I need help guys. The intake ports on our car hit maximum flow at only .450" lift. Their casting number 860, 1973-74 heads that have been converted to Stage 1's. The combustion chambers are modified to match factory Stage 1 heads. When my dad first worked on the heads in 1999, he took the heads and had one intake and one exhaust port flow bench tested after he finished them. Here is the intake port flow numbers: LIFT CFM .050" 42.3 .100" 65.3 .200" 138.2 .300" 192.0 .400" 238.1 .450" 250.9 MAX FLOW .450"-.600" Flow stayed within three CFM. In the 2001-02 offseason, we freshened the motor and did some more work on the heads and valves. Most of the work was done in the ports. Again, when we were done we took the heads back to the same flow bench, with the same operator, different intake port. Here are those flow bench results: .050" 50.5 .100" 77.5 .200" 155.0 .300" 220.0 .400" 265.4 .450" 266.8 MAX FLOW .450"-.550" Flow stayed within 1.2 CFM. As you can see, good progress was made. But, they still maxed out at .450" lift. Obviously, these are not state of the art Super Stock heads. The floors have not been welded up or the ports raised or moved at all. Material has only been removed from these heads, none has been added to reshape the ports like most good Super Stock heads have had done to them. Anyway, I know some of you guys have had a lot more experience with these heads than we have. I hope some of you have seen this problem before, and know what the likely trouble area is when the intake flow hits a wall like that. I've seen flow numbers posted on this board that have very similiar results up to .400" lift, but continue gaining up to 314 CFM@.600 lift. I'm hoping the problem may have something to do with the way the head was set up on the flow bench, but that's probably not it. Any words of advice would be much appreciated on this matter. Thanks in Advance, Steve Cowell
Steve, It is all in the combustion chamber and the area behind the pushrod hole. If you care to talk over the phone about this then send me a private email with your phone number and I will call you. Take Care
Repeating what I was told by another person a lot smarter than me in this area(Charlie Evans), the short turn radius is also very important and needs quite a bit of work. You now know what I do about the subject.
Oh no, not the combustion chamber.:ball: Strange thing with the cylinder head rules for Super Stock. A guy can do just about anything to the ports but you can't legally do anything to the combustion chambers. Although, we might be able to get away with enlarging the cuts in the combustion chambers for the Stage 1 valves beyond what the factory originally did. To my knowledge, NHRA nor IHRA have specs as to how large those valve reliefs in the heads are supposed to be. Also, there are no other Stage 1 Buick Stock or Super Stock cars around here that NHRA could tear down to compare heads with ours. Next time the heads are off and we got some time we'll work on that. I realize that's just one of the problems in the combustion chamber that needs attention, but it's all we can get away with fixing. Today, after looking at some of the pictures I took of the heads before we put them together the last time. It looked like the areas in the ports that both of you mentioned, could stand some more work. Dad didn't want to get overly aggresive in those areas and slow down the port velocity or possibly ruin the head by taking out too much metal. Now we know, and we'll spend some time on those areas when we have the opportunity to work on them. Thank you John, for the offer to talk on the phone about this. Thanks to you and Adam for confirming what I thought the problems might be, we can focus on them the next time. If anybody else has anything to add, please feel free to post any info you might have. Steve Cowell
The short turn can have very profound effects at higher lifts if its not right. If I had to blindly guess, I would say your short turn is too abrupt and needs to be layed back/extended. Good luck.
Port Design Its quite common, when dealing with advanced ports design, to obtain scenarios when changing the ports shape that may not increase or even can decrease the numbers you see on a flow bench, but increase HP and on track performance. Cam design is also critical. We have the most prolific cylinder head development person on our team, Dale Eicke, and an excellent cam designer who has been developing Buick Stock and Super Stock camshafts for over 22 years. Please feel welcome to call us any time. Thanks Brian
