DIY Engine Build questions
 

Not sure whether to post this here or FI.

Picking up a blown motor Monday to rebuild, depending on what's salvageable.
Wanting to look at building something eventually capable of running 400-500 for Autocross, and eventually track days. Currently have a Td05-20g, but will be bumping up to a G25-550 or 660 when I start to push for more power.

But wondering about compression ratio, I'll be running mostly pump E85 for racing, and I'm looking for a wider smoother power band if possible. I was looking at dropping to an 11:1 JE Piston, and maybe even a thicker head gasket (depending on how bad these heads are), but I've had people mention stock compression would be able to do it, if I've got rods that will take it.

Probably not the best engine to build as a first engine, but here we go.
I've read up a lot on oiling, and was going to try to go for OEM bearing tolerances. Any insights to bearing material (King vs ACL vs OEM) or ring gap would be appreciated.

Additional modifications to the engine were going to include GSC 1mm bigger valves, beehive valve springs, reimax high capacity pump, KillerB pickup, MoneyShift racing baffle, (haven't decided rods yet). I'm also considering setting up a return style fuel system for when I start pushing.

If you're sticking with e85 or using flex fuel, stay with stock compression (especially if you need fast response like with autocross). It'll make the power more easily and you'll have a nice knock ceiling on e85.

Anything wrong with using stock pistons and the crower? rods that have the chamfer to fit them?

Have you considered just buying a built short block? When you get into rods, pistons, crank, mains, rod bearings, rod bolts, case bolts, ect you are getting up close to what a built block cost before machine work.

You're not wrong, and depending on the manufacturer, I'd even get a warranty... but I want to do it myself. I highly doubt this will be the last engine I rebuild and would like to even consider doing it for friends in the future.

I think I have a decent idea of how, and access to resources to confirm, but I know my use case is a bit niche.

Nothing inherently wrong with the stock pistons, but if you're going to do the build, may as well make the most of it.

I am with NoHaveMSG on this though, I'd really consider just getting a shortblock that's already put together. There's still plenty of work to do

My IAG stage 2 was 12.5:1 compression ratio and i run a flex tune with 93/e85 but mostly e85. I did get the gsc valve spring titanium retainers. They told me that it could handle 8200rpm and 20psi and something like 580crank hp. That is more than you'll ever be able to put down on autocross.


IAG told me that bigger valves and beehives weren't worth my money so ymmv. I do have a killerB pickup and a bluemoon baffle.


Also going to 3rd and say go with a built short block at least. Even with donor heads, the cleaning and machining alone will cost an arm and leg so if you might as well.

I got a free longblock a while back, J02 victim. I have been holding onto it thinking about building an engine and everytime I price parts out it's a fat NOPE.

I just gave one of my smoked J02 blocks to a friend who wants to buy and learn.. I came to the same conclusion that it's just not worth the investment or time for me.

I still have my blown engine in my garage. Pretty much everyone i talked to said not to DIY it. I honestly think I could have done it myself too but it saved me a lot of trouble having pros do it for me

I'd make sure you research the hell out of it if you decide to do it yourself. If I was doing a built motor I would want to line bore the cases first. I believe you want to go on the tighter side of spec for the bearings for better lubrication. It's been a while since I looked into it.

I may pull this one I have apart and just throw a crank and fresh bearings at it. I don't see doing any more worth it.

I worked in a machine shop for 5 years or so. We had one FA20 and it is not an easy block to do if you aren't used to it. If you plan on using ARP hardware a line bore is an absolute must this one when it was torqued ended up way out of round and ended up needing a mixed set of bearings some -.001 some standard. I would absolutely recommend a good machine shop do block work and measurements for bearing clearance.

We used King on a lot of engines, and I like their bearings. I would keep stock compression especially if you are using e85 anyway.

I know a line bore can be done, I haven't personally looked into it but I know it's needed if you go for stronger than OEM case hardware.
My main concerns were trying to figure out what else may be needed to keep it together on the higher end.

Generally, I know IAG has short blocks, but for 4800 for just a short block it's out of my price range for right now... (student loans and only just starting my career) I know with what parts I already have, and what I'd need to buy to rebuild this engine I'd be well below that. There's a local race shop that can do the machine work, for less than $500 (block, bore and hone, then clean the heads).

I might look at just bore and honing the block, putting in better internals and just refreshing the heads... and then redo them later on. For now, I just want an engine that can comfortably push 350-400, and maybe have a map I can run ~450hp for my last 2 runs. Our autocross courses usually see 70+mph at 1-1.5mi long.

Even stock, it is not uncommon for the cases to be out. NA, I was planning on line boring if I was to build.

pick up a 3.7 or 3.9 FD that is what I'm doing. You are going to need a lot to hold that power

I've heard of this but it's beyond what I know currently...
Is this something you can check on your own or does it require advanced machinery?

Is there an amount that is tolerable if you're still running the engine to only 7400-7500RPM? I know physically more power/RPM will make it considerably worse, but I'm on a factory block now that's been running ~350wheel for 2 years ~40k mi ( at that power level)