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bored .040 engine questions

V

vortex

NAXJA Forum User
Location
Chehalis, Wa
Okay so i got a buddy who gave me an entire disassembled '89 4.0 engine. The top of the pistons are stamped .040. So if its a 4.0 bored .040 over what ill the displacement be? What will the approx. HP be?

Second, number 6 (or number 1 cant remember off the top of my head) piston melted in the cylinder ans left some aluminum in the cylinder some where around TDC so im curious what all would be needed to get the cylinder back to good working order....

Now im also curious, would i be able to reuse the other 5 pistons and just buy a new piston to replace the old melted one?

Also since this is my first engine build, Is there anything i should know about the renix? things to use? things to stay away from?

As soon as my camera finishes charging i will take pictures of the cylinder and the pistons.

If there are any questions i would be more than happy to answer them best i can and i am willing to take pictures of anything you guys wanna see.

Thanks y'all in advance!

P.S. this will be going back into and '89 that has a 4.0 now.
 
Last edited:
1. Cylinder diameter X length of stroke X number of cylinders = displacement

You can find the length of the stroke somewhere on google. I'd do this all for you but I'm having enough fun trying to hit the right keys on the keyboard.


2. A machine shop. Depending on the extent of the damage.


3. Could you? Probably. Should you? Hell freakin no.


I'll let one of the Renix guys continue with this... all I know is there's too much vacuum crap on those things for me to have fun with em.
 
Found it.

3.895 in bore
3.414 in stroke

Now add your overbore, change it all to L, and do your math.
 
In order to get the absolute correct displacement you really need to add in the combustion chamber volume as well.
 
Is it the stock crank or is it one from a 258? The 258 crank (commonly used in stroker builds) has a 3.895 stroke. Redo the equation with that and see what ya get.

IIRC, 258 crank with 0.030 overbore will give you a 4.6L... could be wrong though.
 
mcantar18c said:
Is it the stock crank or is it one from a 258? The 258 crank (commonly used in stroker builds) has a 3.895 stroke. Redo the equation with that and see what ya get.

IIRC, 258 crank with 0.030 overbore will give you a 4.6L... could be wrong though.
Click to expand...

You are correct in your thinking.....I came out with a number of 4.75Liters

And what kinda base HP can i find in a 4.6?
 
Numbers vary depending on the build, but the highest I've seen from a 4.6 is 269hp/340ftlbs peak output (IIRC it was built by Hesco). That engine also had an aftermarket cam though.
 
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Actually.....

The distance from the center of the mains to the center of the rod journals will be half the stroke. So... if the distance is around 1.9" its a 258 crank. If that distance is closer to 1.7" its a 4.0 crank.
 
casting numbers....
 
they will be on the counter weights. as for which numbers just google "amc 258 crank numbers" or something similar and you will surely find a chart. thats what i had to do
 
old_man said:
In order to get the absolute correct displacement you really need to add in the combustion chamber volume as well.
Click to expand...

???

Please cite your formula that uses CC volume in calculating displacement.
 
Well i did some research and it turns out i have the 242 crank....so no 4.2 stroker cranks......Damn.....but hey no biggie im sure i can find the crank im a junk yard....

Speaking of which Exactly what did the 258 crank come out of? Ya know the one with 4 counter balences.
 
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