I know there's a ton of cam threads out there, and I plan on pulling the trigger on one this week. I'm playing with the downloadable cam program from comp cams and came up with a question. When I select F.I. instead of carb'd, it limits my selections obviously. Now are the F.I. cams meant to work with the factory tune of the computer? Since I plan on a custom tune, can I select from the carb'd cams instead?

 

How much tuning to a computer you have / can buy are you willing / able / equipped to do?

 

In the comp cams program on the right side it has a list of notes. It'll say if it is stock computer compatible.

 

I had to read it twice, but it's basically spot-on. Your answer to this will sure help you decide how crazy to get.

 

There's a local tuner here for TPIs, but he's difficult to get ahold of since he does it on the side. I was thinking I'd send all my specs somewhere and have them burn me a rewritable chip to get me started. Then I'll buy the software and fine tune the rest. I'm using a MAF setup. All in all though I'll be using the factory computer just with a different prom.

I also don't get one other thing. They present alot of Retro-Fits for hydraulic roller cams. Will these slide right into a 87-95 roller block? Or since they are retro-fit they only work in 86 and prior blocks? It says cylinder head machining required for some, which makes me think I should not be buying one of the retro fit cams..

 

Any grind that COMP offers in retrofit, they also offer on the '87-up core. Since you have the later block, use the later core.
The cams that call for head machining all have 1 thing in common, and it's not the retrofit thing. It's serious lift.
Note that the XFI cams are listed with lift using 1.6:1 rockers, which isn't necessary. Using 1.6:1 rockers generally does call for head machining.

 

Generally computer compatible cams have a of LSA 112+ ( some factory cams 115 ) ; a good tuner should be able to tune a 110.

It is all to do with the valve overlap and the computer' ability to read the O2 sensor when raw fuel ( from big overlap; small LSA ) is passed out the exhaust at idle .
Doesn't affect carb cars because there is no feedback from what is going out exhaust whereas that is the major fuel control item ( O2 Sensor ) on a EFI car

 

Thanks for the replies. Vetteoz that was a helpful post.

So I started just looking at the XFI series just so I don't need to worry as much about finding a tuner. But they all say 1.6" rockers, head machining, springs, etc. Which I don't want to get into since I just bought brand new heads fully assembled with springs good up .6 of lift and I don't really want to machine on.

There is ONE cam on summit for the '87-'98 OE roller motors that are computer controlled which is a 4x4 extreme energy cam. I'm liking the RPM range 1500 to 5500 (CL08-413-8), but it's the only extreme 4x4 cam compatible? I'd like the one from 1200 to 5200 (CL08-411-8) more but it says its NOT Computer Compatible even though it has the same LSA, same lift, just slightly different duration? Makes me nervous that maybe the first one is a typo?

What a headache

 

Just because the XFI series was designed to do well with 1.6:1 rockers doesn't mean they won't do even better with 1.5:1 rockers.
The 08-413-8 should pass an emissions test, but the smaller Xtreme 4x4 cams will have more vacuum, which makes tuning easier, and will do even better with emissions.
Any cam that doesn't have any overlap at 0.050" will be emissions-ok, and therefore computer-ok. But smaller cams with even less overlap will be easier to tune.

 

Goodpoint. Thanks for the post. Incase it helps, I do not need to worry about emissions at all. The only reason I was interested in cc cams was in hopes that it would be "easier" to have a program written for it. I thought about running the pro-magnums 1.52 ratio, but really didn't know what the magical lift number was to try and stay under to prevent head clearancing if using the XFI cames. This is my first bottom up build on a motor and just trying to keep it on easier side, by just having to worry about assembling everything. Not so much the fitment and clearancing...

I do have the 60cc and 185 runner Edelbrocks, stock TPI, 383, 52mm TB incase anyone would like to throw down some suggestions. Ideal rpm range is 1200 to 5200...

 

The XFI 260 HR 13 will do the job.

 

Thanks, dumb question though. It says 1993 to 1996 years? My stuff is a 1989...

Is it ridiculous to be nervous running that much lift on a stroked motor? Even with 1.5, it's still over .52 of lift...

 

I have been talking to a Tech from Comp Cams and he suggested a XR264HR which is their TPI specific cam, but have it a based on a custom grind for a small base circle because of the stroked motor. How does it compare to the cam suggested above. Will either of these cams be okay for use with siamesed runners? Or do the benefit of the siamesed runners come into account higher in the RPM band than I'm looking to operate?

 

This one would be a fine choice: http://www.compcams.com/Cam_Specs/Ca...?csid=194&sb=2

 

I like it, that's the one they suggested too. Just waiting to hear back from the guy about how a small base circle cam effects the motor. Does it technically flow less since it's not throwing the valve down into the cylinder as much?

 

I just checked out your library of motor builds in another thread. Nice work there.

I saw you used a XR264HR-10 cam in one of your 383 tpi builds, which looks the same as what you suggested just with a LSA of 110 instead of 112. So I would have a slightly less torque curve but it's easier to tune if I'm understanding LSA correctly?

 

Reduced base circle doesn't reduce the valve lift. Not the least little bit. For your rpm range, the reduced base circle won't hurt anything at all.

 

Close enough.
With more cubes (383) you can run more overlap, and still keep the same idle vacuum as the small cube / less overlap combo.
Cubes need overlap, and long tube headers, to compensate for the poorer ratio of valve window area to cylinder displacement.
Please don't ask me to go any deeper into advanced engine theory, the chemo is making me too sick.

 

Come on, you don't want to spend more time talking about it on a Friday or Saturday night? I wish I took classes on this stuff back when I went to mech E school. Would have beat all the other crap I took instead... I do appreciate your help.

So small base cam, got it. I'm happy with the cam you suggested so I'm good to go there. BUT, now do I NEED taller lifters? The comp cam guy suggested them to me when using the small base cam because the lifter will "fall" down into the lifter hole too deep. BUT I didn't plan on buying the $500 linked 853s lifters he said I needed. They are out of my original budget of the 850 rollers for $250...

Lastly rockers. I was planning on just buying a set here second hand, full rollers. But I look on the comp cam website for my years and only narrow body rockers are provided for the '87-'95 blocks?? Does that mean I can't use the normal full roller comp cams rockers? WTF