Bore materials: Steel vs Nikasil (or chrome)
Bore materials: Steel vs Nikasil (or chrome) A post about the Lt5 Engine Got me thinking about this the other day.
I know of several advantages of nikasil bore VS a standard steel bore-
Better Heat transfer into the block, due to not having steel to travel through
Less piston/ring friction
Less wear
better high rpm durability with tighter tolerances
Is there more good things that a hard coating could do for an engine that I am missing? What if any reasons are there that people arent using this to their advantage? Why isnt GM interested in this? seems like the Piston slap issue could be overcome by using a cylinder coating instead of the band aid fix that was done with the LS6 pistons. As a bonus we might get a little more HP out of the same Head/cam combos, IMO.
I know of several advantages of nikasil bore VS a standard steel bore-
Better Heat transfer into the block, due to not having steel to travel through
Less piston/ring friction
Less wear
better high rpm durability with tighter tolerances
Is there more good things that a hard coating could do for an engine that I am missing? What if any reasons are there that people arent using this to their advantage? Why isnt GM interested in this? seems like the Piston slap issue could be overcome by using a cylinder coating instead of the band aid fix that was done with the LS6 pistons. As a bonus we might get a little more HP out of the same Head/cam combos, IMO.
Launching!
Joined: Jun 2005
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From: longview, tx
Better heat transfer isn't always a good thing. Good for cooling, naturally, but not power. Aluminum wicks power from the combustion chamber and top of cyclinders since it transfers heat so quickly. I would think that it would be cheaper to produce a nickasiled block than a sleeved one though, if you were starting from a scratch design.
Teching In
Joined: Nov 2003
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From: Cheraw, SC
Nikasil linings are also harder to get the rings to seat into. There are many honing steps that must be followed as well as a break in procedure in order to get the rings to seal up properly. This takes time which costs money like Ben R said.
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Launching!
Joined: Jun 2005
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From: longview, tx
Almost all sportbike engines are nikasiled. I had one of mine bored and recoated. I've never heard of any particular breakin for a coated bore. Most people drive em like they stole em and I've yet to hear of a coating failure. I'm pretty sure the japs like them cause they must be saving them money otherwise I don't see much reason for them to switch. I think it also lets them stack the bores a tad tighter.
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On The Tree
Joined: Feb 2005
Posts: 178
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From: Odessa, TX
Nicasil is an expensive process no matter how it is done. I have a Pro Stock Truck engine that had it done. The original process was done on a block itself, but if damaged you had to send the block back to the coater to get recoated (time). Then they started sleeving the blocks with liners. Then again expensive, special 3/8 head studs were used along with the liners. We bought our liners from an individual when the trucks died. He told us he had to buy a large amount of the cylinders to get them (10+ sets). There are not many more gains to be had other than the ones you mentioned. I've seen these motors make 50 passes with 1000+ hp (358) and have zero wear. The only reason to teardown was to replace the rods. I know nothing of the bearkin procedure as described above, if you have more info I would like to know more. Also your average machine shop can not even hone these type cylinders. You must hone them with diamonds. My Sunnen CV616 with a very rough stone max to 80% load just breaks the glaze.
Originally Posted by gun5l1ng3r
What is a Merc 2.5 EFI SS, a 2.5HP motor or a 2.5 Liter motor? And that must be some cracy computer to know when a motor is borken in!
my 2.5EFI is a little more basic, it measures air and throttle position, but no tattle tale on me when I run it WFO at 8000rpm untill the tank goes dry
Ahhhhhhh, Another Merc guy.. I had 2 of them. The above mentioned Short Shaft and an Offshore.
I car at 150 mph is NOTHING like a 20' bass boat at 100...
Back to the topic though... yeah, the repair costs are higher but the engines would last longer at a higher rpm for a longer time as stated above.
jmho
I car at 150 mph is NOTHING like a 20' bass boat at 100...
Back to the topic though... yeah, the repair costs are higher but the engines would last longer at a higher rpm for a longer time as stated above.
jmho
TECH Fanatic
Joined: Aug 2005
Posts: 1,691
Likes: 1
From: Sunny London, UK
Nikasil is nice when it doesnt degrade!
Do some searching on XJ8 V8 Nikasil issues or BMW issues and you will see plenty. Basically dodgy gas with higher than normal sulphur content will degrade the coating and the next thing you know you have iron rings ripping away at your now aluminium bore. Not nice.
The Jag fix was to fit Steel bore liners.. My XJ8 appeared to have died in this manner. Life on average is 100K Miles before death. Jag replaced many under warranty.
I for one am glad my bores are Iron. GM isnt cutting edge, but by heck they are reliable in the main.
Richard
Do some searching on XJ8 V8 Nikasil issues or BMW issues and you will see plenty. Basically dodgy gas with higher than normal sulphur content will degrade the coating and the next thing you know you have iron rings ripping away at your now aluminium bore. Not nice.
The Jag fix was to fit Steel bore liners.. My XJ8 appeared to have died in this manner. Life on average is 100K Miles before death. Jag replaced many under warranty.
I for one am glad my bores are Iron. GM isnt cutting edge, but by heck they are reliable in the main.
Richard
So wat would the benefits of this in say a BBC drag motor running up to 7500-8000 RPMS? Less drag? Also if anything would happen to break would this coating be more forgiving (ex. little pieces wouldnt tear up the bore). Anyone really use this on a drag setup? I know people are using coatings on cams, piston skirts, and cranks. But I think that is a different coating
Nikasil is used in almost all racing dirt bike engines at this point (not used on trail bikes for the most part). It is extremely durable, and requires no significant break in. The single biggest advantage is its wear resistance, however if you do nick it (think piston explosion)you do have to send the cylinder in to be redone. The other big advantage is a thinner cylinder wall, promoting more even expansion, rounder bores, thereby improving sealing and wear.
Originally Posted by fastbasser
Ahhhhhhh, Another Merc guy.. I had 2 of them. The above mentioned Short Shaft and an Offshore.
I car at 150 mph is NOTHING like a 20' bass boat at 100...
Back to the topic though... yeah, the repair costs are higher but the engines would last longer at a higher rpm for a longer time as stated above.
jmho
I car at 150 mph is NOTHING like a 20' bass boat at 100...
Back to the topic though... yeah, the repair costs are higher but the engines would last longer at a higher rpm for a longer time as stated above.
jmho
Mint.
Originally Posted by BAD *** TA WS6
So are you the guy on Scream and Fly with "Bullet" the retardedly fast bass boat?
Mint.
Mint.
I miss the thrill of the wild "water rides". Left Sacandaga Lake this morn. Was lookin out and wishin I was ripping across the lake. 
The new toy takes some of the pain away!!
Teching In
Joined: Oct 2005
Posts: 19
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From: Austin tx and Daytona FL.
JUST a thought, GM invented the process in the 60s, the early chevy VEGAS had hi-silicone bores, and if you took care they worked out well, also I owned a 427" aluminum big block that had no sleeves, again silicone aluminum bores drag raced the hell out of it, overheated to many times to count, finally scored the bores, bored it and sleeved it , filled it with concrete, still turned it 8000 a bunch of times. but I do believe the newer nikasil process works well, I know that some HONDA uses blocks diecast with a mix of carbon fiber and aluminum that are 15% lighter than just aluminum and hi-silicone bores. anyway nothing is new, GM has a good track record on a lot of ideas that are lost in antiquity, shame on the bean counters. RON