Build the 400. Screw the high RPM 302 motors, since you will make more HP and torque everywhere with a 400 in a package that is the same size and weight. A 383 is cheaper to build than a 400 and almost as good...the smaller bore will not breath as well however. Want a cheap killer pumpgas 400 combo? Stock crank, block, 5.7" rods and a cheap flattop piston. With the 64cc vortech heads and a comp XE268 you will have a smooth ilding torque monster that will make about 1hp/ci and boatloads of torque. A larger XE284 and some porting on the heads will get you close to 450hp. Keep the XE284 and go with some Dart Iron Eagle Platiums in the 215cc size, or a set of AFR in a similar port size and you will be pushing around 500hp - on pump gas with a maintainance free flat tappet cam. Run a big single plane intake and carb and 1 3/4" or 1 7/8" headers to kill off some bottom end. I don't know of any 302 doing that.
DITTO... How 'bout selling the 302 stuff to a '67-9 Z/28 guy and build the 327....... and I've got just the pistons for ya......
Quote: Originally Posted by JaysinSpaceman The piston spends more time near both TDC and BDC. As the crank turns past TDC/BDC the long rod motor will show less piston movement per a given number of degrees on either side of these positions. ====================================== Actually he's exactly right , a long rod motor will always park piston longer at TDC. If you want to make maximum power in any engine, you park the piston at the top for the longest time possible. It allows the most time for pressure to build, making the biggest explosion, sending the rod down with the greatest force. It's one of the hard & fast rules. Per Smokey also..... That said, build the short throw motor you want, they're a blast.
How can pressure 'build' when it's 'parked'????? Wouldn't pressure bleed off (around the rings) the longer it sat still (parked)??? Just curious....interesting stuff here.....
I keep hearing this and strongly disagree. How many racers are out there wishing for more RPM's when they cross that line at 6500. How many BIG BORE, BIG CID engines can survive above 7000 race after race? I personally like the high RPM motors and have built a few 302 and wish I hadn't sold any of them. You mentioned rules about not exceeding 305 CID, well then that is easy 302 all the way. I woudn't sacrafice 302 rpm band width for a midiacore 305. You later mentioned longer vs. shorter rods. I always prefered the longer rods. Thinking mechanically, the shorter rod will have a greater angle to piston centerline while going through a full stroke. That greater angle will result in greater side loads on the piston skirts. More load, more HP loss, and heat generated. There are argue ments in these subjects, my suggestion is to do your homework and build the motor that will suite your car and driving habits.
Bigger motors have more TORQUE....and that's what REALLY gets you going, and that torque can pull a 'taller' gear for less RPM through the traps......
build the biggest motor you can aford. im rebuilding a 327 to replace the tired 283 in my truck. i would use a 350 or a 400 in a second if i had one. makes sense to build a bigger engine for a hot rod doesnt it?
What he's saying is that the pistons spends longer at TDC (ie parked) so it allows for more complete combustion. The sooner your piston starts back down the bore, the less pressure you're building in the cylinder, because combustion is never "complete" when the piston starts back down. The longer it stays there, and the more pressure that gets built in the chamber, the harder the piston gets pushed back down.
How can pressure build ? The valves are closed and you've lit the fire, and you're holding that space for a longer time with the longer rod. While you're maintaining that space, the combustion pressure of the lit fire is going through the roof. Think of a firecracker loosely wrapped, it just blows out the ends and goes ****, wrap it with electrical tape to hold it in, way bigger bang. Now lock that explosion up in a steel container where after it's burning it has nowhere to go, it evenually goes off with a huge bang. The harder and longer you contain an explosion, the more m***ive it will be. There's no time for bleed down at any rpm if the rings & bore are right, let alone 7000+.
