Okay.....got the new flexplate this morning and took it over to Ed's to have the crank balanced. Carlos had everything setup and we bolted on the new flexplate and started up the machine. This is quite a setup. It is computerized and has a screen that shows two circles divided up in about 10 degree segments. (The segments are a guess on my part).

We spun the crank at 530 RPM and the weight difference is displayed on the right and left of the upper screen and the circles now have a red dot to indicate the place of improper weight. The circle to the left is the front of the crank and the right circle is the rear of the crank. This is an internally balanced 350 and you remove weight from the crank. You do need the flexplate and the harmonic dampener attached to the crank since they are part of the rotating mass. The flex plate that I brought in had weights welded to the plate.

The first spin indicated that the front of the crank was at 28.4 grams and the rear was at 10.8. Some of this difference could be the flexplate and dampener. Carlos told me that NASCAR standards are 3.0grams front and rear. There is a red dot in both circles in different locations. He turned the crank by hand until the solid line on the screen lined up with the red dot. This positions the drill vertically over the crank. The drill is on a rail that slides over the crank and he positions the drill at the front of the crank and drills out some material. Spins the crank again, lines up red dot and drills again. Spins again and drills again. This went back and forth from the front of the crank to the rear of the crank. Until the front of the crank was at .01 grams and the rear was at .38 grams. This is were the experience comes in, knowing how much to take off when drilling to get things as close as you can. Carlos said that he balances a crank to within .5 grams front to rear because that is how he learned to do it. That exceedes the NASCAR specifications and I am happy with the results.

By the way, the flexplate and the dampener are GM! It was very interesting to be able to watch a craftsman at work and be able to ask questions as the balance progressed. I learned a lot today. At the initial spin at 530 RPM you could tell there was a slight vibration. You are only riding on two journals, front and read. After the balance, spun the crank up to 750 RPM and it was as smooth as could be.

A expernally balanced engine (like a 400 block) would have the same set up, dampener, crank and flexplate or flywheel. But in case they would remove weight from the dampener and flexplate.

For those in the greater San Francisco Bay area, Ed's is the place to go.


Signature soooooon to be UPDATED....

 

I read your last post.....kept thinking "why did this guy buy a zz4?" you basically tore the motor down and built it correctly. The zz4 is a basic high performance stock like motor, not a race engine. I mean, from my point of view you greatly improved a zz4 yes, it's just the cost. For what a ZZ4 shortblock sells for you could have bought much better parts and had exact macheine work done. I guess my question is: Why did you start with a ZZ4 when you knew you wanted a better motor?

 

 

Here is a question, if the motor is internally balanced with out the balancer and flywheel/flexplate, can't you just add a neutral balance, balancer and flywheel/flexplate without throwing off the balance?

 

Reasons:

By the time you find block out the junk yard, buy parts and machine the block you are out more $$ than if you start with the ZZ4. The ZZ4 is a new block set up for a roller cam with standard pistons, not punched over, so there could be three rebuilds with the option to go 383. The L98 that I have is not a roller block. So in order to adapt this block to run a roller cam you are out about $400 for lifters, cam button, thrust plate and machine work. Even after the balancing and the extra work, I am still at a lower cost than going with a build and buying parts....and less time on the turn around.

And, yes I could have just dropped it in and it would have run for several years. But past experience had shown me that the last engine I built lasted for 23 years. And that was balanced, mild off road cam, headers, duel exhaust, Edlebrock intake, Holley carb. This stock engine (in a 4X4) would not go faster than 80 flat out (3.07 gears) and was getting about 10 MPG. After the engine build and changing gears from 3.07 to 3.73, top end was 125 MPH+ and 16-18 MPG on the road and would idle all day at 600 RPM if you wanted to crawl off road. I had over 300,000 miles on the engine many off road before I had to change it out. I expect this engine to last....

