Fine tune my stroker build

[Talyn]

I want something that'll give me low end power, good idle(with renix), good fuel economy(close to what a stock cam would get).

You should like the Comp Cam 68-231-4 cam.

I have been hitting jeepstrokes.com and went though their FAQ area.. and found some more info. I read that the 89 renix block deck height is lower than newer 4.0's.. also the height varies. So, am I able to measure the actual deck height, so I can have exact numbers to do my math to figure out the compression raito.

You will probably have to mock the block up to get true measurements.

I am still trying to figure out what machine work I should do. If I am to balance the motor, I'll have to line bore the crank mains ?

No, that isn't balancing. That might fall under blue printing. But it is rarely necessary on 4.0Ls.

I'd rather not do this, or balancing unless its really needed.

I would do it. If you don't you have a change to feel a vibration. Then you can take it apart and fix it or wait until it shakes itself apart.

I also read somewhere that the inline 6's are very well balanced already. I like the idea of chamfering oil holes.

The 6 cylinder engine does not require bob weights during balancing. Basically the crank is spun balanced and all the parts are weight matched to each other.

 

[dan89XJ]

I'm thinking more about doing the balancing now. How is the crankshaft balanced on these inline 6 motors ? Pistons and rods need to be weight matched.. can I do that myself ?

If I buy new connecting rods.. will I need to get the rods resized or will they be good for that ?

 

[stroked88]

pistons should be close. have the rods weight matched, remachined, and new rod bolts. then they just balance the crank by itself with no bobweights

 

[dan89XJ]

I am wondering how they do the crank balance.. is it on a special spin machine ? Or do they put it in the block and spin it somehow ?

 

[Mesh]

The block is not used for balancing.

Here is a video that may give you a better idea.
http://www.streetfire.net/video/rotating-assembly-balancing_157545.htm

 

[dan89XJ]

I see how its done now. I found some info on google as well... so the bob weights that are attached to the crank for the spin machine tells you if that area needs more or less weight to balance out ?

 

[Mesh]

All I know is you give them the parts they ask for then the parts come back and it’s really expensive.

 

[Talyn]

Bob Weights aren't used on an I6

 

[dan89XJ]

Bob Weights aren't used on an I6

So, how is it done ? A friend of mine said his machineist charged $200 to balance his small block chevy. And sounds like it was a flat rate fee. So.. I'm figuring it should be less for a I6, since its only 6 cly.. and depending on what is required.

 

[Talyn]

The throws on the I6 crank are 180* apart, so a bob weight is not needed. The crankshaft alone is spun and weight is removed or added to the counter weights to give it a neutral balance. It is done on a balancing machine. The pistons and rods are weight matched to the least weighing one as are connecting rods. The connecting rods have to be weight matched on each end. You can do the pistons and pins your self if you have a gram scale, and some form of grinding device. If you have to remove a lot of weight form a piston you can shave the pin end a bit. That pin then must be kept with the piston it was weighted with. When I say a lot of weight, it isn't really that much but the aluminum from the piston weight so little that you have to take out a lot from the piston to match it. The connecting rods can be done using the gram scale, but you would need a special tool to balance each end.

When you drop your parts off at the machinist ask him to show you what he uses to balance these items. Usually they are willing to give you a quick walk though at least. I have been at my machine shop so frequently that I watch the machinist do a lot of things, occasionally helping him. They let me do my own work there if need be and have given me a part time job in doing mechanic stuff. Yeah... I spend a lot of time there.

 

[dan89XJ]

The throws on the I6 crank are 180* apart, so a bob weight is not needed. The crankshaft alone is spun and weight is removed or added to the counter weights to give it a neutral balance. It is done on a balancing machine. The pistons and rods are weight matched to the least weighing one as are connecting rods. The connecting rods have to be weight matched on each end. You can do the pistons and pins your self if you have a gram scale, and some form of grinding device. If you have to remove a lot of weight form a piston you can shave the pin end a bit. That pin then must be kept with the piston it was weighted with. When I say a lot of weight, it isn't really that much but the aluminum from the piston weight so little that you have to take out a lot from the piston to match it. The connecting rods can be done using the gram scale, but you would need a special tool to balance each end.

When you drop your parts off at the machinist ask him to show you what he uses to balance these items. Usually they are willing to give you a quick walk though at least. I have been at my machine shop so frequently that I watch the machinist do a lot of things, occasionally helping him. They let me do my own work there if need be and have given me a part time job in doing mechanic stuff. Yeah... I spend a lot of time there.

Very cool.

Sounds like balancing a i6 crank is simple - no weighing of the rod/piston stuff first.. like on a crank that requires bob weights. So I'll have the crank spin balanced.. and install arp studs for the rods and have them checked for round and balanced. The new pistons I buy - I could check them for weight, and maybe get by without working on them. Sound like a good plan ?

 

[Talyn]

If you install ARP rod bolts the rods will have to be resized. You won't get by with out some work on the pistons.

 

[stroked88]

If you install ARP rod bolts the rods will have to be resized. You won't get by with out some work on the pistons.

we ordered Mahle hypertectics and they were close enough that they didnt require any work :dunno: like within less of a gram. theres not really much material on those pistons that you can take off with out risking the strength