I know I started a thread about this in the past but for some reason cannot find it. Last Oct I dropped my heads off with Bob @ Finishline to be CNC ported using the program they developed. Its been a long road but finally got the numbers in. Due to the heads being a very early casting he backed off the cut by 10% afraid of hitting a water passage. The numbers came in at a 366 on the intake for a+ 42 cfm improvement and 283 on the exhaust for a +28. Bob said this would be good for a 90 HP gain. Its not as drastic as I'd hoped for but still way better than it was. For the money spent its cheap power.
Is there an optimum ratio between intake and exhaust? I see that on Briz's heads, intake is approx 29.33% greater than exhaust. If yes, what is the effect on performance when the ratio is skewed too heavily towards intake or exhaust? Steve
The needed Exh to Intake ratio hinges greatly on the motors compression ratio in a NA motor running open tuned collector headers. Once you get below 11 to 1 comp figure you need at least a 72% ratio and then with the proper size primary tube on your headers you will pick up the added 3 to 5 percent flow gain to get to a good 75% ratio. A 15 to 1 motor performs fine with a 65% ratio for the most part.
Bobb did my TE2 heads. Here is how they came out. Even though I have flow numbers to .800 I run into seal to guide contact about .730 I had a little wait on mine too. I believe the delays come at the cnc shop. They have some big contracts and then when the machines open up is when this stuff gets done, but if they had to make a new cut program that takes time to write too 90 hp is a nice gain for what the 1200ish...... guessing...... that the cnc cost
Sorry Briz, not trying to steal your thread but your numbers caught my attention and I now see Ben also has a tighter intake/exhaust relationship. I had my SE1 heads done by TA and they flowed 357/228 if I remember correctly so I was happy with intake but curious about exhaust...seemed like it was on the low side. Have SP1 port matched, 2 inch TA headers with 3 inch mandrel, Dynamax Ultra flo's. Comp is 10.3:1. I'm wondering if I would benefit from trying to improve head's exhaust flow#'s? Steve
They also did the intake to match. It is running 13-1 compression and 2 1/8 " primary tubes with a 5" collector dumping out side exit on the fenders. Some of you guys have seen her runLast chassis dyno it made 472 at the rear wheels and I'll be taking it back to the same dyno for tuning after I get it back together. Plan on using these heads on the new tomahawk build late next year. It did take a very long time to get it done and the reason stated above with the CnC shops big accounts taking priority over a lowly set of Buick heads.
Bought these from Charlie Evans at the BG swap meet several years ago as bare castings. Im thinking they probably go back to one of the first TA runs of the stage 3 TE heads. There are threaded plugs in the front of the heads instead of the pressed in plugs today's heads come with. Dont know how much you can tell from this pic
Bob did my intake as well to match my heads, he had alot of hand work on the runners I know. He didn't remember we were going to run an sv1 single barrel so I had to trim more of the cloverleaf out to clear the 110mm blade I'm very happy with all my work finishline has done. I will be going back. I very much enjoy being to call and bounce ideas off bobb, or to just call to shoot the stuff. Great group of ppl up there
Looking mean Briz, I always like having a good look at CNC' heads to see what can be learnt from tool paths etc to possibly guide my hands on the die grinder. those intake bowls look suspiciously like they might have gone a bit far and cracks are developing, I sincerely hope not and it's the photo.
Get a set of valves that are .150" longer with the matched springs and you should be able to go to .830" lift with .050" clearance.
