2.5 na converted to Turbo II keeps melting #3 piston

[gilpatt]

Ok I took a 1988 2.5 na and installed a turbor II head with super 60 cam and larger Turbo (not super 60 turbo) I installed 803 injectors also It ran fine but i have melted # 3 piston twice in it The boost pressureruns around 15psi What have I done wrong ? I'm thinking this time going back to a 2.2

[lametec]

Too high compression.

No intercooler?

Bad injector.

Combination of all of the above.

[gilpatt]

No I did'nt run an intercooler but I had a cold air intake They were all new injectors and the other cylinders were fine I also had checked the plug in that cylinder and it did'nt show any lean color on it I am wondering why only #3 does it It would seem that the other cylinders would show some damage also but they all look fine

[minimopar]

Too much compression with those N/A pistons.

[gilpatt]

Will the modular 2.5 turbo pistons work in the 2.5 na block and crank?

[glhsken]

Yes

[gilpatt]

The machine shop that did the work put new pistons in it and they are dished are the 2.5na dished also?

[Aries_Turbo]

id take the injectors and fuel rail out and trigger them with a 5v source into 4 same size bottles or some kind of graduated cyl and see what they are putting out to make sure its the same. then id verify your compression ratio.... hopefully there is at least 2.2 turbo pistons in that tall block. (i assume its a tallblock as its an 88) even with 2.2 pistons there will be a higher CR than a 2.2 cause the larger displacement of the 2.5. another thing is the fact that you have no intercooler. what ecm are you running? are you still running the 2.5l tall LW rods?

Brian

[gilpatt]

Yes those are the original rods and it is the tall block I am suspect that the new pistons are for a 2.5na and not a turbo even though they are dished

[gilpatt]

the ecm is for a turbo 1 with around 14 psi of boost I'm running turbo 1 wirring with a turbo II intake on a 1986 woody convertable When I lost a piston the first time I switched the injectors around and checked that cylinder numerous times to see if it was running lean so I'm pretty sure the injectors are working right

[Vigo]

well non intercooled 14 psi on na pistons would consistently equal piston failure imo, so you should make sure those arent n/a pistons.. and even if they arent, back off the boost a bit until you get an intercooler.

[Mario_Boost]

I have a set of 2.5 Turbo Pistons. Only have about 2000 miles on them. PM if you are interested.

[Turbodave]

Quote:

Originally Posted by Mario_Boost I have a set of 2.5 Turbo Pistons. Only have about 2000 miles on them. PM if you are interested.

Stock 2.5 turbo pistons won't work in this application, 2.2 turbo pistons are probably the best bet (outside of custom pistons) but as Brian described above they still may cause problems.

For those that may not know, the 2.5 from 86-88 was a tall block engine, it used a block with a higher deck height than a regular 2.2. The crank had a longer stroke and longer rods were used as well, the 2.5 and 2.2 of this time frame should have the same/similar piston dimensions.

89 up 2.5 and 2.2 used the same block thus the Common Block name. The Common block 2.5's again had a longer stroke than a 2.2 but compensated for this by using shorter pistons and standard 2.2 length rods.

[Mario_Boost]

oh. I thought it was a common block. i was lazy and didn't read.

[minimopar]

If you switch to the G-head and use 2.2L Turbo pistons, I think the compression will work out pretty close to correct. I remember doing the math for my long rod engine article, but I don't see the results there. You could also use a head saver shim to drop CR a bit.