knightmare1964

i just bought a 1997 vortec supercharged mustang gt .they have comp 270 cams in with pi heads that were cut to make 11:1 compression.oh and it has a pms anderson system.some one told me the valves might tap at high rpm.so if so is it possible to degree the cams back one degree to keep this from happing? i forgot its also meth injection.should i just pull the heads and drop the original back on? or can this be tuned to work.

knightmare1964

i'm hoping some one would be able to answer the question about putting the cams back a degree would work or not .thank you

school boy

Im assuming you meant the heads where milled down to create a smaller combustion chamber? Yes degreeing the cams will allow more clearance. Is the bottom end forged?

ctgreddy

if the pistons are aftermarket they are probably notched for clearance. I'd take the valve covers off and throw a ptv checker spring on one of the cylinders and check how much clearance you have tho just so you know.

knightmare1964

yes i do mean milled,but its a stock block.as far as i know.not to sure what to do with this thing.5.0's i know like the back of my hand but all this other stuff is new to me.thank you school boy,that at least points me in the right direction.

knightmare1964

hi let me give you the run down,i have a 97 4.6 mustang gt.it has pi heads that have been milled down to make 11:1 compression.and put in 270 comp cams in.cams are degreed so they wont tap pistons.then we have a vortec supercharger with six pounds of boost along with meth injection.and a on board pms anderson system.heres my problem the pms doenst really do anything ,it really doesnt change anything,in third gear up around 5500 it predetonates really bad.screams like a monster till then.tried alotta things like took out timing and fuel and added it and nothing seems to change.

WhiteFoxGT

have you tried taking it to a tuner who knows what they are doing? that would be where i start. Keep letting it detonate and you'll have a free block venting kit in no time

uberstang1

Get it to a tuner or like whitefox said your gonna grenade it

Z28KLR

That's a lotta compression for f/i. If a good tuner can't get it figured out, you may need to find a set of unmilled heads (or dished pistons, or both - depending on what you'd ultimately like to do with the car) to get compression back down around 9-ish.

Either that, or ditch the blower and spray it instead. N2O loves high compression.

69MustangCoupe393cid

Agreed with all the above. That's a lot of compression if you plan on running pump gas and or any kind of boost. I'm running around 10.5:1 and that's pushing it. I get away with it because I'm running the trickflow heads but the regular PI heads don't do as well because of the chamber design.