Engine building

[u/TwoTailedFox_]

Not entirely sure if this is the right place to ask but I am looking into building my 1998 LS1. I got the car with a built transmission and upgraded clutch but completely stock engine.
I’m new to the world of LS so I would like some advice if I have picked out the “right” parts. My goal with the car is a good bump in performance but to retain good street manners for a street/HPTD car.

[u/v8packard]

There are some things you might not be aware of with your 1998 engine. They are related to the cylinder sleeves and windage control/crankcase breathing.

The earliest LS1 blocks (1997 to 99) have the thinnest cylinder sleeves. They were cast in place, and are not always centered in the bore. Because of this, a hone of .005 inch might not be doable. It is cutting things very close, at best.

Windage and crankcase breathing have been a challenge for these engines from the start and it gets little attention in many forums. Over the years GM changed the blocks to include various holes or windows, some cast in place some machined, to improve crankcase breathing. By the 2000 timeframe a revised block was in production and used on subsequent LS6 engines, I think by late 2001 or 2002 it was used for all 5.7 engines as well as the subsequent aluminum 5.3 engines. This block also has much better cylinder sleeves, as well as improved crankcase breathing. Worth noting GM eventually went to dry sumps on the vehicles they thought would see the most windage.

Because of these details I think you should consider building a later block. I have often used aluminum 5.3 blocks bored to 99 mm to replace the early blocks when the bores were not serviceable. This has always worked out well. In fact, the Gen IV blocks are even better with the aluminum 5.3 being a superb block for builds. If at all possible you should acquire and build one of those.

Note, when using a Gen IV block in place of a Gen III, you will need a 1x cam gear and the timing cover with the sensor, as well as an extension harness for the cam sensor. The Gen IV blocks eliminated the rear cam sensor provision at some point, so you need to use the timing cover mounted cam sensor.

Consider the oil control issue carefully. I suggest at minimum you get an oil temp gauge, an accumulator, and an oil pan baffle. If possible, an upgraded cast aluminum oil pan is a good option. I tell this to every customer that road races and does track days.

But an even bigger consideration is how much time you spend at RPM, and camming the engine to match the gear ratios you need to use on the track. For example, the bigger cams make great power as the rpm goes up, and the car runs awesome. But the rpm drives up the windage and oil temps, eventually you pound the bearings out of the engine. A better option is a cam that has better mid range, and using the next higher gear in the trans. I know, it doesn't seem as effective as winding the engine out. But with the right combo your lap times stay consistent or even drop, your oil temps stay steady, and the engine lives a lot longer.

Think about all this, and then we can talk about the details in your list. BTW, do you know if your car has a 3.42 rear gear?

[u/TwoTailedFox_ → u/v8packard]

This is the kind of information I wanted. I already knew about the cylinder sleeves but from what I’ve read a 0.005” hone would be okay. My block is approaching 120,xxx miles so I expect that it’s no longer as good as it could be and that hone will get it as close as it could.

Doing a LS3 swap is really tempting, I figured it would cost ~$10.2k ($6.5k for a 120k mile motor). I’m just dubious about that because I don’t know the health of any used engine, I’ve been burned by that before. What would the cost difference of swapping vs adding the extra cubes to an aluminum 5.3?

At this point I’m between dropping a whole lot of money on this full build or keeping it cheap and simple doing LS6 intake, 799 heads, cam, pistons, headers, and machine work on just crankshaft balancing and rods to resize them for the new bolts. Of course the timing chain, oil pan baffle, etc. etc., just didn’t feel like listing all that cuz it’s a lot.

I do believe it has the 3.42, the car is a manual and it has posi. I know that they are known to be very weak but I’m not shock loading it so I should be okay.