So here's the story....this is my B20VTEC that I had built for me last year. I only managed to get 4,000KM out of it. Never ran it that hard, it only saw 8,000RPM a few times. It was running ok (no top end, a cam timing issue), but smoked a lot towards the end. We tore it down thinking it was a blown head gasket, but it turned out to be a cracked sleve. Here's some pics of it after I tore it down this weekend. Basically, I was wondering about the wear on the front and back of the cylinder walls and on the pistons. Is that much wear normal? Especially considering that I can still see the cross hatching on the rest of the cylinders. I was expecting to find scratches on the sides of the pistons where the crack might have contacted it, but didn't find any.

I guess what I want to know is if I can salvage these pistons. I can get another block to bore out and get new rings, but I've got a different plan if the pistons are toast.

PS, anyone have any theories on what happened to it?

Thanks in advance.

Cracks down cylinders 1&2


Cracks dwon cylinders 3&4


Wear in cylinders 1&2


Wear in cylinders 3&4


Side of piston 4


Top of piston 4 (a little rich? hehe)


Back of piston 2


Front of piston 2


All of the pistons (wear patter is consistant)

 

I'd reuse those pistons, just with new rings. Boost?

 

detonation from a shitty tune

 

Are the pistons standard bore?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PURPLETERROR &raquo;</TD></TR><TR><TD CLASS="quote">detonation from a shitty tune</TD></TR></TABLE>

pistons scuffed the wall

can u feel any of the wear with ur fingernail on the pisston?

i dont think id reuse them, but ive never tried to reuse scuffed forged internals

 

i wouldnt reuse them, and also, a b20/vtec isnt meant to rev to 8k and be beatin on like that of say a gsr motor.. Looks like exteme piston-wall side loading due to high revs, and small r/s ratio. Time for a rebuild.. Sleeve it, get some new pistons. etc. Im not sure what caused the cracks, its prob a combination of heat, side loading and other variables..

 

They look good besides the scuff on the skirt of the piston. You can clean the tops of the pistons easy, but as far as reusing them, thats up to you.

 

everyone is so worried about the rod to stroke ratio of these motors and ls/vtec's if u look at a gsr it is 1.57 and b20 and ls are 1.54 so if it is a bad rod to stroke ratio so is a gsr its only .03 better.


i would reuse them they seem alright just throw on some new rings and u should be good to go if u are really questioning it take em to a engine builder and ask him

good luck

 

scotch brite will do wonders on those skirts

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JH4DC4-2GSR &raquo;</TD></TR><TR><TD CLASS="quote">i wouldnt reuse them, and also, a b20/vtec isnt meant to rev to 8k and be beatin on like that of say a gsr motor.. Looks like exteme piston-wall side loading due to high revs, and small r/s ratio. Time for a rebuild.. Sleeve it, get some new pistons. etc. Im not sure what caused the cracks, its prob a combination of heat, side loading and other variables.. </TD></TR></TABLE>

It's OK with a proper build and tune (and knowing the condition of the block before hand). Here's a B20VTEC with over 250 dyno pulls and running to 8700 rpm.

https://honda-tech.com/zerothread?id=1267136

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JH4DC4-2GSR &raquo;</TD></TR><TR><TD CLASS="quote">i wouldnt reuse them, and also, a b20/vtec isnt meant to rev to 8k </TD></TR></TABLE>

Thats not what I'm hearing

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JH4DC4-2GSR &raquo;</TD></TR><TR><TD CLASS="quote"> also, a b20/vtec isnt meant to rev to 8k </TD></TR></TABLE>


How so?

 

Im sorry,but im just not a big fan of ls/vtec, or w/e u want to call it.

If honda made the redline of the ls 6800, its not meant to rev to 8200 now is it?

Check out the rod bolts? Weak..

Yet i didnt say they cant rev to 8k, with a proper build, they can. Hell they can even without, but longevity is the issue then. Yes, the head can take it, but can the block is the ?

also , reconditioning the side skirts with any type of material, removes some of the piston material, causing less ptw clearance. You should have this checked, and if it is not within spec, toss em..

