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Top Swap Problem

whitetyler1991

whitetyler1991

New member
Recently top swapped my 01 gt, car runs great until it starts to get any boost and then it just bogs out. has a 3.2 pulley, brand new heads, slp rockers and pushrods, ported blower and intake, K&N intake, 2.5 inch exhaust, MSD coil packs, ZZP PCM tune specifically for the car. can't seem to figure out what the problem is, if anyone has any input on this I'd highly appreciate it.
 


2.5 inch with a blower? gotta be some backpressure there not sure if its the prob though. maybe have zzp double check the tune?
 
at the moment no I don't have headers. the car runs great, better than it ever has, until any boost gets built up then it cuts out, acts like its starving for fuel or something.
 
I see a few potential issues.

First, have you checked for KR? The bogging is likely a large helping of KR trying to save your motor from the Kaboom.

3.2 pulley. This is something that takes a low compression L67 a lot of mods or IC to do successfully. You don't mention rockers, cam, headers and/or IC. Pulley up before it blows up. Say 4.3" type of pulley up.

MSD coil packs are well known for causing misfires at mid to high rpm. Sad as it seems the stockers were better suited for the motor. Literally I saw another post about MSD's causing issues this morning.

ZZP Tune.. one never knows what ZZP puts into the tune they send to you. Swarzkopf couldn't even start his SSM90 kit with the tune they sent him. Although I wouldn't necessarily discount the entire tune, it could be a factor. Might be worth asking ZZP what they did in it.
 
as far as I know theres absolutely know KR, I might try a bigger puller to see if it makes any difference. The PCM I called them for and talked them through the whole process to make sure it was exactly what I needed, I just recieved it yesterday hoping it would solve the problem, it made the car run way better but it hasn't solved my boost problem.
 


I also may have a different set up when it comes to my pulleys, at the time of the build the only idler pulleys and top half of the pulley set up by the coil bracket I had access to was off a supercharged Regal I believe. I'm not sure if that makes much of a difference, because I don't know the specs the car is running on around 10-12 lbs of boost
 
Regal and GP are identical for pullies. The items being mentioned are all possibile. Sounds like you haven't scanned to monitor KR.
 
whitetyler1991 said:
at the moment no I don't have headers. the car runs great, better than it ever has, until any boost gets built up then it cuts out, acts like its starving for fuel or something.
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whitetyler1991 said:
as far as I know theres absolutely know KR, I might try a bigger puller to see if it makes any difference. The PCM I called them for and talked them through the whole process to make sure it was exactly what I needed, I just recieved it yesterday hoping it would solve the problem, it made the car run way better but it hasn't solved my boost problem.
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Given its running BETTER with the tune... jump up to a 3.4 pulley & get some header immediately... make sure its got a 3" downpipe... your prolly getting too much backpressure for the boost your pushing and i personally think your lucky you dont have a blown head gasket already, or worse :th_nervous:
 
I thought they were but I never looked it up, and it has been scanned for KR, like I said theres 0 Knock that I know of. at this point I'm think the 3.2 pulley is just too much for it
 
yeah I think the 3.4 is probably the best thing to try right now, I agree with you on the backpressure, I'm sure its one of the main problems or at least thats the way it seems.
 


The reason a pulley would be too much is too much heat caused by the compression from being an NA lower end and spinning of the charger. This equates to knock. If you have no knock..then you have something off in your tune. However experience tells us that your pulley and other mods are too much for that setup and having no knock would be a miracle. it's simply something that doesn't happen unless there's no timing in the tune.
 
I was amazed to find out there was no knock too, that was my main concern and I decided to take the chance anyways and go for the 3.2. I can give the car quick jabs at the gas and it runs fine, gets boost, pulls, I can slowly rev it to the limiter and its fine, just when you try to lay into it and the supercharger comes in hard, it just bogs out and thats it.
 
because you wont knock unless there is a load on the motor. Like when your driving it. It usually wont knock just sitting in park. i also have a top swapped car, but im running headers and an xp cam...on a 3.4. no way are you ready for that 3.2. take it off and put a 3.8 back on.
 
I'm going to go with a 3.4 pulley and some headers, I have some decent heads I just bought brand new for 800 and slp rockers and pushrods, no cam. thanks for all the input guys, you've definately helped
 
3.8 with just headers, and I cant run 16* knock free somehow....

I believe its false but still.

If you had headers, run a 3.8, if not, run a 4.0.
 


Just wondering who did you topswap.. did you by pass the boost by pass valve?
 
whitetyler1991 said:
I'm going to go with a 3.4 pulley and some headers, I have some decent heads I just bought brand new for 800 and slp rockers and pushrods, no cam. thanks for all the input guys, you've definately helped
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you dont have enough mods for the 3.4 let alone a 3.2. 3.4 unintercooled will Over max the l67 injectors forsure, let alone a 3.2. Im running 98 Injector duty cycle on a pretty lean set up on a 3.4. Theres no way you had no knock on a 3.2 with headers and rockers, unless you had 3 degrees of ignition advance on a 10.0 afr. On your same set up I was able to run a 3.6 pulley knock free with 17 degrees timing. \I ran a 3.5 pulley with the same mods you have with 17 degrees timing and 1-2 degrees KR. It took a intercooler to run a 3.4 with 19-20 Wot timing with little to no KR.
 
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