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phantom

when the block are bored we always make sure the run speed is low ie the bore tool moves slowly up and down the cylinder giving you a finely hatched pattern about roughly 25-35 degrees to the horizon if you where looking straight at the bore from inside. As my engine machinist has now aquirred a torque plate honer i will be using that from now on although the difference is minute its still ensuring the best possible result.

discopotato03

with standard rod and pistons you can run the standard headgasket and using the headgasket on foges with my experiece with arias will give you around 8.6:1 comperssion using the hightops with standard rods, using the flat tops i believe its below 8 around 7.4:1. However the eagle rods being chev arent actually the correct length they are 6 inch not 5.92 that standard rods are and the sit above the deck height enough that you will need at least a 1.2mm headgast to acheive a squish and avoid valve isssue when running bigger camshafts. All this info is based on the 26head but its pretty much the same if you are using a 25 head, but the 20 head is different, correct me if im wrong i believe the cc of the rb20 head is 63cc and the rb26 is 66cc so it changes it all right there.

phantom

when the block are bored we always make sure the run speed is low ie the bore tool moves slowly up and down the cylinder giving you a finely hatched pattern about roughly 25-35 degrees to the horizon if you where looking straight at the bore from inside. As my engine machinist has now aquirred a torque plate honer i will be using that from now on although the difference is minute its still ensuring the best possible result.

discopotato03

with standard rod and pistons you can run the standard headgasket and using the headgasket on foges with my experiece with arias will give you around 8.6:1 comperssion using the hightops with standard rods, using the flat tops i believe its below 8 around 7.4:1. However the eagle rods being chev arent actually the correct length they are 6 inch not 5.92 that standard rods are and the sit above the deck height enough that you will need at least a 1.2mm headgast to acheive a squish and avoid valve isssue when running bigger camshafts. All this info is based on the 26head but its pretty much the same if you are using a 25 head, but the 20 head is different, correct me if im wrong i believe the cc of the rb20 head is 63cc and the rb26 is 66cc so it changes it all right there.

Who is your machinist, does someone in Canberra have a torque plate now ?

  • 2 weeks later...

My appoligies for bringing up old stuff but I couldnt find any photos as most of the pics dont work anymore in older posts.

My engine builder hasnt seen my head yet but he tells me that the rb25det head rear passenger's side water jacket sits out past the block, the na rb25 head doesnt. I'm still scratching my head how he came to that conclusion when my head doesn't have this problem.

Now all kinds of thoughts are going through my head atm, do I have an NA head or are there variances in the 25 turbo heads, VVT is an obvious one (mines VVT) then I go on thinking do I have an na inlet manifold,cams and valve springs...:confused:

The pic below is my bare head, the orange arrow is where i've been told the problem is.

12979rbhead.jpg

The complete top end came off a 33 gtst so I would assume it would be a turbo head.

In the past replies SK and Joel have used na heads, what are the characteristics of the na cams on the new engine? any problems with reversion etc....

Cause if I'm stuck with na valve springs etc..:slap: it maybe time for tomei pon cams and stiffer springs.

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