Thread: Rebuilding tips

First timer, newbie, fresh meat, novice here.

Looking for a general guide to 3800 rebuilding. After my own evening of googling I understand that it's not the typical path to go as a cheap running motor from a yard is the better bet.

I completely understand that. I also am lead to understand that rebuilding these is NOT that simple as one must rely more heavily on a machine shop to balance things. I'm thinking more long term, I want to learn, enjoy myself and have something usable in the end. Yes, I know the time and money aren't worth it, so you can save those speeches.


Anyone know of a general guide, a thread of someone that's done it or??? Mostly all I can find is posts and other forums explaining why it's hard and more expensive than just buying used.



I'm already ready to pull the trigger on one of two 150k 3800 engines, one for 150 with a tranny (99 pontiac) and another for 100 out of an impala. Both N/A engines.

You're pretty much spot on with your post here. When I rebuilt my engine, all I ever heard was "it'll blow up in 500 miles", and "it isn't rebuildable." Well, I'm rolling on 7,000 miles so far with no problems (ast least due to the rebuild.

That being said, other than the fact I had a blast learning, I don't necessarily recommend it. I ended up spending $1500+ just to rebuild a stock L36 that probably would have ran fine from the junkyard. that price is also very low. I found a cheap machine shop, peiced together my own engine kit, and only used the machine shop for balancing, line honing, cam bearings, clean and magnaflux, some tolerance inspection, valve work, resurfacing, freeze plugs, cylinder overbore and hone, and inspection. All the assembly and disassembly I did by hand. However, I can guarantee I probably have one of the smoothest running engines in Missouri, and I know literally every part in the engine bay and how to fix it.

All those pros and cons aide, number one is finding a good machine shop who has rebuilt these engines (there's not many). With 100,000 miles, there is no getting around having to overbore. I only had to go to 20 thousandths. You need to replace all tty bolts, main bearing, side bearing cap, cam bolt, crank bolt, flywheel bolts, torque converter bolts, rocker bolts, head bolts, balancer bolt, connecting rod bolts to name a few. I recommend going arp on flexplate, connecting rods, rocker, but not main. The reason I say not main is that it mandates a line hone. The general rule of thumb is after your crank is ground and your main bearings are in place and it's torqued fully, you should be able to spin the crank with minimal effort and all the clearances should pass, if not, you need a main line hone.

Unless you're building a race engine, don't do mil head gaskets, any surface imperfection will cause an issue so if you insist, you need the heads and the block resurfaced. As far as heads, I recommend magnaflux, new valve stem seals, valve grind, valve seat re-cut, clearance inspections, new springs, new lifters, (do not mix up what connecting rod and rocker arm went to which cylinder).

Have a good torque wench, lots of time, good parts, good gaskets, and recheck everything and you'll be fine as long as you follow machine shop guidance and mine!

My biggest regret is that I didn't learn to port the cylinder heads, didn't use gen 3 cylinder heads (slightly bigger valves and better casting), and that I didn't just rebuild a L67 instead of L36 (L36 connecting rod ends are thinner and weaker and the pistons have less reinforcement so they're more prone to chip). That's only if you intend on modding info the future though.

Feel free to ask any questions as you go, I unfortunately didn't take a lot of photos, but I'll do my best! Good luck!