Engine Pi Swap Problems

Discussion in 'SN95 4.6L Mustang Tech' started by jesse strunk, Aug 29, 2012.

  1. Hi guys and gals,
    im new to the site and this is my first post on any forum so please go easy on me lol. This is also my first modular build and i seem to have screwed up somewhere and cannot get it nailed. ive searched high and low with no luck.... very frustrated and dont know what to do.
    ill start by telling you what it is and what its doing.
    Its a 98 GT 2v. ive done a full pi swap with heads off a 2001 saleen s281 that have been ported and polished by dart heads. im running comp 270 cams, ffrp pi intake, c&l upper plenum, 75mm throttle body, stack racing CAI, BBK shorty tuned headers, stack racing underdrive, bbk offroad x pipe, flowmaster 40 out back, new factory wires, ngk tr-6 plugs and i think thats about it.
    know what its doing.....
    under a load at 1700 rpms it starts what i think is a missfire. the only way i can explain it is my exhaust sounds like a helicopter. its a thumping that i can even feel in the floor. its steady and perfectly consistant. it lessons and gets better up to about 2200 rpms and then it seems to be gone.
    also the sound of my exhaust doesnt sound like its coming out the tail pipes. it is loud and booming under the car and the hood, and it makes a rattling kind of sound in the x pipe, but you can barely hear the flowmaster sound behind the car.
    also, my intake, plenum, throttle body, and CAI get so hot i cant touch them at all. after a short drive, i cant even touch the throttle linkage to rev the car a bit.
    it also seems to rev really slow when warm but on a cold start it revs as fast as your foot can push the pedal.
    and the idle is weird. with cams i understand it should be rough and it is but it doesnt seem right. the only way i can explain it is it sounds like each side of the motor is running out of sync. it will all thump at once for a few seconds and then it will sound like a drum roll for a few seconds.
    and also when i rev it with the CAI off, the intake sounds choppy.
    ive changed plugs and wires 4 times. IAC, egr, o2s have been replaced, pulled valve covers and everything looks good. i didnt degree the cams but i checked them and there within 3 or 4 degrees. cant find any vacuum leaks. no check engine light.
    im at a loss and im sorry for the super long post but i live in a crappy area where it seems that nobody has any experiance with these mod motors.
    any ideas....
    thanks in advance

    also i have the quarter horse and BE for tunning but currently it has a bama tune flashed with sct tuner. ive tried different tunes and that doesnt help either.
  2. Also I had the car at the track today and I'm not the best driver but I can hold my own but the best I could run was [email protected] with a .121 r/t. Does that seem right with the mods I'm running. Thanks again.
  3. I'd start with a basic compression test. What I'd be looking for specifically is one bank being notably lower than the other (possibly indicating a cam phasing issue on the low bank) or individual cylinder(s) being low indicating possible PTV.

    Comp 270s are a pretty aggressive cam to have not degreed them during the install...
  4. Thank you for replying trinity_gt.... I forgot to say that I did you a compression test and all the cylinders where 184, 185, or 186. And yes I know I should have degrees the cams. I couldn't find my degree wheel and I was pressed for time so I really messed up there. With an npi block and pi heads, should my compression be higher than that? My concerne it that I've bent ALL my intake valves just a tiny amount by not degreeing the cams. I'm thinking that is what would make the intake and everything so hot because combustion is leaking back into the intake.
    Thanks again
  5. Those compression numbers look pretty good to me. If you're concerned about bent valves (which I doubt with numbers like those) you might try doing a leakdown type of test where you bring a cylinder to TDC on compression and apply compressed air to the cylinder through the spark plug hole. 20...30 psi, something like that. Listen for lots of air rushing out the intake manifold or exhaust manifold which would indicate valve sealing issues.

    Silly question: Are you sure you got the firing order correct when putting the wires back on?
  6. No I'm not sure about the firing order.... I looked at a bunch of stuff online and followed them but I could have swore my car was different than it is now when I took it apart. I'm not sure though and I don't know why it would different than any other car lol.
  7. Does this look familiar?

  8. Yes that's how it is right now and I just went out and looked to make sure. for some reason it doesn't seem right but I think I'm wrong on that lol. just curious,,, do you think the miss fire feeling could be because I'm running such a steep cam and no stall converter?
  9. Well I'm stuck still.
  10. I did my PI swap a year ago and we had the timing off by one link and it sounded similar to what your describing. Luckily we caught it quickly and it didn't do any damage to the valves. You may want to double check your timing, although I only have the stock PI cams in mine so I can't speak to timing the comp cams.
  11. I've been beating the snot out off this thing. You think it would still be running if that was case?
  12. Before i did my swap I spoke with a Ford Tech at the dealership and asked him a couple questions about timing the motor. He told me that the car would run if I was just a link off, but it would miss, and would be harder to crank over. He said since they have dished pistons I may not be slapping a valve, but it just wouldn't run right. Long of the short, I found that I was off by a link on both sides and once I re-timed it it ran great. Your description of the feeling and sound is very similar to what I was experiencing at the time. My recommnedation would be to take it to a trustworthy shop and pay them to degree and time it correctly since you have comp cams in yours. Good luck.
  13. That makes a lot of since especially because I had a hell of a time setting up the timing on it. I'm gonna take your advice on this because I honestly am so sick of this car if I take it apart again, ill probly never put it back together lol.
    Thanks rife... Great info
  14. No problem man. I just know how frustrating this could be and ran into a lot of unforseen issues doing my swap. One thing I can say is that it taught me how to trouble-shoot these motors more than anything. Let me know if that fixes the issue and good luck with it. I know once I got mine done it was like a different car and much more fun.
  15. Jesse:

    Those 270's really need to be degreed. There are a lot of threads about bent valves with your combination (PI head swap + 270 cams). It is not a question of lift but duration. Those cams keep the valves open a long time so it is very easy for piston-to-valve issues if the cams are not degreed. Also, Comp grinds in 4 degrees of advance into those cams so degreeing is pretty much required. ModularHeadShop.com has some great articles about degreeing cams, if you want more details.

    In summary, you may want to look at milder cams or notch the pistons if you stick with the 270's. No flame intended, just trying to give some helpful advice.

    Last thing I'll mention are the plug wires. The boots slide on the wires and it is possible that the boots are too low on the wires, preventing the wire clip from snapping onto the plug tip. Use an old plug to test fit each boot. You can move the bott about 1/8 to 1/4 inch at a time. Use a little dielectric grease in the boot, too, to keep water/moisture out.

    GL with the teardown.

  16. disconnect the vacuum line going to your egr, then test drive it again. Also, verify your a/f ratio is acceptable. Find a dyno locally or get an a/f ratio gauge in it, and not one that uses the factory O2s either. Good luck.