Anyone else bother to hand lap the irons on a rebuild? Mine aren't in bad shape, just some very minor (i.e. still in spec) wear, so I decided to pick up some clover compound and do some minor polish.

Anyone else who has done it, any tips, warning, tricks, etc? I worked the first pair (front housing and front surface of center housing) for about half an hour, and I *think* I can tell a difference...of course when talking about .004 in amounts, it's tough to really tell.

Travis
93 R1, 84 GSL-SE, 04 RX-8, 92 F150

 

take it to a shop and have it proffesionally done. while your at it get em re-nitrade coated. or... by the time you do that just buy new irons. just remember ever dollar you skimp on now is going to become a $100 bill later. its hard to bite the bullet and justify spending the extra cash but its the difference between a motor that will get 10k and a motor that will get 60k.

to answer your question, no I never have done it.

 

There are no shops I have been able to find in western Washington that are able or willing to lap the irons. They only have 73k miles on them, and as I said, very minor wear...still within shop manual spec before starting. I'm not going to risk freight damage to still usable irons.

 

Its best to have a shop do it. any machine shop worth a damn should be able to. that being said i know someone who has and it has seemed to work fine... then again thats a "friend-of-a-friend-of-a-friend" story so dont take my word.

now you used the phrase "minor polish" you dont want a polished surface. the surface needs to be rough enough for oil retention to occur.

 

I had the same thought that any machine shop should be able to do it...but like nearly everything else on these cars, as soon as I say the "rotary" word, they balk and say they can't do it. After spending a couple weekends calling machine shops in the area, I gave up, and ordered the compound to do it myself.

 

Leave them alone. Your're just going to scratch off the nitriding. If you want your engine to last, don't overheat it or detonate it.

 

this is a stupid question, what are these "irons" in question?

 

^The plates with the intake ports are sometimes called "irons" because they are made of cast iron.

I remember reading on here how theysend them down with a DA (palm sander) with Keroseen. But i don't remember what grit. Plenty of people "resurface" or "lapp" them at home with no problems. But many more **** the plates up by doing it wrong.

 

We don't deal with lapped irons at my shop..... we either use in-spec ones or have the customer buy new ones.

I've seen an extreme instance of an engine where a guy paid for 'professional lapping' and they took off enough material that the coolant o-ring grooves weren't deep enough and it led to immediate engine failure.

No thanks.

 

I have opened a few motors that have been sitting for a while and have crap or slight rust on the surface. The most i do is use a 1000 grit with some WD40 to clean it up. Nothing more. I think your only allowed like .003" anyways. And its to easy to go past that and destroy a plate.

 

"Leave them alone. Your're just going to scratch off the nitriding. If you want your engine to last, don't overheat it or detonate it."

exactly.

"We don't deal with lapped irons at my shop"

exactly...

howard

 

The nitrate coating is .002"-.003" deep. You could try hand lapping them with another plate with a valve lapping solution but it would take HOURS.

IMO, if they're within spec reuse them. If you want perfect irons sell them and buy new ones...

 

re-nitride it

 

http://www.nopistons.com/forums/topi...1&#entry927810


i did this and it turned out great. it actually isn't meant for lapping to get within tolerances though and i don't think would ever work for that. It is to make a good unpolished surface for the side seals to ride so that they wear better and the irons retain oil on the surface. i have pictures and the results were sexy but i'm way too lazy right now to find my camera cord and upload them.

 

^ I wholeheartedly agree with Lynn Hanover's process. Wish I'd have known this in the past, this is a REALLY nice way to get a good finish on the irons.

Lapping just isn't worth it.

Dale

 

Anything written by Lynn Hanover refering to rotary is golden. Take anything he says and just do it...

 

Amen to that

 

AZRR does proper iron lapping, mine where done when my engine was built.

 

Any lapping grinding place can do it, but that's not the issue, telling them exactly what to do is the issue. I've seen people take their plates to get lapped and have had ten thou removed because they felt they have to remove wear marks. Afterwards I told them congratulations, you now can throw all three plates away! All because they had a buddy who could do it cheaper than we do. God only knows what your customer told them to do.

~S~