What is involved in building a 2.5 TIII?

[Force Fed Mopar]

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 :eek:

[iTurbo]

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?

[Force Fed Mopar]

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.

[Vigo]

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.

[Force Fed Mopar]

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?

[HSKR]

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.

[iTurbo]

Some pics of the 2.5L TIII Venolias I have.

5390553906

[iTurbo]

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

5390753908

[Force Fed Mopar]

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

[Dr. Johny Dodge]

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

[Force Fed Mopar]

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!

[ShelGame]

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-Waterproof-Snake-Pipe-Cam-Endoscope-USB-Borescope-Inspection-Camera-Tool-/141607470495?pt=LH_DefaultDomain_0&hash=item20f876859f

[iTurbo]

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.

[Force Fed Mopar]

Pretty sure they had an angled dish wall.

[Dan15]

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.

[turbovanman²]

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 - - -


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.

[HSKR]

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.

[turbovanman²]

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, :(

[wheming]

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

[Ondonti]

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.

[HSKR]

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, :(

What is the CR of a stock TIII? I've gotten mixed signals about how well this was going to work when I did it. Quite a few said it wouldn't run with the TIII Cal I had and would destroy the motor, but it runs quite well with good A/F ratios. Just vibrates a lot compared to the BB Cal. When the Neil Emiro cal, even though A/F ratios are good the car vibrates and above 4500RPM it sounds like crap. The boost button cal smoothed it out and I was able to rev up to 6K without it sounding like the motor was going to fly apart, but the A/F ratio was pegged on my AEM UEGO at 10:1.

Also another interesting note. When I had the boost button cal in, I bumped the G-valve up to run around 11-12psi. WHen I put the old cal back in it peaks at 9psi and I didn't touch the g-valve.

[turbovanman²]

What is the CR of a stock TIII? I've gotten mixed signals about how well this was going to work when I did it. Quite a few said it wouldn't run with the TIII Cal I had and would destroy the motor, but it runs quite well with good A/F ratios. Just vibrates a lot compared to the BB Cal. When the Neil Emiro cal, even though A/F ratios are good the car vibrates and above 4500RPM it sounds like crap. The boost button cal smoothed it out and I was able to rev up to 6K without it sounding like the motor was going to fly apart, but the A/F ratio was pegged on my AEM UEGO at 10:1.

Also another interesting note. When I had the boost button cal in, I bumped the G-valve up to run around 11-12psi. WHen I put the old cal back in it peaks at 9psi and I didn't touch the g-valve.


Stock TIII IIRC is around 8:1 or slighly more, like the 8 valves.

I always set mine around 8:1 ish as I just didn't want to deal with crappy off boost performance. Yours probably runs well with the 2.2 cal because of the lower compression. The TIII has quite a bit of timing Rob told me but if you saw my timing curves, you'd shitt yourself, lol.

My last setup, it would pull like a mofo to 7500 and she was still pulling when I'd shift. That was with a ported head, cams, big intake and header. I put a stock on and it she's done by 6000 rpm with a ported stock manifold, big intake and stage 1 tri flow cams. The stock head is ok but on a 2.5, again, its a bit of a cork.

[turbovanman²]

You might miss that 2.5 torque for that heavy van... I might but the 5 speed will certainly make up for it.


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.

The hybrid isn't sketchy, it just takes a some fabricating to work whereas a TIII is literally a bolt on but you need to either run a dizzy like I did or run the TIII cam and crank sensors, which for an auto, it a little bit hard.

Not sure about the timing, I ran lots of it, more than I should and didnt' have issues with blowing head gaskets etc. Maybe the TIII SBEC is harder to control????? Also, Cliff was playing back in 05 and he was the first to play with a 2.5 TIII IIRC.

[iTurbo]

Does anybody remember what pistons Cliff R was running when he did the 2.5L TIII back in the day? I seem to remember JE but I might be wrong.

I plan to use the Venolias with ARP studs and Cometic .051" head gasket on mine.

[turbovanman²]

Pretty sure JE's.

[Ondonti]

I might but the 5 speed will certainly make up for it.



The hybrid isn't sketchy, it just takes a some fabricating to work whereas a TIII is literally a bolt on but you need to either run a dizzy like I did or run the TIII cam and crank sensors, which for an auto, it a little bit hard.

Not sure about the timing, I ran lots of it, more than I should and didnt' have issues with blowing head gaskets etc. Maybe the TIII SBEC is harder to control????? Also, Cliff was playing back in 05 and he was the first to play with a 2.5 TIII IIRC.

Talking about a crank trigger on the front side. By sketchy I mean, if there are mechanical problems like lack of proper quench, then a 2.5L hybrid would also have issues.

Are there any 2.5L 16 valve records?

