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Amin206

My 550whp v-spec R33gtr Needs help

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39 minutes ago, Amin206 said:

We don’t have many options in Canada highest is 94 octane

Yeah but that's 94 AKI, which is really about 101 RON. Arguably our best unleaded here is BP ultimate 98 RON which has a 92 AKI. 9:1 will be fine.

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I spoke to the machine shop who resurfaced the head he’s also a builder he recommended 1.3mm head gasket over 1.5 as lower gap between squish pad and piston head will prevent detonation in higher rpm but he also said 1.5 isn’t too thick and should be fine too

i think I’ll get 86mm 1.3 gasket And cp 9:1 pistons for better response then I’ll measure piston to valve clearance if clearances were too close then I have no choice To get thicker gasket 

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ECUs have come a long way, there's no need to stress running higher than factory compression just as long as you have all your compensation strategies in place to pull timing and/or add fuel for (minimum):

  • IAT
  • Fuel temperature
  • Fuel pressure
  • Baro
  • Water temp

and you'll be fine.

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11 hours ago, Ben C34 said:

Measure stuff before buying things

If you mean cc’ing the combustion chamber how can I figure out how much the head skimmed by cc’ing ? We can figure out how much material (in cc) removed by measuring the volume of the combustion chamber right now minus the std volume but can we figure out how much the height of the head surface decreased? so then I can figure out some number to see if the valve hit the piston head or not...

if it’s not possible to calculate that then I have no choice to put something in there to measure...right? 

 

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Testing my memory and my maths skills at 4am; but I believe you would need to remove ~6.5 thou to drop the volume of the combustion chamber by 1cc. That won't be exactly correct, but quite close. So if you measured your head volume at 60cc, for example, you could work out that the head has been decked by roughly 25 thou. Which is quite a bit, and unlikely, but you just don't know.

 

That said, it is sort of more important to CC the head for the sake of correctly calculating your compression ratio. In order to work out your piston to valve clearances, you would be better served by doing a dummy assembly using your old gear (you only need to assemble 1 cylinder) and use that to measure your clearances as they were. Then with that knowledge, plus knowing the volume of your head, you can work out a good CR, what thickness headgasket you can use to achieve it, and what pistons you should be getting.

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Yesterday I ordered some stuff to cc the chamber so I’ll be able to get some numbers  tomorrow 

also checking clearance with my old stuff wouldn’t be risky? I’m using a new block and not sure if previous builders decked the older block or not also can’t use the new block for measuring as my older pistons are 87mm and won’t go in there

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Ok bad news is all exhaust valves are leaking instead of one chamber and I measured the chamber 3 times 2 times came up as 64.5cc and 3rd time Between  64.2cc to 64.1cc I would say the 3rd one was more accurate 

but nothing less than 64cc for sure 

if the the standard chamber is 64.5 then I don’t think they skimmed the head that much? Also machine shop told me the head looks new and doesn’t look like it’s been used that much like a 25 year old head... So there’s a possibility that previous builders used a new head
but the amount of carbon buildup on valves is actually a lot and I can tell the same thing on valve seats so might be the reason for leaking 

 

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