I will be the first to admit I'm not an expert and still learning my nailhead facts, but I can read and try to rationalize. I keep hearing that the biggest problem with the nailheads is getting enough air flow. So I'm asking for advice. I'm starting with a 401 and a SP from a 65 skylark. I want to build a hotrod. Probably a Model A sedan style but preferrably a Buick body if I can find one. It will be light so the stock 325 hp rating would be ok, but I really want that mean sound of a rough idle. So can anyone give me advice on a rebuild with a rough idle cam, and a 4bbl on a 401. I'm not trying to build a racer. Is it worth paying for head work or the 2 4bbl? How much over should I go with the cylinder bore? and what sort of gains if any should I expect?
My "Rockers" will enhance the performance & sound of ANY cam you may install. Ask those that have done it. One of the very 1st. things noted was the sound of the exhaust was "Healthier". Right Tony?????
It was the first thing I said when we started the car up, if you remember. About 5-6 seconds into the car being started I asked Tom if he had noticed the difference in sound from the time I brought the car in to the time he had finished changing the rockers. If I remember correctly Tom, you even said you couln't believe the difference in the sound. It had a deeper growl to it, not a tinny/bumpidty bump sound you get from a cam, but a bassy growl. When I punched it I could feel my ass go into the seat deeper. I will recommend them to anyone who wants performance out of their Nail.:TU:
Are Yunick's modifications recorded for public domain anywhere? Does his "Power Secrets" cover the details associated with the 600HP 1964 nailhead?
that book doesn't mention the nailhead or any Buicks that I remember. It covers mainly theory and modifying the SBC for circle track applications.
on my 64 rivi 425 nail head i put on 650 cfm eddlebrock whats the best way to change the rear to posi not shure what gear is there but its not posi the trany is super 400 any thoughts thanks:Smarty:
The rear is a 3rd member type (Ford 9") so you can pull the axles and then pop the third member out and swap what you have. Many came stock with 3.07. Additional common choices were 3.23 and 3.42 which can be had from folks on the board and e-bay. There were some other taller gears made like 3.91 and even 4.56 but they are very rare to come by. A 650 E-brock is a good carb. Only 25 more CFM than the stock Carter. If you want more performance you can go with a 750 or 800 e-brock just make sure you buy the tuning kit so you can change the metering rods and/or jets. I have a 750 and it was too rich out of the box an needed to be leaned out some. Good luck - Tony
I have been waiting to see what others have done but I might as well pass on my limited experience. When I rebuilt mine (401, ~ 0.030 over) back in '99 I dynoed it (8-10 full power runs). I would have to hunt down the paperwork to get details, but I was not particularly impressed. I changed the cam to a Poston 300 (slightly hotter than a GS cam), did some mild port work, reduced the compression ratio with custom forged pistons (9.5:1), fully balanced, radiused oil holes in crank, rebuilt rocker shafts, harmonic balancer, Carter 750. I don't remember the shaft speed corresponding to the HP and torque, but the max HP was ~ 287 (maybe 4,700 rpm) and 384 ft-lbf of torque at ~ 2,800 or 2,900 rpm)..don't remember the shape of the curves. I do remember the torque curve was flat down to the minimum pull speed of ~ 1,700 rpm...so it was a beast down low, just ran out high up....oh yeah, stock exhaust manifolds.
one cheap improvement that you can do is to hog out the partition between the FRONT and REAR barrels of the intake manifold. I did it on my 425 and it helped a bunch. Be sure to leave the partition down the center, that saves the torque.
Wasn't that engine rated for 445ftlbs? If it was, to what do you attribute the differences between the stock ratings and your dyno results?o No:
Well, the first item is the compression ratio...going from 10.25:1 to 9.5:1 is probably good for most of the difference between the 325 and 287 and the 445 and 384. The difference in the rpm at which max hp and torque is generated is probably due to the slightly "hotter" cam. I suppose it is possible that Buick was stretching their original numbers a bit, since they didn't have the same level of scrutiny as, for instance, farm tractors do (i.e. Nebraska Tractor Tests) I'm hoping some senior, more knowledgable, folks out there have some of their own data to share.
the stock compression was only about 10.1 so 9.5.1 only cost you only about 5 hp. .030 over should make up 5hp. if you look at some old road tests and do the math, the real engine hp was about 290 and about 230 hp at the wheels. so you engine at 287 hp sounds about right so far, but a 750cfm carb and open air cleaner should put you at 300hp and the cam should give you 25hp for a total of 325hp. you are missing 35-40hp . new engine needs to seat the rings .do not how much horse power you are losing there?? also did you change jets in the carb . was the total timing at 32-35.
