3.8 cam?

[montess408]

hey guys i am looking to get a cam for my 3.8 its mostly stock. it has headers going to a single 3inch exhaust.i have a 4bbl intake and q-jet to go on it.
the car has a th350c trans.and i am going to change the gears to 3.42 or something close.

thanks.

 

[ek02]

The first thing to think about is the valve guides on your heads. Any cam having over .420-.450 lift lift at the valve will cause the retainers to hit the valve guides and seals. The heads will need to come off and have the tops of the guides machined and new seals installed. That leads to another problem. The stock exhaust valves do not use seals and have a groove in the stem that will tear up a seal. You will need aftermarket exhaust valves with no groove. That being said, you can go for a cam like a Comp252H. It has .425 lift and 206 duration @ .050 lift with a 110 degree center line. It will idle smooth and will not need the guides cut. If you get the heads done for a higher lift cam like the 268H which is 218 @.050, .469 lift om a 110 centerline, it will idle a little rough and the power band is 1800-5800. The 260H is also a good cam with 212 @.050 and .456 lift with a 110 LSA and will idle a little better. If you have A/C you may need to use an idle solenoid to kick up the idle when the A/C is on. If you cut the guides, you might as well pocket port the heads. Grind out the restriction right below the valve seats. There are a lot of cams available from many different manufacturers. Just keep in mind that the more duration, the less bottom end you will have. The higher the lobe separation angle, the better the idle. The lower the LSA, the rougher the idle, but it will have greater mid range power to go with the high RPM power because it has more overlap which creates more cylinder pressure. With you current setup, I would go with the 252H. If you cut the guides and pocket port the heads, go with the 260H. Go on line and see what other cam companys offer. Keep the LSA 110 or above. You need a higher stall speed converter to run a 108 LSA and a vacuum cannister to help the brake booster. Use a spring loaded bearing type cam button from Full Throttle or TA. Do not use a turbo cam in an N/A. Someone else on here can probably give a good recommendation other than Comp.

 

[montess408]

so anything over a 450 lift i will have to mod the heads .what power does this motor make ? and how much will a cam swap give me ??

thanks

 

[ek02]

The old Kenne Bell Mark 1L cam had .420 lift and would work without cutting the guides and the stock springs could be used, so it looks like the 252H would be your best bet at .425 lift. It is very similar to the KB grind, which showed a 14 rear wheel HP gain over the stock cam on a test. If you go any larger and have to pull the heads, the springs and retainers should also be changed. Comp has what they call a K kit that has cam, lifters, springs, retainers, valve stem seals, and a standard timing chain and gears. I would probably go for a roller chain instead of the standard timing set. You should remove the chain tensioner with a roller chain. It may chew it up. I would go for the 252H if you don't cut the guides. If you pull the heads and cut the guides, pocket port them, and replace the springs and retainers, I would use a cam similar to the 260H. You will probably get about 200 HP out of your combination with the 260H. The 3.8 only had about 110 HP stock. If you go to a more radical cam like the 268H, you will loose some low speed driveabilty, but it will sound like you have a cam. Be conservative with your cam choice unless you can live with an engine that idles poorly.

 

[montess408]

i can live with poor idle no problem. but i am looking to make as much low end torque. as i have to move a 4500lbs car.
would a 4.1 give me alot more power to start with ? i can probley get one of them.

 

[ek02]

If you can get a 4.1 you could take your time and build it right, then swap it in. The 4.1 will run better than a 3.8 in a N/A vehicle, plus, the 4.1 has the turbo crank if it is original. With more cubic inches, you can go for a hotter cam and idle better than a 3.8 with the same cam. Consider a higher stall speed converter also since you would have the engine out. A 2000-2500 RPM stall speed converter will help get the heavy car moving. With the intake and carb you will be using, and a good cam, you can make about 225 HP. If you rebuild the short block, you can get some higher compression pistons too. The Jim Ruggles Buick V6 Performance Guide printed back in the 80's details a 4.1 build using the carb and manifold you have. You may be able to find a copy on E-Bay. If your car is running ok now, I would drive it as is and build the 4.1.