If the standard BORE Inner Diameter is within spec, and the standard PISTON SKIRT Outer Diameter is within spec, but the piston-to-bore clearance exceeds the 0.0014" limit, can I only replace that piston with an oversize new one to compensate, without re-boring, and without touching the other holes?

 

this should probably be in the all-motor section

 

Here's what confuses me, the guy says he hot tanked it then measured the clearances, then he honed it. Then he calls me and tells me that the clearance is off by 4 thou, so it needs to be re-bored. But WHY would he hone it and charge me $60.00 if he knew the pistons were un-usable, as now I have to pay for the re-bore on top of the honing, which the honing will just be wiped out once they re-bore.

Very confusing.

 

HUH? - mutually exclusive IMO

FSM EM94 ............ these things run in pairs based on "grade 1,2 or 3" - what did you start with that was "in spec"?

 

Both are in spec but there is a 0.0079" wear limit that exceeds the spec so the clearance can then be off.

 

I still don't get it.

What combination ito those grades did you have that was "in spec"? - if you had any combo of piston and barrel spec "in spec" (as per those grades) you cannot possibly have exceeded a wear limit

 

did you pick a shadetree shop? or a big-name shop? that can make a difference in terms of a) their skills and b) their honesty

 

you usually can't tell if the block needs to be rebored until you hone it and take measurements. usually there's a lip at the top from old ring wear that must first be removed, then they will 'dingle ball' hone the block to remove the scratch marks and prep the surface.
Only then can they get a true measure of the bore and determine if it needs to be bored out or not.

If you're at 0.004" over already, you're halfway to the next size OEM piston. at 87.25mm

 

It's not the grades, it's the piston-to-bore clearance that can be off, even though one of the other 2 is within spec, for that specific piston grade. Because at the upper limit of the bore I.D., there is lee way to the maximum wear limit - although it's within UP TO the maximum, it will then throw off the piston-to-bore clearance becasue the gap exceeds 0.0014".

I'll re-measure tommorow when I pick it up, I'm taking it to another shop, I'd rather pay the original 2 gino's that I was going to go with.

 

This shop was marketed pretty good, they've been in business for 35 yrs, and the guy seems pretty competent, but it does seem a little sketchy in that building when I actually arrived. It's really tucked away in some industrial wasteland area.

They have some lifts and this sketchy looking mechanic doing something on an old car and he was smoking a Alfred Hitchcock pipe. I was really only using it for the hot tank and honing, so I figured - chance it.

 

By the way what does this mean matt - for the Piston Ring Set:

1.5x1.5x2.8

This is the one I ordered - and will it fit the .50MM oversize piston's I have access to new? I don't have access to the 0.25MM oversize. pistons, so I need to go for the 0.50MM ones.

OH ****E - does this mean I have to REPLACE the radiator, if I move to the 0.50MM oversize, because the OEM radiator might not be able to handle the added heat?

 

I must surely be daft then.

What did you measure that originally was "within" spec as per your first post? - this is what I don't get.

Its absolutely no use trying to get to a "new state" 1.4"" piston to bore gap with additional honing on a worn motor if your wear limit on the bore is already (?) approaching 7.9"" - it simply cannot be done - why would you even have considered only honing it if that is what you already knew?

Matt is 100% correct about the rebuild procedure to be followed, but I am struggling to understand why the net result you now have is so confusing to you.

 

4"" off from what? - the std "new" condition spec of 1.4""? ...................... if so then what the heck are you doing with looking at a 2nd oversize rebore and set of pistons? - you are still way within the 7.9"" wear spec of the bore.


Reuse the current std pistons and fit a new set of rings and BOB's surely your uncle - no?

 

I'm not sure what your asking bud - but I think I have it all resolved right now. My only concern is the radiator though.

I'm definately picking up the block to bring it to another shop tommorow though, or i take it to the shop of my machinist friend's friend. I need to get a move on though, it's already getting cold in Canada now, and i'm running out of time....im such a procrastinator some times.

 

He's claiming that the piston-to-bore clearance is 0.004" on one or more of the holes. He claims that I shouldn't exceed 2 thou. The actual limit for the VG30E is 0.0014"

I'll re-measure myself tommorow when I get it home and see what's up.

 

This is exactly what I don't get from all the "facts" you posted here - IMO there is absolutely no need to rebore when the honed bore to piston clearance is close on 4"" within the max wear limit of 7.9"" for the bore spec as per FSM .................... and even less a need to rebore to a 2nd oversize if that block is still in such good condition unless you have money to waste

EM94 FSM says the assembled std piston to bore gap should be 1.4"" ....................... it doesn't spec the "worn engine gap between the bore and piston" because there can be no such measurement other than the max wear limit for the bore which happens to be given as 7.9"". You cannot possibly strive for a 1.4"" piston to bore gap on anything other than a brand new engine with absolutely no wear on any component

 

Let's see after I measure it. I'll post the results. He says he can just knurl the pistons (after I told him I don't want to pay him any more than the original $90.00 for hot tank and hone) ...but as far as I know it's just a band-aid.

