I have a 88 TPI motor that I am rebuilding. I've seen a few cams and the two that have caught my eye are the Xtreme Energy:

Here are the two I am looking at:

Xtreme Energy 501-8
Duration: 212/218
Lift: 488/495

Xtreme Energy 502-8
Duration: 218/224
Lift: 495/503

Both of the cams according to the Summit rep are rated idle to 5500 which is the power band I am looking for. I am not building the motor to be wild, just want a snappy TPI that has a bit more nuts than stock. Therefore I am leaning towards the 501-8 as it seems to be a nice step up from stock which I think is around a 190/200 460/470 or something like that (dont have the sheet nearby).

So its going .030 over w/ new oil pump/bearings etc, Accel 24lb injectors, BBK Fuel Pressure Regulator, Accel cap/rotor/8.8 wires, Delco platinum plugs.

I am open to suggestions! Thanks in advance for your advice.

 

I'am running a cam similiar to the 501-8 but with a little more duration on the exhaust side. It idles very nicely at 700rpm and has plenty of power. I will be going to the track this weekend and see how my combo works. Hoping for high 12's.

I was going to check my 1-2 shift points this past weekend. I was entering the freeway onramp and about 10MPH I punched it. The tires broke loose so bad and for so long I had to abandon the test. I had to settle for the 2-3 test and got some rubber at that. Shift was around the 5200RPM mark. I will have to redo the governor on the 700R4 as the motor was still pulling very strong. I will be looking for around a 5500 or so shift point. Allen

 

That sounds nice! What mods have you made to your motor? I've done a lot of motors but never got this deep into a TPI so I am really not sure what to expect.

The last one I had was a 91 350TPI that was a Mass state undercover car. That car was completely stock and nasty at 95k miles in 98 when I bought it. Did very little to that one and not many people could run with me.

The car this one is going into is a 92 RS so I've got a bit of work to do before it'll be able to drop in and run it.

 

It would help if you gave us some more info... I assume its a 350, correct? What kind of heads are you gonna use? Do you happen to know what the lsa for those cams are?

If you are going to use stock tpi heads, and stock base and runners, I would think the 501-8 would be a better match. If you go that route, you are right at the edge, if not just beyond the point where you should seriously consider burning chips though. The car isn't going to be well tuned on a stock bin.

Keep in mind that TPI makes its peak power around ~4600 rpm. Its not difficult to overcam it.

Either of those cams will require a valve spring change, machining for screw in rocker studs ( or pinning your current studs), and trimming the top of the valve guides for clearance with the retainer.

 

First thing that jumps to my mind with those cams.

Of those 2, the first would be easier to get up and running. Less tuning would be involved. The other, well, more tuning. Then again, to really dial it in, I would tune either, but that's just me.

 

Yes it is a 350 and I have everything to burn my chips in the garage so that is covered. The intake, runners and heads will be stock as well.

I am rather curious to know what you suggest for valve springs? Reason I ask is that is the first time I have heard anyone suggesting it. I definately appreciate the input!

Should I go with a stock replacement spring or change it up a bit?

What cam could I get that would be slightly overstock that would not require me to get into head work?

 

You shouldn't listen to me for valve springs, you should contact your cam manufacturer and see what they recommend with the cam, once you decide on your cam profile. Ask for stock diameter springs (I believe its 1.25"??? don't recall). They make springs in several different diameters, but only one size will fit your head without machining the valve pockets.

The problem with your springs is that they are already 16 years old. When they were new, they were borderline acceptable for the mild cam that came in your engine. They will be nowhere near adequate for either of those two cams. Do a search, and you will find that it IS a big deal to get stiffer springs once you change cams.

As far as trimming the valve guides, it depends on your heads. The only way to tell for sure is to measure the clearance yourself. For the most part, people start to run into trouble around .460 to .480 inches of lift, but like I said before, it depends on your heads.

With regards to machining for screw in studs, I'm not sure at what point it becomes necessary. That depends on your valve springs. As the cam becomes more aggressive, you require stiffer valve springs. As the springs get stiffer, the chances increas of pulling out a rocker stud. The ones from the factory are pressed in. What is commonly done is to remove the pressed in studs, and tap the bosses for screw in studs. If you are on a budget like me, you can purchase a set of roll pins, and drill a small hole through the boss and stud that is already there. Then you just tap it into place, and pressure holds it in. Several guys on this board are running just that (myself included).

 

For both of those, the recommended spring would be the 986-16. However, they are a 1.43" OD. That means that a shop will have to machine the spring seats for a larger spring. The call is up to you. If you don't feel like that, Isky (as well as the other companies, I just happen to have Isky) makes springs with the rates and pressures of the stiffer springs, but on the 1.26" OD, or factory size. The Isky springs I have are the 235-D series, and the specs are as follows:

Type: Outer spring with damper coil
OD/ID: 1.26"/.886"
Seat pressure/installed: 130 lbs @ 1.750"
Open pressure/open height: 320 lbs @ 1.200"
Spring rate: 320 lbs/in
Coil bind: 1.150"


Factory springs are rated at about 85lbs of pressure at the seat, at the factory installed height. From there, they can only get weaker. I've seen a set of factory springs hit the Rimac and show from 45-50 seat. Those came off of my LG4, from '85.

I would have them trimmed anyway. The only accurate way is with a spring installed height checker, and not everybody has one of those laying around. There are also +.050" retainers that can be used. Basically, they move the contact area for the spring up .050" in relation to the valve lock. Good side: it gives you that much more clearance. Not so good side: it lowers the seat pressure which lowers the RPM at which valve float can occur.

Mr. Gasket sells a kit, I think they still do, at least, that allows you to simply tap the factory stud boss and screw in the studs. The screw in part is of different length, so the shop doesn't have to mill off the .400" or so that they do for guide plates. Just another option. However, if it were me, I would just run it to a shop, have them do it up and do it right. but yes, pinning the studs is extremely easy. Cast iron is suprisingly easy to drill through. Just go slow, take your time, and don't overwork the drill.