Need help with Cam for 1990 L98
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 33
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From: Winnipeg Manitoba
Need help with Cam for 1990 L98
Hi Guys, Need your help with 1990 L98 Auto , just cant seen to get this thing to run proper, it appears that there is just not enough vaccum and causing problems with the MAF. The things just gets way too rich and dies. Several burns from PCM for less but no luck, The only thing it could possible be is the cam is too aggressive. At the point of pulling the motor and changing the cam. See existing specs below. Any thoughts on what cam has worked for you so I can get PCM to burn a chip and chqange the cam and not waste any more $$
The specs are based on a ligenfelter grind with the following details: duration@50, 243 Intake, 251 exhaust, adv duration 294 intake, 302 exhaust, lift @ valve .560 intake, .565 exhaust, 1.5 rocker ratio, 1.75 spring height, 100lb springs, closed seat, lobe sep 110. all cylinders are .30 over.
This motor is raunchy and we just cannot get the thing to idle at all and runs way too rich. We are at the point of pulling the cam and going to something a little milder. any thoughts or suggestions would be a great help. Thanks
The specs are based on a ligenfelter grind with the following details: duration@50, 243 Intake, 251 exhaust, adv duration 294 intake, 302 exhaust, lift @ valve .560 intake, .565 exhaust, 1.5 rocker ratio, 1.75 spring height, 100lb springs, closed seat, lobe sep 110. all cylinders are .30 over.
This motor is raunchy and we just cannot get the thing to idle at all and runs way too rich. We are at the point of pulling the cam and going to something a little milder. any thoughts or suggestions would be a great help. Thanks
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 33
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From: Winnipeg Manitoba
Hi Vader,
The entire motor has been built by a reputable racing enginge builder, diamond pistons, all balanced ect, heads have been ported slightly, still have the TPI set up although. I think they felt that PCM could work wonders!! but this might just be too much. I respect your thoughts and suggestions, I am personnally a little lacking in the technical dept to give you all the specs. They want to pull the cam and step it down, on my dime of course! what should I do?
The entire motor has been built by a reputable racing enginge builder, diamond pistons, all balanced ect, heads have been ported slightly, still have the TPI set up although. I think they felt that PCM could work wonders!! but this might just be too much. I respect your thoughts and suggestions, I am personnally a little lacking in the technical dept to give you all the specs. They want to pull the cam and step it down, on my dime of course! what should I do?
Team Owner
Joined: Oct 2004
Posts: 81,241
Likes: 3,063
From: altered state
St. Jude Donor '05
If those specs are right thats waaaay too much cam for the TPI.
Not nearly enough spring pressure, either. 100 lbs, those guys need some talking to. Hate to tell ya, but Id change cams for sure.
Sounds like a cam suited much better to a carb. That thing wont even start coming alive til 3-3500 or so. TPI peters out mid 4k-ish.
Not nearly enough spring pressure, either. 100 lbs, those guys need some talking to. Hate to tell ya, but Id change cams for sure.
Sounds like a cam suited much better to a carb. That thing wont even start coming alive til 3-3500 or so. TPI peters out mid 4k-ish.
Burning Brakes
Joined: Aug 2000
Posts: 1,146
Likes: 2
From: Albuquerque NM
Dude your cam is HUGE! It also doesn't match your intake...thus for both intake and CI going over 236/236 makes for a bad running car. The lingenfetler cam everyone references is the 219/219 at 0.050" lift. Thus your 243 is way off.
Should you take the car back there? Well, I would ask myself if I should pay them in the first place. If they recommended the cam (and it is clearly off), they need to pay to put something reasonably tunable. Anything past a 218/224 or 224/224 would be too much for the setup presented.
Once you get this new cam in there, you'll still need to get a chip. I really worked the idle in my 383. It is a balancing act of timing and giving the ECM only enough authority to correct what it can. But you need to get your base motor sorted out first.
Should you take the car back there? Well, I would ask myself if I should pay them in the first place. If they recommended the cam (and it is clearly off), they need to pay to put something reasonably tunable. Anything past a 218/224 or 224/224 would be too much for the setup presented.
