I am happy to be a nailhead, nailheader which ever is the correct term. I have 425 66 Toronado as well. Totally different engine. My past experience has been small block Chevy's. My 72 Malibu would turn 8,500 rpm before it left its power curve. Had quite a bit of mod to that one. Triple springs, shaved heads and block, ported, largest hydraulic lift cam available 480 lift 292 duration TRW, Mallory ignition. 67 LS7 closed chamber 202 heads. I don't intend to go wild with this engine though. Just best it can run stock with hyped ignition.
What is the max RPM for the 425 dual quad? With hei does it ever get close to a valve float condition or does their shape and size prevent this. Also because the shape and size is there, dare I say, inherent flow problems. I had to do the triple spring job on my Chevy because of float. I have read they like big carbs and lots of CFM so do you have to do work to get it out so to speak?
Hi Sharkey(when you feel comfy enough a real name would be great). Welcome aboard. Since I have had my 64 Rivi' I have learned a TON of information here, and I am still learning. I saw you were like me and had a Chebby SB in the past. Best thing you can do is forget everything about those times cause they do not apply here. The Nailhead is an engine which was designed for low end torque. Anything over 5G on the tach is a waste of time. Sure, the Nail has been known to hold power above that, but you are trying to move a land yacht not a Vega. A Nail will start to pull HARD at 2K as opposed to a SBC that is just beginning to start at 3K. Took me a while to get my head around that but once you do you will understand the dynamics and the limitations of the Nail. My suggestion is to wander through the forum there are many established threads that can answer a myriad of questions. - Good Luck and I hope she runs well for you:TU:
i would consider that 5600 to be the max rpms for most nails.... I have wound one particular engine to 6000 repeatedly, but it had leveled out by that time.... i like to set the governor in the trans to shift rpm and then just stomp and steer....
Most th400 governors shift at 4800 rpms.... There is a mod outlined by Buick that raises that to about 5500 or so... You have to alter the weights and springs.... the toggle is a simple mod ,, just come off a 12 volt source, go to a toggle switch that is mounted whereever you want it and then to the terminal on the side of the trans. When you sw it on the torque converter goes to high stall and stays there untill you switch it off...
I have only read about this in an old Hot Rod magazine article called "Bluprinting Buicks for Action" where you drill four .250 holes in the govenor fly weights and remove one spring, however it doesn't say what that does. Is there a Buick bulletin or somewhere else this is published that would have more details, Doc? What is your method for adjusting shift RPM? Erik
For a time Buick had a publication entitled ''Service reccomendations for heavy duty applications'',,,, this is the source and the method that i have used.... do it just like buick says.... but it has been many years and I dont know if that piece is still available and I have lost mine....
