need some help

[bryans restoration]

i got a 00 gtp and i blew the motor up so i got another motor out of a 98 regal gs. same exact motor (or is it). this motor has 50,000 on it and it runs great however it doesnt get as much boost not even close. when you nail it the digi boost gauge goes one little bar under half way when the last motor had the gauge pinned. a substantial loss in power and u can tell it has a lot more potential but its not putting enough forced air in it. you can tell its not getting enough by the whine of the k&n filter, its quieter, it used to scream. i got the grand prix computer hooked up to it, do you think i need the gs computer?? i had to swap the throttle bodies, and the cerpantine belt was different but thats it. i need to know what the hell is wrong with this thing does anyone know? is the pulley size on the gs bigger or something? this is aggrivating.

[maxwedge]

Not an expert on the super charged 3800's, we have a couple people here that are though. Anyway, boost is dependent on blower condition, pulley size and pcm programming, so those are the things that control this. I just cannot tell you precisely where the issue is, hold on I am sure Bob, or one of the guys will kick in here. BTW a blocked cat can reduce boost also.

[BNaylor]

Thanks Shep (Maxwedge), I might be able to help

The GTP and Regal L67 engines are identical and that includes the Eaton M90 Gen 3 blower. The Regal GS uses a stock SC pulley size of 3.8" just like the GTP. Both generate around 7.5 - 8.0 psi boost. Fuel injectors and delivery system are the same. You will not be able to transplant a PCM programmed for a '98 Regal GS into your '00 GTP. The PCM for a '98 GS and 2000 GTP are different part number wise and they way they are programmed.

Sounds like you have other problems causing insufficient boost. Have you checked the boost valve to see if it is working and adjusted properly?

Do you feel a noticeable lack of power when boost kicks in? I would not depend on the stock gauge to determine you are low on boost. An aftermarket gauge with boost on one side and regular engine vacuum on the other would give you a better indication. Also you might consider running an engine vacuum test to see if vacuum is within specs.

[bryans restoration]

[quote=bnaylor]Thanks Shep (Maxwedge), I might be able to help

the boost valve up front seems to be working ok it flips up and down how it should, i loosened it and pushed it down a little to get it open all the time but that made no difference. i could ask a mechanic freind to do the vacume test and see, but all the vac hoses look good and solid. im gonna chop the cat off too because i live in a no emmisions county, u-bend is gone already, and im gonna swap the 3.4 pulley off the other motor onto the new one. there is a pretty noticeable loss in torqe it used to rip the tires off now it dont. and its got a little exhaust leak coming out where the cat bolts in i can here it ticking but i dont think that affects boost or does it? the motor runs great, like i said the one thing that really tells me its not getting enough air is by the sound or the k&n cone filter. that thing used to whine really loud when you nailed it but now it whined alot quieter like its not sucking nearly as much. whatever it is its gotta be something stupid but do you guys have any more suggestions? i know someone out there has or had the same prob. except im running this gs motor in the pontiac that prolly makes it a little different. p.s i feel more power when boost kicks in its just not getting enough.

[BNaylor]

[quote=bryans restoration]

Originally Posted by bnaylor

Thanks Shep (Maxwedge), I might be able to help

the boost valve up front seems to be working ok it flips up and down how it should, i loosened it and pushed it down a little to get it open all the time but that made no difference. i could ask a mechanic freind to do the vacume test and see, but all the vac hoses look good and solid. im gonna chop the cat off too because i live in a no emmisions county, u-bend is gone already, and im gonna swap the 3.4 pulley off the other motor onto the new one. there is a pretty noticeable loss in torqe it used to rip the tires off now it dont. and its got a little exhaust leak coming out where the cat bolts in i can here it ticking but i dont think that affects boost or does it? the motor runs great, like i said the one thing that really tells me its not getting enough air is by the sound or the k&n cone filter. that thing used to whine really loud when you nailed it but now it whined alot quieter like its not sucking nearly as much. whatever it is its gotta be something stupid but do you guys have any more suggestions? i know someone out there has or had the same prob. except im running this gs motor in the pontiac that prolly makes it a little different. p.s i feel more power when boost kicks in its just not getting enough.

Have you checked for belt slippage. Sounds like something is not right with the supercharger. A Regal GS can fry the tires as well as any GTP. I know I own both.

I noted above you changed the throttle body out. What was the reason?

[bryans restoration]

I noted above you changed the throttle body out. What was the reason?[/quote]


well, im not exaclty sure because a mechanic freind of mine did it while i wasnt there i helped him mainly rip it out. ill ask him but im not too sure why he changed it maybe something with a sensor or something. as far as the belt goes that could be a factor because i reused the SC belt from the motor with a 3.4 pulley. that belt has prolly 35.000 on it. but i thought it would be fine cause i went back to the stock (3.8") pulley. how do you check for slippage anyway do you just pull the gas and watch closely or should i just go get a new belt since that one was used? thanks for the help too man.

[BNaylor]

Originally Posted by bryans restoration

well, im not exaclty sure because a mechanic freind of mine did it while i wasnt there i helped him mainly rip it out. ill ask him but im not too sure why he changed it maybe something with a sensor or something. as far as the belt goes that could be a factor because i reused the SC belt from the motor with a 3.4 pulley. that belt has prolly 35.000 on it. but i thought it would be fine cause i went back to the stock (3.8") pulley. how do you check for slippage anyway do you just pull the gas and watch closely or should i just go get a new belt since that one was used? thanks for the help too man.

The belt is always a possibility. I stick with GoodYear Gatorback.

When you run the vacuum check, check the vacuum at the MAP sensor line. Also, that is the same location to hook up a real boost gauge.

On the throttle body try swapping out the MAF sensors, if that was not the bad sensor on the throtttle body.

[bryans restoration]

Originally Posted by bnaylor

The belt is always a possibility. I stick with GoodYear Gatorback.

When you run the vacuum check, check the vacuum at the MAP sensor line. Also, that is the same location to hook up a real boost gauge.

On the throttle body try swapping out the MAF sensors, if that was not the bad sensor on the throtttle body.

the junkyard raped me of the MAF sensor on the new motor, but im gonna go screw with it today so ill keep u updated and i appreciate all your help.