| 2point6 |
07-18-2010 02:33 PM |
Alright, just a little update for you guys...
This engine has only been to the dyno, then driven to the track, made 4 passes, and then driven home. Total is 14 miles. Chrissy ran a best of 12.01 (as I mentioned earlier) and without any other driving, I took the set-up out of her 2500lb EX coupe and put it in a CX hatch. No other changes were made. I had planned to take the 400lb lighter CX out and get it in the 11's, but got stuck on a couple issues. We fired the car up and it started fouling plugs and missfiring. I did a leak down test and it was killer, but I was getting oil out of the exaust ports coming from the guides, so I decided to do some digging...
When I got the head returned to me from Bisi, I noticed a few things that I consider weren't finished. Even thought this engine made some great power right away, I always felt I could get more out of it. I got the flow sheet from Bisi, and the numbers seemed almost "unbelievable" in my opinion. Few "radical" K series heads flow like the numbers I saw on this sheet, so I decided to have them verified and then try to modify it to see what other gains I could make. Let me say that I was kind of dissapointed at first. at .500" lift the head flowed 34 cfm less than what my sheet said it did. This was a consistant loss across the board. Despite the head flow difference the engine still performed amazing!
We made a few modifications and now the head picked the 34+ cfm back up, but my thoughts are "why the difference"? Why didn't Bisi include this work in the first place? The flow sheet also had someone elses name on it so was this even my sheet? who knows... I asked Bisi these questions about what I thought needed to be changed and why he didn't do them in the first place. He told me that it was "unneccessary to do" and he wasn't aware of the wrong name on the flow sheet. I decided to go by my own experience and make the changes I thought were needed and now the numbers increased and now match the original flow sheet. I am very suprised that simple changes made this much of an increase. It would be interesting to note that if my changes had been made first, what would the head have flowed on Bisi's flow bench...hmmmmm? The sheet came from a superflow SF600 bench and mine was retested on a computer controlled SF650. They are different benches, but this is supposed to be fairly consistant and not a 30+ cfm difference. Very strange in my opinion.
The oil issue came from a couple guide seals that made contact with the spring retainers. I also found this interesting because I was told that this head was "ready to go" by Bisi himself, so finding a retainer to guide clearance issue was suprising.Chrissy is running a custom Bisi cam and we were told there would not be any of these issues. I have now fixed that too. Two last issues that really suprised me about the work that Bisi had done for me was, that the valve job was very bad and that the head had been surfaced on a "belt sander". I did look at the head when I first got it, but who am I to question Bisi, right? Well... I am glad that I have the resources to verify and improve if needed. We improved.
Currently, I am waiting to put the head back on the car then it will be back to Locash for a retune. Hopefully we will see a positive gain as I am looking to hit 300whp with a plenum manifold.
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