Just talked to the local machine shop and talked to the guy about a rebuild. Now I'm in collage for auto tech and know a few things to talk with some understanding. He was telling me that even a few upgrades 6000 rpm is not a number that a buick 350 can be spin up to safe and still have long life. so i was just wondering what you guys are spining your motors to and what mods were needed?
I've spun my 350 up to and probably past 6 grand quite a bit, and it pulls like crazy. I have the T/A 310 cam, T/A big stainless valeves and ported heads, T/A roller Rockers, Cap screw rods, Crossdrilled crank. For engine longevity tho, I've tamed it back to about 5800 rpm on shifts. Actually I want to program the governor in the trans to shift automaticly around 5500 rpm under full throttle. What your machine shop says does have some truth, Buick motors are designed for low rpm torque, sure you can wing em up to whatever rpm, but its hard on the rods and rod bearings. Ive probably gotten away with it so far because of my crossdrilled crank. I'd feel safer with a max of 5200 to 5500 rpm ceiling on shifts. Remember the factory stroke on the 350 is 3.85 inches, and even tho the Buick Cap screw rods are probably the strongest factory cast rods made, they do have thier limits :3gears: Mark
"Most" engines have more problems with the valve train than the bottom end. Therefore, it's cam choice and valve springs that set the RPM limit. You want to be able to safely rev past whatever RPM peak power occurs at. How much past peak power depends on your gear spread and the spread between peak power and peak torque--you want to be able to hit the next gear in order to make use of the torque peak. So "redline" depends on power production, which depends on port and carb sizes, which determines the cam, which determines the springs, rockers, and pushrods used. Very complex. For those engines that are bottom-end limited, you have to choose a cam to give you peak power below the actual RPM limit where the rods want to drop out of the pan, and with some safety margin.
I've heard of quite a few guys turning Buick 350s 6K with stock rods and pistons. The above comments about cams are dead on - a stock cam runs out of air at about 4300rpm, and it's pointless to wind it further. Matter of fact, I don't think I've ever been able to rev my 350 to 5K. Frankly, don't need to when it shifts at 4200 and chirps the tires going into 3rd. I've never been real clear on why you'd want to do that to any engine for long, though, unless you're talking a drag racing engine. 6K seems to be a break-point for engine longevity, you're not going to get 100K miles out of any engine that you like to rev that high.
I set my tach redline around 4800...mine is made more for pulling in the truck, but I see no reason to push it above that point. I can still sling mud without going too high with 4:10 gearing :laugh: I do know that @ 6200rpm, when the oil pump goes the motor will only last a little longer...in my case 200 miles ou: Wayne S
