cam for my 91tbi 350

[big_blue_chevy2006]

im lookin for a cam for my 91tbi 350. first off i want to know what kind of lifters are in it, and 2nd does neone know the lift and duration for a stock cam? and any suggestions on a nice cam? i dont like crane cams and i want something with a range no larger than 4500, and i dont care how low of rpms, i want something with a real rumpy idle that sounds like is got a huge cam in it but doesnt hurt my gas mileage like crazy (which isnt that great neways) and adds some nice power and torque.

[brokengear80]

Hmm, well the stock cam should have 0.3848 " valve lift on the intake and 0.4035" on the exhaust. This is with the 1.5 ratio rockers. I would bet a small sum of money that your truck has hydraulic flat tappet lifters because most all of them did. The duration on the stock cam is in the very low 200's like around 202-206 deg for both sides, maybe as high as 210 on the exhaust. This is at .050" at the valve. I have an 88 with the tbi 350 and I put in a comp cams CS 252AH-12 wich has .425" on the intake and .440" on the exhaust with 206 deg. of duration on the intake side and 212 deg. of duration on the exhaust and the truck runs great. I love it. It's got a 112.0 deg. lobe separation. I had put headers, duals with H-pipe, powerchip, open element intake bolt ons before and all of them put together did not make nearly the increase in power as the new cam, of course maybe all the mods complemented each other when the cam was added. My seat of the pants feeling tells me that it upped the stump pulling low end torque considerably. Local driving milage remained the same, but highway mileage dropped about 1-2 mpg. However, the lumpy rough idle you speak of is not really going to work well if you're keeping the fuel injection. The "lumpy" idle which usually comes with big duration cams will produce vacuum fluctuation that will not make your map sensor happy and your fuel injection will not work very well. Also, forget using overdrive with a big duration cam as your low end torque will go right down the drain. A guy that I work with put a cam in his '90 350 tbi with slightly more lift and a moderate amount more of duration and he lost his bottom end torque and overdrive is only good for going down hills now. There is no noticable difference in how either of our trucks idle when compared to a factory engine. You will have to go to a different fuel injection setup if you want this idle which spells more mods and more $$$, or else a carburator, but I don't know what your emission requirements are. I think my cam is 50 state legal.

[JohnnyR17]

Brokengear is absolutely correct.

If you want that rumpity-rump idle, youll need a camshaft that is not well matched to your stock components. Low end torque will suffer and the truck will not have enough power to pull itself in overdrive. No overdrive = poor mileage.

To answer your question, a comp 270H would definately lope in an otherwise factory 350. I ran this camshaft in an stock, carburated 400ci. It had an mean lope to it, but it was too much cam for the engine. Bottom end was horrible.

To enjoy an engine with a lumpy cam, youll need to match the other components to the camshaft. Good heads, adequate compression, and improved intake and exhaust are all necessary.

Stuff in a big cam and youll probably hate it.
But, the only way to learn is to try it once!