Current motor builds: 350, SB400, 454; also balancing question

[mountainexplorer]

Well, I think I finally figured out what combinations are going together, and what motor is going where:

350 4-bolt main 1978 truck block, cast crank 10/10, bored .030 over with hypereutectic flattop pistons, Comp 270 duration/.470" lift cam, gear drive, 186 casting Camel hump 64cc chamber heads with accesory holes, 1.94 intakes valves, Z28 springs, hardened seats, roller rockers. Topped off with an Edelbrock Performer intake. This will go into my '76 Camo Blazer with 4.88 gears.

SB400 2-bolt main, bored .040 over, cast crank, hypereutectic flattop pistons, Comp 280 duration/.480 lift cam, Cloyes gear drive, 041 casting 64cc chamber heads with screw in studs and guide plates, 1.94/1.50s, Z28 springs, Erson roller rockers. With an Edelbrock Performer RPM intake and 625cfm carb. This will go into my Blue '84 K5 with 35's and 4.10s.

454, 1976 block bored .030 over, flattop pistons. This is currently a running motor I want to make the following changes to: Comp High Energy 268 cam (and new cam bearings), and possibly a Pete Jackson noisy gear drive. I have the 781 open chamber (118cc) oval port heads that came on this motor... but am debating using the 215 casting semi-closed 101cc chamber heads that I have instead. This motor would go into my '82 Stepside with 4.10s running 36's and 39.5's. If I use the open chamber heads on this 454, the closed chamber heads will go onto a 496- and vice versa.

Most of my reasoning for using these parts I listed is because it's what I already have or was able to get through a trade. On the 350 and the 400, I have the option of spending an extra $100 cash on each motor and having the cranks balanced. Anyone think I should have either motor balanced?

 

[jk3078]

From everything I've been hearing lately balancing is the way to go if you want to rev. them and get them to live very long. Maybe balance the 454 add a rev limiter and run the pee out of it!

 

[sled_dog]

you don't want just the crank balanced. Is that what they are offering? You want the whole rotating assembly balanced. If they tell you to just bring the crank, don't go that route. Balancing is definetally a good way to go though. It puts less load on bearings(extending life), less of that load means the engine is freer to spin up, means better RPMs and quicker getting there. A really well balanced engine with a good valvetrain is really something to hear. Just raps from idle to 5k with a throttle blip.

 

[mountainexplorer]

It's a guy I know that has a crank balancing machine. I don't think he has the resources to balance the entire rotating assembly (well, I think he does for race motors that he builds... but I'm sure it's a bit more than the $100 crank balancing).

 

[sled_dog]

if he does the stuff he should know whether its a good idea or not. IMO its not worth the time and money to just balance the crank. Balancing the rods is just a matter of matching their weights, weighing them, attaching simulation weights to the crankshaft journals that act as if the pistons and rods are attached to the crank and then balancing the crankshaft. Its time consuming, and I'd also bet it more than $100. Oh well its worth the expense in my book. Never not balance an engine again. I just pulled apart the unbalanced 355 I built a few years ago. It never liked to rev much, didn't get their in a hurry, and the bearings weren't too pretty when I pulled it apart(granted they took a bath in antifreeze at the end too).

 

[dyeager535]

When I had all the parts on my 355 balanced, it was right around $125.

That was the crank, pistons, rods, flywheel and balancer.