Well, I blew a head gasket in October and haven't had the time to tear things down. With 235,000 miles on the engine I finally made the decision rather and just replace the gaskets to do things right.

I ordered a ZZ4 350 short block on Friday the 11th from Summit and it arrived today talk about a quick delivery. The other parts I ordered arrived the next day, Saturday the 12th.

The short block comes with pistons, rods and steel crank all assembled. You have to add cam, timing set, oil pump....etc. Most of what I have will transfer, but have ordered new parts as well. But you may not know that the ZZ4 is not balanced from GM . So I am pulling it apart to have it balanced.

That is the background, now the questions:

1) Since the ZZ4 is a new motor, can I use the old "standard torque values"?
a) connecting rod caps 45 pounds
b) main bearing caps 80 pounds
2) Is the retainer that holds the cam in at the front of the block torqued?

I am not too worried about the other things. I have torque values on the AFR heads and the SR. This will be a mild build, nothing radical. I will install the Lingfelter 74211 roller cam with 1.6 RR's. I have to change out the springs on the heads. My old 85 with the AFR heads and SR using the stock cam and pistons was at about 346 HP at the crank and 434 lbs of torque. I am guessing this new combination will be 375-400 HP and close to 500 pounds of torque. We will see what the numbers are when I have TJ Wong dyno and burn a new chip for this motor.

 

I assumed the ZZ4 was balanced the same as other 350s...

 

Are sure about the balancing?? I have done a lot of research on the ZZ4 short block, and everything I read said that it was internally balanced. My car is a six speed w/ a dual mass flywheel, so that was inportant. Before you start taking things apart, I would double check that. Now the 383 short block in externally balanced, which I always thought was strange, but thats what thw ad's have said.

Randy

 

what's so important about the balancing?
thanks

 

An engine that is not balanced will not run at high RPM's for very long.

 

Balancing is important to keep things from shaking apart. A low rev'n motor will not react as much as one that you spin to 6000-7000 rpm. But in the LONG run, if you balance the engine it will last much longer than one that is not balanced.

I talked two Chev dealers in the area and asked specifically if the ZZ4 was balanced and was told it was not. Now don't get me wrong, GM does a minimal balance on the crank like you would with a set of tires. But they do not weigh the pistons and rods and remove weight as needed to insure that all weigh the same. Todays parts are much more accurate than they were 20 years ago. But a balanced engine will perform and not create vibrations to limit performance and longivity. The 350 crank has more room than the 400 crank to balance internally, which is why a 400 or a 383 which uses the 400 crank are balanced externally using the flexplate or flywheel and the balancer. My friend who will do the balancing for me is in the crank grinding business. They usually will balance a "external balance" set up like the 383 or 400 internally, it is harder to do but they feel it is better.

The last engine I built was 26 years ago from the bare block up. I had this balanced. It would wind up quickly to 5500 rpm before shifting. This was in a full sized Blazer 4x4 and lasted 23 years and about 300,000 miles many, many off road.

 

Thanks for the info, John. I thought that these engines were balanced form reading the ads. This is a good thing to know, I was thinking of getting one.

Randy

 

thanks for the info!

 

I don't know about the shortblock, but the longblock ZZ4 I'm getting - the mechanic specifically told me has been balanced. Maybe because it's a complete block, or maybe it was balanced after received, but it would seem rather stupid to sell a shortblock that has the potential to destroy itself. Just my thoughts.

 

I was of the belIef that the ZZ4 has the same balance setup as all the other 1 pce seal blocks.Neutral at front and ext at rear.

 

I am sure it has the same factory balance as any other replacement engine.

RACE ON!!!

 

Absolutely - it's just a question of to what tolerance/spec. I think the ZZ4 longblock redlines at something like 53-5400 rpm a speed where the factory balance is more than fine. If you plan to spin 6k+ all the time, it would be worth getting a balance to within a gram and change. Your rods will thank you.

 

you'll need a new cam retainer plate for that block. i found this out. Not sure if your gonna use a roller cam or not but GM uses a different cam retaining plate for 91-99 blocks, my 89 plate didnt work for my 383 shortblock that i have

 

zz4 = L98 - TPI ... thus most things "should" be swap. It'll be a shame though not to install at least the "hot cam".

 

I am installing the Lingfelter 74211 cam (roller cam) which has a 534 lift for intake and 567 lift for the exhaust with 1.6 RR. This is still a healthy cam that will pass the smog police!

 

I took the pistons, pins and rods with bearings into my friends shop who will do the balancing. We did a quick check on two pistons. There was a 3.4 gram difference between the two. When these are fully balanced they should be the same or within .1 gram.

They are going to keep track of each piston and rod weight before and after balancing. I will post this information as it is processed to show what GM thinks as acceptable for their engines.