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[supercowmoo3]

I know that the stock n/a motor has a 9.4:1 compression ratio but im wondering what exactly theyre made of. ie are they forged alluminum pistons on top of forged alloy connecting rods or are they both just cast? Also how tough are the valve springs and at what rpm do they float? What is a safe rev limit past the 6200 factory redline? Im contemplating adding cams to my engine for more power along with heads and such but anyways would a stock bottom end and valve tran hold up to more agressive cams?

[Rocketman]

The stock pistons are cast eutectic aluminum, as are almost all OE pistons.
The stock rods are cast iron or cast steel, I'm not sure which.

Both of which can handle over 200hp. The weak points are the rod connecting hardware, then the rods, then pistons (if you have a proper tune)  you will blow through many transmissions before killing engine internals, if you are doing things properly with the engine.

The lash adjusters / springs start to pump up/float somewhere just above 7200 RPM.
You can run more agressive cams with the stock bottom end without any issues. But there are a lot of cam options, and some have too much lift for the stock valvesprings. Do your research before purchasing one! The bore to stroke ratio is pretty even on the 1.6L so it likes to make its torque down low, there's not a whole lot to be gained up top without spending $$$$$

Also to note: these are not big V8's that pick up 50-100hp with a new cam. You may gain 10-15 hp. MAY. That money could be well put towards an XR2   just an FYI, around $500 in mods on the XR2 will put you in the 160+whp range

[chrispoe]

The stock rods are cast steel.

[supercowmoo3]

everything seems to be pointing toward an engine swap or n/a to turbo xr2 conversion. I probably wont do anything but exhaust and intake for now but thank you for the useful information. How much power would you say an xr2 transmission can handle before breaking the teeth off of the ring gear or something? lol

[Rocketman]

The ring gear is fine. 3rd gear strips at ~300+hp
The differential spider gears gall on their carrier, causing diff failure. This comes from spinning one wheel, either thru burnouts or too much power for your tires/suspension. As I said in other posts you can kill a stock XR2 transmission with a stock engine just by doing burnouts. There's the MFactory limited slip differential that you can toss in there, but it's a spendy piece.

Want to stay N/A but still gain a ton of power and tq's? Look into the BP swap. It's the 1.8L "Big Brother" of the 1.6 in your Capri. It's still a fair bit of work but depending on your location you can find parts to pull it off a lot easier.

The BP responds a LOT better to N/A mods than the 1.6 does, and theres a very healthy aftermarket for it, pistons cams etc

[chrispoe]

From my experience, you wouldn't gain a ton of power from the BP.  The stock BP is an extra 27% hp. When mated to the taller geared N/A tranny, you'll be slightly faster then a stock xr2.
I've read your other posts about adding higher compression pistons, hotter cams, intake, and an exhaust. With all of those mods combined you'll be lucky to even get to the stock BP's power. Then to add insult to injury the BP swap will be way cheaper and easier to do and if you still decide to go FI, the BP has a 8.8:1 compression which is more boost friendly too.

[Rocketman]

Well, the stock N/A transmission is shorter geared. It's got a 4.11 FD vs the XR2's 3.85 FD. (larger number is shorter) They made it shorter so it would still feel similarly peppy with less power, but it tops out much lower than the XR2 does.

Personally if I did a FWD BP swap I would not waste the time with the N/A tranny, though I suppose it could be done that way. Ideally I'd go with the transmission from the donor vehicle, it's also a G-Series but it has a hydraulic clutch so you don't have to mess with the pedal assembly. It requires some attention to the drivetrain mounts, as the BP tilts forward several degrees with it's flavor of G-series.

But yeah, talking economy vs power here, a stock BP will likely have more power than a 'built' (built as mentioned above) N/A 1.6, and the same mods put toward a BP would have more gains because "theres no replacement for displacement"

[supercowmoo3]

you guys have been a lot of help in making me realize that i want to do something entirely different. And by that i mean a rotary capri. Wish me luck this summer because im pretty much set on doing this lol

[chrispoe]

Personally if I did a FWD BP swap I would not waste the time with the N/A tranny, though I suppose it could be done that way. Ideally I'd go with the transmission from the donor vehicle, it's also a G-Series but it has a hydraulic clutch so you don't have to mess with the pedal assembly. It requires some attention to the drivetrain mounts, as the BP tilts forward several degrees with it's flavor of G-series.

I originally felt the same way when I did my swap. At the time I was only 17 years old and I didn't have the extra funds to buy the G tranny and XR2 axles/shaft. I figured I'd just use the F tranny til it broke, then I would upgrade it.  I tried to break it, even had a 40 dry shot of nos a while back.  All I managed to do was find the limit of the stock clutch. LOL

Good luck with the rotary swap!
If you do it,  you should do a build thread.

[supercowmoo3]

I definately will do a build thread and probably film it and upload it to YouTube. I was also thinking of putting nos in my car just to see how it reacts. Mostly because if I do blow it up I can just get started on my rotary build. I just turbod my rabbit so this car in its stock condition only has to last until I can do the exhaust on my rabbit. That might be a few months then before I get started but I'm thinking I'll do some cosmetic things to it and post about that:)