OK, as many of you know, my engine came off the dyno last week with disappointing results. As I pushed for more info; knowing the results had to be wrong, the dyno shop agreed to measure the actual CR and do a leak down test on the heads. (New Eddy Performer RPM's)
Although my builder assured me he got 9.8:1 CR, I didn't really believe him. Turns out the dyno shop is coming up with more like 8.75:1 using a tool called a whistler and by adding the known CC volumes. A major "unknown" is the volume of the relief valves on the pistons. He used 6cc in his calcs, but thinks they are bigger. Despite my continued requests to get the part number of the pistons so I can find this out, builder is stalling me and has been for months. In addition, dyno shop found a 15% leak in one of the exhaust valves and some other leaks less than 5%, from what I hear that is acceptable??
OK. Moving on; the engine is being torn down again to see what can be done about getting a REAL 10:1 CR. I'm told the pistons are .010 in the hole, the Eddy heads have an 84CC volume, 4.28 bore, 3.375 stroke, using .040 gasket thickness (not sure of this). I think the builder's solution is going to be zero decking the block and milling the heads, but I'm thinking (I know almost nothing about this) that they will have to be milled quite a bit to get the numbers we need.
What would you guys do? Is it better to find different pistons (not sure what kind)? I was told these pistons have valve reliefs for a reason so not sure anything else can be used.
I've decided that while it's torn apart to add a bigger cam (Comp XE285HL) and an 850 Holley Double Pumper and stick with the dual plane intake. I'm told that's easy stuff to change and that the heads will be no issue to fix the leaks. So, my big problem is the CR. Can you guys throw me some ideas?
Sorry for the long post.
John
Although my builder assured me he got 9.8:1 CR, I didn't really believe him. Turns out the dyno shop is coming up with more like 8.75:1 using a tool called a whistler and by adding the known CC volumes. A major "unknown" is the volume of the relief valves on the pistons. He used 6cc in his calcs, but thinks they are bigger. Despite my continued requests to get the part number of the pistons so I can find this out, builder is stalling me and has been for months. In addition, dyno shop found a 15% leak in one of the exhaust valves and some other leaks less than 5%, from what I hear that is acceptable??
OK. Moving on; the engine is being torn down again to see what can be done about getting a REAL 10:1 CR. I'm told the pistons are .010 in the hole, the Eddy heads have an 84CC volume, 4.28 bore, 3.375 stroke, using .040 gasket thickness (not sure of this). I think the builder's solution is going to be zero decking the block and milling the heads, but I'm thinking (I know almost nothing about this) that they will have to be milled quite a bit to get the numbers we need.
What would you guys do? Is it better to find different pistons (not sure what kind)? I was told these pistons have valve reliefs for a reason so not sure anything else can be used.
I've decided that while it's torn apart to add a bigger cam (Comp XE285HL) and an 850 Holley Double Pumper and stick with the dual plane intake. I'm told that's easy stuff to change and that the heads will be no issue to fix the leaks. So, my big problem is the CR. Can you guys throw me some ideas?
Sorry for the long post.
John