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202 "stroker" kits- opinions? +knifedged bmotor cranks

Started by orangeLJ , Aug 03 2012 04:25 PM

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163 replies to this topic

#101 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 08:34 PM

i try to keep overbore to a minimum and push the head over.
i moved it over .160".
yes mate getting there hopefully should be a bit quicker too.

Fair enough,i only moved this one .060,but i will move it more and maybe angle mill a bit to get the valve away from the bore in the next rebuild.When you moved it .160 were you able to still us a race series head gasket or do u have to use a copper gasket.

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#102 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 08:40 PM

I haven't got any specs from the 2 heads, but I know a 12 port is limited to around 280hp at the flywheel & the 9 port can be 300hp +. The 12 port ran a best of 104mph & the 9 port 105.5 using the same cam.
The alloy Yellaterra wouldn't be too bad a starting point if they made it with a 47cc chamber instead of the large chamber, as Bomber has already pointed out.

Was it the same comp with both heads?. .On yt alloy heads 060 " brings it down to around 47cc.

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#103 _Bomber Watson_

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Posted 17 August 2012 - 08:42 PM

Cheers mate.

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#104 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 08:49 PM

i didnt think 060" off would take 6 1/2cc out of it??

Suppose it might.

How much deck is left on one of the "high comp" 12 port alloys?

plenty left mate ,the 70cc and 56cc YT head is the same casting ,you chisel .100" off the 70cc to get 56cc ,a further .060 gets you about 47cc.Just get a syringe off the beach ,fill it with 47cc of cooking oil and squirt it into a 12 port chamber then measure from the deck to the top of the oil to work out how much to take off.Mick

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#105 _Bomber Watson_

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Posted 17 August 2012 - 08:52 PM

Cant say i've heard of anyone doing it that way, doesnt the cooking oil form a meniscus which would give a false reading?

Cheers.

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#106 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 08:55 PM

Cant say i've heard of anyone doing it that way, doesnt the cooking oil form a meniscus which would give a false reading?

Cheers.

forms a what?

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#107 Heath

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Posted 17 August 2012 - 08:59 PM

A meniscus is an effect that occurs with liquid because of the surface tension, where at the edges of the fluid where it meets the solid surface (i.e. the walls of the combustion chamber) it actually reaches up the walls a little, theoretically throwing off your measurement. But I don't think it would be too detrimental to your accuracy DJ. Put a straight edge across the chamber and reach down into the middle with a measuring device. Close enough

Mountains of molehills.

Edited by Heath, 17 August 2012 - 09:00 PM.

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#108 _Bomber Watson_

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Posted 17 August 2012 - 09:01 PM

Can also pull down a little, depending on the specific gravity of the liquid

Heath, looking at say water in a glass i would think the meniscus would be more than a couple of thou??

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#109 _Bomber Watson_

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Posted 17 August 2012 - 09:07 PM

And to add to that, i was under the impression that a meniscus was actually a concave or convex shape over the entire surface of the liquid, not just the edges, although the edges are more prominent generally.

And would cooking oil form a concave (like water) or convex (like murcury) shape??

I usually use ATF for ccing.....

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#110 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 09:09 PM

A meniscus is an effect that occurs with liquid because of the surface tension, where at the edges of the fluid where it meets the solid surface (i.e. the walls of the combustion chamber) it actually reaches up the walls a little, theoretically throwing off your measurement. But I don't think it would be too detrimental to your accuracy DJ. Put a straight edge across the chamber and reach down into the middle with a measuring device. Close enough

Mountains of molehills.

Yep it does do that at the edges but you can work it out well enough with a vernier to get the job done.
Good enough for the bush I reckon.

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#111 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 09:15 PM

And to add to that, i was under the impression that a meniscus was actually a concave or convex shape over the entire surface of the liquid, not just the edges, although the edges are more prominent generally.

And would cooking oil form a concave (like water) or convex (like murcury) shape??

I usually use ATF for ccing.....

fair enough, but in the end after machining,if you fill the chamber with a perspex plate on top you will get the correct cc.

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#112 _Bomber Watson_

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Posted 17 August 2012 - 09:20 PM

Correct, after machining and finding out its wrong lol.

Good idea to get a rough guide though, never thought of that myself.

Cheers.

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#113 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 09:22 PM

Correct, after machining and finding out its wrong lol.

Good idea to get a rough guide though, never thought of that myself.

Cheers.

it can only be a few thou out mate

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#114 _Bomber Watson_

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Posted 17 August 2012 - 09:26 PM

Sactly, like i sasid good idea for a guide.

My ccing gear is "within a cc" anyway

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#115 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 09:42 PM

Sactly, like i sasid good idea for a guide.

My ccing gear is "within a cc" anyway

All good,Hey Bomber ,have you heard of a cylinder head porter in Mackay named Steve Gay,he's old school aparently good with holdens

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#116 greens nice

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Posted 17 August 2012 - 09:43 PM

still using race series gasket.
the alloy 12 port i had the chambers welded in had roughly .060 -.80 of the deck ( dont know the real reading as it had been effed with before i got it).
machine shop checked the thickness of the deck and said its already too thin and not to shave again, chamber came out at 47 cc after welding and porting.
i thought this was the reason they stopped selling the original closed chamber alloy YT's, because the squish pad was caving in.
even if you do get the compression up, they have no squish area.

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#117 _Bomber Watson_

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Posted 17 August 2012 - 09:49 PM

Not having had one infront of me, how do they compare to an open chamber holden cast Kev?

Mick, negative, might look him up though.

Cheers.

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#118 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 09:54 PM

still using race series gasket.
the alloy 12 port i had the chambers welded in had roughly .060 -.80 of the deck ( dont know the real reading as it had been effed with before i got it).
machine shop checked the thickness of the deck and said its already too thin and not to shave again, chamber came out at 47 cc after welding and porting.
i thought this was the reason they stopped selling the original closed chamber alloy YT's, because the squish pad was caving in.
even if you do get the compression up, they have no squish area.

People have said they made small chamber version but i have never seen one,have you actually seen one.I did hear they had some chambers collapse on the earlier batch.they seem to have fixed it up with the last batch.Yep would be better with a good squish area.Do you know what the intake flow was on your head?

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#119 greens nice

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Posted 17 August 2012 - 09:55 PM

same as.

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#120 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 09:58 PM

same as.

Are you using that head now?

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#121 greens nice

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Posted 17 August 2012 - 10:00 PM

no i havent seen one with my own eye's, i have a yt book here with a part number for them though, they were called the "road racer" version, or something like that.
was around 135cfm at 10 inch's IIRC, 340hp worth of air.

This head is on the Grumpy Humpy FX, photo in the fastest holden 6 thread.

Edited by greens nice, 17 August 2012 - 10:01 PM.

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#122 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 10:03 PM

no i havent seen one with my own eye's, i have a yt book here with a part number for them though, they were called the "road racer" version, or something like that.
was around 135cfm at 10 inch's IIRC, 340hp worth of air.

thats good inake flow ,did you do anything radical to get it

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#123 greens nice

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Posted 17 August 2012 - 10:08 PM

thats good inake flow ,did you do anything radical to get it

nothing radical, just heavily ported.

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#124 _STRAIGHTLINEMICK_

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Posted 17 August 2012 - 10:14 PM

no i havent seen one with my own eye's, i have a yt book here with a part number for them though, they were called the "road racer" version, or something like that.
was around 135cfm at 10 inch's IIRC, 340hp worth of air.

This head is on the Grumpy Humpy FX, photo in the fastest holden 6 thread.

Thats a cool looking FX, Wow that must be an old YT catalogue mine only has the large chamber version.