Replacing 1.8 with a 1.6
 

So I will start out by saying I am new to the forum and just recently purchased my first miata. It is a red na (1995), and I have had it for two weeks now. Here comes the bad news, yesterday I discovered that the head gasket is blown!! Awesome... So I have been looking at new engines on eBay and I noticed a significant price difference between the 1.6 and the 1.8. I still have a solid tranny and rear end so I know the only thing I need to swap out is the engine. Would it be a bad route to go with a 1.6? Either one I am going to turbo in the next year and my ideal number HP wise is 200~ to the wheels. Any help will be appreciated!!

This just might be the worst idea I've seen in ages.

??

Why don't you replace the headgasket? It's not a difficult job on these.

Im not much of a mechanic, but this is my first car that I want to actually work on myself. The current engine has around 200k on it, so I was going to get one of the jdm imports from japan that has around 50k on it so it would be relatively fresh.

:vash:

Would it be worth it to replace the head gasket on a motor that has that high of mileage???

Yes, very much so. While the heads out, have it surfaced, cleaned, pressure checked, and valve seals replaced. Should cost around $200-$250. Then do a timing belt job with front main seal, cam seals, water pump, thermostat gaskets, water neck o-ring, and CAS o-ring.

These parts will cost you about another $200, and you'll be left with pretty much the oil pan, rear main, rings, and bearings left that haven't been replaced. There's a bunch of little seals and rubber bits on the head you could easily replace at a later date if/when they fail.

All this is just as difficult as pulling and replacing the engine, if you're uncomfortable with one you should be uncomfortable with the other.

While I am at it is there anything else performance wise i should change to prep for turbo?? IE cams, valve springs, valves, pistons?? This is probably a dumb question i know but like I said im new to this.

If you're actually removing the engine, pull the pan and drill and tap it for your oil drain. Check, double check, then triple check you've got the right location with pictures from here and google, it all depends on things like AC, PS, etc. After you drill and tap it, put a bunch of JB weld around it to keep it from leaking. You'll want a NPT-AN adapter, the barbed hoses have a tendency to leak.

Pistons are known to be good to ~300hp(??) more or less, but I'd replace the rods first, they'll go at around ~225 ft/lbs and are known to be the weakest link unless you have a 1.6 differential.

springs and valves are find unless you wanna rev past the stock red line. Cams are also not a huge performance gain unless you're hunting for the very last bit of power and/or known a lot about cam angles and internal combustion theory.

So mainly what I'm going to be changing is a bunch of gaskets and seals right??

Uh, sure. The head should be dropped off at a machine shop and not touched by you. While they have your head, clean the old head gasket off the block, get it REALLY clean. place a new gasket on, place the head on, and torque it down. After that it's pretty much just a timing belt job, including valve cover gasket and CAS O-ring. Instructions for that can be found all over the internet, from m.net, cr.net, and of course mt.net.

I was planning on getting the head done, haha definitely won't touch that guy!! Should i get the block honed or anything??

Are you pulling the engine or not? In order to hone the block, the pistons and oil squirters will have to come out. In order to do that, you'll have to pull the engine and then the pan. Can't do it with just the head out.

Yep, im buying a hoist and engine stand next paycheck and im going to pull it out and start taking it apart hopefully next weekend

Check the cross hatching, if it's fine I don't think there's a need to hone. Some may say differently. If you've got the money, definitely pick up some ACL bearings and Manely rods from Trackspeed Engineering.

I will definitely check those out!! Thanks for the advice!!

FWIW - as an alternative, you could also just buy an Escort GT 1.8L at a junkyard and swap it in. They are mechanically the same engine, and are almost always cheaper to purchase than a miata engine. I have bought two over the last couple of years for around $200 - so about the same price as a head rebuild and gasket replacement. But, there are several downfalls:
-Unknown condition of a junkyard engine. Some come with a warranty, but would require you to pull the engine twice if it ended up being bad.
-Is actually more work to swap over all of the Miata components to the Escort engine, than it is to simply do a head gasket.

If I was in your condition, I would simply replace the head gasket. Which brings me to:

Alternative #2 - Replace head gasket on existing engine and continue to drive it. Taking your time, Buy Escort GT engine. Buy strong aftermarket rods and pistons, new bearings and gaskets. Rebuild Escort GT engine with said parts. When complete, swap with existing engine and install monster turbo. Win.

QCB is having an exciting morning.