Quote:
Originally Posted by ULTRAZLS1
Good luck man. Enjoy.
I plan on a set down the road when I do a cam. PRAY is the man.
Still torn between a big cam and converter deep into the tens or a mild cam stock converter consistent mid to high tens...
I feel like a mild cam with some milling and thinner gaskets could get decently close to a large cam and sacrifice very little drive ability
I also dabble in roll racing from time to time and the stock converter may be better for this...
What kind/size of cam do you suggest with these heads pray?
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Thanks buddy. I would really like to get a set of my heads on your car. Another guy that races would be awesome to back up my current results.
A converter won't hurt your roll racing. Once you click over to manual mode you are all locked up. It is just like putting it on the dyno. You can also adjust your converter lock up mph to cover down on roll racing speeds.
Any cam above 223 intake duration will usually require enough idle rpm that it will pull on a stock converter. I am not sure how the A8 stock converter fares with this but that is about the limit for all the GM converters before it.
My heads flow enough air and high enough into the lift range to handle any cam you want to throw at them. However, I am not sure on cam specs yet. It appears that there is not nearly as much PTV as I was originally lead to believe in this motor. This severely limits how far forward we can advance the IVO/IVC. The IVC directly effects the DCR we can get and therefore effects the tq we will be able to produce and where in the rpm band we can make it. Given the flow characteristics of my heads I have had the best luck running cams with a tight lobe separation 110-111 and a 6*-8* split on duration. Advance is now the issue. I would say that running a bit of advance and using the computer to retard the cam would be best. But again there is the PTV issue. We are also finding out now that there are cam retard control issues with valve spring pressure overcoming the cam phaser. I have seen this first hand on the dyno with unexplained tq dips in the curve. Once we logged cam retard we found out that cam was not following the commanded retard at all. It was retarding the cam up to 5* in certain spots for no reason. Some manufactures are now offering 0*-4* limiter blocks now vs. the 25* block that comes with the comp phaser limiter kit. We are assuming that the oil pressure and spring in the stock cam phaser can't overcome the spring pressure required to run the cams being produced right now.
I still can't wrap my head around the wide lobe sep we are seeing with most of the cam manufactures right now but no one seems to want to have a conversation about it. It seems like a double whammy to me for tq production down low. I feel it would be much better to run a tighter lobe sep with no advance than run a wide lobe sep and some advance.. There must be a definitive IVO that will maintain the minimum PTV. The other issue is ramp rate. By degreeing different cam manufactures cams there is a definite difference in ramp rates. It is the .020"-.050' that seems to be the issue for PTV with some cams and not others. So duration and IVO aren't the only issues to plan around. I will figure it out eventually with a buddy of mine and then come out with my own line of cams to match my head porting.