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Thread: What is involved in building a 2.5 TIII?

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    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    What is involved in building a 2.5 TIII?

    I just picked up a Spirit RT that is supposed to have a 2.5 TIII setup. Would like to know what is needed for that so I can verify it. I guess I can measure the stroke w/ a rod through the plug hole. From what I read, stock 8v 2.5 pistons would fit but cause a lower compression ratio. The proper way is to use the custom ones FWD-P sells?

    I'm hoping it has all this and was done right
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

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    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: What is involved in building a 2.5 TIII?

    Sounds like a good plan and you could probably use a small bore scope camera like what we use at work for finding leaks in walls and peering down sewer pipes to look at the tops of the pistons for the 4 valve reliefs. I have a 2.5L TIII short block here on a stand and the pistons are forged Venolias from FWDP. They look just like a 2.5L TI piston top, but two more valve reliefs. I would guess the compression ratio might be a bit on the low side but I would not take my uneducated guess as fact..

    Have you driven it yet? Thoughts/opinions on the combo?

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    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: What is involved in building a 2.5 TIII?

    Haven't driven it yet, car's pretty gutted, tank's out, rad's out, seats, interior pieces and bunch of other parts stuffed inside. Engine and trans are installed but were not connected otherwise. I just finished hooking up all the factory plugs to verify they were still there (car had a Megasquirt installed and removed). I'll start a project log on it here shortly. Just been too cold since I picked it up to do much.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

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    Moderator Turbo Mopar Staff Vigo's Avatar
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    Re: What is involved in building a 2.5 TIII?

    I think the stick through the plug hole is probably the easiest and most unequivocal test you could do if you're just trying to figure out if it's 2.2 or 2.5.

    Dont push the red button.You hear me?

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    Moderator Turbo Mopar Staff Force Fed Mopar's Avatar
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    Re: What is involved in building a 2.5 TIII?

    The guy I got it from says he's 99.9 percent sure it has the forged FWD-P pistons in it. He got it from a guy named Kevin Geary on the RT mailing list. Anybody know him that can ask and verify for me?
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

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    Hybrid booster
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    Re: What is involved in building a 2.5 TIII?

    I've got a stock 2.5L block from my Daytona IROC with the TIII head in my Spirit right now running on the Neil Emiro TIII cal. I don't get on it too hard and havn't taken it much over 5000RPM. My new BoostButton cal should be here in a couple days.

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    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: What is involved in building a 2.5 TIII?

    Some pics of the 2.5L TIII Venolias I have.

    Attachment 53905Attachment 53906

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    Re: What is involved in building a 2.5 TIII?

    And here is a Wiseco 2.5L TIII piston from TU.

    Attachment 53907Attachment 53908

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    Re: What is involved in building a 2.5 TIII?

    I'll have to stick a bore scope down the plug hole and see what it looks like.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

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    turbo addict
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    Re: What is involved in building a 2.5 TIII?

    you could probably feel around for the valve reliefs with the stick you were thinking to use to measure the stroke

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    Re: What is involved in building a 2.5 TIII?

    So I verified it is a 2.5 (stroke is over 4"), and borrowed my buddy's bore cam and it there are 4 valve reliefs in each piston. So I feel safe in assuming it has the forged 2.5 TIII pistons in it. Turns over by hand and feels like it has good compression. Now I just need to put a tank back in it and make it run!
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

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    Visit www.boostbutton.com... Turbo Mopar Contributor ShelGame's Avatar
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    Re: What is involved in building a 2.5 TIII?

    Quote Originally Posted by Dr. Johny Dodge View Post
    you could probably feel around for the valve reliefs with the stick you were thinking to use to measure the stroke
    This - http://www.ebay.com/itm/2M-Mini-Wate...item20f876859f
    https://db.tt/SV7ONZpQ
    Rob Lloyd
    '89 Daytona C/S

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    turbo addict Turbo Mopar Contributor iTurbo's Avatar
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    Re: What is involved in building a 2.5 TIII?

    You can probably use the bore cam to determine the brand of the pistons if need be. If you look at the piston pics I posted, the Venolias have a simple angled dish 'wall' (like 2.5L TI pistons); the Wisecos have a concave dish wall like a skateboard ramp. Those two brands are probably the most common "2.5L TIII" aftermarket forged piston by far, although I would swear the dish on the Venolias are a little deeper.

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    Re: What is involved in building a 2.5 TIII?

    Pretty sure they had an angled dish wall.
    Rob M.
    '89 Turbo GTC

    2.5 TIII stroker, 568 w/ OBX and 3.77 FD

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    Garrett booster
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    Re: What is involved in building a 2.5 TIII?

    Not to hi jack the thread but it seems to have died off and this is along the lines of the original title of the thread. What really is involved in building a 2.5 TIII? Can you take a 2.5L block, stick the custom 2.5L TIII pistons in it and then bolt up the head with no further work? Unlike the hybrid setups that require custom machining and etc. Any more info would be great. Thanks.

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    Re: What is involved in building a 2.5 TIII?

    I wouldn't use pistons as a way to verify looking thru the hole, I'd pull the pan and look at the crank for the 2.5 stamping.

