Considering NPR 1.7L Big Bore kit...many questions, and kinda long

[Minh Nguyen]

o.k. y'all,
I'm new to this and my questions are plentiful, but I'm more than willing to learn anything that anyone here wants to teach me. Please be patient if you can )
Alright, I have a 73 1.7L; it's the EB block with the 7.3:1 compression ratio. I presently need a valve job and new P&C's (and all the other little things). I don't know if I should purchase the stock 90mm 1.7L P&C's or the 93mm Big Bore kit that brings the displacement up to the 1.8L specs (I am also be open to other size BB kits if anyone has any suggestions). Also, if it can be factored into the equation, I have access to a pair of rebuilt 1.8L heads that may be comparable in price to the 1.7L head work. From what I've read and the information that I've gathered, I am under the impression that I cannot use the 1.8L heads with a 1.7L with stock P&C's. Can I use the 1.8L heads if I got a BB kit? I don't know which route is the most feasable. I'm swaying towards a BB kit unless there is evidence that otherwise suggests me to go with the stock set-up. Next I have the issue of the 7.3:1 compression. I would like to bump that up a bit for a little more performance, maybe to 8-8.5:1, depending on what would be a good safe number. What kind of numbers are you guys out there running and with what kind of success? I know that a BB kit will bring it up some and that I can have the heads flycut for more. How would the 1.8L heads factor in if I was able to use them? Would they hold up better for the higher compression than the 1.7L heads? That's just some of the stuff I can think of right off the top of my head---no pun intended. There's more rattling around up there and I'm sure I'll add it soon. Oh yeah, I have a pair of Weber 40's that I plan on using to supply the fuel when it's all said and done, but would be able get an L-jet FI if I would be better off. Any suggestions on the optimum set-up with what I have to work with would be great. I know I'm going to have to spend some money to get this all done, but much like my brain cells, there is only a limited supply.

To all of those who have actually read this far, you already have my appreciation.
Thanks,
Minh

[rich]

Check out the big bore kit in the 914 parts ads on this site. Great price!!! By far the best bet. Higher compression means more power. As I understand no adverse effect on the injection. Go for it.

[JP Noonan]

There are a few ways to go.

1. I'd suggest that if the rest of the motor is in poor shape then the bottom end needs rebuilding. And, if the case is split anyway you might as well bone up and get a hi-po cam to match the carbs (catch is, you can NOT use FI with a cam designed for carbs, i.e. "no turning back"). Then use the 1.8L heads (bigger valves than the 1.7L but I've been told it has a larger combustion champer so they may need fly-cutting) ans some BB 1.8L cylinders. Whatever way you go COMMIT NOW, have an overall plan, you'll save money/heartache in the end.

2. Next is to use the 1.8L heads and BB 1.8L cylinders with either stock ( but slightly tweaked)FI or carbs. Compression boosts either from fly-cutting and/or leaving out the head gasket.

3. Use the 1.7L heads with bigger vavles, the 1.7L BB kit, no head gaskets, FI or carbs.

As far as price goes it's a toss up. The 1.7L PC's are only $170 1.8L PC's are maybe twice that. But the 1.7L has smaller valves unless you but in new larger ones, that ofsets the price of the already rebuild 1.8L heads.

1.7L and 1.8L cranks and rods are the same 2.0L is different.

1.7L heads can be modified to be used with 1.8L/2.0L PC's but not the other way around.

A 2.0L crank is needed to use the 2.0L PC's, a 2.0L crank can;t be used with 1.7L/1.8L PC's the wrist pin location is wrong.

Valves sizes 1.7L I=39 E=33, 1.8L I=41 E=34, 2.0L I=42 E=36 some sources disagree slightly.

General consensus is 8.5-9.0:1 CR is the limit for the street, higher than that kills the motor. Also this assumes that the stock cooling and fuel system are in perfect shape. No missing cooling tin or gaskets, a working thermostat, a perfect A/F mixture, 93+ octane...

Buy Tom Wilson's book on rebuilding Aircooled VW motors by far the best book of it's kind out there, the Lash International is next in line, the Haynes is O.K.