69L71

Interested in opinions about tradeoffs of a nice modern 350 vs a torqey 406. The 350 build up I'm considering is along the lines of this one built by Chevy High Performance magazine. http://www.chevyhiperformance.com/in...rticleid=49083
Its based on a late-model roller block, LT4 HOT cam, and Vortec heads and makes 412 hp at 5,600 and 423 lb-ft at 4,400. It also managed 400 lb-ft from 3,500 all the way through 5,300 rpm, so its not a high RPM screamer. Plus the LT4 HOT cam kept things pretty docile. Plus, the parts are relatively cheap so it looks like an awesome motor for the money.

The 406 option is obviously a bit more old school. 2-piece rear main seal, no hyd. roller (don't want the expense of aftermarket pieces). Still, the extra stroke makes for awesome torque. Not looking for anything above 5500 to 6000 rpm but love the nice flat torque curve. I'd probably consider aluminum heads along the lines of the Summit/TFS units which breath well and are affordable. The engine would likely be something like this: http://www.chevyhiperformance.com/ed...1320&sidebar=1

Ideally, I think I could build either motor for around $2K and i could keep both looking like a stock 350/350 for the sleeper appeal.

I'm considering this for a 69 convertible with an M21 and 3.70s. I'm thinking this drivetrain lends itself more to the 350 where the gears make up for some of the lost torque but is more comfortable spinning the higher RPM cruise speeds. The alternative (and more $$) is to install a Richmond 5-speed or ROD with 3.08s. This leads me to the 406 where the car would be a great, all-purpose performance car without the need for high revs.

Thoughts?


[Modified by 69L71, 8:10 AM 6/20/2002]

mrvette

I just can't see going with an early block, no factory rollers and 2 piece seals...plus the high prices associated with 400 blocks and stroker cranks...
seems to me a 355 engine is pretty damn close in performance for the differance n bux....about 15% gain for what??? another 1500 bux??...maybe more, depending...
Of course I allready hada commitment to the L98 style system going on my original engine, so stuck with it, looks good & hairey, even today...
but of course it got opened up trick parts also, along the way....

I might be tempted for the 383 route now that internals are so cheap compared to say 5 years ago....

GENE

69L71

I thought about a 383 version of the roller 350 but don't want to spend the cash for a new crank. Besides, if I go with a stroker I might as well go 400 and get the bore increase as well.

I have access to a cheap late 350 roller block (its in a truck and doesn't have the roller system but I can get it from Scoggin Dickey) and rotating assembly. I also have a complete 400 2-bolt in my basement, so I'm not sweating the expense of finding 400 parts. I payed $300 for the whole motor, and its standard bore! :D

You're thinking along the lines I am though. Modern roller 350 vs. old-style 400. The roller 350 is quite an impressive performer across the board so its not as easy as 'bigger is better'.


[Modified by 69L71, 8:29 AM 6/20/2002]

71coupe

The 3.08 gears and a 5 speed (with a final 1 to 1, no O.D.) is a good idea. You still end up with an overdrive like gear without having a high driveshaft speed.
Whatever you build, build it to rev. I know that long stroke motors work best at lower speeds, but most people rev the snot out of the motor anyway.
You have a good plan except for the price. $2,000 sounds a little low
After you start adding up all of the nuts and bolts, it gets out of control :eek:
Good luck

The Money Pit

I've been building 350's for 20 years and know what the limits are for street use. The 406 is the way to go for street manners in addition to major power. I just built my first 400 chevy ( done pontiac's before) and am quite pleased with the result. I run 10.1:1 flattops, AFR 195 heads (74cc) a Comp XE-274 cam and port matched Edelbrock RPM Q-Jet inatke. The whole package was designed for street use on pump gas. I estimate 450hp/500 lbs tq. Air Flow Research guestimates over 500 hp with this combo. The pull is strong off idle with just a hint of lope,and doesn't let off until over 5500 rpms. If I were to do it over the only change I'd make is the cam. I didn't realize how much cam a large displacement engine could tolerate,and to be safe I under cammed. The cost of the 406 including block and machinework was around $4500. I started with a bare 4 bolt block and had to buy everything,including bolts. I have clocked 15mpg with the 406,as compared to the 17mpg I got with the 355, so running the 406 isn't that big a difference. Save the money on the roller cam and spend it on your better half.
The only other option to match the torque would be a 6-71, and that means jigsaw to the hood and tickets from every cop that wants a closer look.

69L71

Sounds like a nice motor money-pit. I never questioned that the 406 would have quite a bit more ***** than a 350, but there are associated costs too. I'm lucky because I have a nice 73, high nickle, 2-bolt block and a stock crank so I dodge the bullet somewhat, but still the basic costs of parts on a 400 are more than a 350. Plus, the key to a good 400 is the head choice. You used AFRs. I'd consider the TFS. Both will add at least $1000 to the cost of a build up. Probably very worthwhile mind you, but money is money. The Vortecs are only 170cc so I think, as good as they are, they'd run out of steam on a 406.

The 355 that CHP built up is based on a low-cost shortblock and Vortec heads. The LT4 HOT cam is is quite inexpensive. The LT4 kit, which includes cam, 1.6 LT4 roller rocker arms, valve springs, valve caps, valve keys, and valve spring shims for $499. The hyd. roller lifters are $120/set. This is pretty much in line with hydraulic flat tappet stuff. Vortec heads are dirt cheap and only need spring pocket machining to install the LT4 springs. Again, pretty cheap.

I still think the 355 is cheaper to build and comes with the benefit of technology to build a nice torque curve and impressive power, but the 406 will always have more grunt.

Fevre

A stroker crank will run you less than $300 and will add way more than $300 in fun. A 383 roller cam would be one bad a ss engine.

The Dude

406.

It's a good place to start with lots more power potential down the road when you feel like tinkering.

0Mike69@ECS

Go for it!

BTW.... Which car are you doing this for now??? :crazy: :D

74vetteman

I've built 3 high perf 350's and now have my first 400 in my Vette. I would never go back to a 350 sized engine again for performance use.