Time to say goodbye to the freakishly fast GP GT.... - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 07-27-2006, 03:42 PM   #1
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Default Time to say goodbye to the freakishly fast GP GT....

As much as I've enjoyed my time in the L36 GT, and as well as it runs, I knew eventually it was time to move up. For a few months now I have been considering doing an L67 topend swap, I've been holding myself back because it seems kinda stupid to me to put that kind money into a car with over 200k on it. I also enjoy my 30+mpg, and the car has been nothing but reliable for all of the 10,000 miles I've put on it since I picked it up in February.

However, this past weekend, I decided to finally bite the bullet, and its time for a change. I was driving it around and took off from a stoplight and went WOT. Well, I let off right before my 1-2 shift and when the engine revved down, all I heard was a clanking noise. I wasn't sure what it was so I threw the car in neutral and did it again and it revved up then clanked again as it revved down. Sitting idling it runs smooth as can be and as long as I don't let it rev down quickly, everything seems fine. But if I rev it up and let off the gas abrubtly it will definately make a clanking noise. Upon further inspection I have pretty much figured out that my timing chain dampner is worn out and the timing chain is loose. With the amount of miles I put on this car, I really can't drive it around like that too much because it wouldn't be cool to destroy the engine because of something stupid like that.

Since the weekend I have been debating with myself on if I should just throw a tensioner in it and keep on driving it like it is, afterall it is my dd and needs to be reliable, or if I should throw a GT1 cam in it and drive it like that, or if I should just say **** it and go XP cammed with an M90.

Well, being me and all, I convinced myself that I wouldn't be happy if I halfassed it. Went to ZZP today and $596.87 later I have my XP cam, springs, retainers, cam kit, timing chain, and valve seals all on the way. I emailed Morad and talked to one other connection I have about an L67 topend, and I'm just fixing the problem the right way. I was trying to convince myself to take a different route with it, but I knew this was gonna happen in the end.

So, if all goes as planned, it looks like next week sometime I'll be throwing the cam and topend swap on the car. I have a set of PEM'* that have been sitting here for a while that I'm gonna throw on it as well. I've also got my PCM work lined up, and I'm gonna throw a happy **** and mini-afc that we have lying around here on it and all will be gravy. The tranny should suffice as long as I keep the street tires on it and don't launch hard. I'm still not sure what to run for a pulley, but I think I'll start with a 3.5 and go from there.

Really, the only other thing I want to do to the car is get a 3" downpipe and a power log for the front and I will be done with it performance wise until I am out of school for sure. This should keep me happy. The power level is going to be all that I really want for a dd anyways if I want to keep the tires planted, especially with my 3.29'* and the stock GT convertor (3000 stall).

I am very excited as I think you guys can tell and I can't wait! I'll definately fill you guys in on how it performs. I'll try to get some pics of the engine during the swap too.

So much for the bigger turbo/intercooler/tranny for the STE.... :(


Shawn
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Old 07-27-2006, 04:18 PM   #2
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NICE....that car should do very well with the new power
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Old 07-27-2006, 06:15 PM   #3
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SHAWN...... NOOOOO!

Dude, I thought you were going to go the NA route! I was looking forward to trying to figure out what made your car so quick. You're going to the dark side!
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Old 07-28-2006, 02:44 AM   #4
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Quote:
Originally Posted by big_news_1
SHAWN...... NOOOOO!

Dude, I thought you were going to go the NA route! I was looking forward to trying to figure out what made your car so quick. You're going to the dark side!
I was never meant to have an N/A car. Forced induction is nice because you can make good power while still getting good mileage. To run as quick as I will be running with my M90/XP cam setup, I would pretty much need a cam, heads, 3.69 gears, 4000 stall convertor, headers, ported everything, a real intake, etc...., and I'd have to drop some weight. Then my car would get shitty mileage and it would cost me a lot more money. There is nothing wrong with N/A, but this is my DD and I'm going for gas mileage and reliability more than anything. If I had the money it would be cool to stay N/A, but I'm a broke college student, I can't really afford to do what I am doing, but IMO it would be stupid to replace the dampner and leave everything else in there that has 212k miles on it too.
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Old 07-28-2006, 03:08 AM   #5
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A little voice said something about your dampner taking a dump wasn't sure if it was true or not - I was waiting for you to pipe in. Sorry to hear it is true but... XP cam, higher compression, 3.29'*, 3000 stall all in a LW 2-door GT! That is going to be a really nice DD!
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Old 07-28-2006, 03:12 AM   #6
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Quote:
Originally Posted by llBlazin_llLo
A little voice said something about your dampner taking a dump wasn't sure if it was true or not - I was waiting for you to pipe in. Sorry to hear it is true
Yeah, its not what I would've liked to see, but with those kind of miles, and the way I treat the car, it wasn't unexpected. And part of owning a car is maintaining it, so it must be done.

