600 horses

I have seen a lot of valvetrain swaps on high mileage motors and most have been successful, but the motors haven’t been full rebuilds. Have any of you that have done a full rebuild notice any issues with the seats or guides that might cause concern when installing bigger cams and stiffer springs? My 5.3 isn’t too far from 300k but still runs strong. Just not ready for a full build yet.

RedXray

My LQ9 engine with 317 heads had 120,000 on them when I rebuilt the bottom end. With the heads I only pressure washed and replaced the exhaust valves (normal pitting) and PAC 1218 springs. Everything I've read the LS is pretty easy on the guides. I have about 9,000 on the re-build with two different performance camshafts (.597 lift) with zero guide issues.

1FastBrick

iTrader: (17)

Guides on LS head typically don't have issues unless you run it for long time with no oil or if you damage a valve.
The seats are the same way. Unless you overheat the engine, Typically no issues. Lapping the Valves wont hurt if the heads are coming off.

arthursc2

iTrader: (5)

I once tried to sell a set of PRC heads to a guy who was absolutely convinced they were only worth 50% of my asking price because he was have to do gonna need guides and seats 😂

the only LS motors that's I know have valve problems are the LS7s

generally speaking I feel like the LS stuff has a pretty stout top. Hard to mess up something so simple

1994Vmax

iTrader: (4)

The stock powdered metal guides are nearly indestructible. I have had more high mile guides clearanced because they really are too tight for something like a blower or turbo. Guys that mash in bronze guides or much worse being bronze liners just are looking for a worn out mess. Had a shop build some 243s and install bronze liners which I didn't ask for or want. Ended up pushing that junk out into the garbage and installing new stock guides again. Most expensive 243s ever lol.

The only complaints I have seen is 706 and 862s intake valves. On high mileage they knife edge pretty bad against the seat... no surprise as if you drop a 2" intake in the head they fit the seat perfectly lol. Obviously need to be cut but still. Only other LS head issue I saw was 317s that the valve tips were destroyed from an oiling issue. Pretty solid... kind of like the rest of the engine lol.

pknowles

iTrader: (1)

I had my 317's redone at 265K miles and the machine shop said the guides were fine.