Questions about the Xtreme Energy Cams for the L67 and L36...

[SubZero350]

I was surfing the grand prix store site and noticed that the xtreme energy cams have been released for the 3800 II and SC engines. According to the specifications supplied, valve lift for both cams is over .500" w/ 1.6 rockers. Also, there are no springs available either.

Last time I went thru my L36 heads in engine machining, I noticed that the stock heads would only accomidate up to .430" valve lift (w/ the .050" clearance taken into account) with the seals installed because of the guide height. I am missing something here? I know that these can be shaved down, but according to GPS, they just "threw" this cam in without doing anything else!!!???!!!

Anyone else running one of these cams? Please let me know how good they are and if they are worth $289.00.

 

[T-Keith]

If you look over at clubgp.com they are a couple people experiencing problems with cams. One member measured max lift at .505. Also the stock springs may not be strong enough.

 

[TireFryer]

heads

U mentioned u measured the L36 heads....I am sure you are aware that those heads are different than the L67 heads. A friend of mine will be installing this very cam in his 2000GTP this weekend...w/o addition of any rockers, or springs or anything else. Will publish findings as they happen. As per measurements done by a reputable race shop, it should work w/o problems in clearence or other issues. TEP cams were having problems and were setting codes, but those were more aggressive than the GPS cams.

 

[SubZero350]

According to TEP, the only difference between the stock N/A and SC heads are the fact that the SC heads have holes machined for the injectors. The N/A heads still have these bosses there, just not machined. In fact, they claimed that the N/A heads could be used on an SC engine if these holes were machined. According to ALLDATA Parts, the cams are the same for the SC and N/A engines. I would find it hard to believe that GM would machine down guides on one head more than another for the same lift cam; although, as I have never had an SC head apart myself, I cannot be 100% sure if this is the case.

As I stated before, a .510 valve lift cam would probably work in the stock heads, but there would be less than .020" clearance between the guide seals and retainers. According to many head, valve, seal, and cam manufacturers, there must be at least a .050" clearance between the seal and retainer at max lift.

 

[Onyx Dragon]

Re: heads

Originally posted by TireFryer
U mentioned u measured the L36 heads....I am sure you are aware that those heads are different than the L67 heads. A friend of mine will be installing this very cam in his 2000GTP this weekend...w/o addition of any rockers, or springs or anything else. Will publish findings as they happen. As per measurements done by a reputable race shop, it should work w/o problems in clearence or other issues. TEP cams were having problems and were setting codes, but those were more aggressive than the GPS cams.

The GTP guys are the ones that have noticed this problem first, since not many, if any at all, L36 guys have a cam in that I'm aware of. My question is, with the current cam having the following stats..

206°/212° at .050"
Intake Lift .320" (.512" lift at 1.6:1 rocker ratio)
Exhaust Lift .325" (.520" lift at 1.6:1 rocker ratio)
113 Lobe Separation

What would a good custom ground cam stats be? We know the above is too much. How can we go about deciding what is not too much?

 

[SubZero350]

My guess is that depending on what version of OBDII misfire monitor your vehicle has, you might have a problem with any "good" aftermarket cam you put in. This is assuming that the computer is interpreting a rougher idle as a misfire detection. I'm not sure, I haven't had a chance to try one out. Sounds like anyone running an OBDII system is going to need some programming done to fully utilize the advantages of the bigger cam anyway. I am going to be using the 95 computer system on my '97 3800II engine with a turbo because I already have the software to do the '95 SC chips, so I shouldn't have these compatability issues.

 

[Onyx Dragon]

Originally posted by SubZero350
My guess is that depending on what version of OBDII misfire monitor your vehicle has, you might have a problem with any "good" aftermarket cam you put in. This is assuming that the computer is interpreting a rougher idle as a misfire detection. I'm not sure, I haven't had a chance to try one out. Sounds like anyone running an OBDII system is going to need some programming done to fully utilize the advantages of the bigger cam anyway. I am going to be using the 95 computer system on my '97 3800II engine with a turbo because I already have the software to do the '95 SC chips, so I shouldn't have these compatability issues.

The GPS cam is not causing any misfire codes to pop up, so that's not an issue with it.

 

[SubZero350]

do anyone have the specs on the gps cams?

 

[Onyx Dragon]

Originally posted by SubZero350
do anyone have the specs on the gps cams?

L67 Lobe Specs
200°/212° at .050"
Intake Lift .315" (.504" lift at 1.6:1 rocker ratio)
Exhaust Lift .325" (.520" lift at 1.6:1 rocker ratio)
115 Lobe Separation

L36 Lobe Specs
206°/212° at .050"
Intake Lift .320" (.512" lift at 1.6:1 rocker ratio)
Exhaust Lift .325" (.520" lift at 1.6:1 rocker ratio)
113 Lobe Separation