Chris' XJ stroker project

[Chris]

Allright guys, been playing with some more numbers, and I've finally decided to go full bore into this project and spend the extra money...Of course this means it will take longer to complete, and I don't have many patience...lol Here's what I've come up with now.

Bore the block .030 and deck it .030.
Plane head .010
go with the silvolite 2229c pistons and dish them out to 24cc's

With this setup and a .51 HG, it gives me 9.2\:1 CR with .002 better than stock quench.
Or I can go with a .45 HG, and change it to 9.3\:1 CR with .008 better than stock quench.

If someone else runs these numbers, double check my work as I am new to this. Also, is it worth giving up the extra CR for the better quench? Which one is "more important" when it comes to a daily driver driven on 87 octane?

[gradon]

Your #'s are right: 9.2:1 with the .051HG, 9.34:1 with the .043HG. You should be able to run on mid-grade with no problem.

[Chris]

Your #'s are right: 9.2:1 with the .051HG, 9.34:1 with the .043HG. You should be able to run on mid-grade with no problem.

but between the 2, am I better to keep the CR down, or work on getting the quench up?

[seanyb505]

From the research Ive done, getting the quench to around .060"-.040" will help your engine run better than just having a lower CR.

[Flash]

Allright guys, been playing with some more numbers, and I've finally decided to go full bore into this project and spend the extra money...Of course this means it will take longer to complete, and I don't have many patience...lol Here's what I've come up with now.

Bore the block .030 and deck it .030.
Plane head .010
go with the silvolite 2229c pistons and dish them out to 24cc's
With this setup and a .51 HG, it gives me 9.2\:1 CR with .002 better than stock quench.
Or I can go with a .45 HG, and change it to 9.3\:1 CR with .008 better than stock quench.
If someone else runs these numbers, double check my work as I am new to this. Also, is it worth giving up the extra CR for the better quench? Which one is "more important" when it comes to a daily driver driven on 87 octane?

Cris, my self, I would go with .045 HG and dish the piston to 26cc(the silvolites have been dish as high as 30cc before) then you would still be .008 better then stock and you compression ratio would be around 9.1.....a much better chance of running on 87

remember, cleaning the combustion chamber of edges and points that can and will cause point of ignition is as important as compression ratio and quench.
Piston need a good looking over for sharp edges after it has been dish also

Flash

[Diamond-x]

Chris,
Fantastic information concerning quench, CR and lifter shims. I dropped my 4.0 block and head at the shop last week and have been busy running calcs. Not to steal the thread but what CR is acceptable for 87 octane fuel?
Thanks again, great thread.