3.9L LZ9 engine internal upgrade & performance?

[IsaacHayes]

Hmm. From looking at the CR calc, that would be a .2" overbore on an LX9... LOL. So I'm assuming you can't really use the LZ9 heads on anything older than the gen4s... Darn.

[mrtohil]

Well I measured by cylinder bores last night. What I found was that the bores were consistantly 3.8985-3.898in. Not the 3.9in stated for the spec for this engine. Once I find out what piston I'm going to use it'll probrably mean little if any boring and mostly honing to get it big enough for the pistons. The pistons I'm looking at are 3.905-3.908in.
I finished grinding the main caps to prep them for the line hone. Which should be tomorrow hopefully. After that I'll be decking the block and stating the deck height.

[IsaacHayes]

Take a 3400, bore it to 3.5L (or max it can be bored) and put on 3900 heads. That way you don't have to deal with cam phaser, it will fit and bolt in older cars, and no crank trigger or other stuff to mess with. Just bolt on the good 3900 top end, and run a 3500VVT UIM (since its not variable). That is if you can bore the 3400 out enough to fit the 3900 heads combustion chambers.

[mrtohil]

I'm trying to understand the question you might be asking or posing. Please restate.

[IsaacHayes]

I wonder if a 3400 bored to a 3500 size would be enough for the heads... I wonder then if the valve train geometry would still work with the pushrods and such. I haven't looked into the #'s for bore sizes so don't shoot me if I'm asking a silly question.

[mrtohil]

Here are the specs that I found in my engine. The OEM spec is 2.840-2.841. Which is pretty anal of spec. I set up for a measurement of 2.8405.
Here's the measurement of the main caps, front to back(1 through 4) with two additional measurement per cap, front(F) & back(B). With the OEM bolts.
1. F:+.0019; B:+.0020
2. F:+.0024; B:+.0027
3. F:+.0024; B:+.0025
4. F:+.0013; B:+.0017
As you can see the main bearing bore is bigger than it should be.
Here are the measurements taken after installing ARP studs:
1. F:+.0011; B:+.0011
2. F:+.0013; B:+.0015
3. F:+.0009; B:+.0007
4. F:+.0007; B:+.0002

So as you can see the ARP studs DO make a difference! I didn't think it would make that much of a difference, but I was wrong.
So now I have to grind the main caps down and hone it to spec.
Oh, before I forget, the cylinder head passages and bolt pattern are pretty much the same as a 3.1L. I laid my head gasket on the block of a 3.1L that a classmate is doing and it all pretty much lined up. Only noticable difference was the cylinder bore. Which was massive compared to the 3.1L. Thought you'd like that bit of 411.

[mrtohil]

Sonic testing revealed that there isn't much metal left to play with. The following spec are in thousandths...Each cylinder was checked at 12 locations. If looking at a cylinder from the top, it would be at 12 (front of motor),3,6 & 9 o'clock. And then at the top, middle and bottom of the cylinder.
The highest value obtained was 320 @ cyl.5 9 o'clock middle.
The lowest value was 153 @ cyl.3 12 o'clock middle.
SO, this means I can only safely bore to about 30 over. SO no 4.0in bore unfortunately. But it's such a nice whole number. Oh well. Deal with it and move on...

[mrtohil]

Okay. I got two things accomplished today. I 1. installed my ARP main studs and found out my crankshaft main bore diameter specs and 2. sonic tested the block to find out how much I can bore this thing out. Which unfortunately is pretty much nothing.
I'm going to let you know that I initially checked my main bearing diameter spec with the stock bolts...
And what sonic testing revealed...

[Nightingale]

Don't know its wierd like I said I had it measured by pauter rods and then I added up stroke and compression height and it all checks out on my engine. It might have been that on earliar engine they might have used a different length rod and piston. This wouldn't be the first instance of inconsistancy or lack of information from manufactuer.

[mrtohil]

I'm serious looking into forged rods of 5.9in for this motor (yes-yes, before I get it from all sides. I know the options. I've thought it through. I just can't don't like the welding crank option on this really nice crank. And this will help with the aftermarket performance options, or lack thereof, for this motor). So far I think I get them made with the same crank rod journal size but I'm changing the wrist pin size from .941(I can't remember the size off hand) to .927. Which is that same wrist pin size for an LS1.

[mrtohil]

I measured them again. I actually did two of them. We came up again with the same number of it being slightly longer than 5.9in. Dunno what to tell you.

I measured one of my rods today. It ended up being 5.925in, which is pretty close to the 5.9in advertised in the spec sheet.
I don't think the school has a scale intended for this. I'll find out. If it ends up too much of a hassle I might as well get a small electronic one of my own.
Well, this weekend I'll have to dedicate on knocking on everyone's door who makes rods and find out how much for some forged rods. Let the Benjamins start flying out my wallet!

Check your rod length again to be extra sure because so far at least two other members have measured 5.827" rods including myself instead of 5.9", unless a change was made somewhere I can't see there being two different rods under the circumstances.

A small block chevy rod is the best route to take except in an extreme build. That is what was done with the old 2.8L for increased strength. For the cost of custom rods you can buy a set of forged chevy rods good to at least 600 hp or more and have the crank welded if necessary and offset ground. The pistons have offset pins if I recall correctly to help reduce side thrust loads so going with a 5.7" rod shouldn't cost you any sacrifice especially with todays metallurgy and design. The LS1 pistons also have offset pins which is another plus for them being used in the 3900.

[Nightingale]

I would just shave the crank rod journals and use sbc rods. All said and done it'd be cheaper then custom. Pauter quoted me around 1200 for a set of rods, but they are pretty much indestructable. I am probably gonna go with eagle 3d rods with l19 rod bolt upgrade. It will give me a slight bump in displacement (like 3.9l to 4.0L lol), but I still want to keep the rod/stroke ratio good and keep up revability versus just going for max displacement. I know I can pick up more stroke from going to the small journal sbc rod vs the big journal rod, but not sure how much it'd affect the integrity of the crank if at all.

[mrtohil]

I measured one of my rods today. It ended up being 5.925in, which is pretty close to the 5.9in advertised in the spec sheet.
I don't think the school has a scale intended for this. I'll find out. If it ends up too much of a hassle I might as well get a small electronic one of my own.
Well, this weekend I'll have to dedicate on knocking on everyone's door who makes rods and find out how much for some forged rods. Let the Benjamins start flying out my wallet!

I knew the weights wouldn't be in the manual, I thought you had parts at the machine shop that can be weighed.

The Helms manuals aren't cheap, and probably cost ~$ 135, years ago they went fromt about $45 to more than double that I discovered on attempting to order a Fiero manual a few months after having ordered one for my camaro.

Electronics wise it should have some valuable info on the VVT module and that would be good to have.

You can search the HELMS company on line for the manuals, I'm sure you won't be interested in the $400 CD sets.