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Discussion Starter #1
Thanks to Cervan in this thread
http://www.d-series.org/forums/engine-building/111577-z6-y8-crankshaft-differences-indifferences.html He has prooved that the z6/y8/y7/a6 are all the exact same size and interchangable.
But my question is which is the better crank for a race engine.
I have read where a lott of people say that the z6 is seperior cause of the cross drilling.And this is all i can gather that they say it is seperior.
Well according to this CRANKSHAFT TECH - "SAY NO TO CROSS - DRILLING" And many other links after searching.The y8 crankshaft should be better than the z6 because it ISN'T cross drilled.
The oil pump in the z6 and y8 are basicly the same thanks to the research from, 97-civic-ex: http://www.d-series.org/forums/engine-building/137709-z6-y8-oil-pumps-same-part-2-a.html so this rules the oil pumps out.



Well can any one enlighten me why the z6 crank is seperior the y8/y7 crank?

And why is it seperior to the earlier design of the a6 or a1 crank?
Is it the material in the z6 is stonger?Is there any links or supporting proof other than "ya it is".or "I read it on HT once"

Sorry for beating a dead horse.But i see all these crank threads and what every one says is "get a stock z6 crank".Why???
lm building my race engine for this year and i was hunting a z6 crank.But not sure if i want to spin my bearings again and just might get a "better" crank.

Which one is the best crank for a race engine?Cross drilled or single drilled.
 

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All I know is every Y series block I find has a spun bearing. But most every Z or A block I find is good to go. Maybe just simply chamfering the holes would help the Y?
 

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y8's have one oiling hole in the rod journals. z6's have 2 holes in the rod journals.

z6 cranks are better
 

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^You didnt read ANY of what he posted. Did you?
 

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yes i did... z6's are known to have better oil supply to the rods... i know of many y8's that spin bearings... even stock y8's... they are KNOWN for spun bearings
 

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But according to the article, single is better than cross drilled.

So if this is true, then the only attribution to the Ys spinning more than Zs and As, is due to chamfered holes?
 

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pretty sure the y-series of blocks having failed is a bit of blanket statement. none of the y7s i have encountered have spun bearings. this includes the 4 i have personally owned, 1 being the built one in my avy.

also, there are z6 and a6 blocks whom have spin bearings as well. if any of you paid attention, its a more common thread title then people care to admit.

personally, i feel that any of the d-series blocks used when equipped with a vtec head are slightly prone to spinning a bearing. havent really noticed a lot of d15bx spun bearing threads... just saying.
 

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i cant be certain what the cons and benefits are of one vs cross drilled cranks, but im pretty sure alot of people have ran on the cross drilled cranks for a long time and have yet to have issues.
 

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Even in the V8 world many people debate this and many also have had success(many things are compared to NASCAR). Also, just because an article says something, doesn't always mean it's true or there's more to the story.

Off the bat(concerning our D-series engine); you can counter with the D-series having shorter strokes than V8s and the oil pumps can maintain the necessary oil pressure just fine. IIRC, with Subarus, the STi engines are cross-drilled differently than the regular WRX so there's probably many different methods for cross-drilling.
 

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I think this thread contains a two-pronged question : 1) Which crank for our D-series motors are truly the best (Z6/A6 of course). 2) Would a crank (outside of the Honda world) w/o cross-drilling be better? This question, I've got no clue.
 

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Discussion Starter #13
well why is it the z6/a6 of course?

The a6 has only one oiling hole.And supposedly not as hardened as the z6.If thats the case then the y8 should be better than the a6 since the steel should be the same tensle strenth as the z6 just the y8 only has one oiling hole.Maybe it should just be camphered and it would fix the problem.
In hte v8 world they argure that the longer throw cranks benefit more from the cross drilling than a short stroke high rpm engine.Just they need a high flow pump and and higher oil PSI.Hence our short stroke cranks shouldnt need x drilling.
I also found that a lott of cross drille cranks used in high output engines had a plug eithor half way or one the opposite end of the oiling hole.To prevent the main journal from starvation due to centrifugal force.Since cross drilled cranks are only effectrive till the oil has to fight aganst centrifugal force and cuts of oil flow to the rods due to high rpm's.
I mean hell.Eagle doesn't even make cross drilled cranks any more cause the v8 world wants the older straight shot oilng hole cranks.And they make what the consumer wants cause thats what sells.

Does the vtec of the y8 maybe have something to do with the bearining failure?Not sure but is the oiling supply in the head and block somewhat different in the y's than the z6?Which could possibly contribute to the failure.

I my self think it is more a theroetical statement that the y cranks are not as good.After being thrown arownd on the net and people saying it over and over every one believes it without any other evidence than what they read.I know i have read probably just as many if not more threads with z6 cranks having spun rods than the y8.
Not so much the y7 or a6.I think this is contrubuted to no vtec.
 

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Ok, I read teh article on cross drilled cranks, and I don't know if anybody else caught this but.

"Only increased oil pressure will overcome the "crack the whip effect" "

So they basically say that with everything else being equal, a cross drilled crank would require a higher oil pressure, which I believe the Z6 is said to have no? So if that is the case, would cross drilling still be a disadvantage? I don't see how it could be.
I'm not 100% on this, because I know one engine has a higher psi rating and the other flows more, not sure which, so if somebody could link up the pages in the shop manual where they quote the oiling capacities of the pumps that would be great, we'd see if I make any sense whatsoever.

nick
 

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Rushi said:
Y8 pump displacements is 33.4liters/min @ 6800rpm
PM3 45liters/min @ 6300rpm
D16A8/9 DOHC oilpump is 63liters/min, something over 6000rpm too.
The Y8 should still be able to keep a A6/Z6 "well fed", and the pressure is regulated by the relief valve. Why they made it flow less could be to reduce drag/wasted energy(no point in pumping so much oil if it's just being relieved through the relief valve).
 

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its gonna come down to how the motors built and what clearances are used, how its drivin and taken care of, i have a y7 top to bottom in my car and used 3 different tricks to help not spinning a bearing and the bearings look perfect revving the car bouncing limiter 8500+ almost every time i drive the car. i have used both cranks in motors i have built and they both work
 

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Discussion Starter #17
its gonna come down to how the motors built and what clearances are used, how its drivin and taken care of, i have a y7 top to bottom in my car and used 3 different tricks to help not spinning a bearing and the bearings look perfect revving the car bouncing limiter 8500+ almost every time i drive the car. i have used both cranks in motors i have built and they both work
I am guessing theese be the 3 tricks.

Cllearances.......What were your clearances?
Ported pump.......If so,which one?
And a good oil......What oil?Brand and viscosity?
 

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I am guessing theese be the 3 tricks.

Cllearances.......What were your clearances?
Ported pump.......If so,which one?
And a good oil......What oil?Brand and viscosity?
I'll take a noob shot at a guess also.

Self Ported pump........OEM

Chamfered oil holes on crank.......not sure if you would also do mains or just the rod journals (I still have much to learn)

Ported/bored rod bearings.....maybe main bearings too?

Seemed to be a good opertunity to bump a good thread :biggrin:
 

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I am guessing theese be the 3 tricks.

Cllearances.......What were your clearances?
Ported pump.......If so,which one?
And a good oil......What oil?Brand and viscosity?
clearances are right at .0015

1.fully reworked oil pump in house
2.fully chamfered crank in house
3.and i drill out and taper both my mains and rod bearings in house


and i run like a castrol 10w40 non synthetic
 
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