Im **** about builds, i want EVERYTHING in honda spec. Thats just me, but do whatever you would like..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JH4DC4-2GSR &raquo;</TD></TR><TR><TD CLASS="quote">Im sorry,but im just not a big fan of ls/vtec, or w/e u want to call it.

If honda made the redline of the ls 6800, its not meant to rev to 8200 now is it?

Check out the rod bolts? Weak..

Yet i didnt say they cant rev to 8k, with a proper build, they can. Hell they can even without, but longevity is the issue then. Yes, the head can take it, but can the block is the ?

</TD></TR></TABLE>


Ok I think we are on the same level here. I agree with you.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JH4DC4-2GSR &raquo;</TD></TR><TR><TD CLASS="quote">Im sorry,but im just not a big fan of ls/vtec, or w/e u want to call it.

If honda made the redline of the ls 6800, its not meant to rev to 8200 now is it?

Check out the rod bolts? Weak..

Yet i didnt say they cant rev to 8k, with a proper build, they can. Hell they can even without, but longevity is the issue then. Yes, the head can take it, but can the block is the ?

also , reconditioning the side skirts with any type of material, removes some of the piston material, causing less ptw clearance. You should have this checked, and if it is not within spec, toss em..

Im **** about builds, i want EVERYTHING in honda spec. Thats just me, but do whatever you would like..</TD></TR></TABLE>

Like it matters what the stock rod bolts look like. There are plenty of motors w/**** rod bolts that get up there in the revs w/arp hardware. Thats no sign that the block is a POS, its made out of the same aluminum every other honda block is made out of.
Removing material from the piston skirts will increase clearance, not decrease...

When building a motor you don't just have your block honed and then see if the piston to wall clearance will magically be within the piston manufacturers specs.

You could re-shape those skirts and re-use them without a problem - just measure the diameter and add the amount of clearence suggested by the manufacturer and have the block honed to that certain size.

Thats good that you want everything built to honda spec, I just hope you do that with honda parts rather than aftermarket forged pistons.
I'm just glad you don't build any of my motors :x

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bigjdog84 &raquo;</TD></TR><TR><TD CLASS="quote">

Like it matters what the stock rod bolts look like. There are plenty of motors w/**** rod bolts that get up there in the revs w/arp hardware. Thats no sign that the block is a POS, its made out of the same aluminum every other honda block is made out of.
Removing material from the piston skirts will increase clearance, not decrease...

When building a motor you don't just have your block honed and then see if the piston to wall clearance will magically be within the piston manufacturers specs.

You could re-shape those skirts and re-use them without a problem - just measure the diameter and add the amount of clearence suggested by the manufacturer and have the block honed to that certain size.

Thats good that you want everything built to honda spec, I just hope you do that with honda parts rather than aftermarket forged pistons.
I'm just glad you don't build any of my motors :x </TD></TR></TABLE>

Sorry im not a genius like you, and get everything right. And yes i go by honda spec FOR HONDA, pistons..

And yes, you know wtf i meant from ptw clearance.. So no need to nit pick here.

Some knowledge of piston-wall clearance -
you can run tighter piston to walls with high silicon content oem pistons than aftermarket ones but those numbers look to be much tighter than what I know (but then again, I don't do this for a living to know off the top of my head each piston manufacturer's piston to wall clearances)...

they will vary with each company including Honda.

for example according to JE/SRP pistons , 2618 aluminum alloy (softer, less silicon, more expansion when heated up ) vs. 4032 alloy (harder, more silicon in alloy, less expansion) forged pistons run completely different piston to wall clearances. 2618 expands 15% more than 4032 alloy.

4032 approximates OEM clearances in the 2.0-2.5 thou clearance range whereas 2618's run 3-4 thou.

btw if the piston to walls are too tight the piston will expand into the wall and load the rings harder. the rings will be the first thing to go and usually crack.

if the piston to wall is too big, the engine will smoke (lots of blow-by).

OEM Honda piston to wall clearances with high silicon content cast pistons are in the ballpark of 0.0012-0.0016 in. (1.2-1.6 thou) which are less than the aluminum alloy forged aftermarket ones.

what I have never understood is the fact that the rate of expansion of the cylinder wall material (usually a different alloy or metal than the piston) is different than the rate of expansion of the piston. So the clearance you measure at 78 degrees F may not be the actual clearance when the engine is hot while running.

