I left a message at TP a couple days ago and never heard back, figured it might be easier here so you can respond at your leisure....

I will be buying an XCAL2 and a couple other things hopefully soon, thought I would have them by now actually, but I'm having to rebuild my 5.4 first as it $#^$ the bearings out.

While its apart I'm porting the heads and changing to '01 Cobra pistons with a 2.8cc dish. If I open the chambers to 48cc I should be at 9.8:1, 50cc should give me 9.6:1. Whats the highest compression ratio you recommend (and want to tune with) running 91-92 octane, which is all I can get? The sharp edges on the swirl dam (possibly the whole swirl dam) will be gone and the chambers will be polished.

Thanks.

 

As of yesterday engine is out and torn down, block is off to get honed, crank to get turned, etc.......any input?

 

hello?

 

Hello Dan,

Briefly............

There are far more factors that go into deciding what CR to build any engine to than just octane of fuel to be used - FAR more. Like the port work done, the cams, the metallurgy, the actual cylinder pressures seen when the engine is running and so much more. It's not just what octane of fuel, not by a long shot.

For one quick example - assuming the use of STOCK pistons, heads & cams in a 1999-2003 PI 5.4 2-valve motor, I would probably leave it at not more than about 9.4:1 if I ever wanted to be able to run 87 octane fuel - if I didn't care about 87 octane, and was willing to use only the very best 93 octane pump premiums always, then I would do the cooling mod to the back of both of the cylinder heads to properly route engine coolant evenly and try running it up to maybe 10.0:1 (yes, with proper tuning it may very well take more, but I am not going to give "on the ragged edge" advice! )

I hope that helps!

 

Mike, thanks for the response. 93 octane simply isn't a possibility, 91 or 92 is the highest available in the small town where I work and I'm not driving 10 miles the other way every time I need gas....

No need to run 87 ever again once the rebuild is done, I'll assume 91 and shoot for that 9.6-9.8:1 range I mentioned. Cams will be stock, pistons will be '01 Cobra (2.8cc dish), heads will be ported and chambers opened up to appropriate size to achieve desired comp ratio.

Does TP sell rings, head gasket changing kit, etc... for rebuilds? Need to get that stuff ordered as my block should be done early next week.