Hello,
I am trying to plan a rebuild on my stock GSR. My compression numbers are currently over the +/- 10% between cylinders.

After a lot of research I am confused on which pistons/rods/bearings to order. I am looking to stay in the 10-11:1 CR but would like the more torque. Currently car is daily and autox. List of mods is below. I wanted to not build a high static compression in case i choose to supercharge or put a small turbo on in future.

Does the 2mm of stroke make a huge difference in power?
Do you use GSR pistons? Wiesco 11.8:1 a good choice? Also what does +5cc mean on pistons? Do you have to run dish valves then?
How do you measure for crank/rod bearings when you buy brand new and dont have the original bearings as reference?
If boring .50 over do you have to replace sleeves? If do go with sleeves is 84mm safe? Would a dry sleeve be good for less than 400hp?

If its not worth going to LS crank and Rods, then can you reuse GSR bearings if they are withins spec? Is it a wear item? I thought there is always supposed to be oil in between.

Thanks for any input, hoping to do rebuild before next spring for next season.



99 GSR Engine
00 Si Trans
No name CAI and 2.25" Exhaust
Stage 3 clutch (dont remember brand)
K tuned short shifter
Koni Yellow/GC (500F/600R)
No Front Sway
24mm ASR Rear Sway and Brace
15x8 Enkei J Speeds
225/45-15 Rivals

 

Ls pistons, ls rods. Ls crank makes a difference in power and torque but i dont know how much. The block and crank are coded so you decode the stanpings and it tells you what bearings you should get, but even then, you need to measure the clearance to make sure its right for the application. The coding on my engine was 2 steps too tight for my liking.

Never reuse bearings. They are absolutely a wear item and should be replaced any time the engine is disassembled.

+5cc dome means the pistons have a dome that has a volume of 5cc. +0 is a totally flat piston, and negative numbers mean a dish.

By .50 over i assume you mean 0.50mm. Thats fine. 81.5mm is a pretty common overbore for stock sleeves.

Aftermarket sleeves can be bored up to whatever limit the manufacture states. 84mm bores on aftermarket sleeves is fine

Stock sleeves with an 81.5mm bore is fine under 400hp. Between 400-600hp CSS is a good, cheap alternative to full on sleeves.

Im running 10.7:1 pistons on my LS and plan to boost it. Im shooting for 350-380hp.

It sounds like you havent built an engine before so i would look up guides on engine building

 

Thanks for the reply. No I have not built an engine before. Read a lot about rebuilding and the series from evans tuning on youtube.

i want to build myself but may ask the machine shop to measure/blueprint for me.

So you are saying you buy LS pistons when you put into GSR block? Does the deck height get affected? Will the pistons push up higher into the head with the longer rods or does the longer stroke of LS crank take care of that?

Thanks again

 

Gsr blocks have the same deck height as the ls. You use ls pistons on ls rods with an ls crank. Ls rods are shorter than gsr rods.

 

Take a look at my wife's GSLR build. It's a full build thread with some nuances and features you'll find useful.

Don't worry about the "camshaft" section, that's more for another topic altogther.

Shown here:
EM1 B18C1 - "GLSR"

Good luck to you. It's definitely worth the effort, I'll say that from experience.