I am going to be using SLP/edelbrock tpi stuff on my L98 will either of these newer cams improve performance over the L-98 cam ... and are there any mod's needed to put either of these cams in my engine. I haven't decided on what heads I'm going to put on this motor but I'm also considering turbocharging the engine as well so will either of these cams work well with that to.

I'm concerned about idle qualities and vacumm since this is a speed density motor and how much will emmissions be affected.

lets hear all the good and bad about swapping to one of these cams and do they offer any better lift than what the L-98 cam has.

 

funny you asked, I am looking into one of these cams to plug into a vortec 350 GM crate engine.
I will try to answer some of your questions. The stock L98 cam -----duration at .050 is 202 intake and 206 exhaust, lift is .403 intake and .415 exhaust. Lobe sep is 115 degrees. As you can see it is rather small.
The LT-1 cam----duration at .050 is 201 intake and 208 exhaust, lift is .447 intake and .459 exhaust. It is slightly bigger the L98 cam. If you install this cam with 1.6 rockers you will be almost exactly at the lift and duration numbers of the LT-4 production cam.
the LT-4 cam is rated with 1.6 rockers. specs are duration at .050 203 on intake and 210 exhaust, lift is .476 intake and .480 exhaust. It also has 115 degrees of lobe seperation.
This is the cam I was thinking of going with on the stock vortec crate engine since the heads will except nothing larger than the .480 lift this cam has. Should run nice and smooth, and with the vortec base and some aftermarket runners and a few other bolt ons, it should be nice and torquey and fun to drive.
I am sure there are other people on here that have plugged these cams into stock L98 engines since these things have been around for years. Maybe someone can give you some real world results. Also keep in mind cam technology has come a long way in the last 10 years and there are even better aftermarket choices out there. I have not ruled out these myself either and have been checking with comp cams on a nice small hydraulic roller similar to the LT-4 but maybe with a little more duration. Hope this helps, Larry.

 

From his description - it says 1982 'bird, so which L98 cam is he refering too? Obviously that car didn't come with one out of the factory.

My L98 cam is much bigger than the cam stated by firebirdjones, 207/213 .415/.430

You said the system is S/D, but is the entire engine out of a S/D car.... if so the below cam is correct. If not, you may actually be losing size by going with an LT1 cam.

 

One thing I wanted to clear up, since it brought up a flag in my head. I can picture people being confused, so I though I'd mention it.

There are two cams which are commonly confused with each other. The production LT4 cam, and the LT4 Hotcam. The specs between the two are very different. I don't know the specs exactly off the top of my head, but I remember the Hotcam having 218 228 @.050, an LSA of 112, and lift was .495 ish.

 

Yep I did not mention the hot cam, I was referring to the production cams only. I was not sure if JP was interested in those or not.
Hey GOY, from what you said, it sounds like when GM got away from MAF and went speed density, the cam profile changed slightly? Just curious, I was not aware of that and can't find it in any of my books, but that doesn't mean much Larry.

 

I'm not sure if it was in 90 or 89, but the 88 I know for sure had a larger cam profile than the one you listed. There is a technical article here on the board someplace with the specs of both L98 cams.... I'll see if I can dig it up.

Any luck with the TPI setup?

 

https://www.thirdgen.org/newdesign/tech/techdb.shtml

All the way at the bottom:

88/89
305 5spd / 350 AT 10066049* .415 .430 207 213 117.0

90-92
305 G92 5spd / 350 AT 10111773* .413 .428 202 207 114.5

 

sorry about the confusion, obviously your right my car didn't come with a L-98 LOL .... this L-98 is from a 1990 corvette, and yes it does have the aluminum heads as well.

I plan on doing more porting on the SLP/edelbrock stuff I bought and will probably have the cylinder heads ported a little too. Guess my next step will be a six speed LOL

 

Goy, 88 and 89 that you have listed would be an MAF car as I am sure you know. It appears it has the larger cam as well? I am guessing that this change cam about in 1988 and had nothing to do with MAF or Speed Density? So the 88 L98 Iroc I have would have this cam in it? I was thinking it was the smaller one I listed. Thanks for any insight, Larry.

