LZ4/Fiero Swap

I dont know if the cam sprocket bolt pattern is located somewhere. Quick search for me turned up nothing. Finding one is cheap but if it doesnt work its a waste of 20 bucks.

I was thinking along the lines of a off thenshelf cloyes double roller if the bolt pattern is the same.

[neophile_17]

If interchange is to be believed then the crank sprocket and timing chain are the same for the LNJ and 99+ LA1. So that should definitely fit under an early timing cover provided the cooling system can be made to jive with the LZ stuff.

Melling 3700SC picture from rockauto - https://www.rockauto.com/info/583/3-...-KIT__ra_p.jpg

Is the bolt pattern of the iron head cam sprocket documented somewhere? If so I'll check it against LNJ cam holes, otherwise it might have to wait for the next parts order.

That's very interesting about the LS7 rocker. I might have to pick one of those up.

It looks like the lnj cam is shorter then the lz cam. Understandably so as it doesnt use vvt. It might fit under a stock fwd timing cover or a fiero timing cover.

Got pics of the timing chain and sprocket used on the lnj?

According to that engine builder article the heads are the same on the lnj as the la1. Which means the bore is not 99mm like on the lz engines..

Since the lnj cam is so small you might be able to use 1.8 exhaust rockers from a ls7. Please check valvetrain geometry though. The ls7 hardware shares the same rocker bolt as the lz head I believe. It could be a quick way to get a bit more lift.

I havent tried it I just researched it. A single ls7 rocker from gm I think is under 20 bucks

I highly doubt it but curious as to 3 bolt pattern in the lnj if it matches up with the old flat tappet timing sprockets.

[neophile_17]

If the lnj and lz9 have the same journal diameter then I wonder if the lnj uses the lz9 block.

I doubt this would be the case, GM would have to produce another crankshaft with an even shorter stroke than the LZ4 to get 3.4L.

Here is the engine builder article that got me started down this path- https://www.enginebuildermag.com/201...4l3-5l-engine/

Get some pics of the lnj cam. I am curious about the bolt pattern on it. Single bolt or 3? You might not be able to get new blanks cut from a cam company but they might be able to regrind it for more duration and lift.

Let me know if there's another view you'd like to see. As seen in the picture it's a 3-bolt and looks to be the same pattern as the LZ motor cam. I was initially thinking we could just bolt up a new cam timing sprocket to the LZ cam and not even have to swap the cam but the LZ cam has a raised portion that fits inside the phaser. Any regrind companies you've heard good things about. I may have to look into this more.

Even if not, getting an stock lnj cam installed is easier than installing bearing spacers and new aftermarket cam.

My thought exactly! And the LZ cam bearings are aluminum and don't wear as fast. In my 175K engine they were almost new.

When installing a wot tech cam in an lz9, a stock GM timing chain from a la1 can be used. I used one from an lx9 though.

I'm going for the 98 and earlier stuff for the extra strength. Good to know that works.

The lnj cam should have a part number. Curious as to its cost

Part number is: 12596567
The engine builder article mentions another part number but google found none for sale. I couldn't find a 12596567 for less than $275 which is why I went used.

If the lnj and lz9 have the same journal diameter then I wonder if the lnj uses the lz9 block.

The lz block is identified under the timing cover in the block itself.

Get some pics of the lnj cam. I am curious about the bolt pattern on it. Single bolt or 3? You might not be able to get new blanks cut from a cam company but they might be able to regrind it for more duration and lift.

Even if not, getting an stock lnj cam installed is easier than installing bearing spacers and new aftermarket cam.

When installing a wot tech cam in an lz9, a stock GM timing chain from a la1 can be used. I used one from an lx9 though.

The lnj cam should have a part number. Curious as to its cost

[neophile_17]

OK! So I've measured a few camshafts in the last 24 hours. Here is the boring warnings before I get into the details. All measurements were taken with a micrometer on the lobe itself by measuring the base circle and then the lobe 90 degrees apart. This is a Brown & Sharpe micrometer so not a Harbor Freight deal but I'm not an expert metrologist either. This means that lobe separation is not measured which is an important question. That being said here we go.

I took measurements of the following cams: LA1/LX9, LZ4, LNJ, and WOT-Tech Street/Strip.

The late 07 and presumably later LNJ camshaft have the same journal diameter as the LZ4/LZ9!

All three of the GM cams had the same lift- 0.271" +/- 0.001" which matches pretty close to the specs I've seen. I wouldn't swear to it but the center of the lobe seemed to have a slight crown- ie measuring the edge of the lobe yielded a slightly smaller lift than the center.

The WOT-Tech Street/Strip cam measured exactly to spec.

Take away thoughts: From my reading on the various forums I was under the impression that the LZ* cams with VVT had smaller lobe lifts such that the valve lift (with 1.7 vs 1.6 rockers) was the same as the LA1. My measurements show this not to be the case- the lobe lift is the same and the valve lift is greater by 1.7/1/6 = 106.25%.

