yet another build formula

[mcart]

Okay, another rookie signs on... I have been reviewing to this site for awhile now, so
I joined up and am ready to ask some questions so bear with me. I am looking for a stroker build formula that includes reusing the 4.0 liter stock pistons with a 258 crank and rods, I have not been able to locate this formula, can anyone steer me in the right direction? I see comments hear and there about this, but has anyone successfully reused stock pistons? thanks for the help

[RenoF250]

Does not sound like a great idea as it will not allow you to bore the block. I suppose you can just hone it but reusing the old pistons is only going to save you $200 which is not much compared to what you are paying for everything else.

[SilverXJ]

x2. I would recommend boring the block to the smallest over size accounting for wear. The pistons and rings will be traveling on unused portions of the cylinder walls that do not have wear not to mention the wear already present.

[Cheromaniac]

Okay, another rookie signs on... I have been reviewing to this site for awhile now, so
I joined up and am ready to ask some questions so bear with me. I am looking for a stroker build formula that includes reusing the 4.0 liter stock pistons with a 258 crank and rods, I have not been able to locate this formula, can anyone steer me in the right direction? I see comments hear and there about this, but has anyone successfully reused stock pistons? thanks for the help

I used to have a recipe on my site where the stock pistons were reused together with the 258 crank & rods (4.5L simple stroker) but I removed it a long time ago since most 4.0L engines now have pretty high mileages on them (the newest are 8 years old) and it's inadviseable to reuse stock pistons in high mileage bores.
Check out the other recipes on my site and see which one most closely fits your requirements.

[mcart]

Thank you for your replies. A common theme from all answers centered on the condition of the block and bores. I would rather not bore if not required. The block I am using is a 2001 in what appears to be excellent shape as the cross hatch is plainly still visible. It seems to me that my first move is to move the block to the machine shop and check the block and bores for condition. Depending on what the shop finds, that would make the decision on which piston to use very easy... does that sound reasonable?
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[RenoF250]

Thank you for your replies. A common theme from all answers centered on the condition of the block and bores. I would rather not bore if not required. The block I am using is a 2001 in what appears to be excellent shape as the cross hatch is plainly still visible. It seems to me that my first move is to move the block to the machine shop and check the block and bores for condition. Depending on what the shop finds, that would make the decision on which piston to use very easy... does that sound reasonable?
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If you are into re-using pistons. I think most of us are not. Aluminum has no fatigue limit and those pistons have taken a fair amount of stress so they are more likely to crack etc. Cost wise it just does not seem worth it to me personally. I would just run it as a 4.0.

[mcart]

I understand your point . Back to stroker basics for me.

[Cheromaniac]

Thank you for your replies. A common theme from all answers centered on the condition of the block and bores. I would rather not bore if not required. The block I am using is a 2001 in what appears to be excellent shape as the cross hatch is plainly still visible. It seems to me that my first move is to move the block to the machine shop and check the block and bores for condition. Depending on what the shop finds, that would make the decision on which piston to use very easy... does that sound reasonable?
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I still think it's a bad idea to reuse the stock pistons in a stroker build. The block & pistons are 13 years old so if you elect not to rebore the cylinders and reuse the stock pistons, you're effectively going to start off with a 13-year-old engine that'll have a reduced lifespan. Piston ring/bore seal will be less than perfect and you'd be risking having excessive oil consumption, so is it worth cutting corners just for the sake of saving a little dinero?

[jeepxj3]

Getting beyond the used piston is a bad idea notion...Your build formula will come up short.
If I got the numbers correct-

258 crank is 3.895", /2= 1.945"
258 rods are 5.875"
stock 4.0 pistons have pin height 1.601"

All adds up to 9.421" and the stock deck is 9.453", so your pistons will be 0.032" down the bore.
With a 0.043" head gasket, your Quench is 0.075", that is a lot, even more than stock 4.0L.

You could live with the Quench of 0.075", not recommended
You could deck the block 0.025"-0.035", $$
You could find custom rods 5.900"-5.910", $$$$
You could find custom new pistons with a longer pin height 1.624"-1.634", $$$$

Or you could use one of the 'recommended' formulas for a stroker build.

[Cheromaniac]

Getting beyond the used piston is a bad idea notion...Your build formula will come up short.
If I got the numbers correct-

258 crank is 3.895", /2= 1.947"
258 rods are 5.875"
stock 4.0 pistons have pin height 1.601"

All adds up to 9.423" and the stock deck is 9.453", so your pistons will be 0.030" down the bore.
With a 0.043" head gasket, your Quench is 0.073", that is the same as a stock 4.0L (higher than is desirable).

The biggest issue is that the SCR will be 9.9:1 (assuming 57cc head chambers) so it would be quite a challenge to prevent the engine from pinging even with 93 octane gas.

[jeepxj3]

Thanks for my division correction. It was early.

[mcart]

The math doesn't lie and a SCR of 9.9 is unacceptable. I appreciate the candor and experience of this site... a review of tried and true formulas is in my near future. Thank you

[str8-6]

I've done that:stock reused 4.0 pistons,258 rods and a heavy 12 weight 258 crank.
Heard and read different numbers about compression in that combination some say it will end up at 9.5,9.6 and some say 9.7 and now Dino says 9.9 soooo since i thrust on Dino's words I suppose that is what I got, I can't do the math's even if my life depended on it so I just check my compression the old and probably wrong way: I'll use my old comp-meter and cranks the engine... Results are "12-ish" on all cylinders except one that I didn't check since my ignitionsystem told me not to

"pulled the ign.-cable from the 48000 V coil to the distributor,wifey operated the cranking and me holding the comp-tester to the #3 cylinder,coil just to the left... Wifey said it looked awesome when a spark from the coil jumped 3 inches from the coil to my hand...ithcy feeling..."

Oh well if the comp-ratio is 9.9 static i will live whit that...ignition set at 37 deg. at 5500 rpm 24 at 1000 and no pinging,had it at 39 deg. earlier but the it pinged a bit on 95 octane. (Ron) If I use 98 ron it won't ping with the timing set at 40 degrees.
"Not hearing it anyways so I'm happy with that"

Planning on shaving the head 0.020-0.030 on the next head that I'm in progress of porting right now,"need more power" wonders what C/R that will leave me with?

[mcart]

If you shave the head, won't that raise your compression ratio even more ? how does shaving shaving the head equate to more power? compression gauges are rated in pounds, correct? did you mean that you are getting 120 PSI on the gauge? lots of questions today...