i have a 90 rs with a 5.3 swap. its all stock with just a dtr stage 3 cam and a tune. it has bottom end knock. mated to a new 700r4 trans.

question is..... should i rebuild mine leaving stage 3 cam in it. maybe some 799 heads and 4.8 pistons.
OR
should i get a low mile used motor, have my cam installed. and save money for other mods?
OR
is there something else i should consider

im shooting for 380-400hp.

looking for it to be a driver not a track car

 

Cams are cheeeeep. In the grand scheme, either use what you've got, or buy another; no sense in using the same one if it doesn't fit whatever motor.

That said, given what you have now, you could just grab another stock 5.3 from the buzzard nest and jam your cam in it, and you'd be right back to where you were.

Or, go get a LQ9, stick the same cam in it, and ... go faster.

Either of those things would be cheeeeeeper by far than "rebuilding" (new pistons, bore & hone, etc.) a 5.3.

Alot depends on what you want the car to be; and of course, what the car IS NOW. Converter, gears, usage, and so on.

 

 

Those springs aren't enough for any kind of really aggressive cam.

You could probably run the cam you have, if you liked how it ran in the other motor. Probably would work fine. Or, call BTR, Vinci, CamMotion, Texas Speed, etc. and see what they have to say. But in any case you're going to need to upgrade those stock springs.

Once you pick a cam, then choose a converter. My guess though is that for a DD you'll probably want something in the 3000 - 3200 sort of range, probably smaller dia than stock.

Out of curiosity though, if you're buying a motor anyway, why a 5.3? Why not 6.0 or 6.2?

 

As sofa said, most likely the true cost of a rebuild will be more than the cost of a replacement. 400 horsepower is easy to accomplish with a stock LS so there would be no reason to build an LS. I wouldn't build one unless you wanted big turbo power or an engine that sees lots of higher revs.