Hi, I'm hoping that tou can help me out. I have a '01 f250 (PI) that I put a '05 shortblock in. I noticed that the pistons sat about .090" higher in the bores of the newer shortblock. Wondering if I made a measuring error, or maybe if anyone else has measured and came up with the same thing. The reason I ask, is that now that I have the truck running, I have MAJOR pinging, and I have to run 92 octane to not have an anxiety attack from the paranoia that I'm going to grenade the motor. I think that the bump in compression may be too much. I pm'd one member here who has the same setup. Just wondering if anyone else has done the same swap, and had the same trouble, and if so, what can be done? Maybe a 5 star tune, or is there possibly something else wrong? No CEL or other codes.

 

Do a static compression test.
Also did you change cams?

 

are the pistons different for the 3V 05+ engines ???

that might be part of the problem, im not sure if the change to the 3V heads was only in the actual heads for that year of motor +

 

The 3V Piston is a 6.5 CC dish. The 3V head is a 49.6 CC chamber.
The PI 2V is a 17 CC dish and a 42 CC combustion chamber.
They both have around a 9.7-1 compression ration stock.

You now have a 6.5 CC dish and 42 CC head togather, making you CR somewhere in the 10s.

Call Mike at 5 star. Tell him that and he will set you up with tunes so you can run 87 agian.

Good news is your making more power due to this, or at least will be with a tune.

 

What cams would you use other than the stock PI's that match the heads?

 

So, I have contacted Mike about getting a tune, and thank God, he has tunes for the 3valve shortblock conversion the only thing standing between me and them is $$$. But until then
i'm trying to baby this thing thru the detonation issues. I have a genuine concern, I pulled the front plug from each side for a peek. 1st pic is driver's side, 2nd pic is passenger side.




I had just ran a full tank of 87 thru and was down to 7.1 MPG from an even 10.00000 with the previous tank of 92. I was under the impression that running lower octane was supposed to HELP mileage. Detonation made the truck terrifying to drive (I have a serious emotional investment in this as I built it myself) I have done a perfunctory search for loose vacuum hoses, all looks ok. Shouldn't the plugs have at least some color?

 

Excessive detonation will royally screw your engine. If high octante pump gas gets rid of the detonation ok but I wouldn't be using the truck with detonation issues.

 

I would not drive it without a tune.