Out of curiosity, who'd you hear that from?

Quote:
but... XP cam, higher compression, 3.29'*, 3000 stall all in a LW 2-door GT! That is going to be a really nice DD!
Thats the plan. I'm getting REALLY sick of every car I own running mid 14'*....

After the engine work my mods will be:

Open cone filter
No cat/ubend/resonator
PEM'*
UD Alternator & WP Pulleys
Shift kit
180 tstat
HumPerformance Ported M90, hopefully with a 3.4 pulley
Ported Lower Intake
XP Cam/springs/retainers

And of course all of the usual like 103 plugs, mini-afc, and happy ****. The PCM will be a DHP with a lot of custom stuff added on. This will be with the L36 compression (9.4:1 IIRC), and 3.29 gears, and a 3000 stall convertor. Keep in mind also that my car weighs in at 3150 without me in it. With slicks I can't see 12'* being an issue, but I don't plan on putting slicks on it due to the tranny so who knows what it will do on street tires.
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Old 07-28-2006, 08:25 AM   #7
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Sounds like a fun project Shawn. You may want to do a leakdown test on the cylinders before adding a bunch of boost to it, 200k is a lot of miles for those rings and running at the higher compression could do them in if they are in bad shape. Just a thought
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Old 07-28-2006, 11:09 AM   #8
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Quote:
Originally Posted by Rogue
Sounds like a fun project Shawn. You may want to do a leakdown test on the cylinders before adding a bunch of boost to it, 200k is a lot of miles for those rings and running at the higher compression could do them in if they are in bad shape. Just a thought
I'm really not too worried about it. If I lose the bottom end, whether it be a popped piston, bearings, or throwing a rod or just worn out rings, then I'll just end up having to throw a new bottom end in it... Not what I want to do but if I have to do it then I have to do it.

I've never done any sort of leakdown or compression test on the engine before, however it doesn't smoke at all. It also uses no noticable amounts of oil between changes. It seems to be pretty healthy. I do appreciate the heads up though.

Shawn
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Old 08-01-2006, 04:00 AM   #9
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So we started tearing it apart on Sunday afternoon. We got the heads off and then pretty much quit there. We started back on it today and I dropped the tranny pan and fixed (hopefully) an issue I was having with it. I cleaned my heads up with a wire brush and then we got the new springs, retainers, and valve seals on them. We pulled the front cover, yanked the cam out, then put the XP cam in. Got it all timed and threw the front cover back on. I also bolted down the front head, and I bolted the PS pump back up, and a few other things.

Suprisingly enough, the tensioner/dampner looked to be in very good shape and wasn't even as worn as I had expected. It definately was worn, as was the chain, but nothing like I expected. It was quite obviously not causing the noise like I thought it was. Oh well, I have a new one anyways and already have the cam and all that fun stuff so I might as well throw it all together. However, while pulling the harmonic balancer off we had to wedge a screwdriver in the flexplate to hold the engine from turning over and it appears that my flexplate has a huge crack in it. I didn't think this was very common for GT'*, but its definately cracked. I'm guessing that was what was making the noise. I'm working on getting a new one, but until then I'll probably drive it like that because I have no choice.

I plan on putting the engine the rest of the way together tommarow after I get out of class and then taking it for a test drive. I won't have any boost until I get my PCM done later in the week because I won't be running the supercharger belt, but I should definately be able to work out most fo the issues during this time.

I'll post pics tommarrow when I get it all done.


In all honesty, everything I pulled out of the engine was in much better shape than I expected. The heads looked decent and so did the cam and timing gear and all that, it really was suprising.
Shawn
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Old 08-02-2006, 01:51 AM   #10
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That is an awesome project! And you make it sound so easy....
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