That's what I always thought too. Ina former life part of what i did for a living was very very powerful small displacement motors (2 liter-ish 4 cylinders) We did a whole ton of research into what rod ratios were doing inside the motor, to the point of doing piston speed spreadsheets, and building an identical motor three times, with three different lengths of rods. Anyhow, something learned was that short rod motors really do keep the piston on the bottom longer. I cannot really explain in words the geometry that causes it, but it has to do with relative motion. I don't think I really stated that one clearly. And it's arcane as hell, so not sure why i bothered at all. The basic gist is that due to the longer dwell time at BDC, it isn't pumping the intake charge back out during overlap as much as a long rod would. Anytime you have a piston headed away from bdc with the intake valve open, you're creating a positive pressure situation in that port, which has a slight effect on overall vacuum in the plenum. If you google "rod ratio" there is a lot of people that are better at explaining things than me...sometime to get from brain to words is more than I can do.
well its true, opinions are like ****-holes everybody has a diferrent one. light weight car =302/4speed
I think I actually get this. The pin is closer to the centerline of the crank at BDC. The closer the rods length is to the throw ...the more noticeable it will be. Go to the extreme of a 4" throw with a 4.2 inch rod. From 90* to 270* the rods arc is almost identical to the crank...then from 270* to 360* it shoots up like a rocket and then screams back down to 90* I may have to get out some parts and actually measure some angles. Doesn't change what I'm going to build but...really got the wheels in my head turning.
7000+ rpm 50 second 302 burnout... : http://videos.streetfire.net/category/Burnouts/4/wm/a026b51e-3c76-46d6-9413-98080105d4bf.htm Here's one at 8500 http://s22.photobucket.com/albums/b339/belairbobs/?action=view¤t=302Z.flv . .
Man, you guys know your ****!! I have wanted to build a 302 because of the hi-rev factor, but am torn now... I worked at a machine shop for years and have gathered up a lot of parts, so I'll throw this out for some "constructive critisism" and an answer for the "right" cam: by the way in ALL of this I have $250.00 invested!!!!!.... Here is what a have, FIRST set of items: 283 block, sonic tested, and bored to 4", alighn honed, and square decked, Eagle 327 small journal, floating pin rods, 4" bore 13:1 domed -302- pistons with zero gap rings, steel 283 crank that was drilled and tapped for the balancer bolt, camel hump heads that have gasket matched runners, mild, VERY- mild porting, screw in studs stainless stock valves, hardened seats, TRUE-double spring, Z-28 springs, 1:5intake, 1:6 exhaust true roller rockers, balanced rotating ***embly, solid and hydro lifters. All federal mogoul bearings, and an old mallory dual poit dist. with the big dual condensers, oh yeah and (I know what some of you think about theses..) a gear drive, high volume oil pump. THE ONLY THING I DON"T HAVE IS A CAM, 'cause I don't know which one to use. Next set of parts: another sonic tested 283 bored to 4 inches, alighn honed and square decked, 4" 13:1 pistons and zero gap rings, 327 rods shot peened, magnafluxed and polishing of the beams, 327 steel crank drilled and tapped also, balanced rotating ***embly, camel humps just like as described above, stock- NEW rocker arms, hydro and solid lifters, another same type of mallory dist. and the same type brngs. another gear drive, BUT another no cam 'cause I was unsure of what to get for it... So; one motor is intended for my '30 Chev coupe, and the other WAS, but now may not go into, ('cause I want a hemi for it) my '23 T!! What do you guys think of these 2 combo's, and what cams would work best for these 2 motors??? AND if you think I have a bunch of KRAP, let me know also so I don't waste my time. Even though I only have a small amount of cash, I have MANY hours of labor for the trading I did to get all this stuff, so I am not wanting to "experiment" and blow them up...Thanks in advance...Ken P/S: Yeah I know about the 13:1 compression, I have an airport less than 3 miles from me that I can get "Av gas" from so thats NOT a problem
OK, My only thought is. Come on, dude! Build someting that runs on pump gas. Trust me you will thank me later. Not that your high pressure scheme is unworkable, but I think if you back it off to a pump gas runner you will have more flexability, like, for instance, you could take a road trip farther than the limit of your gas tank's "1/2 from my Av gas supplier" point.
So what years and model numbers should we be on the lookout for as far as all things 327. Blocks and Head casting numbers...I need to find something for the current mosquito killin' Wagon...
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