 

IMO you need to get the honed block and FSM to a reputable machinist that can read and not suggest arbitrary thumb-suck (however close) specs for rebuild criteria on a piece of machinery that IMO is still in a pretty good state of wear given its mileage.

 

Ya that's why I think i'm going to take it to my machinist friend's friend, who he worked with for 15 yrs, and i'll print out the specs. Only reason why I didn't go to him in the first place is because he didn't have the caustic tank, he used some biodegradable friendly environment stuff - which I wanted the absolute worst corrosive nasty for the environment stuff. Supposedly from calling around, about half the shops in Toronto still use the caustic.

 

Again... You're discarding the advice of highly experienced and talented mechanics in order to try and do things yourself. You have absolutely NO CLUE what you need or what you're doing- all you can do is quote numbers from a manual. It's time to pay the professionals to do their job.

Drop the block off at the shop (my recommendation is to leave it at the shop that it's at now). tell them what you want in it. leave the block with them and leave it up to them on how to achieve the final results you want.

 

if the spec is out on grade 1, go to grade 2, or grade 3. not difficult concept.

 

Glad you think that helped at all....................... ever heard of manufacturing tolerances yet?

 

Cool bud - I'll do that.

Thanks, Bros.

 

Just call Nissan and tell them you need the upgraded "overbore radiator", grade 2. Personally I would just get the grade 3 overbore radiator for extra cooling since its the same price as grade 2.

 

Turns out I did get slightly scammed - in the end he didn't even have the caustic. Before the owner got there I asked one of the employees and he said it's not caustic, they aren't 'allowed to use it' anymore. So I picked it up and paid him the $90.00, and he didn't even open the oil galleries - he didn't know how to, so it turns out the cleaning is probably a waste and didn't do much. The block looks very similar to how I gave it to him, except for the honing. The crank and bearing cap are the only things that didn't get cleaned in the tank, but those were cleaned in some booth type thing, and they look fully clean. He said there may be aluminum in the crank so he wouldn't put it in the hot tank. You should have seen how abrupt he was with the equipment, he even almost knocked down someones crankshaft right in front of me. There's like 100 blocks all lined up, and he was practically throwing my parts around right in front of me.

The owner is funny, although made mistakes, but at least he's a nice guy so I don't feel completely ripped off. He admits to me he's new to the engine stuff and only bought the plant 1 yr ago

 

So Maxpwer, is there any way I can run the OEM standard radiator with those 0.5 overbore? I'd like to avoid buying it if I can get away with it, or will it overheat? The FSM doesn't mention replacing the radiator when replacing the pistons.

It turns out I'm going to have to re-bore. He slipped a 0.004" feeler gauge between the piston and the bore right in front of me, and it fit in. Out of curiosity i'm going to measure the honed bores to see how much he took off on the machine.

 

nope. you need a Koyo racing radiator. the stock ones aren't up to the task.

 

Hey buddy - is this the one you are talking about? The one at the bottom.

http://www.thepartsbin.com/catalog/?...294963637+9235

It doesn't mention racing though.

 

no.. those are a stock replacement radiator. you need a better one than that.

 

I have done perhaps 10s of overbore replacement radiators and have always found that the single core version (as opposed to the more expensive double/triple core versions) always improves cooling because its got less wind resistance ..................

 

i heard that the triple-core ones work just fine as long as you install an extra set of electric cooling fans on the front side end to help boost airflow even with the increased wind resistance (rewired to spin the opposite way of course... otherwise you're blowing air away from the radiator! )

 

LVR I used all my measuring equipment, following exactly the service manual, and here are my clearance results (Post honing machine). Please look at the ones that failed and by how much, and let me know if I can ignore the machinists recommendation of re-bore:

PISTON-TO-BORE CLEARANCE "B" (CYLINDER BORE DIAMETER - PISTON SKIRT DIAMETER)
OEM Limit: 0.0006" to 0.0014"

Result:
#1 GRADE 3 0.0017" FAIL OVER LIMIT
#2 GRADE 2 0.0015" FAIL OVER LIMIT
#3 GRADE 2 0.0012" PASS UNDER LIMIT
#4 GRADE 2 0.0014" PASS @ LIMIT
#5 GRADE 2 0.0014" PASS @ LIMIT
#6 GRADE 2 0.0014" PASS @ LIMIT

 

By the way Ben, I read your response right now above and it makes no sense. Have you even overhauled an engine yourself before?

