shwine617

My friend has a 383 stroker and needs a crank damper and flywheel. He has a flywheel and damper from a 350, but I am pretty sure that you need a different one for the 383, but I may be wrong. Also, how can you tell for sure that it is a 383? Any help would be great.
thanks

Damon

If you're talking about a typical "street" 383 that is externally balanced, then yes, you need a different dampener and flexplate/flywheel.

For 86-down engines that use the old 2-piece rear main seal you use the dampener from a 400ci small block Chevy- pick a year- 1972, 1975. They're all the same. 8" diameter, has an obvious counter-weight to it that you can see if you look inside it from behind. Flywheel/flexplate ditto. Old 400 stuff of any year. All the same. Obvious counter-weight welded onto the outter diameter. These will be the larger diameter 168 tooth design so make sure your starter is designed to work with a 168 tooth flywheel/flexplate.

87-up (bot NOT LT-1 engine) 383s you still use the 400-style dampener on the front but you need a SPECIAL counterweighted flywheel/flexplate to work with the one piece rear main seal used in 87-up blocks. It's like an old 400 flywheel/flexplate but the hub is designed to fit the back of the different crank used in a one piece rear main block. In short, it's an aftermarket-only piece. There were no 400ci one piece rear main engines ever from the factory (400s were not produced after about 1976).

Word on caution: 87-up non-LT1 engines from the factory already use a counter-balanced flywheel/flexplate. They are easy to pick out- the counterweight looks like a set of "bird's wings." However, it does NOT have the right amount of counterweight or in the right location to work with a 383 stroker. It's a head-fake. Don't use it. Aftermarket is the only way to go for a flywheel/flexplate for an 87-up one piece rear main stroker motor.

shwine617

Its the 69-80 350 block, manual trans. So can I just use any damper and flywheel from a 400 crank? Also is there any way I can tell for sure that this is a 383 stroker? And if the flywheel doesn't have 168 teeth, then its not the right one?And if it does have 168 teeth can it still be the wrong one?
Sorry for so many questions, I just want to make sure I don't mess anything up.
Thanks for all the help!
Cory

OldSStroker

Checking to see if it's a 383 or a 350/355:

The positive way is to pull a head and measure the stroke.

If the crank is out of the engine you an measure it fairly easily by putting it in the block with 2 bearings, reaching down the center of the bore with an ruler or scale. Measure to a rod journal with the crank at bottom of stroke, then again at top. Subtract the measurements. It should be 3-3/4 inches for a 383, or just under 3-1/2 inches for a 350/355. A ruler is accurate enough to determine that.

If the engine is apart there a number of interesting ways to determine it's displacement. Anyone think of a way if you just have a piston and rod to work with?

shwine617

The motor is already together, is there any way to tell when the motor is together with no damper or flywheel on it. I already know its bored 30 over because it said it on the piston when the heads were off.
Thanks again
Cory

OldSStroker

A local circle track or NHRA drag strip may have a "P&G Meter", device that measures displacement with air put thru the spark plug hole. They call it "pumping the engine".

Here's an explanation from NHRA:

Q. Why don't you have any engine displacement or pounds per cubic inch rules?
A. The minute a displacement rule is imposed, even if it is a simple "maximum displacement" limit, all qualified cars must be verified BEFORE first round of eliminations. We do not do the winner and runner up in NHRA, we make sure all the qualifiers are verified before eliminations. There are only two methods of checking displacement at present. One is to pull a head and physically measure bore and stroke. The other is to use the P&G meter, or "pump" as we call it. This requires disabling the valves on a cylinder and turning the engine over. While this is a simple deal on a two-valve, pushrod engine like a small-block Chevy, it requires physically removing the cams on most overhead cam engines. Neither option is particularly appealing with an overhead cam engine, especially in the dark on a Saturday night in the pits. Eventually, we will have displacement rules, it is inevitable. But hopefully some innovative engine builders out there will help us develop new, user friendly tools with which to enforce them.

Damon

Yes, you can use the dampener and flywheel/flexplate from any 400 SBC engine. They were the same diameter and used the same amount of counter-balance throughout all years the 400 was produced. ALL 400 flywheels/flexplates were the alrger 168-tooth type. None came with a smaller 153 tooth-style flywheel/flexplate from the factory.

I always cringe when I use the word "ALL" because there's always somebody with some weird combination that doesn't fit the rule. But for all intents and purposes the answer is YES, ALL 400-style balancers and flywheel/flexplates will work.

Damon

And now for the fun stuff..... Figuring displacement from just a piston and rod.

Required assumption #1: The piston is going to be at zero deck height at TDC.

Required assumption #2: We know the block's deck height from the center of the crank to the top of the block's deck

1 Measure the piston's wrist pin center height from the true top of the piston (minus and domes or dish) to the center of the wrist pin. To do this measure from the true top of the piston (not the dish or dome) to the top of the wrist pin bore. Take that measurement and add it to exactly 1/2 of the measured wrist pin diameter. That's your wrist pin height number.

2. Measure the rod's center-to-center length. Similar to the wrist pin height measurement, measure from the top of the big end to the bottom of the small end. Add 1/2 of the big end diameter and 1/2 of the small end diameter. That's your rod length.

3. Add the wrist pin height and the rod length. That will give you the total distance from the center of the big end of the rod to the top of the piston. We'll call this the "reciprocating assembly height," for lack of a better tem.

4. Knowing from assumption that the piston is at block deck height at TDC we can now calculate the stroke. Take the "respirocating assembly height" number and subtract it from the known block deck height. Multiply the result by 2 and that's your stroke.

5. The bore? Easy. Measure the diameter of the piston.

6. Take 1/2 of the bore diameter and square it (multiply it by itself). Then multiply the result by pi (3.14159). Then multiply the result of that by the stroke and that's your displacement for that cylinder.

7. Multiply that by the number of cylinders and that's your total engine displacement.

Ta da! Magic. That was fun. I never did it from that starting point before. Not bad considering I've got 5 of Anheuser Bush's finest running through my veins right now, eh?

I'm wondering if there's any way to factor out either of my 2 assumptions. I can't think of a way to do that right now, but I'm not really the brightest bulb on the Christmas Tree.