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Old 03-15-2014, 06:03 PM   #1
knightmare1964
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Cool to much?

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.
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Old 03-17-2014, 08:01 PM   #2
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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
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Old 03-18-2014, 11:13 AM   #3
school boy
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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?
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Old 03-19-2014, 08:40 PM   #4
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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.
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Old 03-19-2014, 08:43 PM   #5
knightmare1964
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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.
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Old 08-12-2014, 09:41 PM   #6
knightmare1964
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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.
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Old 08-13-2014, 08:05 AM   #7
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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
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Old 08-13-2014, 09:54 AM   #8
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Get it to a tuner or like whitefox said your gonna grenade it
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Old 08-18-2014, 05:04 PM   #9
Z28KLR
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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.
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Old 08-21-2014, 09:06 AM   #10
69MustangCoupe393cid
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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.
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