Once you get this new cam in there, you'll still need to get a chip. I really worked the idle in my 383. It is a balancing act of timing and giving the ECM only enough authority to correct what it can. But you need to get your base motor sorted out first.
Hi Vader,
The entire motor has been built by a reputable racing enginge builder, diamond pistons, all balanced ect, heads have been ported slightly, still have the TPI set up although. I think they felt that PCM could work wonders!! but this might just be too much. I respect your thoughts and suggestions, I am personnally a little lacking in the technical dept to give you all the specs. They want to pull the cam and step it down, on my dime of course! what should I do?
The entire motor has been built by a reputable racing enginge builder, diamond pistons, all balanced ect, heads have been ported slightly, still have the TPI set up although. I think they felt that PCM could work wonders!! but this might just be too much. I respect your thoughts and suggestions, I am personnally a little lacking in the technical dept to give you all the specs. They want to pull the cam and step it down, on my dime of course! what should I do?
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
... it appears that there is just not enough vaccum and causing problems with the MAF. ...
I agree about that cam; for a 350 SBC try the ZZ9 or 219 cam.
Also not enough spring as stated.
With a stock cam and 1.6:1 RRs I'm running more than 100lbs at the seat. If you go with the ZZ9 cam use the springs recommended & sold by TPIS.
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Thread Starter
Intermediate
Joined: Jun 2007
Posts: 33
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From: Winnipeg Manitoba
Team Owner
Joined: Sep 2001
Posts: 62,160
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From: Athens AL
C7 of the Year - Unmodified Finalist 2021
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The only intake that is even remotely suited to the current cam is the Miniram. But its still way too big. With a cam like that I wouldnt do anything less than 200cc heads and a 396 underneath, and I still wouldnt bet it'd idle all that great. Its a terrible cam choice for what you have now.
If its a 350 TPI intake motor with '113 heads, you really cant take advantage of anything more than 220/220, and I wouldnt even give it that much. More like 212/218, so a TPiS ZZ9 or Accel 211. A 219 needs more intake than you have.
After a custom chip for one of these smaller ones, it should idle and run just fine.
If its a 350 TPI intake motor with '113 heads, you really cant take advantage of anything more than 220/220, and I wouldnt even give it that much. More like 212/218, so a TPiS ZZ9 or Accel 211. A 219 needs more intake than you have.
After a custom chip for one of these smaller ones, it should idle and run just fine.
Racer
Joined: May 2006
Posts: 426
Likes: 16
From: Concord CA
Bigger is not always better...
Selecting a CAM you really need to pick one that fits all of the parts and setup (intake, Stroke, compression Ratio, Transmission, rear gear ratio, etc) and intended driving style and usage.
Just going big is not always the best route to go and is a mistake made way to many times.
Selecting a CAM you really need to pick one that fits all of the parts and setup (intake, Stroke, compression Ratio, Transmission, rear gear ratio, etc) and intended driving style and usage.
Just going big is not always the best route to go and is a mistake made way to many times.
Melting Slicks
Joined: May 2007
Posts: 2,382
Likes: 2
From: Kathleen FL
LAWLZORZ, I bet the cam kills drivability like a ******.... A nice stock replacement cam should be in the range of 210-220 degrees at .050 on both the intake and or exhaust. a 243/251 cam would be ok either for a high compression 350 that revs to like 8000 rpms or for a bigger motor. It would be a nice cam for a hot street 406 though... 
Thread Starter
Intermediate
Joined: Jun 2007
Posts: 33
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From: Winnipeg Manitoba
Well, ZZ9 has been ordered and I will give that a try. just to clarify the 100lbs spring is actually 100lb closed so it will be just fine.
The builder wanted to give it a little extra and wanted a good cam for nitrous and the high compression ratio I am running and it just backfired so back to the drawing board, he is comming good for the labour and cam and all is good.
The builder wanted to give it a little extra and wanted a good cam for nitrous and the high compression ratio I am running and it just backfired so back to the drawing board, he is comming good for the labour and cam and all is good.
