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| forged piston selection for a boosted 3.4 (Page 1/2) |
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jjd2296
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DEC 20, 05:49 PM
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For you tech guys. I will be swapping in forged pistons and gapless rings in my 3.4 fully built up with a v5 supercharger. I am getting way too much blow by and now I believe my rings are toast. after I installed WCF long tube headers in exchange for my sprint headers, I have oil leaking out of the exhaust. I am assuming that is because my piston ring issue is getting worse and the WCF header on the firewall side (where the oil is found in the crossover) sits angled downward as opposed to upward on the sprint headers. It was also way colder the day I started the car up (minus 2 Celsius I never start the car when its that cold) so I assume the rings and pistons were even smaller at start up due to the cold. I have been having a starting issue all summer where the battery needs to be fully charged (above 13v reading) to get it to start. I believe this might all be linked to the blow by issue and lack of compression. should I do a compression and leak down test first? my oil was getting gassy fairly quick and I was changing it every 2000 kilometers this year.
Now to my other question re forged pistons. A- on this build I want the compression to be lower than the 9:3:1 that is stock for the 3.4 PR engine. So I am looking at other forged piston options. B- I want to use sealed power gapless rings. anyone here have experience using those? C- I am looking at using forged pistons from 1994 dodge stealth turbo as my research suggests that they will work (that engine is a 60 degree block as well) and will bring my compression to 8:3:1.
Stock 1994 3.4 PR pistons details - Bore 92mm, stroke 84mm, compression 9:3:1, compression height 1.457, height 0.200 mm, pin OD 0.9054, recess 0.080, top ring 1.50mm, second ring 1.50mm, bore stroke ratio 1.1
Stock 1994 3.0 turbo stealth pistons details - Bore 91.1mm (they come in 92mm, 92.5 mm), stroke 76mm, compression 8:3:1, compression height 1.256, height 0.590 mm, pin OD 0.8661, recess 0.134, top ring 1.20mm, second ring 1.50mm, bore stroke ratio 1.2
Now since these are used in 60 degree engines I believe all that matters is the piston bore, compression, and recess (stealth is lower recessed hence the lower compression?) ?
could some tech person chime in and let me know if these pistons would work for me if I get them in the right bore size for the 3.4 block? they are much easier to find of the shelf in forged then 3.4 pistons are which need to be custom made.[This message has been edited by jjd2296 (edited 12-20-2023).]
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pmbrunelle
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DEC 20, 06:44 PM
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Oil in the exhaust looks like bad news 
Compression heights are different...
Piston pin diameters are different...
These parameters are not defined for a piston alone; they only make sense when talking about an assembled engine:
Compression ratio
Bore/stroke ratio
I think that you need to do more research into what makes a piston fit before you start mixing and matching.
Custom pistons specified by a reputable manufacturer sounds like a good way to go.
Otherwise, stock replacement Gen 3 60°V6 3400 pistons are listed as hypereutectic and will drop your compression ratio. They're not forged though as per your stated requirement.
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jjd2296
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DEC 20, 06:52 PM
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What would be the years that engine came in?
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pmbrunelle
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DEC 20, 07:13 PM
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La fiera
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JAN 02, 06:46 PM
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| quote | Originally posted by jjd2296:
Stock 1994 3.0 turbo stealth pistons details - Bore 91.1mm (they come in 92mm, 92.5 mm), stroke 76mm, compression 8:3:1, compression height 1.256, height 0.590 mm, pin OD 0.8661, recess 0.134, top ring 1.20mm, second ring 1.50mm, bore stroke ratio 1.2
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If you use the 1.256 comp height you'll be .208" in the hole. You'll need rods with about 5.9" in length.
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sleek fiero
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JAN 02, 08:55 PM
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Check out WOT tech. They had diamond racing pistons for 3.4 iron head engines in suitable CR
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sleek fiero
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JAN 02, 09:03 PM
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I just checked and they have them listed you just have to let them know what CR you want. In their search just type 3.4 iron head pistons
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jjd2296
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JAN 03, 12:54 PM
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yes I saw this, wait time is 4-6 weeks they are not off the shelf. I was trying to look into an off the shelf option fist. and UPDATE- not oil but fresh coolant in the exhaust. blown had gasket confirmed as well as a broken piston ring.
| quote | Originally posted by sleek fiero:
Check out WOT tech. They had diamond racing pistons for 3.4 iron head engines in suitable CR |
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BillS
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JAN 14, 01:27 PM
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There are several race piston producers that can supply what you want.
When I did my turbo engine (it was in the early 90s before 3.4 engines were easily available, so i used a 3.1 crank and 0-040" overbore for about a 3.2 displacement, I had Ross Racing make me some custom pistons to suit. They are forged and held up beautifully for almost 20 years.
FWIW I ran 8.5 compression and a max boost of 10 psi (intercoolers are difficult to mount in Fieros and was OK without one using that boost)
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82-T/A [At Work]
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JAN 14, 02:38 PM
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| quote | Originally posted by jjd2296:
I installed WCF long tube headers in exchange for my sprint headers
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By any chance... are these Sprint Headers taking up space in your garage that you're willing to exchange for a heavier wallet?
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