MM Z

[The B killer]

I am looking for oversized pistons for my Z. I called Welters and the lady I talked to told me they only have 20 and 40 over now. I have a set of stock domes for it but I dont know how much more power that would give me. Any help or suggestions would be great. Thanks in advance.

 

[KJS]

Let me see I need to do some math here:

You don't say what size of a Z engine it is so I will assume it is the 206 cubic inch.

First you take the engine displacemnt and devide it by 4 for the 4 cylenders

206/4=51.5 ci per cylender.

Next devide that by 5 for the 5 inch stoke to get the surface area of the piston

51.5/5=10.3 sq in

That is how much area the exploding gas gets to put force on. The bigger the area the more it can push down on. The more stroke the engine has the more torque it has. (but thats nothing that can be changed).

The standard piston is a 3 5/8 piston diameter. In decmel form thats 3.625 for standard. Now I will do the math to show you what size of an egnine .040 pistons will give you.

3.625+.040=3.665

3.665/2=1.8325

1.8325*1.8325*3.14=10.54 sq in

10.54*5=52.7 ci

52.7*4=210.8

With .040 size pistons it gives you a 210.8 engine which is rounded up to 211 ci. that was only a 5 ci gain where .020 would only be a 2.5 ci gain.

My opinion is if the .020 and .040 cost nearly the same I would go with the .020 so the engine last longer. If I was gready for power I'd go with the bigger.
When I did my JS3 super I went from std. to .040 only because .020 cost 3 times as much. So that is another thing to look at.

If you want more horse power just turn up the carberator too.

 

[Dieselbear]

Call Wendel Everett 740-922-3335, he will have what you need
Glenn

 

[MM ZAck]

I'm surprised Lois or Sally didn't mention the Jahns pistons they sell. They are 3.81", which means they are 0.185" overbore. They should give you a good power boost (228 cu in).

Also, domed pistons won't work in a Z block with the blind bore. There is a danger of the piston hitting the top of the bore. You might have a set of late R pistons (same bore) with the little domed area on them but they don't have the right pin location and won't work either. Trust me, I looked into those too when I rebuilt my ZA. Oversized Z pistons are tough to find, that's why I went with the Jahns. They work great.

Zack

 

[Roger H MI]

Charlie has good oversize pistons at http://www.external_link.com/ Very good to work with