Hello everyone. I have yet another question for you. I currently have the option of building either a 350 or a 406 for my '72 Vette. My question is, How would both of these engines perform if they were built identically(same heads,cam,compression,etc.)? Part of the reason I ask is because of budgetary constaints I may be limited in the cost of some parts, namely heads.I probably will not be able to get a nice ,high dollar set that would be optimal on the 406(at least to start with).
Could someone run DD2000 an dtell me the differnece between these two engines if every thing were identical. Lets say 9.5 to 1 comp, maybe vortec heads or S/R Torquers, Comp Cams XE268,RPM intake,headers, 650 or 750 vac sec carb.
Any info on these combos or any suggestions would be greatly appreciated.




[Modified by piratemike, 8:29 PM 12/29/2002]

 

The 406 can make more power in typical user RPM ranges (6500 and under), but it will also need larger heads and cam to be able to use it's larger displacement to advantage. With the "same" cam and heads (especially small ones like you mentioned) the 400 probably would not make noticably more power than the 350.

For what it's worth, in DD2000 you may see it showing less power for the 400, as (in it's analysis especially) the small cams really hurt once the displacement is increased. For example, if I run my 454 boat engines heads (stock rect port) and cam specs (296/306, .553/.571) with a 540" displacement, the estimated HP goes way down at all RPM's. The cams and heads are pretty good for the 454 displacement, but are much too small for the bigger engine

-Greg

 

I have 200cc Sportsman II heads on my 406, and they work great. The engine has absolutely no problem breathing to 6200 rpms (my rev limiter). Aren't the Sportsman IIs similar in price to the S/R Torquers?

 

on a given rule for 1hp for every inch you could pick up 50+hp plus a decent amount torque

 

Thanks everyone for the info. Now I need your suggestions. Regardless of which of these I build here is basically what I am looking for.
I would like to stay in the 9.5 - 10.0 to 1 comp, not spend over about $800 on heads(I'm on a budget), hydrualic flat tappet cam, noticeable idle but enough vacuum for power brakes, headlights etc.. This engine will probably not see over 5500-5800 rpm so, I would like a broad torque curve from about 2000-2500.
And I want my cake and eat it too.....:) LOL. Any suggestions on what parts and pieces for either of these engines to try and get what I am looking for?

Later,

Mike

 

How about Trick Flow aluminium heads? They are quite cheap, not sure about the quality - I have no first hand experience on them. Check the latest Summit catalogue for pricing.

Comp Cams Xtreme Energy series is quite good, I use their XE262 in my 327. Maybe XE274 would be quite close for your application. I would call CC tech line and ask their recommendation.

Hope this helps,

Tapio

 

Mike, A 406 with a set of 180cc Iron Pro Lighting Cylinder heads ($830-855)
assembled. A cam in the 230-240 @50 500/520 lift, a Performer RPM intake,
750 holley and your looking at 450+hp and close to 500ftlbs. A 406 would be perfect for what you want.

 

As a general "rule of thumb," with iron heads stay at 9.5:1 or lower on compression ratio. With aluminum heads, you can go to 10.5:1. If you violate this rule, you will have to run race gas, or octane boosters to stop detonation.

 

ALWAYS BUILD THE BIGGEST ENGINE YOU CAN AFFORD. COMPARING THE 355 AND THE 406 WITH IDENTICAL INTAKE AND VALVETRAIN PARTS LIKE YOU MENTIONED WOULD GIVE YOU A 355 WITH ROUGHLY ABOUT 350HP AND 380FTLBS OF TORQUE GIVE OR TAKE A FEW @ ABOUT 5500 PEAK HP AND 3500 PEAK TORQUE. THE 406 WOULD BE ROUGHLY ABOUT THE SAME 350HP BUT ABOUT 500-800RPM LOWER THAN THE 355 AND TORQUE WOULD BE ABOUT 450FTLBS @ ABOUT 3000RPM GIVING YOU A MORE LOW-END THAN THE 355 . THE NEED FOR GEARS TO MAKE UP FOR LESS TORQUE WITH THE 355 IS ELIMINATED. THE 406 WILL ALWAYS MAKE MORE TORQUE AND POWER WHEN THE ONLY DIFFERENCE IS THE DISPLACEMENT. SINCE CAMS COST THE SAME REGARDLESS OF CID YOU MAY WANT TO ADD 10DEGS TO INTAKE AND EXHAUST DUR@.050 IF YOU DECIDE TO GO WITH THE 406. A GOOD 2500-5500RPM DURATION FOR A 406 IS ABOUT 220-228 FOR INTAKE AND 228-234 FOR EXHAUST, WITH 9.5:1 CR STAY AROUND 110-112 LC. I' VE SEEN LOTS OF 355 MAKE 500HP WITHOUT FORCE INDUCTION BUT MANY WERE NOT AS STREETABLE AS 500HP 406. I BUILT ONE FOR A FRIEND IN A 85 VETTE EFI SIMILIAR TO YOUR COMBO BUT WITH FUEL INJECTION AND IT MADE 440HP WITH 500 FTLBS OF TORQUE AND IT DOESNT RUN HOT. ANYWAY IF YOU BUILD THE 406 BUILD THE SHORTBLOCK WITH ANY FUTURE CHANGES IN MIND THAT WAY ANY FUTURE UPGRADES CAN BE MADE WITHOUT PULLING OR TAKING THE SHORTBLOCK APART. GOOD LUCK!

 

a cheap 200cc head like the dart or pro action iron, little bigger cam and the 406 won't cost much more than your 350. to get the power out of that 406 you need more runner and more cam. it's also not too spendy to get it if your going somewhat mild.