3.9L LZ9 engine internal upgrade & performance?

I can't tell you what GMPD is doing for pricing, but the only 60V6 to use left and right heads are the 3.6 DOHC. There could be different casting numbers, like the 170 and 487 for 3400, but they are identical minus the newer 487s got 8mm rocker stud bosses.
The 3900 heads have holes on both ends for the coolant to go, and the other side of the head uses a gasket to seal it off.

I know the heads can be turned around and that the rear of the head has a freeze plug in the hole that serves as a water outlet on the other end, but for someone who knows nothing about the engine and is considering a swap the point has to be made that turning a head around on the 3900 is not a simple process and if you fail to specify which head you're ordering you can wind up having to remove and install a freeze plug, I'm pretty sure about the assemetry of the coolant passages.

wrong...same part number...12594246...same number on AFM, Flex fuel and regular, with or without the tunable upper

If you're talking about the VVT 3500 you're on a different page, I'm refering to an old thread on the non VVT 3500. Same part number or not the combustion chameber in my 3500 cylinder heads was different than what was posted here and not being able to find a different part number doesn't change that.

No one has been able to explain the 5.827" connecting rod in an engine advertised as having 5.9" rods, and a couple of years back when I was being told my 3500 engine did not have a steel crank in it because GM said it was only installed in the 3900 found in one of the 06 sport utility vehicles, I wound up proving they had been installing the steel crank in the first year 3500 as both my 04 and 05 engines had it.

Assuming not because there are no part numbers to support what I'm telling you is a gamble. I'm telling you guys what I saw clearly with my own eyes.

If I find I'm mistaken the next time I examine the heads I will post a correction.

[gectek]

wrong...same part number...12594246...same number on AFM, Flex fuel and regular, with or without the tunable upper

[SappySE107]

I can't tell you what GMPD is doing for pricing, but the only 60V6 to use left and right heads are the 3.6 DOHC. There could be different casting numbers, like the 170 and 487 for 3400, but they are identical minus the newer 487s got 8mm rocker stud bosses.

The 3900 heads have holes on both ends for the coolant to go, and the other side of the head uses a gasket to seal it off.

I have 6 heads with the same casting number 12590746.

GM Parts direct listed different prices for the same parts for the 3.5 and 3.9 engines based on production year before rearranging the site. If you go their now you should find at least 3 different prices for the cylinder head between 2006-2007 ranging from ~$ 134, 178 and over 200 by the 07 year using different vehicle applications for the same engine, 06 G6 vs 07 Uplander, I have both, and the 07 Malibu Maxx. I also noted two different connecting rod prices. Whether something is added or excluded part wise I don't know.

I had this issue with a set of 3500 heads that I'm certain I'm correct about regarding there being two castings. I noted the difference in the combustion chamber of my cylinder head vs what was posted here on the forum and was also asked by a parts supplier upon looking for a set "Which casting number do you have".

Recall there are also two crank castings one of which you don't see much of anymore and that being the cast iron crank. When I return home shortly I'll take pictures of it but I'm sure my eyes did not deceive me in noting the difference in the cylinder head coolant passages from one end to the other.

[SappySE107]

I have 6 heads with the same casting number 12590746.

The heads are left and right? I don't recall that one and I have plenty of 3900 heads here. What is the casting number difference?

Having coolant flow outlets at one end makes them left and right and I distinctly remember the deck surface flow pattern varrying from one end to the other apparently to assist in proper cooling for the u-flow coolant design.

I'm not able to get numbers right now but GM does seem to show more than one part number for various parts in which case this may also explain why two different connecting rod lengths have been measured; 5.827" and 5.9".

[SappySE107]

The heads are left and right? I don't recall that one and I have plenty of 3900 heads here. What is the casting number difference?

[IsaacHayes]

^^ Cool, so you can get a 3900 and leave it alone and just slap a turbo on Of course that means less potential if it's already close to optimal from the factory. I'm really curious to see the #s from a turbo 3900.

iirc there were other changes in the block that made that head swap not work. Something about coolant ports not lining up...

The heads are left and right and their deck surface coolant passages differ as you move from the front end of the head to the rear. They also have a larger surface and would overhang on the non VVT motors deck surface towards the sides. They are made very well and after looking at mine in consideration of some port work I lost motivation as the area around the valve guide in the bowl is pretty neat as well as the overall port, so aside from widening the passage beneath the valve there probably isn't much to gain.

[Superdave]

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.

iirc there were other changes in the block that made that head swap not work. Something about coolant ports not lining up...

[Nightingale]

Wiseco has one of my stock pistons from which to engineer a forged piston. Once its done you can call them up with the job number and request modifications for it for your application. The one they are making up for me is 8.5:1 compression dish piston, extra valve clearence, zero deck, and a sbc wrist pin diameter.

[gectek]

LS valves are too long and alot bigger...wont work. dont know where you read that but they were smoking something

[mrtohil]

Okay, is there any information as to what valvetrain can be used on this motor. I somewhat remember GM messing around with the intake and placing LS6/7 intake valves on this motor. Next semester is cylinder heads. Might as well start researching now.

Sorry I'm late to the thread.

With the huge 2.250 crank pins there would be no welding if you wanted to stroke the crank. You'd simply grind the crank to the desired offset and use Chevy SBC 2.000" rods.

This was discussed in length here.

http://60degreev6.com/forum/f96/3500-crank-t38267

That would be the best route to take if he's planning to take advantage of the LS1 piston options. Otherwise the closest chevy rod I've found to 5.9" is a 5.85" rod. The power output should be the ultimate decision maker because up to about 450 hp the stock rods should handle that and can be rebushed for the .927" pins down from .941. He could also have the crank offset ground and use the stock forged 5.7" rods with the correct piston compression height combo, to avoid modifying chevy rods.

If he plans to go all out then after market modified rods would be the way to go. There are a lot of options since the engine shares the same cylinder bore with a very popular motor.

[Monzsta]

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.

Sorry I'm late to the thread.

With the huge 2.250 crank pins there would be no welding if you wanted to stroke the crank. You'd simply grind the crank to the desired offset and use Chevy SBC 2.000" rods.

This was discussed in length here.

http://60degreev6.com/forum/f96/3500-crank-t38267