I guess they correlate the numbers in the "colder" measurement with actual seal numbers when hot...analogous to valve adjustments in the cold

No **** you dont just bore/hone the block and hope your ptw will be within spec.. Blueprinting is what should be done, and thats what i do.. I ended up with a ptw of .0010 well within HONDA SPEC, for HONDA pistons.

I dont even want to argue about stock rod bolts, id you dont believe that these are a very very weak part in a high revving motor, thats your problem..

Cheers!

 

When I said that about the rod bolts I meant that there are alot of motors that have garbage rod bolts from the factory. These motors are then taken and built w/larger rods and arp bolts. Then people rev the **** out of them. Just because it came from the factory with weak rod bolts doesn't mean that the block itself can't take revs (what you implied in your first post).
But getting back on topic. Re-use those pistons and pay for some good machine work. Your piston to wall clearance was probably incorrect, but more than likely didn't lead to your cylinder walls cracking : /. Those are some really nasty cracks. Was the block checked for cracks before assembly? It either had a crack in it previously or it was a REALLY bad tune that was pushed too hard.
Later/joe

 

go here

https://honda-tech.com/zerothread?id=1271544

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by JH4DC4-2GSR &raquo;</TD></TR><TR><TD CLASS="quote">Im sorry,but im just not a big fan of ls/vtec, or w/e u want to call it.

If honda made the redline of the ls 6800, its not meant to rev to 8200 now is it?

Check out the rod bolts? Weak..

Im **** about builds, i want EVERYTHING in honda spec. Thats just me, but do whatever you would like..</TD></TR></TABLE>

I think you are missing a few important ideas here.

1). The LS/B20 redline is 7,200, not 6,800. 8,000rpms is a mere 800 rpms highere
2). The weakness of high rpms comes from the LS head more then it does the block
3). There would be no need to put larger/stronger rod bolts in something Honda doesn't think will ever see the stress levels that dictates they are needed
4). If you are so "Honda ****" then you wouldn't ever be dicking with an LS/Vtec or B20/Vtec. So why are you arguing?

I don't like Ls/Vtec's or B20/Vtecs. I am not sticking up for them. I just think its gay sometimes when people argue things without looking at the whole picture. You never once stated that a B20 wasn't designed to rev to 8k, in which I would agree. You did however say that B20/Vtec aren't made to rev to 8k, in which I would partially agree. It has more or less to do with the build, as has already been stated. Even the ones left "stock" can last for quite a while at those load levels. Quit preaching r/s ratios also. Engines ran for decades back in the 60's before anyone cared about r/s ratios and they made craploads of power and saw over 7,000rpms with v8's in those times.

 

Do all the rings spin freely while in their ring land. If so, the pistons are probably ok. Just replace the rings. If you look at a B20 funny, it will crack on you for no reason. Just a weak block.

 

Thanks for the comments everyone. I wasn't expecting this to turn in to an LS/VTEC debate, but it's interesting to read everyone's opinions.

Here's some more background on the build:
The pisons are JD 11.5:1 pistons (84.5mm)
The rods are Crower H-Beams (rod bolts shouldn't be an issue with these)
The entire engine was rebuilt (The block was cleaned and checked out before any work was done. The bores were done to JE specs.)
The bottom end was all balanced

The engine was running rich for a while and the rings never really seated properly. I was told that this was an issue with the JE rings....basically that they take longer to break in.

The car never made any power after 6,000, but had lots of bottom end. I was told this was because my Crane stage 3 cams were set at 0 degrees. As a result, it was rarely pushed past that.

The concensus seems to be that the pistons should still be good. Just need new rings (obviously)

I'm just going to clean them up and sell them off along with all the other parts. I just got a deal I can't refuse on a B18C5, so I'm going to use that for my next build.

Is it safe to say that this looks like a tuning issue and not a machining issue? Either way, I'm very dissapointed with this build and don't really want to let the same tuner touch my next engine.

Thanks again everyone.

 

Judging by the pics, looks like the pistons can still be used. You could always send them in to Top Gun Coatings and have them ceramic coated to ensure smooth skirts, reduce friction, and temp slightly.