help on pistons and piston rings for 351W?

nitequill · Jan 8, 2007

Hello guys im rebuilding my first engine and need help on pistons and piston rings for 74” 351W? First should I replace my pistons? Is this nessacery? They look to be in good shape; second piston rings, I was watching a do it yourself video and the guy was using Keith Black rings which needed to be filed to fit. Is there any rings that I could buy that do not require me to file them? Or do I even need to replace my rings?

gt500lw · Jan 8, 2007

If the pistons look ok than you don't need to replace them. Depends on what you are doing with the car. As far as the rings go...I never used the rings you are talking about, and I had never heard of filing down the rings to fit.

If you have bored the cylinders out at all than you would need new pistons and appropriate rings.

classic boost · Jan 8, 2007

gt500lw said:
... and I had never heard of filing down the rings to fit.

seriously?!? umm, very common. ALL rings should be checked and filed if needed.

rbohm · Jan 8, 2007

it is mire than just the pistons that need inspection, the cylinder bores also need checking for taper and out of round. more than about .005" of either and you really should bore the cylinders to make them straight and round again.

for piston rings, if you choose to use the same pistons, you can get a set of rings that dont need gapping per say. but as indicated you do need to check the ring gaps to see if they are in spec.

gt500lw there are two types of rings sold, those that are gapped close to spec from the factory, and those that need gapping as they are designed to be custom gapped by the engine builder.

nitequill · Jan 8, 2007

If the rings need to be gapped, is there a standard I should follow?

rbohm · Jan 8, 2007

nitequill said:
If the rings need to be gapped, is there a standard I should follow?

yes there is a spec for ring gap. any repair manual worth anything will give you the spec you need.

nitequill · Jan 8, 2007

thanks

classic boost · Jan 8, 2007

the instructions included with the rings will give you the specs.

ratio411 · Jan 8, 2007

If you don't put in new rings and refresh the crank and bores to some extent, you are not rebuilding the engine.
You are just disassembling it and putting it back together.

Now, I am going to offer some advice since you are working on a 351w...

Instead of turning the crank, pay just a little more and get a cast 3.85" stroke crank.
Then, instead of buying new 351 pistons in .030" over, buy cheaper 302 pistons in .030" over. (get the block cleaned up .030" over, of course)

These two mods will go back together just as stock, however you will have about 42 more cubic inches. 393w instead of 351w for only slightly more dough than turning a crank and using 351 pistons.

Dave

jb1dsl · Jan 9, 2007

ratio,
Does the block have to be clearenced for this setup?

milner351 · Jan 9, 2007

Nope!

I have a scat 3.85 crank, I went with DSS pro lite pistons and H beam rods for this combination, but, even with a stock 351w rod and stock replacement 302 piston, you don't have to worry about grinding the block.... at least I didn't.

Italian-LX · Jan 9, 2007

milner351 said:
Nope!

I have a scat 3.85 crank, I went with DSS pro lite pistons and H beam rods for this combination, but, even with a stock 351w rod and stock replacement 302 piston, you don't have to worry about grinding the block.... at least I didn't.

I agree.

I just finished my 351w with a 4.100" stroke and my block didn't need clearing. My block is a D2 (1972).

ratio411 · Jan 9, 2007

milner351 said:
Nope!

I have a scat 3.85 crank, I went with DSS pro lite pistons and H beam rods for this combination, but, even with a stock 351w rod and stock replacement 302 piston, you don't have to worry about grinding the block.... at least I didn't.

The beauty of this particular stroker is that it only adds a little to the cost of a stock rebuild...
I see you took it to the max though!

classic boost · Jan 10, 2007

if he's not upgrading heads, intake, and cam, then the 393 route isn't that good of an idea. the engine will hit a wall before 4,000 rpms.

302 coupe · Jan 10, 2007

but it will be a torque monster off idle, lol.

classic boost · Jan 10, 2007

302 coupe said:
but it will be a torque monster off idle, lol.

if he's going to pull a camper with his stang, he'll be on the right track.

nitequill · Jan 10, 2007

my 351w is going to be a daily driver, i upgraded the carb, intake and cam slightly but not much... i dont want to pull a camper and not trying to beat everyone on the street just the 350 buick butthead friends of mine

ratio411 · Jan 10, 2007

paul302 said:
if he's not upgrading heads, intake, and cam, then the 393 route isn't that good of an idea. the engine will hit a wall before 4,000 rpms.

I don't agree.
40+ more cubes for maybe 200 extra bux on the rebuild...
Can't beat it.
If you keep a 2v and stock cam on a 351 it hits that same wall.
So what's the difference?
By your reasoning, they never should have used the 289/302 design and made the 351w to begin with.
Most of them had heads, cam, exhaust, and intake same-same as any smogged 302.
Agree?

gt500lw · Jan 10, 2007

Hey, go back to this gapping thing. I have built about four engines (new rings and all that good stuff). I have also helped my dad rebuild engines. He has been a mechanic for over thirty years. This is the first time I ever heard about gapping your rings, other than checking the gap of the old rings that you are pulling out.

Italian-LX · Jan 10, 2007

gt500lw said:
Hey, go back to this gapping thing. I have built about four engines (new rings and all that good stuff). I have also helped my dad rebuild engines. He has been a mechanic for over thirty years. This is the first time I ever heard about gapping your rings, other than checking the gap of the old rings that you are pulling out.

Who picked your rings out? Certainly anybody who has done any kind of ring "shopping" has heard of file-fit rings.

Ask your machinist -- I bet he has heard of them.

. . . if not, then you may want to find yourself a different person to do your machine work.

help on pistons and piston rings for 351W?

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