RezinTexas

Due to cost reasons I decided to build another LS motor rather than a Gen 3 6.1 hemi. That will have to wait.

I picked up an '03 LQ4 short block for cheap. The previous owner had blown a head gasket and 2 cylinders filled up with coolant. He let it sit for 2 months and of course resulted in light surface corrosion inside the cylinders and seized rings.
This is great for me because the block is in otherwise excellent condition with no issues at all. A 0.030" bore will completely eliminate the corrosion.
Here is the current plan:

Host Vehicle: TBD
370 cu inch shrot block
Stock crank, clevite P bearings, new OEM main bolts
Scat forged I-beams with ARP bolts
4.030" forged pistons -4cc, Mahle
rotating assembly balance
All machining by H squared racing engines
cam: TBD
heads: TBD

As with my previous build, all clearances will be painstakingly measured and recorded.

Here are some pics;






measuring deck height of OEM pistons. The readings are slightly off due to some tough carbon buildup on the deck surface, but the readings are +/- 0.003" from each other.


measuring depth of dish in piston = 0.048"

Deck heights as measured. This tells me that the deck is most likely square and does not require deck machining, however I will measure again when the deck is cleaned and the new rotating assembly is installed, just to be sure.
1: 0.009"
2: 0.009"
3: 0.011"
4: n/a
5: 0.012"
6: 0.012"
7: 0.013"
8: 0.009"

I also measured the OEM crankshaft main/rod journal dimensions. Everything checked out within spec:



cam bearings look good as well. I measured all the inside diameters with the bore gauge. Readings are right on spec, so I do not plan to replace these bearings. Cam bearing clearance will likely be in the range of 0.0025" - 0.0035". But won't know for sure until new cam journal OD measurements are taken.




removing the PITA metal ring from the knock sensor seal. This little puller worked perfectly.

RezinTexas

Here's a couple pics of the Gen 4 rods from my last build, '04 LM7.





These rods were setup with a 0.945" pin, press fit.

Will typical aftermarket pistons work with that, or is it a special size?

Jimbo1367

I personally wouldn't bother reinstalling OEM PM rods. Budget (Scat/Eagle/Procomp) would be better than PM rods. JMO

KCS

iTrader: (20)

Not too many aftermarket options with the OEM pin diameter, basically hypereutectic pistons or something like Wiseco's new "Junkyard Dog" line up. Most aftermarket pistons use a .927" pin.

RezinTexas

good to know, thanks guys. I'll update this soon.

JakeFusion

iTrader: (7)

Diamond makes them with the .945 - but they're like $650 a set without rings. Probably the best street/strip piston out there tho. PN is 11510

Wiseco "junkyard dog" pistons w/rings run about that. But I don't see a .945 option with at .030" over. Just .020" in their catalog.

smws6ta

iTrader: (5)

I might be misinformed but I thought 408's had to have a new crank, like a stroker, to accommodate the new length of the connection rods.

The new stroker crank + cylinder bore 0.30 over + shorter connection rods = 408 ci.


Am I wrong, please explain.

cpolaris502

iTrader: (2)

Where did you see 408? He is doing a 370ci. Stock stroke+.030 over bore= 370.

smws6ta

iTrader: (5)

ok now I see, so I was correct in that a different crank will be needed to make it a 408.

Got it.



Thanks.

RezinTexas

yeah, sticking with the stock crankshaft for this one. I would like to do another stroker, but I have 2 excellent condition truck cranks on the shelf ready to go. All journals are perfect and within spec.

RezinTexas

thanks for the reference. I might look at the Scat I-beams with some probe pistons. Seems that plenty of people run those without issues, but I don't know yet.

JakeFusion

iTrader: (7)

The Probe pistons are a good budget option. The Diamond, even tho that's their low end piston, is still better than just about any other shelf piston you can get. So it's probably overkill.

KCS

iTrader: (20)

Scat I Beams are great, and with a .927" pin it will open up your piston choices. I have used the H Beams several times in 700whp engines with great success and the machining is pretty well done.

As far as Diamond, they're nice but Wiseco usually has more features for the same price which is why I'd go with them. Coated skirts, multi fit valve pockets, etc are all standard features that you don't typically get with the Diamond pistons.

Probes are pretty decent for a budget piston that won't see high rpm or big big power. They're a little thinner in key areas making them a little weaker, but very light. The Probe 3.905" pistons I have are about 390g where Wiseco's are more like 420g.

Jbigs268

What final compression ratio are you looking to achieve? I myself am doing an lq4 bored .030 over and am just looking to see what you will be around, also what heads are you going to run?

RezinTexas

Thanks man, sounds like the Scat I-Beam with Probe pistons could be a good platform for a high-revving NA engine.

probably 11.3 SCR and 8.5 DCR - same as my last build. Don't know about heads yet, will decide that later.

RezinTexas

I'm reviving this build finally Other stuff got in the way, but its back on track now.

Here is the updated plan:

370 in^3
Mahle pistons (Probe no longer available when I checked on 24-Jan-14)
Scat 6.125" Rods
New GM main bolts
Clevite P Bearings
Block machine work (bore/hone, decking, cleaning) by H squared racing engines in Houston.

I just ordered the Bearings, bolts, and a new Mitutoyo 4-5" micrometer (for the pistons), and a 50mm sub-anvil for the bore gauge. Planning to order the pistons/rods next week.

I installed and torqued the main caps with the old bolts to check the bore dimensions. Here is the initial low-torque pass per the Potak book:



This was my first experience with an angle gauge. As you can see I had to jerry-rig the gauge to keep it from moving heh heh



Measuring the bare bores (no bearings) with the bore gauge:







All the main bore dimensions were spot-on, so I don't think it needs any main bore honing.



Thanks for looking! I'm planning to have the shortblock done in about 6 weeks.

RezinTexas

A few questions:

1. Apparently this LQ4 engine is from 99-00 as the crankshaft is the long one. I'm planning to use an '04 LM7 crank instead and have it properly balanced. Any issues with doing this? The LM7 crank is in pretty much perfect condition, all dimensions well within sepc, and no grooves or lines.



2. I got the new Clevite P main bearings and installed the #1 main bearing set and measured the clearance. Clearance to the LM7 crank (2.5590" journal) is 0.0012" - 0.0018", so this is too tight for an iron block. Is there any way I can remove 0.001" of material from the crank journal? Am I better off getting different bearings? Which bearings would I need?



3. I've already ordered new GM main bolts/studs, but how many people re-use these with success? How many torque-cycles have you done on them? The Potak book recommends to replace after just a few cycles.

KCS

iTrader: (20)

1) I don't see any problems with interchanging the cranks, it may need a little more heavy metal to balance.

2) You can grind the crank. There's a guy here that everyone uses right off of 1960 and Jones. His name is Pete. You'll need to give home the exact size you want each journal to be ground to. He's kind of...finicky.

3) I've used the stock bolts/studs in several applications. You shouldn't have to torque them too many times, maybe two or three more times which would be fine.

RezinTexas

Parts just ordered from WS6store.com:

1. Scat rods (26125716)
2. Mahle pistons (LS1314030F04)

A big thanks to Mike, always a pleasure to deal with.

Great, Pete sounds like a good reference

garygnu

ls3 top end ?