    - - - Updated - - -

    Quote Originally Posted by Dan15 View Post
    Not to hi jack the thread but it seems to have died off and this is along the lines of the original title of the thread. What really is involved in building a 2.5 TIII? Can you take a 2.5L block, stick the custom 2.5L TIII pistons in it and then bolt up the head with no further work? Unlike the hybrid setups that require custom machining and etc. Any more info would be great. Thanks.
    You need 2.5 TIII pistons and a 2.5 common block crank and a cal, that's it. ALL CB blocks are interchangeable except the TIII block is better cast and doesn't have a dizzy hole. The TII block doesn't have provisions for balance shafts. The part number for the 2.2 TIII balance shafts are different so if swapping to a 2.5, eliminate them or run the 2.5 shafts.
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
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    Hybrid booster
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    Re: What is involved in building a 2.5 TIII?

    Good luck on a Cal for it. My first boost button cal wasn't right, and he said I was the first 2.5 TIII tune he has tried to do. Still waiting on an update. Went back to the old Neil Emiro cal meant for a stock TIII as it ran better. Other than that the car has ran flawless for about 10K miles with the 2.5 CB out of my T1 Daytona with the TIII head on it. No special TIII pistons, just the factory 2.5 T1 pistons. Bumped it up to 10lbs of boost. A/F ratios are good all the way through RPM range.

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    Buy my stuff!!!!!!!!!!! :O) Turbo Mopar Vendor turbovanmanČ's Avatar
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    Re: What is involved in building a 2.5 TIII?

    I've been running a 2.5 TIII since 2007, Rob did his best but its a different beast. Cliff Ramsdel was the first IIRC and he kept blowing head gaskets using the TIII SBEC. I kept the dizzy so maybe that's why she stayed together? Rob did a few but found doing my own worked best.

    Interesting on using 8 valve pistons, the compression is in the 7:1 range.

    I think a 2.5 TIII is good for an auto and heavy car/van but going to try a 2.2, mainly because I am switching to a 5 speed and I have a few 2.2 pistons kicking around, damaged another piston after having injector issues,
    1989 FWD Turbo Caravan-2.5 TIII, GT35R, auto, a/c, cruise, pwr windows/locks, fully loaded with interior and ran with full exhaust. RETIRED FOR A FEW YEARS! 12.57@104 :O)
    1984 Chev Getaway van, 6.2 Diesel with a remote mounted turbo setup burning WMO-For sale.
    2003 GSW 2.0L TDI, auto, fully loaded, modified, 360K-wife's.
    2004 GSW TDI, 5 speed, fully loaded, modified.

    Aurora ignition wires for sale. Link to info

    Super60 roller cams or custom/billet cams. Link to info

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    Slugmobile & MeanMini Caretaker Turbo Mopar Contributor wheming's Avatar
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    Re: What is involved in building a 2.5 TIII?

    You might miss that 2.5 torque for that heavy van...
    Wayne H.

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    turbo addict Turbo Mopar Contributor
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    Re: What is involved in building a 2.5 TIII?

    Quote Originally Posted by turbovanmanČ View Post
    I've been running a 2.5 TIII since 2007, Rob did his best but its a different beast. Cliff Ramsdel was the first IIRC and he kept blowing head gaskets using the TIII SBEC. I kept the dizzy so maybe that's why she stayed together? Rob did a few but found doing my own worked best.

    Interesting on using 8 valve pistons, the compression is in the 7:1 range.

    I think a 2.5 TIII is good for an auto and heavy car/van but going to try a 2.2, mainly because I am switching to a 5 speed and I have a few 2.2 pistons kicking around, damaged another piston after having injector issues,

    How sketchy is the 2.5 hybrid in comparison? I don't think I buy the idea that 2.5 only belongs in heavy stuff because literally I bought it.

    More seriously though, unless your quench is rubbish, you guys are way off on these tunes. If every 2.5 16 valve ever built couldn't take the timing needed to make good power then I would think there is a problem. There must be some 16 valve exceptions out there beyond the 2.5L 8 valves.
    Brent GREAT DEPRESSION RACING 1992 Duster 3.0T The Junkyard - MS II, OEM 10:1 -[I] Old - 11.5@125 22psi $90 [U]Stock[/U] 3.0 Junk Motor - 1 bar MAP [/I] 1994 Spirit 3.0T - 11.5@120 20 psi - Daily :eyebrows: Holset He351 -FT600 - 393whp 457ft/lb @18psi 1994 Spirit 3.0T a670 - He341, stock fuel, BEGI. Wife's into kid's project. 1990 Lebaron Coupe 2.2 TI/II non IC, a413 1990 Spirit 3.0 E.S. 41TE -- 1993 Spirit 3.0 E.S. 41TE -- 1994 Duster 3.0 A543 1981 Starlet KP61 Potential driver -- 1981 Starlet KP61 Parts -- 1983 Starlet KP61 Drag 2005 Durango Hemi Limited -- 1998 Dodge 12v 47re. AFC mods, No plate, Mack plug, Boost elbow -- 2011 Dodge 6.7 G56

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