For comparison I dyno'd my stroker and tuned it with premium I vary off the stock fuel curve plus or minus 5%, with 89 octane I have to run it up as high as 10 and 12%. So basically if you want to run cheap gas buy an air fuel controler (expensive) like the Apexi so you can tune the fuel curve or keep the CR ratio low.

AARON

 

[old_man]

I took the route of controlling the quench height. I am running the H803CP pistions and decked the block .030". That coupled with the Mopar performance thin head gasket made it so that I can run even the cheapest gas with no ping. My CR is 9.6 if I remember right.

 

[3XJFamily]

Dino's stroker recipe for the 4.6L Low-buck, low CR "rockcrawler" gives a 8.8:1 CR and 0.058" quench height which after alot of searching on various forums, it appears it will run fine on 87 octane.

How to go about "Increasing piston dish volume to 30cc on the Keith-Black Silvolite UEM-2229 +0.030" bore pistons"? Any idea typical cost?

Also, my engine had a cheap rebuild compliments of the previous owner,if I bore it further (40 or 60), what will this do to the "recipe" ?

Thanks for all the info. I really need a working recipe to follow.

 

[Dr. Dyno]

A larger bore will have minimal effect on the recipe, and the Silvolite pistons have plenty of meat to allow them to be milled. A competent machine shop should be able to do that for you. All you need to do is deepen the piston dish by a further 0.100".