You get what you pay for. The ZZ4 block was cleaned per GM standards, and balanced per GM standards. But if you have been hanging around this Forum for awhile, you have discovered that just because GM built it that way doesn't mean you can't do it better. For years GM built (as did other car companies) engines that were a compromise of many factors. You can get more out of that old stock engine with some modifications. Could GM have done these mods..YES. In their newer cars they have discarded the cast iron heads (which my 85 came with) and gone to aluminum, dumped the pressed rocker arms in place of roller rockers. Changed out flat hydraulic lifter for roller lifters, gone to roller cams instead of the old cam. Vortec heads are flowing better than the head of 5-6 years ago. Exhaust changes.....and many newer changes to the newer corvette. The new ones out of the show room still with paper plates are running 12's at the track . My stock 85 was 230 HP stock, with the modifications that I made before this ZZ4, I am at about 346 HP at the crank. I used to get 25-26 MPG on the road, now I get 27.2 with all those extra horses. Do I go to the track each weekend or street race.....NO. Once or twice a year at the track, and last year my oldest son and traded turns running the car down the track.

In answer to the balancing question concerning netural damper and flexplate, yes you could switch without changing the "GM balance". But are you happy or will you accept the standard used for their balance tolerances. Is 4 to 6 grams difference acceptable for piston and pin weights? Is 28.4 to 10.8 acceptable for the crank?

 

I think his point is,why would you use a gm flexplate with weights on it to balance your motor?If this motor is being used as a perf build,you would want a sfi approved flexplate on it which they sell neutral.
You balanced your motor using a swiss cheese flexplate with weights that i would not trust on a perf buildup.
I have seen sfi flexplates crack before and would never trust a stock gm one.
The way i understand it,since you balanced your motor using a flexplate with weights,you cant now switch to a neutral balanced flexplate without throwing off your balance.
Am i missing something here?
I just dont understand why they would balance it that way.
Your motor is still externally balanced in my eyes,you just improved the gm standerds but it is still not a true internally balanced motor that you would be able to bolt a neutral flexplate and balancer too.

 

I was just trying to provide information concerning the status of a "GM balance" all the way from pistons/pins/rods to the crank assembly for those who are not familiar with balancing and what can be achieved beyond GM standards.

This is an economic build that is not radical in compression, RPM range or high cost parts. I am transferring most parts from the old engine. I am putting this back together myself, not paying a shop to do all the work.

Forget about taking off the current dampener and flexplate and replacing them with a netural set. Go check out a business that balances assemblies and you will find that they want all the pieces. I got the GM plate because it was the only one available. And based on GM standards this would have been balanced to their standards. Am I building this engine to run 9's through the 1/4 or to road race? No, it will be a daily driver. I don't have the time frame to wait a week or two to get a new plate in. I have to get this together, take it to Vancouver Washington to burn a new chip all before June 8th. I am working 7 days per week at least 12-14 hours per day, so pulling this engine and puttting it back together again is a trail. So time is not an option. Regardless of weights on the flexplate or not. The assembly is balanced and I am happy with the way it was done and how it was done. I expect this to last much longer than a standard ZZ4 crate engine. Would a netural flexplate have been better for the assembly? Probably. In the motor that lasted 23 years, I never had to replace the flexplate or the dampener. On any motor that is internally balanced, If you have to replace the flexplate or damper, you take it off and they stick it on the balancer with a duplicate on the other side and balance to the same. You would have to do the same thing with an external balanced engine if you needed to replace the flexplate or dampener.

 

Oh i totally understand the why, i have a gram balanced motor in my car. all you have to do is glance at the stock high performance imports that are gram balanced and reinforced at the factory. 8,000+ rpm and 250,000 miles, that's a honda b18c, same goes for ours, wear is reduced and the rpm capibility is much higher. i mean what you did is a great idea if money is no big deal. the more you type, the more i see you created what fits your needs, that i totally see. it was a good read, just think you could use higher end parts on a seasoned core for not too much more. gen 1 roller blocks sell for around 200 in my area. pistons, 300 for speedpro forged, 100 for hellfire rings, 200 for eagle 5140 rods or 300 for a scat 4340, 200 for a 9000 crank or 500-600 for a forged one, 200 for bearings and misc parts and you're only at 1000-1500, add in machine work and assembly and you are right around the $2000 mark, isn't that where the zz4 sells before you do everything that would be included in a custom build?