For those of you with older engines, realize the role of the excentric (or camshaft) the opens and closes engine valves. Swapping cams is NOT difficult (if you have mechanical experience) and much can be achieve to improve the performance of your engine.Details if you want to discuss this.
Dave
Live every day as though it were your last; someday you'll be right.
Trish Davis wrote: Before anyone goes changing cams, crankshaft first.
Crank is 1/2 the size of the cam yet turns twice as much, twice as fast.
Please, no one say "it's just to turn the engine over" unless you actually realize how much force is needed to turn over a flywheel.
*ALWAYS* replace crankshaft and main bearings at the same time.
Then move on to the cam.
However, look to sloppy connecting rods before the cam.
They must have done a lot of changes to engines since the last one i rebuilt 5 years ago. All i have ever seen the crank is a lot bigger than the cam. JMHO
James (Naomi and Tut the Mutt, Both deceased and missed)
2005 georgie boy Pursuit
Trish Davis wrote: Before anyone goes changing cams, crankshaft first.
Crank is 1/2 the size of the cam yet turns twice as much, twice as fast.
Please, no one say "it's just to turn the engine over" unless you actually realize how much force is needed to turn over a flywheel.
*ALWAYS* replace crankshaft and main bearings at the same time.
Then move on to the cam.
However, look to sloppy connecting rods before the cam.
They must have done a lot of changes to engines since the last one i rebuilt 5 years ago. All i have ever seen the crank is a lot bigger than the cam. JMHO
And the crank turns at half the speed of the cam, not twice.
On edit: OMG, I must be getting old. I actually got this backwards!!!
I guess it's been too long since I did any wrenching.
* This post was
edited 11/26/07 05:07pm by ScottG *
Scott, Grace and Wesly
2003 Dodge 3500 4x4 Cummins (lightly bombed),
2004 Forest River 25RKS many, many mods.
Assuming the crank is ok as on a new engine, the cam shaft can be changed to achieve different valve openings and closings. The sliding cam shaft design allows for valve opening and closing to be change as engine accelerates. But if the older engines needs fixing, I agree, to start at the bottom working up to the cam shaft after checking pistons, valves and lifters. With today's labor costs most people buy a new long block and while your at it drop in a better transmission. Compression test usually tells you what's going on before even attempting to do an engine job.
What he is talking about is performance enhancement, not mechanical failure.
Dave in regards to my other post what would you recommend in a cam?
I’m not real sure what the duration and lift is on a stock 350, it has been a while since I have turned a wrench on a SB Chevy.
Also with that motor being in a MH it is more than likely a 4 bolt main but is the cam different for a stock 350in a MH verses a 350 in a truck or car?
Let's get this straight: (Assuming 4 cycle engines have not been completely redesigned in the last couple of years)
Camshaft turns at half the speed of the crankshaft (Valves open and close every OTHER crank revolution)
Crankshaft is W A Y bigger than the camshaft, probably at least 10 times the weight.
As for the OP's post, cams in conventional engines are not hard to change (provided the lifters can be raised) and can certainly add to the power, but often at the expense of low-end torque. Worst part (on GM engines at least) is dropping the oil-pan in order to get the timing cover off!
Changing cams on a 4-cam DOHC V engine is a slightly more daunting task. May be easier to get at the top end, but synching four cams is a trick!
But before anyone goes making ANY changes to boost engine power they should ensure the bottom end (crank, bearings, pistons) is in good shape first.
Keith J, Retired from GM Engineering
2005 GMC Sierra 2500HD SLE 2WD/CC/SB/DA.
1999 Sunnybrook 27RKFS Fiver
Bilsteins, Line-X, Westin steps, Prodigy, Retrax, 16K Superglide, 5th-Airborne pin-box, Multi-vex mirrors.
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