 

Well if you can find them, the radiator out of the JDM turbo 3rd gen maxima, or the upgraded radiator that comes with the Nismo 3rd gen maxima turbo kit provides even better cooling! I had to call A TON of nissan dealerships but I finally found a Nismo turbo radiator and have never looked back!

 

Here's a novel idea:

Can somebody please explain to me what this limit is all about and what it means ito a rebore requirement?

 

1993-VG30E-GXE - Lets make it official then - I am now with Matt, and have to agree that you have absolutely no idea what you are doing.

You have absolutely no idea how to read a service manual - you also have no idea about the implication of the figures you see printed there.

That statement alone should have been enough to get this thread closed/locked and stuck up in the stickies as a perfect example of how not to go about sorting a 3rd gen motor.

You have lots of money you are going to be relieved of in this "rebuild process of the VG motor" and in the rebuild process you are undoubtedly going to also end up screwing up a perfectly good motor with close to pristine "ex-factory" tolerances by unnecessarily "re-boring" ................ and re-boring to a 2nd oversize on a std block with no significant wear (for F**k sakes!).

Its painfully obvious that not you, your original mechanic friend, his 15 year long engineering friend, your recent "friendly but ripping you off caustic friend" nor any of the other people you first mislead by supplying wrong FSM information and then interact with to illicit yet another (300th?) opinion that is completely useless on rebuilding this particular type of motor. Granted the VG's FSM doesn't go into the sorta detail the equivalent motor in the Pathfinder manual goes into (EM49 and EM50 goes into a bit more machinist detail) while confirming all the questions and concepts I have asked in this here thread, but any machinist that knows what he is doing will know the implications of those figures in the VG's FSM ............. thats why I suggested taking the motor away from the "friendly screwer" and giving it to a reputable machinist.

I have tried in this thread to make you see how absolutely ludicrous your mission is, but obviously failed miserably because you simply cannot do simple maths or comprehend what the figures in the FSM means - on top of that you plead ignorance, bliss and proudly proclaims the you are actually sorted irrespective of not understanding the question.

I simply don't have the time to teach you either thermodynamics 101, engine construction 101 or engine rebuilding 101 via the net on a open forum. Suffice it to say that with the time I had to devote to helping on this extremely complex topic, not a single logical argument has come forth from your side.

Very good example is this stupid idea about the replacement radiator required for a re-bored motor - WTabsoluteF! .................... and then on top of it when people starts taking the p*i*s*s out of the situation you don't know/understand that either - the fact of it all is that a 350cu" Chevy V8 can most likely be adequately cooled by the standard Maxima's radiator ................. and I found it quite hilarious that you asked Ben if he ever rebuilt a motor even though he obviously doesn't/didn't understand my questions about "in-spec" grade combinations and wear limits for re-bore requirements either.



............. and for those that will now have a cadenza about my response let me quote some of my exact words I have typed in private responses to questions on this topic over the last nearly 4 months:

 

Woahh - someones a little unstable.

I will take a look at your blob of info....but MAN OH MAN that's alot of info - but it looks to me like you took something personal, that I said to you - and I promise LVR I didn't mean to offend you in any way, and I don't mean to be a threat to you in any way either.

I shall get to this later, but I'll be using the Mitutoyo Dial Bore Gauge with 0.0001 resolution so I don't need to fiddle with those snap gauges anymore.

 

Just because you have the good equipment doesn't mean you know what to do with it.

He's absolutely right in every aspect of his statements above

 

LOL!!! Look the stock radiator can handle it...You're thinking to much into it dude.But there are some 2 core all aluminum rads available...
That .5mm/.020" overbore is the minimum get yourself some Oem.5mm oversized piston or someother aftermarket piston brand (Sealed Power).
Unless you've measured it for taper which involves measuring the cylinder /piston in three different location ( top of piston/cylinder, middle of piston/cylinder and bottom of piston(skirt)/cylinder) then at each of the three locations you'll measure your thrust dimensions and longitudal dimensions which are non thrust...
Personally you should have mic'd all your piston/cylinder dimensions b4 your send them off, so you would know what you had b4 you send them off. I told you in the hot tanking cont'd thread that i'd already disassembled pretty much everything for my machine all ready (lower cost) and we knew together that an overbore was needed due to an extensive gouge in the cylinder wall ( due to previous owner overheating the car)!
Get a good oversized piston and move on!

 

Oh man - you dudes are hilarious. You need to get out into the real world a bit - this website is driving you cooky. Don't take this stuff personally - it's CAR REPAIR