Folks,

How do you balance a 400 sbc? I think I need to replace the crank shaft. If I bring the crankshaft, harmonic balancer and flex plate to a machinist, can he balance the crankshaft for me?

I look forward to your response. Thank you.

Take it to a machinist who does balancing, and have the entire rotating assembly done, rods, pistons, crank, flywheel, balancer. And next time you install in your 400, make sure the bolt holding the balancer is torqued to spec with a drop of lock tite.

Thank you brother, that's what I'll do.

The 400 sbc is externally balanced, so it requires a counter weighted balancer and flywheel. it is possible to put a neutral balance on the 400 crank, but it requires drilling large holes in the crank weights and filling them with a heavy metal. If you don't want to spend the extra money making a neutral balanced 400 crank, you can still get your 400 balanced better at the machine shop, using the stock counter weighted balancer and flywheel.

I wonder what it would cost approx? to have the crankshaft neutral balanced? I’m thinking of buying a new 400 sbc crankshaft and taking it to a machine shop. Would it have to be a specialty shop or can any machinist do this for me? I really like that idea and had never heard of that before. This would honestly make the rebuild a heck of a lot easier for me. Please correct me if I am wrong, but I should be able to use the 350 sbc 168 tooth flexplate and 350 sbc harmonic balancer: right?

I am new to the forum (any forum for that matter) but, really truly enjoy what I read and learn more every time I log on. Thank you for your help
This is Great !!! Modern Technology

that is right. you could use all the 350 stuff (balancer and flywheel)

takes kind of a special shop to balance a 400 crank like that. However, I'm sure you can find a neutral balanced 400 crank at summit racing.

350's are balanced internally so the flexplate and harmonic balancer from a 350 will not work on a 400. A 400 is balanced externally and use a flexplate and harmonic balancer just for that purpose.

__________________
Hotrodding is much more than just owning a hotrod...It is a state of mind!

http://store.summitracing.com/partd...7I&autoview=sku

check out this crank. neutral balance, 3.75 stroke, for 300 dollars.

454,

Thanks Brother,

I did not know that an internally balanced 400 sbc crankshaft existed. Wow! I found one on the internet and affordable too!!! Thank you ... really useful and helpful !!! .... This will save me a lot of time and money ... Tufel Hunden

my pleasure. make sure to get the crank that fits your engine block. there are lots of cranks out there. one piece and two pieces seals and cranks with different bearing sizes and chamfers and strokes. do your research!

good luck.

Keep in mind, you should still get that "internal" balanced crank to a machine shop to check the balance for your actual bobweighted assembly. It might be close enough to balance to your parts, but there is no way it will be "dead nuts". There are too many rod and piston combinations that will change the balance of any crankshaft, so dont assume it will be fine and ready to go without checking it first. They achieve this by adding more counterweight to the crank, eliminating the need for a counterweighted balancer and flywheel/flexplate. But keep in mind this also can cause block to counterweight interference. You will need to install the crank first in the block with some set-up bearings to see if you have any issues before you proceed. Nothing would ruin your day more than paying to have your crank balanced, and then find out you need to grind a 1/4" off some of the counterweights to clear the block, and have to pay to get it rebalanced.Also, your other question about cost of internally balancing varies of course to the region you live in. It also is dependant on the total # of pieces of mallory metal required to be installed. Some shops charge as much as $40-$50 per piece of mallory installed, + a $125-$150 balance charge! Depending on the bobweight, the heavier the bobweight the more pieces of mallory required, also the lighter the bobweight the less mallory required. Many internally balanced 400's can have at least 3 pieces in the front, and 3 in the back,so that will give you a base reference. Not to bust anybodies bubble, but when the automotive market began to see a lot of these "offshore" stroker cranks(You know,countries that have 4 year old kids making engine parts)come on the scene. Many consumers were swepted up in the fact of the cheap cost for buying one, until the took it a machine shop to get balanced or other work done. And quickly found that more times than not, it cost more to balance these cranks than an OEM 400 crank. Even staying external on the balance required mallory to be installed on some. The counterweight structure was and is not correctly designed on many of them still to this day. So dont be quick to make a decision on an aftermarket vs. OEM 400 until you price all your options....Having written engine building tech columns for many car magazines, and having companies offer there products for evaluation on article projects, I've seen the best and the worst of what is out there....believe me!

Check out Eagle rotating assemblys

http://www.eaglerod.com/products/Ch...assemblies.html

they will balance it for you....and give you the correct flexplate and balancer.

I used the above listed kit in my 383. it was balanced, stroker clearanced, and had the correct bearings for the .002-.003 clearances even though the mains were +.001.

I couldn't have been happier with it and it runs great.

Thank you all for the advice.