you have to unshroud the bigger valve else there will not be much flow gain just by putting a bigger valve in.
Time to fire up the die grinder I see where the intake floor could be cut down as that is the choke. It may have some detrimental effects at some low rpm range that I don't worry about.
you can easily lose your velocity and hurt your low end torque. i guess strictly for racing it might not matter.
just throwing that out there about unshrouding and velocity for the guys doing their heads for the first time. I know Walt and 69hellcat know what they're doing.
On my stock intake port @ the min (choke point), width was about 1.70", height about 1.05. = 1.78 sq MCSA in if you ignore the rounded corners. This is about 1.25-2 " into the port on the ceiling. Bob was going up to 2.0 MCSA.(Edit: one set was 1.92, the other was 2.0) I chose to raise the roof a little, to about 1.09" height for MCSA of 1.85. Looking at the cross section pic, one could lower the floor instead/too. I don't know what's better, maybe do a little of both? Lowering the floor would be further in, maybe 2.5" and towards the short turn. The TA oversize valves are only +0.040" dia , so +0.020" one one side towards the chamber wall. I ground the eyebrows out for more room.... only about 1 cc change in chamber volume. The TA valves have less dish in the face, about 1.6 cc (TA) vs 4.5 cc of the stock valves.... the valves more than make up any loss by modding the chamber. BTW, I do have an issue with the oversize intake-exhaust valves being too close together on some cylinders.
Not really! (for me anyway). I don't have a flow bench, but I'm reading Vizard's book and watch a lot of YouTube vids! I've studied Bob's posts as well as a bunch of pics I've found online. David Vizard, Eric Weingarter, and Charles Servedio have some good vids. I do recommend making molds of your ports to see what they really look like. I'm now using Startso World silicone from Amazon.
no the set on Bob's car was his own set he did for himself. koffel had 1.94-1.50 size valves. Bob would use 1.92-1.55 valves. can't recall if he ever told me the flow numbers on those heads.
Looking at the chart Walt put up comparing heads, the intakes labeled Magnotti stock are stock heads with a 1.94” valve installed by Carmen. Compared to the stock heads, the 1.94 valve flows roughly 1o CFM better at every lift point until .400.” At .400”, these heads flow the same as stock valve heads. Beyond .400”, the heads flow roughly 10 CFM less then stock heads. This is a direct result of the shrouding. The intake labeled moderate Magnotti are same 1.94” heads after unshrouding the valve by about 5CCs and some moderate porting. The effect is a little more flow at the lower lifts for the same head, but a large increase in CFM at .400”lift and beyond compared to stock head and the same heads before porting and unshrouding. This again is due mainly to unshrouding. Cheryl
the most important number is the at 300 lift on the intake valve. the exhaust is towards the higher lift numbers like 500 lift. koffel = 186 flow don't know how accurate that number is. Bob = 177. Gessler = 171. lewis =165. Having access to a flow bench would really be a great help in porting heads if you're going to get into deep head porting
Thats great background information.. for as many years as thing chart has made the rounds , I wasnt aware of that..
The original chart at Buicks.net explains most of the background on the heads. It was originally posted at 10 inches of water but later converted to 28. Notice of the edit was overlooked. It has been cut and pasted over time to different sites and some of the labeling and identifying information was lost in reposting. It makes the most sense in the original form over there.
According to Bob there was nothing to be gained on the roof as it was a dead area in flow. Bob had actually picked up flow when he added clay to the roof. He & I had spent lots of time on this subject. The same with Mike to some extent. I had always asked Bob about doing more work on the exhaust. His reply was "the more you get in the more Pressure/bang there is & it has to go out" as it has no other choice. That's one reason he worked on the intakes so much. Tom T.
^^^ Well, ok then!.... I dove back in and took 0.035" from the floor @ the pinch point. Extended the grind into the short turn and went over it a little. MCSA is now about 1.92. I think I'm done now!
Spelling repaired in post. Do you have any thoughts on the porting comparisons? Is there a way to outdo yourself? Cheryl
