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Discussion Starter · #1 ·
The following ad is listed in our classified section:

NOS 11.1 Venolia Pistons for 1.9---3.750"--makes your 1.9 a 2.0 liter. I bought 2 sets when I built my engine--they are a work of art! You will need rings and pins,easy to get.

I've thought about doing a 1.9 to 2.0 conversion as a winter project. This sounds like the right pistons, yes? Decent price? This is a bit early to be accumulating parts, but if this is the right part at a decent price I might go for it. Comments please.
 

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It is a very good price. There's good news and bad news. The good news is that these will give you high compression which means more HP... the bad news is that these will give you high compression. What that means is that you probably can't run pump gas with these pistons. Depending on what is done to your head, you may be able to run with octane booster.... but conceiveably you may have to go to race gas. So, if you don't mind going with octane booster/race gas, then there is no bad news.

All that said, this is such a good deal that I'm supprised that these have not been sold yet.

James... what do you do for fuel.
 

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Discussion Starter · #3 ·
Thanks, so glad I asked. I don't I want to go that radical, so I think I'll pass on these.

Didn't realize the "11.1" meant 11:1 or I guess 11.1:1, that's kicking compression. Bit too exotic...race gas/high test&octane booster only, that's not for me.

I've done just about everything I can simple mod-wise(32/36 Weber, ported intake, Sprint exhaust, custom 2"/2.5" turbo exhaust, Pertronix, hot coil, electric fan) and the stock engine just ain't cutting it.

I'm looking to rework my '73 1.9L up to the "high compression" HP the earlier GT's had, and/or perhaps bumping up to 2.0L displacement in the process. New cam, upgrade to dual 38 Weber....that kind of stuff. Thanks again for the info.
 

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Pathologic Opeler
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no replacement for displacement

why not go for the 2.2 complete engine from our same classified ads.$1500 would seem cheaper and less problematic than rebuilding a 1.9l
 

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Discussion Starter · #5 ·
...and just how dirty (and for how long) would my hands get doing that?

My wife once actually suggested "paying someone" to fix a broken automobile. Aside from automatic tranmissions(?) and exhaust systems(I hate crawling under cars and getting rust in my eyes) that's never happend in my 30 years of owning cars.

Creating something is much more rewarding than just installing something. "It's all about the journey, not just arriving at the destination".
 

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Pathologic Opeler
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opelmotorsport

there are some beautiful "destinations" at www.opelmotorsport.com

he has some 1.9 suggestions on rebuilding and carbs...

check it out.I was studying his tuning of the 32/36

thank you Jimsky..I plan to do addco sway bars like yours this winter..
that is my journey.
 

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Discussion Starter · #7 ·
Thanks for the link. My wife is just about fed up translating German website for me. You get some pretty funny translations using Babel Fish, but it gets you where you want to go.
 

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Pathologic Opeler
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opps. I left out the "gt "

the site to check out is www.opelgtmotorsport.com It is all in english..his has some nice engines/carb info
 

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I used these pistons when I built my engine. I use NOS off-road additave to keep it from pinging and almost no advance. A local race car fabricator suggested running a 92/av-gas mixture. He said it is safer than running straight av-gas and will give about the same results as the $5+/gallon trick fuel.
 

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What would be the risk in milling some of the dome off of these pistons to lower the compression ratio to something around 10 to 1? Would the piston tops get too thin? What is the "cutoff point" in terms of compression ratio, for having to run greater than 91-93 octane pump fuel.

I know that anyone running higher compression should debur and round over ALL sharp edges within the combusion chamber, piston tops and such to help prevent detonation.

Paul
 

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I beleive that what you are describing is what James did with his other set of pistons that are the same as this.

Another thing that can be done is you can unshroud the intake and exhaust valves in the combustion chamber. This increases the volume of the combustion chamber which lowers compression some. With this you get the advantage of better intake and exhaust flow.

The limit on compression depends on a number of other factors... Such as when the intake valve closes. A later closing intake valve reduces dynamic compression. Another factor is ignition curve. If ignition is "retarded" a little in the low to mid range RPM, and "advanced" a little at higher RPMs, then you can run a bit more compression.

All that said, a "rule of thumb" for max static compression would somewhere between 9.5:1 and 10.0:1 would be safe. Up to maybe 10.5:1 might also work but even at 10.0:1 you are running the risk of needing to run octane booster.

James... are you out there. Let us know your set-up for these pistons.

Rally Bob... Have you got any high compression "tricks"
 

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One thing I found is that you guys in California have junk gas available to you. Can't run much compression with 91 octane, maybe 10.5:1 if the cam is healthy.

However, with 93 octane, I have run 11:0 to 11.4:1 compression with street cars. The real key is to compliment the compression with a hotter cam. Each works better with the other. A big cam with low compression sucks....no torque, low cylinder pressures, etc. Conversely, high compression with a small cam sucks too. Too much cylinder pressure means retarded timing and/or high octane fuel. You'll either lose power from the retarded timing or have to run $5 a gallon race fuel. But a hot cam with high compression is well-matched.

So if you run a hot cam with say, 245-250 degrees of duration @ .050", and 106-108 degree lobe separation (more overlap), plus 11:1 compression, it will live on the street with pump gas and a recurved distributor, running 34-36 degrees total timing. Run 10.25-10.5 if you have 91 octane available. If you run a stock cam, then 9.5:1 to 9.8:1 is about the limit with that octane, depending on climate (heat), and air/fuel ratio.

Bob
 

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Gee, a guy goes Offshore for a few days and all hell breaks loose!

Here's the story....I bought 2 sets of these pistons a few years back. I used one set. I have a TGSI head and hot cam. I didn't think I wanted to run the full 11:1, so I thought about getting the pistons cut down, as there is plenty of meat. I don't mind useing octane booster, but I didn't want to run race fuel. What I did instead was spend some time smoothing all the sharp edges off the piston tops as they are quite angular. I feel this might have dropped the ratio 1/4--1/2 point. I put it together and measured the valve clearance, which was fine. I didn't take the time to CC the combustion chambers, so I don't know for sure what the compression ratio is. At first, it did ping with octane booster, so I modified the distributer to limit the advance. This can be found in other threads by our Guru's. Mine is a 1970 which was one of the worst years for total advance.

Since then, I have not been able to force it to ping at all, even if I lug it. I just add a bottle of booster at fill up to be safe.

James
 
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