Technical chevy 350 153 to 168 interchange

Hi all - Im sitting with an older 350 153 tooth flywheel and want to convert to the 14" - fyi this is not in a car so no tranny/fitment issues.

Will the 14" bolt in? I have starters for both sizes too - Just curious, I think the 350 is externally balanced so the flywheel "should" bolt in right? I know the pre 86 chevys had 2 sizes, 153 (12.75"0 amd 168 (14") on the same crank bolt pattern (3.875 iirc?)

Also - how do the newer starters work on both size flywheels? or am i wrong in that assumption?


Thanks!

 

How about a casting number off the block or an engine ID off the right front of the deck surfaced to give us an idea of what year make and model was talking about

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The pre86 are internally balanced except the 400,and big block 454.

 

The 86-up 350 is external balance, the earlier ones are internal.

Which starters? the aftermarket "high torque mini starter"? The original GM starters only fit one size of flexplate. They either have the two holes in line, or staggered.

 

sorry dont have casting numbers but the motor is def old style (long/short bolt - straight/not staggered) - the starters are not to much of an issue.. if internal then that means the flywheel balancing shouldnt affect it? I could use an aftermarket started if needed -

So balancing wise ill be ok - i can figure the rest out i guess- i have a few starters lying around

 

There are flywheels that have a counterweight built into them, and there are ones that don't.

There was only one pre-1986 small block Chevy that had a counterweight built into the flywheel (or flexplate), and that was the 400. Now, a lot of 400-cranks made it into 350s, to turn them into 383 strokers, so there is that.

You absolutely MUST NOT use a flywheel with a counterweight on a pre-1986 SBC.

A non counterweighted flywheel should be zero-balanced. You may see shallow holes drilled in the back side, to remove material, to make sure it runs true.

Only aftermarket mini-starters can be used with both flywheel patterns. The tooth pitch is the same, so the gear works on either. Aftermarket mini-starters have straight across mounting bolt holes, and more than one set, so they can be mounted in two different distances from the crank center line, to accommodate different flywheel diameters.

Here, you will see two pairs of mounting holes:

 

Note, I am not sure what diameter these flywheels are, but it shows how to tell them apart:

If you see this:

That is a built-in counterweight. Don't use that on a 350. It will fit, but it will shake itself to death.

These are the aforementioned shallow drilled holes for balancing:

Those will be anywhere necessary to achieve balance.

 

tx gimpy! ill have a look - much appreciated. This is in a boat (just a chevy 350).. tx for clearing that up!

 

Incidentally, the straight across starter bolt pattern is not the old-style. Prior to 1960, the SBC only had the staggered bolt pattern, as they only had 168-tool flywheels or flexplates.

Later blocks were dual-drilled. Single-pattern drilled blocks are a later cost-saving measure. Every procedure costs money. If drilling that hole, for no reason, cost $1, over the lifetime of a produced part, you could be looking at millions of dollars in wasted money.

 

finally got starter in yesterday - no idea but they must have used an early style long/short delco style block cos thats the starter i needed. All running gr8 again - thanks for the info!