Going for the drop-in build at English Racing
Nov 8, 2011, 11:10 AM
#46
I stopped by ER yesterday to see how things were going and had a chance to look at the port work on the cylinder head. Aaron and I had talked several times over the last the last year about porting the head, and Aaron had always mentioned "core shift" as one of the key items to address with a port job. I had understood that core shift was due to variability in the casting process and that it affects port shape, but I never bothered to really understand the nature of it until yesterday when Aaron showed me my cylinder head and said it was one of the worst cases of core shift that they had seen.
Based on what I saw, the Evo cylinder head is cast in a two piece mold with the interface between the halves creating upper and lower pieces. Core shift is a measure of how much the two halves are misaligned at the time of the casting. The misalignment can be shift and/or rotation. The interface cuts across all the ports, and when core shift occurs, a step is created in the port geometry. The interface is roughly 3/4" from from the valve seat right at the location where the port is turning to point into the cylinder, ... basically right at the location where core shift can really mess up flow.
Turns out that my cyl head was mostly rotated around one end of the cyl head, so there was almost no core shift on one side, but there was a full 1/8" core shift at the other end. That means there was a 1/8" step in all the ports at the core shifted end of the head. Luckily, they were able to remove the step, and get things looking pretty good. I imagine that if there is some interest, perhaps Aaron can post up a few examples of core shift.
Based on what I saw, the Evo cylinder head is cast in a two piece mold with the interface between the halves creating upper and lower pieces. Core shift is a measure of how much the two halves are misaligned at the time of the casting. The misalignment can be shift and/or rotation. The interface cuts across all the ports, and when core shift occurs, a step is created in the port geometry. The interface is roughly 3/4" from from the valve seat right at the location where the port is turning to point into the cylinder, ... basically right at the location where core shift can really mess up flow.
Turns out that my cyl head was mostly rotated around one end of the cyl head, so there was almost no core shift on one side, but there was a full 1/8" core shift at the other end. That means there was a 1/8" step in all the ports at the core shifted end of the head. Luckily, they were able to remove the step, and get things looking pretty good. I imagine that if there is some interest, perhaps Aaron can post up a few examples of core shift.
https://www.evolutionm.net/forums/ev...head-tech.html
Nov 8, 2011, 11:22 AM
#47
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I did-
https://www.evolutionm.net/forums/ev...head-tech.html
We tow cars all the time from Seattle to here.
https://www.evolutionm.net/forums/ev...head-tech.html
We tow cars all the time from Seattle to here.
I know lol. It's just the block right now
. I really like supporting you guys. I'll be down soon to return the help you guys continue to provide time and time again!!If my block needs some work done, or I need a new bottom end, we'll be talking soon!
When is the next time are you guys coming up to Kent?
How much for head porting?
Last edited by Graphic; Nov 8, 2011 at 11:28 AM.
Nov 8, 2011, 11:24 AM
#48
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So if you have the means to pull the motor and ship it, I'd do it.
-Bink
Nov 8, 2011, 02:14 PM
#52
And this is after grinding on it for a bit already. Its not hard to see how bad some of these heads are and therefore why some stock cars make power than others. I've always joked that it was because one is a monday/friday car and one is a wednesday.
Aaron
Aaron
Nov 9, 2011, 09:26 AM
#54
Its hard to say without pulling it apart and measuring. We have measured 100k mile 4G64 blocks with stock pistons and they are still at factory PTW without variation from what we can tell. That is only a 140bhp motor that probably doesnt get raped the way an Evo does.
I would presume your car would be okay but everything is open to variation of course.
Aaron
I would presume your car would be okay but everything is open to variation of course.
Aaron
Nov 20, 2011, 06:32 PM
#57
Done. I picked it up Friday evening, and have been driving it and doing baseline street tuning this weekend. As usual, English Racing did a great job. Its amazing how good it feels. Off boost performance is as good or better than before. Absolutely no loss in low end from the MAP rev3 intake manifold and English Racing port job.
Performance on boost is definitely increased at the same WGDC settings. Its holding 1-2 more psi and load is significantly increased. The single Walbro is not keeping up any more. AFRs are drifting up into the high 12s at higher rpm and not coming down when I richen AFR in the fuel map, and pressure across the injectors is dropping into the high 30s (instead of the target 43 psi). FIC1100s are not yet tapped out. Current plan of action is to install a DW301 without a rewire and see whether that does the job. I'll be logging fuel pressure to measure the response of the pump. I meet with Lucas on Friday to do more tuning on English Racing's dyno. Can't wait to see what it can do.
Performance on boost is definitely increased at the same WGDC settings. Its holding 1-2 more psi and load is significantly increased. The single Walbro is not keeping up any more. AFRs are drifting up into the high 12s at higher rpm and not coming down when I richen AFR in the fuel map, and pressure across the injectors is dropping into the high 30s (instead of the target 43 psi). FIC1100s are not yet tapped out. Current plan of action is to install a DW301 without a rewire and see whether that does the job. I'll be logging fuel pressure to measure the response of the pump. I meet with Lucas on Friday to do more tuning on English Racing's dyno. Can't wait to see what it can do.
Nov 20, 2011, 07:08 PM
#60
Done. I picked it up Friday evening, and have been driving it and doing baseline street tuning this weekend. As usual, English Racing did a great job. Its amazing how good it feels. Off boost performance is as good or better than before. Absolutely no loss in low end from the MAP rev3 intake manifold and English Racing port job.
Performance on boost is definitely increased at the same WGDC settings. Its holding 1-2 more psi and load is significantly increased. The single Walbro is not keeping up any more. AFRs are drifting up into the high 12s at higher rpm and not coming down when I richen AFR in the fuel map, and pressure across the injectors is dropping into the high 30s (instead of the target 43 psi). FIC1100s are not yet tapped out. Current plan of action is to install a DW301 without a rewire and see whether that does the job. I'll be logging fuel pressure to measure the response of the pump. I meet with Lucas on Friday to do more tuning on English Racing's dyno. Can't wait to see what it can do.
Performance on boost is definitely increased at the same WGDC settings. Its holding 1-2 more psi and load is significantly increased. The single Walbro is not keeping up any more. AFRs are drifting up into the high 12s at higher rpm and not coming down when I richen AFR in the fuel map, and pressure across the injectors is dropping into the high 30s (instead of the target 43 psi). FIC1100s are not yet tapped out. Current plan of action is to install a DW301 without a rewire and see whether that does the job. I'll be logging fuel pressure to measure the response of the pump. I meet with Lucas on Friday to do more tuning on English Racing's dyno. Can't wait to see what it can do.
Dan (drb)