[Pat]

Talking about a crank trigger on the front side. By sketchy I mean, if there are mechanical problems like lack of proper quench, then a 2.5L hybrid would also have issues.

Are there any 2.5L 16 valve records?

Probably Slowe. I believe he was still 2.5 into the 9's.

[turbovanman²]

Talking about a crank trigger on the front side. By sketchy I mean, if there are mechanical problems like lack of proper quench, then a 2.5L hybrid would also have issues.

Are there any 2.5L 16 valve records?

The quench could be wrong but I never really had detonation issues except for my +40 crapping out and didn't know it until it was too late.

I think one person attempted a crank trigger with a TIII as he was going auto. I just felt going dizzy and SMEC was easier with an auto. Hybrid guys use the dizzy or go aftermarket EFI.

Larry B has his 2.5 RWD hybrid Shadow in the 10's, a few 8 valve 2.5's are in the 10's.

[Ondonti]

Probably Slowe. I believe he was still 2.5 into the 9's.


The quench could be wrong but I never really had detonation issues except for my +40 crapping out and didn't know it until it was too late.

I think one person attempted a crank trigger with a TIII as he was going auto. I just felt going dizzy and SMEC was easier with an auto. Hybrid guys use the dizzy or go aftermarket EFI.

Larry B has his 2.5 RWD hybrid Shadow in the 10's, a few 8 valve 2.5's are in the 10's.

Kinda sounds like 2.5 16 valve is not a problem, its the tunes people are feeding it... Unless the very successful cars were covering something up with octane.

No detonation but you had lots of indicated knock???? I remember you unplugging your sensor on some passes. You have this thing about mixing race gas and pump gas so maybe a full tank of the best stuff would have helped with all that timing. I don't know if I could ever get myself to pay for good fuel.

[turbovanman²]

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.

My detonation was due to me giving it tons of advance so it was fun on the street, lol. I also didn't realize it but I had an injector going on me, which kept giving me AF and detonation issues and finally showed up when I melted a cylinder because of it. I had the same problem with 8 valves, it was ping off the line and go into full retard and would screw up the runs. I was going to monitor it better but never got that far.

Not sure why Cliff had head gasket issues, that was the least of my worries, lol. Maybe the cals back then weren't as good as they are now plus we have we more access to adjustments, or maybe not.

[iTurbo]

Talking about a crank trigger on the front side. By sketchy I mean, if there are mechanical problems like lack of proper quench, then a 2.5L hybrid would also have issues.

Are there any 2.5L 16 valve records?

If anybody is serious about building a TIII with automatic transmission, I have a front side crank trigger setup I would sell. It was made by a 'eyeball' if I remember right.

[Ondonti]

If anybody is serious about building a TIII with automatic transmission, I have a front side crank trigger setup I would sell. It was made by a 'eyeball' if I remember right.

That makes 2 of us?
I need to get a picture of mine.

[iTurbo]

That makes 2 of us?
I need to get a picture of mine.

Cool! I will work on getting pics of the setup I have. I had planned to use it until I had a local machine shop modify the bellhousing on a Cliff Ramsdell built A525/A555 hybrid to work with the stock TIII crank sensor. Don't need it anymore. (Plan was to retain a rod shifted L-body beast).

[Force Fed Mopar]

I just took the crank trigger wheel off this '91 RT I bought a couple months ago. They had it installed for running Megasquirt, and apparently it was working as the car ran, they were trying to tune for the 2.5 TIII then got sidelined by a rusty gas tank, which lead to the owner selling because of more rust they found. The guy I got it started removing the Megasquirt setup to go with AEM then it got sidelined again by life things he had going on.

Anyway, I have the Megasquirt box but no harness lol, so I took the trigger wheel off and plugged all the factory harness back in. The sensor bracket is still there and I can pop the wheel back on easily if anyone needs pics.

- - - Updated - - -


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.



I measured the stroke, just over 4".

[Force Fed Mopar]

Trigger wheel setup.

[Force Fed Mopar]

So is anyone actually running a 2.5 TIII right now? I'm seriously considering putting mine into my Lebaron. Just trying to decide between using the SBEC w/ a flash module, or reuse the Megasquirt that came with it (I found the harness for it, just have to splice it back together). Timing tables in the T3 cal look kinda complicated lol.

[HSKR]

I have my T1 2.5L block with my TIII head running just fine in my Spirit R/T using the stock harness and a boost button cal.

[Force Fed Mopar]

I think that's what I'm gonna end up doing, splice the '91 TIII computer and engine harness into the '89 body harness and use MP Tune to tune it with.

So, anyone interested in a MS unit w/ an internal map and a base cal on it? :eyebrows:

[Spiritman]

which ms unit is it

[Force Fed Mopar]

Looks like a MSII