1.7 piston & cylinder replacement options, any help would be appreciated Options

[Chromatech]

What options are available for replacing pistons & cylinders on a 1.7? Is there any advantage going to a larger bore? if so, what other work would need to be done?

Thanks

[r_towle]

aircooled. net has p/c for the car.

I think that the problem with going bigger is that you have two roads...

The bore in the 1.7 head is small.
The bore in the 1.8/2.0 liter head is larger and the same on both.

So, if you get bigger p/c kit for the 1.7 you have a cylinder wall that is to thin, fails and has a really bad reputation.

of you can bore out the head to the 1.8 liter size and open up a new set of parts...1.8, 2.0 liter p/c...96mm p/c

But now you have a head that has really poor flow.

stock might be the best way to go...

Rich

[lapuwali]

Aircooled.net only has 1.7 Bus setups (at least on their site). These have heavily dished pistons that lower the compression ratio and will lose you both power and fuel economy. The 90mm cylinders with high compression 914 pistons aren't all that easy to find. You might have the best luck looking at Porsche dealers. 96mm P&Cs would very likely be a lot less expensive than stock 90mm P&Cs, though you'd then have to modify your current heads, or find later heads. Then you'd have the problem of making the stock EFI work with the 1911cc engine you'd end up with, or switching to carbs or aftermarket EFI.

[dmenche914]

you can also play with compression ratio, some pistons are flat, some dished, and the head volume can be changed, heads cut down, shims installed. The earlier 1.7's ran higher compression, had MORE power than the later 1.7's My understanding that the only significant difference was compression ratio done for smog reasons.

you can maybe bump up the compression but don;t go crazy, too high and you will have a time bomb for an engine, also higher compression may mean premium gas. There are a lot of factors that limit compression for a given octane, timing, operating temp, other components etc.... However if you have a later 1.7 that was lower compression, I see no reason why you should not upgrade to at least the higher compression factory spec for early 1.7 engines, that will gain you power and efficiency, without the issues in displacement increase.
The larger bores cylinders for the 1.7 can have thin walls, and is a big concern in an aircooled engine, cause the cooling is not as even as in a water cooled engine (one side gets a blast of cool air, the other side is out of the blast) hence the thin walled ones warp (don;t stay round) which leads to rapid wear, leakage etc...

I'd go for the older higher compression 1.7 spec (maybe more, check with your engine builder, tell him if you want more power at expense of engine life or premium gas. There should however be some wiggle room for a compression increase when you do a head repair. Heck a big bore, but low compression is not going to help you. You want to have your head volumes matched and a target compression ratio met on any head repair.

The 1.7 in the early form (high compression) is a perfectly fine motor, and can really make the 914 move, it has good torque at low rpm, I have run 1.7 faster than some of my 2.0 liter friends can. Also the early 914 wieghed less than the later ones (less crash protection in doors, bumpers, etc... so the small 1.7's with high compression are not that far off the performance of the later 2.0 powered cars (that gained wieght). (the later(75-76) 2.0 was dropped in power also, the early (73-74) 2.0 had more power)

Just beware of too high a compression on todays gas. i am sure you can get some good info by asking a post about it on this club site.

1.7's rock! (and get better milage)

good luck

[davep]

Talk to Mark Henry, our local engine builder.

[Bleyseng]

Pelican Parts has listed 90mm Domed pistons and cylinders just like the oem ones for $365 IIRC. I haven't seen these for sale in years......

Makes a 1.7L really scream to have the right 8.2to1 compression vs the 7to1bus pistons (IMG:http://www.914world.com/bbs2/html/emoticons/sad.gif)

[Twystd1]

I would do what was mentioned above.

Except for the one that doesn't work.

Unless I had to because it was needed.

MattR

[Tom Perso]

I have to agree with dmenche914 if you're looking to do a stock 1.7 displacement build. Other thingi I would suggest is a Webcam 73 FI camshaft. It's a little warmer, works with stock FI, and if you can get it running just right, I have heard 100hp at the crank is possible. There is a guy over on the STF (Ray Greenwood) who can make 1.7l's RUN.

If you want to go bigger, do the same cam, run the 96's with your 1.7L heads opened up, some 2.0L 914 heads, or if you can find them - 1.8L bus heads. These are P/N 021 101 371H or 371S. They are 41 x 34 in stock form (same as 914 3-bolt heads) and would work well for a mild 1911 build.

Hope this helps.
Tom

[Bleyseng]

I am trying a Raby 9550 cam in the 1.7L we are rebuilding. Works with Djet and should improve oil temps alot.

The Webcam can be tricky to get to idle.

Going to larger valves helps too but I am going with the stock heads we have.