30th-trans

I have a 1999 Pontiac Trans am LS1, the problem is that I had to emergency downshift into too low of a gear and the engine over reved for only a few seconds max, the car started to run very bad and stalled, since then when I crank the engine it will do something different every time including starting for a few seconds to cranking freely with seemingly no compression, the timing chain is intact, the oil is clean with no meatal shards in it, and the plugs are not tapped out (suggesting to me that the valves might not be bent) but I have not compression tested it as of yet and would like more advise befor i do.
My question is- is there a sensor or fail safe that theses cars have that could cause this to happen, or are there any suggestions that could be made to help me out.
I really don't want to pull the heads so I am trying to rule everything out that I can
Thank you for any help you can offer

It seems like you all are the best of the best and i need help i dont know to much about the LS1, I usually work with cars from 1966-1974 so the newer cars are hard for me.

deuce_454

the valves are most likely bent, valvefloat and fast moving pistons makes for contact=bent valves... the easy way of checking is to just loosen the rockers and blow compressed air into the plug holes, of you hear hissing in either the TB or exhaust you have a winner....

sounds its time for a valve job

bills98ta

iTrader: (14)

Agree, the valves most likely floated out and hit the pistons. Are you running stock valve springs, or the comp cam 918's ?

30th-trans

thank you for the good advise I will do exactly that on tuesday (one of the few days i can work on my car), so to be clear pull the valve covers loosen the rockers, have all the plugs out and one by one just blow compressed air into the plug holes and listen, if there is air hissing out the exhaust or the TB then i have a bent valve. sounds easy enough like a simple substitute for a compression test

and i do have stock valve springs my car is mostly stock with only 31,000 miles on her

30th-trans

i have a easy question for you all, if it turns out to be the valves and i pull off the heads, like us all i like power, if i have the heads ported you know go all out, what will have to be done to the computer to accomiate the changes will it adjust or will the computer need to be programmed for the changes, and what about other internal parts such as A adjustable timing chain, cam ect. can theses parts just be installed or will the computer need reprogramming.

and to kill time untill tuesday, and to give me a few more otions i really want to know if there is there a sensor or fail safe that theses cars have that could cause this to happen that would trip at an over rev to save the valves, or is it just as simple as it seems over reve the engine and look for the mechanical carnage caused by that.

bills98ta

iTrader: (14)

Your car will run fine with a port job. Get a set of comp beehive 918 springs, which are great for a future cam upgrade, that will require a tune.
I over-revved my stock springs and bent at least four intake valves a while back...

30th-trans

thanks for tha advise,
i have the timing chain exposed right now and am thinking about replacing it with a dubble roller adjustable chain,(although the stock one looks great due to the low miles) first what are you thoughts on that and will advansing the timing require me to program the computer for the change
and i figured i would relpace the stock oil pump also
I really appriciate all the help

elias_799

iTrader: (8)

you might run in to some clearance issues with a dual roller and some of the oil pumps. but nothing a little bit of grinding can't fix. don't let this put you off a dual roller, i just wanted to give you a heads up on something that might happen.

30th-trans

elias 799
thank you for the info, I appreciate it.

I got tied up Tuesday so I only got as far pulling the push rods ill know about the valves Thursday night when I get a little time to work on the car again

Sunset01TA

iTrader: (7)

It may just be push rods.
If the car was stock the push rods are the first thing to go.
Just pull them out you'll see real quick.
Had this happen to a bunch of cars at the drag strip missed shifts and over revving.
Changed push rods and the cars ran great.
Plus it is very easy to do.

elias_799

iTrader: (8)

^^ yea i heard that the pushrods very specifically designed to break before anything else.

but since he took them out already and has not noticed anything unusual the search continues.

good luck

30th-trans

The search is over I bent most of my valves, no suprise (7 out of 8 intake valves, and probably as many exhaust), just one reason not to set the revv limiter at 6,600, I got as far as pulling the driver side head today, will get the passenger side off Tuesday

now i need to decide if i should port the heads or just replace the valves myself, the reason to do it is well FUN!!!! but on the other side that is what my 68 dodge is for

I probably will leave it stock but i don't know yet, can you all give me some ideas on what valves and springs to buy if i leave it stock, and what you think about leaving the heads stock, i dont want to buy heads if i do anything it will be a mild port.

91ZLS6

iTrader: (2)

I bought a '00 Trans am parts car, that was the same thing.

Went to hit 4th racing, and hit 2nd. Over revved it, bent all of his pushrods, and 7 pistons hit valves.

That being said, they didnt "Smoke" the pistons, as the pistons just had little nicks in them, and the valves bent the slightest bit.

Good luck to you on getting it back together!

30th-trans

thanks for the luck,
i guess i got lucky all of the pushrods are in good shape, but my pistons got little nicks on them also, but no real damage to anything but the valves

BADD SS

iTrader: (4)

Sucks, but since it was a mechanical over -rev it has nothing to do with a 6600 rpm rev limiter. Im on my stock bottom end, and el cheapo heads turning 7200 rpm for quite some time now...

I would at least do something with the heads, since they will be off anyway. You know, with a stock like or even stock cam, lightly ported heads with a good valve job (not hogged out) will only increase your efficiency, and give you some more power to boot.

IMO you are doing the hard part of pulling the heads, might as well do something with them...

30th-trans

thats what i figured I dont want to go through all that work for nothing, for a few hundred extra i might as well have a nice mild port done, ive got a great enginge guy down here, he does all of my heads, engine, and trans builds, and is in my book one of the best out there, so as soon as i get a little extra money ill have my heads done.
thanks for the comment it helps make me feel like im on the right track

SlowFRC

iTrader: (2)

I agree with this, the rev limiter can't save you in a situation like this. A few months ago I over-revved (doing the same thing you did, shifted 6100rpm in 3rd to 2nd) and bent 11 vavles and left some noticable marks in my pistons. It sucks but while your heads are off you might as well do a cam swap. If you want to do something head wise you can pick up 243 (ls6) heads for cheap on here or corvetteforum.

30th-trans

slowFRC
thanks for the advise, i didnt realise just how useless the rev limiter is in a situations like theses. as for the cam, im not ready for that yet, and i would rather have my heads done than buy LS2 heads if you knew my engine guy you would understand, i mean he is the best he builds everything from simple rolbars to 6 sec race cars (ground up) and i have always been happier when i go to him instead of buying aftermarket or swaping for diffrent parts, but that is my prefrence.
as for the cam again all i can say is probally soon but not right now


to anyone in south florida send me a message if you want a great engine guy and ill help you out.

RoDan

Good luck on the fix man, sucks. I was hoping it would just be bent pushrods...

mtuggle86

iTrader: (7)

I did the same thing on a 3>2 shift but I lucked out and it didnt damage anything sorry for your luck man