who is a bonified sbc "CAM" guy here?

BustedPinion · Apr 21, 2008

yes i have cam questions and in all my years as a tech thats still mysterious to me. i have a 1991 GMC Suburban, 5.7 TBI 350.. stock & soon to have a 6" .. and want to bump up my sound and torque without having to modify other **** like heads exhaust or computer.. and also not slaughter my already aching MPG..

anyone know the numbers on my stock cam and what one would be a good step up? i dont want an RV cam, nothin lumpy i dont wanna buy the gas for it lol:flipoff:

Binder · Apr 21, 2008

I've been told that if you call comp cams tech they will help you choose what cam would work best for you. Be carefull with TBI or most any injection system to not get a cam with too much valve overlap.

jeepmauler · Apr 21, 2008

There is/was a guy on here that lives over in Yakima(?),he owns an S-N 4 seater and races roundy round cars.He is the GM GURU and could answer youre questions for sure.He is good buddies with the guys up at S-N...and I can't for the life of me remember his name.....

:looser:

Brian H · Apr 21, 2008

BustedPinion said:
yes i have cam questions and in all my years as a tech thats still mysterious to me. i have a 1991 GMC Suburban, 5.7 TBI 350.. stock & soon to have a 6" .. and want to bump up my sound and torque without having to modify other **** like heads exhaust or computer.. and also not slaughter my already aching MPG..

anyone know the numbers on my stock cam and what one would be a good step up? i dont want an RV cam, nothin lumpy i dont wanna buy the gas for it lol:flipoff:

What ever you do the computer is going to get false readings other than stock. I found this out on my 89 v8 tbi camaro. I put a built 307 bottom end in it and put in a bigger cam and it set off the knock sensor and damaged the engine fast.

Boonie Buster · Apr 21, 2008

ya, mess with cam, mess with TBI, My old boss put a TB space on his TBI setup, and it never ran right, he ended up taking it off....

zukkev · Apr 21, 2008

BustedPinion said:
yes i have cam questions and in all my years as a tech thats still mysterious to me. i have a 1991 GMC Suburban, 5.7 TBI 350.. stock & soon to have a 6" .. and want to bump up my sound and torque without having to modify other **** like heads exhaust or computer.. and also not slaughter my already aching MPG..

anyone know the numbers on my stock cam and what one would be a good step up? i dont want an RV cam, nothin lumpy i dont wanna buy the gas for it lol:flipoff:

Careful about who you go thru for the comp prom mod... I tried to get one for my '92 Niv K tbi 5.7, and noone offered a prom for my particular Application---(there was no reburned chip avail for my prom # on mine) I ended up selling the truck, as I wanted a diesel anyway...

datsunon40s · Apr 21, 2008

if your worried about gas leave it stock because the bigger cam = more flow = less mileage any way you look at it

my vote is the comp 268 grind keeps low end torque but flows well at high RPMs the power range is 1500 to 5500 RPM

Oh and the lumpyness you were talking about is all about the lobe separation keep it around 112% for a smooth Idle 108% for choppy 102%for dragster status

BustedPinion · Apr 21, 2008

i dont want it cammin hard but definetly a little light & tinny tink ta tink tink with some rumble when i get on er' :redneck:

Binder · Apr 21, 2008

BustedPinion said:
i dont want it cammin hard but definetly a little light & tinny tink ta tink tink with some rumble when i get on er' :redneck:

You're going to need to retune your ECM..

moparmagician · Apr 21, 2008

My suggestion, go to comp cams website, then the catalog, page 140. I have sold a few of these, guys like them and haven't had any problems with the computer that I know of. The grind # XR258HR is specifically designed for your engine, and since yours is a 91, it should be a roller cam engine. Here are the specs.

HYDRAULIC ROLLER-For throttle body 305 or 350, very good economy and power.

1000 to 5000rpm, advertised duration 258 264, @.050" 206 212,
lift .480 .488, lobe sep. angle 112

jeffs88toy · Apr 21, 2008

I have a 320 with 550 lift it's a little rough:haha:

BustedPinion · Apr 21, 2008

Binder said:
You're going to need to retune your ECM..

i was kinda figuring lol. whats that cost?

leadfoot067 · Apr 21, 2008

a comp 268 with throw off the puter for sure, crane and comp both make computer specific cams,none are really big enough to make a lopey idle,the TBI wont like it. they will make more power, mabye a little better mileage but doubtful....it WILL run like **** if you over cam it or even if you stick in a small non computer cam it wont run right....

BustedPinion · Apr 21, 2008

moparmagician said:
and since yours is a 91, it should be a roller cam engine. Good luck

mine should be just a generic 5.7 hydraulic, its not a vortec..

Binder · Apr 21, 2008

BustedPinion said:
i was kinda figuring lol. whats that cost?

I don't know what a shop charges. Best bet is to find someone who has the equipment and is willing to help you with it. Get the wrong cam and no amount of tuning will help you.

BustedPinion · Apr 21, 2008

leadfoot067 said:
a comp 268 with throw off the puter for sure, crane and comp both make computer specific cams,none are really big enough to make a lopey idle,the TBI wont like it. they will make more power, mabye a little better mileage but doubtful....it WILL run like **** if you over cam it or even if you stick in a small non computer cam it wont run right....

Hi Shane! kinda what i was thinkin, but i see people with TBI and a little bit of cam and they seem to do fine. just what are they doing to get it?

BustedPinion · Apr 21, 2008

Hmmmm does GM offer thier "suggested" performance cam that should go with it? I wonder, seems they would have an option thast might be tested to work :stirpot:

moparmagician · Apr 21, 2008

BustedPinion said:
mine should be just a generic 5.7 hydraulic, its not a vortec..

I am not absolutely sure, but I can check at work tomorrow for you and let you know. But I beleive all small blocks built 1987 and later were roller. Dodge and Ford were close to that also. My 90 dodge 360 is roller as is the 88 3.9 v6 in my crawler. I'll check the books, I've been wrong before, well once or twice maybe.

Binder · Apr 21, 2008

BustedPinion said:
but i see people with TBI and a little bit of cam and they seem to do fine. just what are they doing to get it?

Probably running it in open loop mode (no O2 sensor).

bigd9247 · Apr 21, 2008

I'm running a Crane Cam in my 1993 CPI injection Vortec 4.3L without any mods or problems with the stock computer. It has an advertised duration of 260/276 with 112 degree lobe seperation. I don't know if this helps or not but maybe it will...