 

88/89 MAF 350 and 305(5spd) cars got the bigger cam.
88/89 MAF 305 automatic cars got a smaller cam.

90-92 350 and G92 305(5spd) cars got the later L98 cam, which wasn't as big as the 88/89
90-92 305 cars got some small dinky bumpstick according to that article.


If you 88 is a L98 from the factory, you have the bigger cam, yes.

 

Thanks GOY, good info,,,, Larry.

 

did the 90 vette L-98 have the bigger cam. at 245hp verses the f-bodies lower rating I would think so and were there any differences between the the six speed vettes cam and the automatics.

My plans so far are this engine equipped with slp runners, edelbrock intake, larger throttlebody, ported aluminum stock heads 113 heads, possibly extrude honed intake, shorty headers, flowmaster catback, 3 inch cat, 5 speed, 373 gears.

does this sound like a nice combination and capable of putting my car into the high 13's verses is embarrasing mid 15's performance, Stock this L-98 was rated at 245hp will it make 300 with mods I'm planning. The car isn't a 1/4 mile car but I do want the stoplight to stoplight power since it now gets beat by most imports. So how do you think it will perform I'm also looking into turbocharging the car as well ( not twin turbo's though ) probably just a nice T-04 to give it a little extra.

I just basically want this car to be a very streetable solid 13 second car and be able to sound nice and not have a lumpy sounding idle.

 

All SD TPI cars auto or manual got the same L98 cam. That is fact and in my cars case, dyno proven.

Now the fact that the MAF 350 and manual TPI cars got a bigger L98 cam than the later SD cars is new to me. This is the first I have heard about that.

 

Yep I did some digging after GOY posted that info and verified it over at the local GM dealer I use all the time. He did find that what GOY has posted here is accurate, in 1988 the L98 did have a cam change to something slightly larger. He also found that GOY was correct when he stated GM went to a smaller cam when they switched to SD, probably to make them easier to tune since the MAF cars were a little more forgiving. At least this is what I am told from a long time GM employee. Pretty interesting stuff. Now when I do the math with 1.6 rockers on my 88 L98, I will basically have an LT-1 cam but with slightly more duration, so it will be bigger than the LT-1 cam ever so slightly (duration wise). Will be interesting to see how much the 1.6 rockers pick up my stock L98, only some track time will tell. Larry.

 

If that is the case, then the power decrease isn't much because timewise, the SD cars are every bit as fast, if not faster than the MAF cars. Maybe it's because of the SD system? Faster processor or something, better fuel management?

 

Not sure on the ET differences, even though the MAF cams appear to be slightly bigger in 88-89, the difference is so tiny I seriously dought that there would be any time difference. According to what I have seen so far, the difference is only a couple degrees of duration at .050 and only slightly more lift with .002 more on the MAF car compared to the SD car, not enough of a difference to make a performance improvement. the only real big change I see between the MAF and SD cams is the lobe seperation and that would be in the SD's favor. The SD is tighter at 114 compared to the MAF at 117. The tighter seperation will help the engine build a little more low and mid range torque but again, I don't think such a small change would be that noticable. There was more of a change with the cam profiles during the MAF years. After 87 is where they made a significant change with a noticable jump in both duration and lift, but I am not sure if the 88 cars run any better than the 87 cars though. Would be a good comparison with 2 bone stock cars. How about it, anyone have a bone stock 87 L98 car with a time slip? My bone stock 88 L98 ran 14.60 at 94 mph. Anyone? I think I just opened a can of worms,,,,Larry.

 

mid 15s with aluminum vette heads?! you must be exagerating. I am going to be gunning for 13s in my 305 with stock 85' LB9 heads and cam. If anything, If you can hook i would say 12s should be no problem if you get some work done to those heads and pick out a good cam and do the intake and exhaust stuff you were talking about.