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Discussion Starter #1
I might be purchasing a set of Venolia forged 11:1 pistons for my 164S. The whole engine is currently being rebuilt and I thought that this would be a good chance to maybe upgrade a few things. Any advice would be appreciated. I have my doubts on this being a good idea on a daily driver, but what do you guys think? I think this would add some nice power, but what are the downsides to adding forged pistons, and what type of stuff should I look out for? This is a stock motor with a stock head and only S cams with stock management.
Thanks again,
Mike
 

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Go with the 10.5:1 JE forged pistons from PaulSpruell.com . I've used them for 3 years. Low expansion type so no slap when cold.
 

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Discussion Starter #3
I've emailed him several times and no answer back:( maybe I should give him a call. What kind of gains did you get from those pistons?
 

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Call Michelle Spruell. She really knows her stuff when it comes to Alfa.
1-800-552-2532 or (770) 457-2532 .

Paul
 

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Compression by it self does not equate to big power gains, unless you really good very high and turn lots of RPMs. If you are in the process of rebuilding your S motor and want power increases, for a little more money on the front end - mill the heads for more compression, a street port done on the head, port matching at the intake runners, cleaning your injectors, headers, chip/modified engine management and possibly upgraded cams. The deciding factor is what are your expected results and how much do you want to spend. Good Luck.
 

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Richard Jemison
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Engine mods

I totally agree with Andrew, that it`s much more reasonable to approach compression on the 12v V6 by machining the head. Very inexpensive HP gains. With the "S" pistons you have 1/2mm (.020) milled from the heads it will give you 10.5 to 10.6 to 1, about all street fuel will allow. Your existing cams could be improved on, however since you are in an area thet likely does emmission testing I would be cautious. (FYI, measured volumns inc. headgasket have always indicated the "S" piston and stock combustion chamber to be about 9.7 to 1 static):eek:
The "S" cams correctly timed, should respond well to the compression increase. Avoid going overboard if this is a street car. If you want to do more check out: http://scuderiagiallo.com/SixCylinderCams.htm
( you will need adjustable sprockets since head milling changes the distance between all drive & cam pulleys, there are some for sale here on BB I posted a couple of weeks ago.)
Good luck with the 164S
 

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While I won't have a direct comparison of before/after, we will have a Milano Verde running with 164S pistons installed in a couple of weeks. I thought that doing the bottom end up as an S spec engine wouldn't hurt the performance (higher compression pushes things a little closer to ideal engine efficiency) and made it so one could go to S specs with a simple cam change later, if that appeared desirable. You're indicating that I should also do port matching on the gaskets and manifolds. Not a bad idea while it's apart. Thanks for the reminder. We're not very familiar with this stuff here, nor do we tend to leave big black patches on the roadway or push the limits of our speedometers (well, _she_ might).

edit: I should have referred you to the Milano guys, who routinely discuss the merits of S spec'd Milano motors and other mods. They may have informed opinions on what happens when the compression is ramped up to 11:1 in a 164 engine on the Milano platform.
 

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A compression ratio of 11:1 might be a little high for pump gas. Especially if you live in an area like I do where the highest octane fuel you can buy is 91 (r+m/2).

Richard and Andrew have built a lot of hot Alfa engines. If they say 10.5:1 is about all you want, that's probably good advice.

Personally I don't like to mill the head because it's not reversable. However I do understand the economic reasoning behind it.

Forged Venolias don't rattle in the bores when cold unless they are set up really loose for a full race application. We have use 4 sets in 4 different engines and I really like them.
 

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Do not get me wrong, higher compression is a good thing. To get the full benefits you might consider so of the other items mentioned. You do not have to break the bank to get a noticable power improvement.
 

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Another budget approach that we have done over and over is to install new small-end bushings (probably a good idea on a high mileage rebuild any way) and then just have the machinist off-set the wristpins up by about .7 to .9 of a mm...

Then you have the valve-releases in the pistons machined deeper by about 1mm (to be safe) and voila - 10.5 to 10.7 compression and NO irreversible machining to the heads (never know when you over-heat, warp a head and NEED that meat to plane the heads again...)

Do Total Seal Gapless rings, recondition the injectors, mild porting, port-matching the runners etc etc...

Good cams and programmable fuel & spark and the world is yours!
 

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Discussion Starter #12
ok so i guess these pistons are not worth the trouble, but I will take all these other options into consideration. Maybe just cams and some fuel management? I might call up a local machine shop and see what else is out there.
thanks again guys
 

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Now, nobody said the pistons "aren't worth the trouble." You might still ask on the Milano forum or the Alfa Digest venues (majordomo email list and 164 online forum) whether anyone has done 11:1 pistons on a V6 or a 4-cyl and what their experience was.
 

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Years ago, I built a Groupe A 2.5 engine for a customer. The pistons were 1 mm oversize and had a compression ratio of 11.5. He decided not to use the matching Groupe A race cams and instead when with CB 11.5 lift race cams. This was done before affordable EFI systems. The GTV6 would run nose to nose with Mustangs and F-Bodies stop light to stop light to stop light. Once on the move or a rolling start it would take their lunch. Once you get that high in compression you must be mindful of pinging, how much advance you are running, and how hot it is outside/type of traffic you are in. Motor was disassembled years later when emissions checks can into effect.
 

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Not quite off-topic question: how, width a catalytic convertor, would the emissions be adversely affected by the things you mention? The cat should remove extra NOx from higher combustion temps caused by the higher compression. The cams might cause a bit of extra enrichment, more CO and unburned HydroCarbons, but would it swamp the cat's conversion capacity? Just wondering....
 

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Discussion Starter #16
So are you saying that there is a good chance that I would not be able to pass emissions if I were to put these pistons in?
 

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I passed CA SMOG II test with 10.5:1 and CB cams :) . I have autronic SMC though, sequential injection at low rpms might help. This was on a load dynamometer.
 

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My Verde running L-Jet with S cams and pistons always passes smog with no problems on the dyno in California. The emissions are actually very low.
 

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with what does it swamp it, Dear Liza?

I seriously doubt an Alfa V6 with L-Jetronic would pass an emissions check with anything hotter than "S" or fast road cams.
Any hints for a technically focused person about just what parameters the car would fail? I'm really curious about it because I don't understand with what the engine would overload the catalyst (unless it's hydrocarbons from too much overlap and sweeping some unburnt fuel mixture into the exhaust).

Michael
 
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