I installed a 406 in my 88 last year and wasn't aware that you have to modify the crossmember to fit the balancer. I want to know what is the best way to do this I'm going to be lifting the engine up this week to do it. should I just cut it with a sawzall or what. any feedback is appreciated

 

Well, to begin with you should've had it internally balanced so you didn't have to use the big 8" damper. But, if that's too late you'll have to do the same thing we do when we put a big block in one. Take a plasma cutter or cut-off tool and section a clearance out of the cross-member, then reweld a new section in it to clear the damper...
-Jeb

 

Another approach - buy a smaller balancer and have it match balanced to the big one you have on there now. I have a 7 in ATI balancer on my motor and no clearance issues.

Good luck

 

skidwn it slightly modified his with a hammer, if i remember reading that correctly.

 

I even bought a 6 1/2" diam balancer from... can't remember the name brand but very popular - Fluidamper I think. Anyway, the OEM ext balanced damper is 8" and that won't clear. Buy a smaller diam. ext balanced damper and it will be the same size a stock with NO clearance issues AND externally balanced.

That stuff about having it internally balanced won't work without a specially designed crank (not easily or cheaply anyway). The damper I bought was $250 at summt. Be sure to clear-coat it before installation though, as it's a bare metal I believe.

 

That's incredible...
I open the corvetteforum c4 tech perf to ask a similar question...and i see yor question...
I bought an Eagle BALANCED 383 kit . I ordered BALANCED just to be sure to have it balanced. (I'm in Italy and if i purchase separately the crank, the rods, the balancer, pistons etc.. and I go to an engine shop asking for balacing it... for shure the ask 1 million dollar and the for sure they make a mistake because in Italy no one uses 8 cylinders engines...)
The kits for 1 pc rear seal (except LT series) are sold only external balanced.
Since they supplies the kit with a generic flexplate (the option is 153 or 168 and I chosen the 153 th one) and a generic 400 balancer (and i suppose it is 8" diameter).
Is it for sure that this big balancer (compared to the neutral one of 6 3/4") does NOT fit the front engine compartment (crossmember clearance) ??
Does not exists a 6 3/4" or 7" 400 balancer??
Thanks
-Beppe-

 

I've gone around on this for a while.
If your block is internal balanced - Like mine you need an internal danpner.

As far as I know all GM stock motors are internal balancer (Talking about the C4 L98 and LT1s)

There are may companys...

Got to take my dauhger to school..... I'll be back....

 

I don't think so...
If I bought the kit B13005L (L is for later and is supplied with a 1 pc rear seal 86-later, B is for Balanced) and the kit is EXTERNALLY balanced (for this reason they supplies the ext damper..) this means that a L98 (L98 87 and later ARE with 1pc rear seal CAN run externally balaced.). The only problem here with corvette is that (it seems) that we have not clearance to clear the big balancer ....
...And if we want to be accurate... a 1 pc rear seal 350 I generation engine is Internal Balance in Front and external in the rear and they needs a counterweighted flexplate for proper engine balance.
When i bought (two years ago) a balanced 350 Eagle kit it comes with a 153 flexplate (with the wheight...) and I reused the old NEUTRAL front balancer.
-Beppe-

 

My 406 is internally balanced at the front, and externally balanced at the rear.

Option 1 = smaller damper
Option 2 = ding the cross member
Option 3 = have the crank internally balanced.

IMHO

 

Generally the lower-end "balanced" reciprocating assemblies for 383's ARE externally balanced. This is due mainly to cost... It's simpler and cheaper, as well as less time consuming to counterweight the damper and flexplate than to match all components and then possibly have to add mallory for a neutral balance internally. 383's are generally built with a 400 style damper and flywheel/flexplate for this reason. Eagle, Scat, CAT, all of those that sell less expensive components don't profile the crank counterweights, their pistons and rods are usually heavier or have one component light and another heavy (ie., not matched according to purpose) which is usually accompanied by balancing via counterweighted damper and lightening the counterweights. Internal balancing is more expensive and time consuming and therefore would up the price of the reciprocating assembly considerably. Higher end kits from Callies, Lunati, and some others are almost always internally balanced and have very nicely match-weighted components, but they are also considerably more expensive.

As for a smaller external balance damper, that is a possibility I had forgotten. ATI, Fluidampr, Fischer, and others build 7" counter-weighted SBC dampers... You could certainly do that, I would before "modifying" the cross-member.
-Jeb

 

I found a couple of 6 3/4 balancers on ebay for externally balanced 400's. for $50. If I order one of these do I need to take it to a machine shop and have it balance matched to the 8" one that is on the engine right now? or can I just put it on?

 

Make sure they are SFI approved.

 

There is a beautiful set of pictures on here somewhere, which shows how the mod is done with two big ballpeen hammers (no cutting necessary). I was directed to them when I asked the same question 3 or 4 months ago but now I can't find them. The procedure is basically as follows:

If your engine is in place, with chalk or paint stick mark the cross member at the front edge of the damper and about an inch eather side just outside the point of contact.

Remove the engine.

While standing in the engine compartment, place one hammer with the ball against the crossmember and smack it sufficiently with the other large hammer to dent in the cross member. Move the ball contacting the crossmember each time, until the area inside your marks is completely displaced. Repeat until you have smashed the crossmember under the damper by 1/4" to 3/8" (6 to 8 mm). Beat it to a fairly smooth contour and spray with black semi gloss paint.

Replace the engine and check clearence.

 

I really don't want to remove the engine again. why do the balancers have to be SFI approved?

 

these are the Balancers I'm lookin at
http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWA%3AIT

http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWA%3AIT

http://cgi.ebay.com/ebaymotors/ws/eB...RK%3AMEWA%3AIT

 

Balancers do not "have to be approved." This is an NHRA safety issue in a high revving performance engine....so they don't grenade and ruin your day. Cheap insurance IMO

 

88421vette, this is my same question...
Now you have an external Balanced system . All is balanced.
All is good, the problem is that your Balanced (again...) system has a 8" damper on front that do not clear the crossmember.
Now you (and me ) are asking if JUST swapping the 8" balancer with a 6-3/4" will destroy (or unbalance) your Balanced system.
400 balacers are with a conterwheigt (usually 26 oz???).
What happens if this wheight is on the outer part of the balacer ? on a 8" balancer will create a momentum, with a 6-3/4" a lower momentum force...
I will be happy to be answered to this question .
-Beppe-

 

http://temp.corvetteforum.net/c4/ski...stallation.htm

Middle of the page, the ballpeen hammer technique....

 

Good pics!

-Beppe-

 

SFI is cheap insurance for your motor. Also, depending on the times you run, the tech inspector may look for the SFI rating. Its worth it.
My question now is, where to get a 350 balancer that uses a "bolt on" weight for external balance? I've never heard of one. In the process of doing a 406 myself. Probably use the stock size flexplate, balancer, and internally balance it.