wiseco pistons

[mattsaks]

i have heard when using wiseco pistons, they need a greater piston to bore clearance than factory pistons. is this true? if so, what clearance do they need?

 

[ozarkjeep]

Re: wiseco pistons

The are forged, and they tend to swell up more when they get hot.<br /><br />they are great pistons if your machinest knows how to set them up, the specifications come with them, and the bores have to be machined correctly! ( yes they usually require a larger clearance to compensate for the size change when hot)<br /><br />and they must be warmed up before the engine gets put under load. ( a couple of minutes)<br /><br />they are much tougher than cast pistons though, and they will stay together instead of crumble if they take a smack. saving from bits of aluminum all thru yoru engine.

 

[mattsaks]

Re: wiseco pistons

can they be used in conjunction with factory pistons? ie two wiseco and one factory or vice versa if you are fixing an issue that didnt affect all cylinders? doesnt sound like such a good idea if they have different properties?

 

[walleyehed]

Re: wiseco pistons

All of the new series Wiseco pistons have been manufactured to fit the std over-bore sizes.<br />For a .020 piston, the block is bored .020 over STD, not .021 as it used to be. The only case I believe you will want to go over, whether it's .020, .030, .040, etc., is if high performance features are incorporated which would generate higher temps.<br />The Wisco expert is Dhadley, but I would recommend going with all pistons of the same manufacturer if possible.

 

[Dhadley]

Re: wiseco pistons

We have run outboard motors with mixed piston manufacturers with no problems at recreational rpms. We ran one V6 crossflow with 4 different brands. There has only been 1 brand piston that truly had manufacturing issues and that brand has been gone a long time.<br /><br />While its true the older 30 series Wiseco outboard pistons (part numbers that begin with 30) were better suited for a larger finished bore the new 31 series (easily identified as an electra coated piston) requires the same finish bore as any cast piston. Each Wiseco piston comes with the finished bore size recommendations.<br /><br />Cylinder and piston apperance will not necessarily be the determining factor as to what will need to be bored. Actual cylinder size will tell. The cylinder can look fine yet be worn past the wear tolerances. Many times the dial bore gauge is the only correct way to know.

 

[mattsaks]

Re: wiseco pistons

ok, thanks. thats what i wanted to hear. a mate has asked me if i can re-build a motor for him that has had a seize and damaged two pistons. i will get it all measured up first but of course he wants to spend as little as possible. perhaps the amount spent will have alot to do with the amount of warranty i put on it!!

 

[Dhadley]

Re: wiseco pistons

How true!!<br /><br />The biggest thing is to figure out what caused the problem with the 2 pistons and get that corrected.<br /><br />Good luck!

 

[mattsaks]

Re: wiseco pistons

Well, i finally got into this job. A lack of oil was the major contributer! Only got as far as the bottom two before it locked up. The top one seems to have got away unscathed. I have convinced him to go oversize on all three with the wisecos. Is there anything i need to look out for?

 

[rodbolt]

Re: wiseco pistons

double check the fuel system. lack of oil usually leave marks on the rod journals before siezure of a piston. why do you suspect lack of oil and what steps are going to be taken to insure it does not happen twice? maybe a year model and horsepower will help

 

[DJ]

Re: wiseco pistons

Agree with Rodbolt. Lack of oil is NOT piston selective. Carburetion can be.

 

[prolinews]

Re: wiseco pistons

I have only rebuilt two OB motors a 89 omc v/6 and a 50 yamaha 3 cylinder . On both motors only had one burnt piston . Being that I from a automotive background (drag cars) I could"nt restrain from a total rebuild . I used the wisecos on both motors . zero problems with the pistons to date .Both motors had cooling problems before the rebuild .

 

[Kiekhaeferscurse]

Re: wiseco pistons

A little off topic but, hoping Dhadley can answer this for me, we have been using the wiseco for a few years now,(v6's) we always noticed that the oil retention grooves were far wider than Mercs pistons, last year wiseco began narrowing the grooves, then all of a sudden, they went back to wider grooves...any ideas why, whats better?<br />Thankyou

 

[mattsaks]

Re: wiseco pistons

It had a big section of air in the oil line. The line feeds into the bottom carb first, then the middle and then the top. It looked to me that the lower ones got no oil first as the bottom piston is the worst. Does this sound reasonable? Or am i barking up the wrong tree?

 

[rodbolt]

Re: wiseco pistons

what type of motor is this ?

 

[Dhadley]

Re: wiseco pistons

As for the oil retention grooves, there are several theories about which is better -- wide, narrow, none, depth etc. On paper I'm sure that every engineer can explain why his idea is best. In the real world we all have seen all styles work (wide, narrow, none).<br /><br />So it basically comes down to cosmetics. Generally folks like the look of the narrow grooves best. In the past Wiseco has copied each OE piston as close as possible. Sometimes to a fault. They have, in the past number of years, begun to deviate from that. The pistons are being produced now with the narrow grooves regardless of what the OE does.

 

[mattsaks]

Re: wiseco pistons

Sorry, Tohatsu 3 cylinder.

 

[Kiekhaeferscurse]

Re: wiseco pistons

I have noticed that the narrow grooves seem to scuff a little more on the major thrust side at the wrist pin boss, but with no ill effects.<br />Thank You Dhadley<br />Mattsaks sorry to butt in on your thread

 

[mattsaks]

Re: wiseco pistons

No worries Kiekhaeferscurse. The pistons arrived for it today so I hope I'm on the right track with my diagnoses!

 

[rodbolt]

Re: wiseco pistons

mattsaks<br /> if you had air in the injection lines check the oil system carefully. some models of tohatsu had an oil filter. make sure all the lines, tank as well as the pump are in good shape. myself I would start it on 25 to one mix while confirming the oil consumption and if the oiling system tests good switch to 50-1 premix for the rest of the breakin. but do confirm the oil system integrity before extended running.

 

[mattsaks]

Re: wiseco pistons

Thanks rodbolt. I will be keeping an eye on the system till there is no air. How can you test the pump? If i spin it by hand oil comes out. Its hardly scientific though. The cause was the filter being cleaned out and the air wasnt bled out of the system afterwards. Nasty. What sort of breakin do you recommend?