If we take the best hp figure I can find for each engine I see that the LA1 has 185hp, LNJ has 185hp, LX9 has 215hp and LZ4 has 225hp. I'm going to attempt to draw a couple conclusions from these numbers based on the information I have. The LA1 and LNJ (both early and late) have essentially the same cam, rocker ratio, architecture, and hp so I will consider them the same. The LA1 and LX9 have the same cam, and rocker ratio, but the architecture is different. The argument could be made that ignition also changed but the LNJ has the same ignition as the LX9 but no more hp than the LA1. Assuming displacement is linear with hp the difference between a 3.4L and 3.5L accounts for about 5hp- not the 30hp difference between the LA1 or LNJ and LX9. So in the stock cam range the 3.4L engine definitely benefits from an architecture upgrade ie heads and intake. Now, going from the LX9 to the LZ4 one would expect that the obvious architecture improvements would make a significant improvement. This is not what we see. It looks like despite VVT the only improvement is from the additional valve lift offered by the 1.7 ratio rockers (valve lit increases by 6.25%). At his point it seems that the engine becomes cam limited. This is reinforced by the fact that the efficiency of the 3.5L in a 3.9L would yield 250hp but the LZ9 is rated at 240hp. So! There are a lot of assumptions here but, I tried to make them all clear and I'm more than willing to discuss any of their merits or lack there of. That being said if I was trying to upgrade an LA1 I'd focus my efforts on the heads/intake and for the LZ engines I'd start with a cam...which I know is expensive because I'm doing it now.

Other random thoughts: There is a good possibility that you could buy a LZ4/LZ9 from the junk yard and an LNJ cam timing sprocket that would allow you to run without VVT without much if any of a hp penalty. The crank sensor is still 58X or you'd have to get an external 7X sensor but eliminating VVT for $40 seems to be new.

[neophile_17]

Spotted an 07 Equinox cam on ebay and bought it. The sprocket mounting pattern doesn't look right in the photo which had me a little worried. After a little more research I saw a three hole non-VVT camshaft sprocket as Melling timing set 3700SC. I'll do some measuring when the cam arrives and then maybe order the timing set.

Could it possibly be the same bolt pattern as the old iron head timing set?

[ericjon262]

I think it's just the three of us at the moment(actively on here) I didn't know the LX9 and LZ9 had the same stroke... learn something new every day! so far, I'm 2 for 2 on forged cranks, both were out of LX9's from G6 GT's, I think both were 2006 models.

[neophile_17]

I believe that those 3400's also got the lx9 style PM rods... maybe they got a forged crank too! Lol

It's very possible. Considering the LX9 and LZ9 share the same stroke as the LNJ and classic LA1 it wouldn't surprise me in the least. the real question is would it be worth it to get the crank and rods from an LNJ to build the LA1 block you already have? I can't answer that but it would be interesting. Unfortunately I don't see a lot of activity around here so it might be awhile before we find out.
OTOH if anyone out there is interested in the bottom end I'd probably be up to buying the cam to help you recoup some of the cost of a whole engine.

[1QUICKHATCH]

Thanks for the info!

Warning! This is all preliminary information based on an offhand comment I saw in a Enginebuilder article and some of my own digging.

The LNJ was the 3400 produced in China and it lasted until 2011 in some cars/SUVs. When GM switched to a 4X cam sensor they apparently upped the bore size of the cam journals. The LNJ didn't receive VVT but it did get the 4X sensor later on. The cam bearing part number is the same as the LZ4 but parts interchange is often wrong (I searched 2008 Equinox). I'd love to put my hands on one of these but it's not my top priority at the very moment. I'll update if I can track one down.

I believe that those 3400's also got the lx9 style PM rods... maybe they got a forged crank too! Lol

[neophile_17]

Thanks for the info!

Warning! This is all preliminary information based on an offhand comment I saw in a Enginebuilder article and some of my own digging.

The LNJ was the 3400 produced in China and it lasted until 2011 in some cars/SUVs. When GM switched to a 4X cam sensor they apparently upped the bore size of the cam journals. The LNJ didn't receive VVT but it did get the 4X sensor later on. The cam bearing part number is the same as the LZ4 but parts interchange is often wrong (I searched 2008 Equinox). I'd love to put my hands on one of these but it's not my top priority at the very moment. I'll update if I can track one down.

If the spacers and bearing are already installed I wouldnt worry about pulling them back out except for maybe the number one bearing at the timing cover.

I would leave the rest to save the hassle. It was the first bearing my machinist took issue with poking out into the timing cover area.

Pretty sure the later 3400 does not share cam bore with the lz engines. Never ever heard of that before. Not one block I have seen is like that.

Please take pics and remeasure

The lx9 has the same bore size for the cam as the 3400. If GM had a larger bore for 3400 they would have transfered that to the lx9 too. No spec GM lists has it that way.

[neophile_17]

Thanks! I'll have to pull the SBC bearings out- will be tricky but I think I have a way.

I just came across an interesting tidbit while doing research for my other build. The later LNJ 3400s have no VVT but do have the large cam journals. That would mean you could swap a LNJ cam into a LZ* motor and get 0.462 lift (assuming 0.272 of cam lift and LZ* 1.7 ratio rockers) without VVT or cam spacers. I wish I'd known that tidbit earlier!

I bought the wide bearings too. I ditched them as my machinist said once installed in the block the front bearing hung outside the block. He wasnt comfortable with it. I took his advice.

Once installed in the spacers and pressed into the block you will see what I mean.

Use the wide ones on other engines but not on lz engines with the spacers

[neophile_17]

the buckets also probably allow oil to pool around the spring, which should help keep it cool. you driving this thing yet?

Unfortunately not. The racecar needs a motor first so this is going back in the corner. On the bright side I'll have to finally pull the bruised LX9 out so that I can use the crank and street tune the race motor. It's going to be a busy winter. But I have all the parts so I can build that next year while my wallet recovers from getting married.