This should be a good topic with a lot of feedback. I currently have two motors that I can build and I'm having a problem with making the big decision. I have a 400 small block that is ready for machining. I also have a 71 LS-3 402 that is bored 30 over to 408 CI. I like the sex appeal of the big block and the fact that my car was cloned prior to me buying it (the only way I could afford one). It looks like a 68 SS-396, only it has a 350 in it with a 4-speed and a 3.55 Geared 12-Bolt. I also like the idea of a 406 small block due to it's lighter weight (the car may see some strip duty, but mostly street cruising) and cheaper speed parts. The big block is ready for assembly and I just need to pick the type of cam I want to use, but I don't know if I should use the small block or not.

Big Block :D 150 lbs of weight and gobs of torque to move it.

If it were me than it would be the SB because you wouldn't have to buy motor mounts/springs plus it's lighter. but the main journals are bigger on a BB which would mean it could spin higher RPMs right? JMHO

BB. i had to choose between a 350 and a 400 sb and chose the 400, which is fine. however if i would have been in your shoes and choosing between a 402 and a 400 it wouldnt even be a question, i would have gone with the BB. the reason is not performance, it is the overall reliability and quality of a big block vs. a 400, siamese cylinders, sb. now if you leave that BB close to stock there will be some built 406's that could seriously spank you, but even then you will still have the better engine. and if you build it a bit, you will have the best of both worlds.

Don't even screw around with the 402 motor and go pick up a mid '70's, 454 P/U core motor and build it instead!!

About the same price as the 402 and if the 454 has a bad crank, then for not all that much more then what it will cost to keep it a 454, you can make a 496 out of it !!

pdq67

Originally posted by young gun '71:
If it were me than it would be the SB because you wouldn't have to buy motor mounts/springs plus it's lighter..you don't have to change motor mounts and you don't need to change springs.Small block springs with a big block..maximum weight transfer graemlins/thumbsup.gif works better than those "trick" springs :D
I would pick the big block..a 400 small block is a damn good motor...but comparing the 2 in stock form (especially using stock heads),use the 402 IMHO..cam it right and gear it right,you'll have one fun combo

I like both big and small block. If you have the 402 motor ready to go - use it. Didn't catch what heads you were using, only downside is if you have the '71 open chamber heads and the stock pistons, the CR will be really low. You can still get a lot of power out of it, but you will need to get a short duration cam to make power.

Verify the compression, and don't overcam the motr.

Originally posted by mr 4 speed:
you don't have to change motor mounts and you don't need to change springs.even the rubber part??? that's cool! I dunno if the springs would work in a place like where I live though because my friend put a SB in a '74 nova that had a straight 6 and he mashed his headers, his rear end followed shortly after :D . :eek: we have crappy roads... even the new ones. :rolleyes:

IMO the SB would be way cheaper to build.......with a set of vortec heads they scream.

I would imagine you have open heads on your BB. My guess is with the BB you would have more headroom to go fast (at a price LOL )and more points on the "Coolness" factor. I'm no expert on these as I am currently learning how to make one fast graemlins/clonk.gif

There is no feeling better (well maybe a few ;) )than banging a 4 speed behind a BBC. The tourque they produce is amazing. After going BBC, I wouldn't do anything but have more cubes, except for maybe a 427 ;) Go BB! graemlins/thumbsup.gif
Chris

Thanks for all the opinions, guys. A little more info on the 402: It has the original heads, fully ported but probably needing guides and new valves. The pistons are TRW Forged closed chambered with a dome that should make 10 to 1 or maybe 10.5 to 1 compression. I believe that they produce 11 to 1 with the correct closed-chamber heads (L-78 Replacements). I haven't purchased a cam yet, any suggestions? What about calve to notch cleareance, you know, the notches on the top of the cylinders? Anybody have specs for the largest cam (lift) I could use without interference problems? I will also be using a stock 1968 SS-396 hood and will be buying a new intake for it. Right now, I have an Edelbrock Torker for the motor, but I'd like something a little more modern that will make more torque and HP-maybe a Performer RPM if it will fit. The car will see mostly street duty, but WILL go to the track a few times, to be sure.

the Performer RPM Air Gap will clear with a spacer on it. I'm going with a solid roller in the 656/661 lift range and the heads had to be clearanced,valve guides for that. I imagine you could go to a slightly smaller street grind with no problems

If you going to keep the 3.55 gers and 4 speed i would put a mild solid cam it. something around high 230s@50 low 240@s on the intake and alittle more on the exhaust. If you already have all them parts just build,