BTW, this is the build... >>>It was a stock rebuild other than mild port job, 425 GS cam and Tom's Bad A$$ rockers! ....with a stock 4bbl and a 660 Holley. There was more in it. The engine had about 140PSI cranking. Which is about 9-9.25:1 mechanical compression. We ended up with some problems with the 2 4bbl carbs we had (which is now aleviated)<<<< Mike, that's not bad for a basicly stock rebuild....You're 15 hp over the stock rating. At least it's not lower than the stock rating like the 401 that Street Rodder built! How much more do you think that combo has left in it with tuning changes? From what I can make of the data, it looks like the mixture is rich at 12:1. Leaner is meaner...so how much more hp could be gained with a leaner mixture? I wonder if a different carb would make much of an improvement.
So if I see this correctly: The 401 rated @ 325 hp was actually closer to the 425 rating coming in at 340 hp. I wonder it a lot of these engines were underrated or that Tom's Rockers added 25 hp. (Probably the latter) Do people run hydraulic roller lifters in Nailheads? This along with tom's rockers would free up another pretty good chunk of power plus give a lot of flexibility of cam choices. Inquiring minds want to know. Thanks, Ty
I dug up these power curves from some '66 Buick literature. First is the standard Skylark GS 401, rated at 325hp. To the right is the optional Q-jet 401, rated at 340 hp. P.S. the optional 401 340hp Q-jet engine was called the 'Wildcat GS' engine....
And here they are overlaid... The AFB engine makes more hp below 3200 rpm, but the Q-jet takes over and makes more peak power. The Q-jet engine also has more torque over 3500 rpm, tho it's slightly lower than the AFB engine at lower rpms. Now I wish we could find curves for a 2x4 engine...
And for the heck of it, here is the dyno curve overlaid on the Buick curves. Now, realize the margin of error must be huge, but.....wth! Still, it's interesting to see that they are close.
I thought the torque and HP curves had to cross @ 5250 rpm- "Because torque and rpm are divided by 5252, torque and horsepower are always equal at 5252 rpm. If you solve the equation at 5252 rpm, the rpm value cancels out, leaving horsepower equal to torque. If you plot torque and horsepower curves on a graph, the lines will always cross at 5250 rpm (rounded off). If they don't, the curve is undoubtedly bogus." (from http://www.carcraft.com/techarticles/horsepower_vs_torque/index.html ) I have to look at the graphs again with what Jim said in mind now. If there are different scales, they curves are not going to cross at 5252. Not thinkin' right, musta been at work.
It Looks Like Family Guys Specks Would Cross At The Rite Rpm But Buick Must Have Just Made Up Their Lines
Different carb would HAVE to make an improvement. A 660 Holley is not enough for 400 inches. Actually. when it comes to air fuel ratios, each engine is different. I've found 11.7-12.1 is the best for the most HP. I think a better distributor/ a curved one would have been the better bang for the buck in this instance. Mike
AAALLLLLRIGHTY FOLKS!!! The moment we've all been waiting for!!! Tonight I got in the first break-in run, and one quick pull to get a starting place to tune. She got broke in at 1800-2000RPM, then pulled the oil filter and cut it open ('Normal). Attached are the dyno pull sheets. We pulled just from 3500 to 5000 RPM. showed 361 HP @ 4600RPM and Torque was on it's way down at 459 ftlbs on the first measurement at 3500RPM. It wasn't pretty for a first quick run, but here it is in all its glory just the same. Again this is the "out of the box" numbers. #4 cyllinder was running hot for some reason, Not exactly sure why. We moved the EGT probe and confirmed it was that cyllinder. We will likely change metering rods (richen) over just that carb bore. All the rest weren't too bad, except a little rich. My water pump also sprung a leak so the testing ended there. She sounded B-E-A-UTIFUL!!! here is a vid on U-tube: <object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/xuIKyzct4Sc"> </param> <embed src="http://www.youtube.com/v/xuIKyzct4Sc" type="application/x-shockwave-flash" width="425" height="350"> </embed> </object> <object width="425" height="350"> <param name="movie" value="http://www.youtube.com/v/TWGYfCwEvO8"> </param> <embed src="http://www.youtube.com/v/TWGYfCwEvO8" type="application/x-shockwave-flash" width="425" height="350"> </embed> </object> Me--->p Erik
Stock #'s so far o No: I am sure some tweaking is in order, but my guesstimate is 410HP 490lbs./ft. when all is said and done. Good luck Erik- don't break it!!:TU:
Don't dispair, or give up so quick. That one doesnt even coun't! I was debating not to even post that one. That wasn't a fair or complete pull as we were only looking for a starting place on the carbs. There will be many more pulls to come. Erik
You're off to a great start Erik! Ted's built 401 pulled 377hp. His Nail has a bigger cam, but you have more cubes. Can't wait to see how yours does! These Nails seem to be maxing out the hp at 4700 RPM, so we're not gonna see real big hp numbers like you would with an engine that peaks at 6500 RPM....I gotta find more dyno curves to see how other engines compare at 4700 rpm. This is cool!:bglasses:
