I think I ruined my motor!

phalcrow · Oct 24, 2006

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Joined: 10/23/2006
Status: online I have a 1996 GT with a 1997 block and PI heads. I have been running the Comp Xtreme energy cams XE-262AH (comp part #102500) for quite some time with no problems. I just swapped them for the XE-270AH (comp part #102600) cams and as soon as I started it up, my motor sounded like a diesel. I couldn't pinpoint it the noise, it wass all over the engine. After driving a few blocks, I decided to put the old cams back in (8 hours later) and had a new noise, sort of like an exhaust leak. I reved the engine to 3-4 grand and POP! TACK, TACK, TACK, TACK every revolution. Sounded like a midget with a sledge hammer in my block. I think I have a piston to valve clearance problem. I'm more worried about that last part. Any suggestions?

Robs96 · Oct 24, 2006

Sounds like the new cams weren't quite timed right and jacked the valve(s) up causing the problem since it didn't go away when the old cams were put back. Or a broken spring. Use a stethoscope to pinpoint the exact location. On another note, an inlaw of mine had a same year, same motor thunderbird that blew a sparkplug out of the head that made the same noise as you describe.

Mike97gt · Oct 24, 2006

sounds to me like you droped a bolt or somthing down a intake valve..

'01 Steed · Oct 24, 2006

It sounds to me like those Comp cams definitely weren't timed right! This is why you NEED TO DEGREE THEM, especially Comp cams! This is NOT new news, and there are plenty of posts on all of the boards on this topic.

I feel bad for you. You're probably going to need a couple pistons and a new set of heads. Then again, you may get lucky, and it could be something else but I have a bad feeling it isn't.

BTW, when you heard the noise on start-up, why did you take it for a drive? ?????

Mike97gt · Oct 24, 2006

either way he is screwed.. if it's PTV then he probally damaged some pistons and the heads.. if it's a bolt down the intake then he will have piston and head damage...

most of the time a car will not run after PTV thats why I think it's a bolt or other metal object down the intake. but it could be either one of them,.

jasonh_86 · Oct 24, 2006

If you need heads, let me know. I've got a set of PI heads with Manley Nextek valvesprings already installed that I need to get off my hands for cheap!

d98gt · Oct 24, 2006

Damn, hate to see that you ran into such a problem that isn't going to be a cheap fix

Hopefully the damage is limited and you'll get it back up soon

DropTopPony · Oct 24, 2006

Dusstbuster · Oct 24, 2006

After hearing Jason's car in that video post-bearing spinnage it could be a spun bearing as well couldn't it?

BlackenedSVT · Oct 24, 2006

DropTopPony said:
PTV

whats a PTV???

hotmustang331 · Oct 24, 2006

PISTON TO VALVE (CONTACT)

SOunds bad man...most likely slammed a valve or 2 into the top of the piston.

trinity_gt · Oct 24, 2006

A 1997 shortblock has a smaller piston dish than the later 99+ engines do. You've therefore got less margin for timing error when using a bigger cam with PTV being the likely result.

phalcrow · Oct 24, 2006

Wish I knew that before hand. Oh well, I guess I learned the hard way. I'll give an update sometime this weekend when I pull the heads. This might be a good excuse to go to ported heads and forged parts. Maybe I'll invest in dished pistons too.

DropTopPony · Oct 24, 2006

trinity_gt said:
A 1997 shortblock has a smaller piston dish than the later 99+ engines do. You've therefore got less margin for timing error when using a bigger cam with PTV being the likely result.

not true...when ptv occurs on a 2V it makes contact on the perimeter not in the dish area so you could have a 30cc dished piston and still have ptv.

look at this pic of a notched 2V piston and see where the notches are located....on the outside not in the dish cause thats where it touches.

Mike97gt · Oct 25, 2006

please update when you get the heads off. It still might be a metal object droped down a intake valve.. this will cause noise similar to PTV... most likely it's PTV but take it apart before you go ordering things.

Pennywise2 · Oct 25, 2006

hotmustang331 said:
PISTON TO VALVE (CONTACT)

SOunds bad man...most likely slammed a valve or 2 into the top of the piston.

+1
Take your engine apart and check it out before you decide to
purchase parts.

the98stang · Oct 25, 2006

sounds like you need a VT engine or mmr900

pull the heads, check out the damage. might as well check out the rods/pistons too

'01 Steed · Oct 25, 2006

DropTopPony said:
not true...when ptv occurs on a 2V it makes contact on the perimeter not in the dish area so you could have a 30cc dished piston and still have ptv.
...

BINGO!

It is a common misconception that dish volume affects PTV clearance.

phalcrow · Oct 25, 2006

Is there any chance I ruined any rods as well? What's the best way to check if so?

Mike97gt · Oct 25, 2006

phalcrow said:
Is there any chance I ruined any rods as well? What's the best way to check if so?

it's not the rods that would suffer from PTV it's the rod bearings

Assuming this is PTV, since it stayed running there was only light contact so your rods and rod bearings should be ok. There is no way to check this without disassembling the engine.

I think I ruined my motor!

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