stephenmsweigart

Bought a 502 stroker with the components listed below. The engine was dropped in 1970 4spd manual vette along with a new 850 holly carb...car has had the transmission dropped and checked...also included new motor mounts. The the carb was adjusted and timing set and the engine idles real nice. Took it for a spin and when the rpms exceed 3500 there is a slight engine vibration. The mechanic at this point does not know where the problem is. I'm hoping someone can direct me to any possible situation that would correct my problem. Here is a list of the engine build:


1. THIS BLOCK HAS BEEN OVEN CLEANED(HAS NO RUST OR SCALE), SHOT PEENED, MAGNAFLUXED AND PRESSURE TESTED.
2. THE BLOCK IS FRESHLY BORED AND TORQUE PLATE MOLY HONED TO .060 ALL BLOCKS ARE ALSO SONIC CHECKED TO ENSURE CONCENTRIC CYLINDER WALL THICKNESS AFTER BORING AND HONING.
3. THE BLOCK HAS BEEN LINE HONED, SQUARE DECKED, AND NEW CAM BEARINGS INSTALLED ALONG WITH NEW BRASS FREEZE PLUGS. ALL BOLT HOLES AND THREADS ARE FINE.
4. THIS ENGINE HAS A BRAND NEW SET OF LIGHTWEIGHT, FULLY CNC MACHINED WISECO FORGED RACING PISTONS AND SPEED PRO PLASMA MOLY RINGS ( 5/64X5/64X 3/16 OIL) THESE PISTONS YIELD A PUMP GAS FRIENDLY 10.25:1 COMPRESSION RATIO. WISECO IS AN INDUSTRY LEADER IN RACING PISTONS.
5. NEW KING H BEARINGS FOR RODS AND MAINS, ROD AND CAMSHAFT BEARINGS WERE INSTALLED. THE CAMSHAFT IS A NEW ELGIN INDUSTRIES E1143P AND WITH A TRUE CLOYES DOUBLE ROLLER CHAIN SET. THIS CAMSHAFT IS A HYDRAULIC LIFTER GRIND .576 LIFT 246 DURATION @.050 ON BOTH THE INTAKE AND EXHAUST AND IT IS GROUND ON 108 DEGREE LOBE SEPERATION. THIS CAMSHAFT HAS A DISTINCT LOPY IDLE AND IS DESIGNED TO MAKE MAXIMUM POWER IN THE 2500-6500 RPM RANGE. INSTALLED ALONG WITH THE CAMSHAFT IS A NEW SET OF ELGIN HYDRAULIC LIFTERS.
6. RODS ARE BRAND NEW PRO-COMP ENTERPRISES FORGED STEEL H BEAM CAP SCREW WITH 7/16 BOLTS AND FULL FLOATING WRIST PINS. THE RODS ARE 6.385 (STOCK ROD LENGTH IS 6.135) THESE RODS ARE .250 LONGER THAN STOCK. THE INCREASE IN ROD LENGTH PRODUCES LESS SIDE LOAD ON THE PISTON WHICH RESULTS IN LESS FRICTION AND GREATER HORSEPOWER AND TORQUE THROUGHOUT THE RPM RANGE.
7. THE CRANKSHAFT IS BRAND NEW AIRCRAFT QUALITY CAST STEEL SCAT CRANKSHAFT.THE CRANKSHAFT IS SHOT PEENED FOR STRESS RELIEVING AND HAS A FULL .125 RADIUS ON THE MAINS AND ROD JOURNALS!, THIS CRANKSHAFT IS ALSO INTERNALLY BALANCED AND IS THE BEST OF THE BEST!!(4.250 STROKE, 1/4 INCH LONGER THEN STOCK 454), FRESHLY MICROPOLISHED AND STANDARD ON THE ROD AND MAIN JOURNALS. ENGINE IS INTERNAL BALANCED. USE NON WEIGHTED BALANCER AND NON WEIGHTED FLYWHEEL.
8. THIS ENGINE IS FULLY BALANCED ON OUR NEW RMC COMPUTER BALANCER AND IT IS ALSO BLUEPRINTED. PISTONS, RODS AND CRANKSHAFT ARE BALANCED TO LESS THEN 1 GRAM. ( MOST MACHINE SHOPS ONLY BALANCE TO A 5 GRAM SPREAD) BEARING CLEARANCES WERE SET AT .002 ON BOTH THE MAINS AND RODS.
9. THE CYLINDER HEADS ARE NEW RECTANGLE PORT HEADS WITH 320CC INTAKE RUNNERS AND WITH D PORT EXHAUST PORTS FOR THE BEST RECTANGLE PORT BBC CHEVY HEAD!!. HEADS HAVE BEEN ASSEMBLED WITH NEW SET OF 1 PIECE STAINLESS STEEL SWIRL POLISHED SEREVE DUTY QUAL CAST VALVES (2.25 X 1.88). THESE VALVES ARE 11/32 STEM AND .250 LONGER THEN STOCK, A NEW SET OF DOUBLE SPRINGS AND CHROMOLY RETAINERS WITH HARDENED LOCKS AND A NEW SET OF PC SEALS. THESE HEADS ALSO HAVE NEW ALIUMIUM OR STAINLESS STEEL 1.7 RATIO FULL ROLLER ROCKER ARMS, NEW PUSHRODS, NEW ROCKER STUDS ,GUIDEPLATES AND A NEW SET OF CHROMALLOY 12 POINT CYCLINDER BOLTS WITH TEFLON TAPE. .PAN, BALANCER,TIMING COVER AND PUMP NOT INCLUDED.

427Hotrod

Does it happen when you rev it in neutral or only when moving?

It says it's internal balanced (but it's a cast crank)...so it can't use a 454 flywheel or balancer. Must use a plain flywheel like a 350 or 427 would use.

If it does it in neutral you can remove belts and eliminate anything rotating on front of engine. Past that it's likely an engine balance issue.

A 502 is actually a big bore 454 since it uses a 4" stroke crank. Really not a stroker. Hard running engines when things are right. You're going to have fun!

JIM

CanadaGrant

"USE NON WEIGHTED BALANCER AND NON WEIGHTED FLYWHEEL."

Are you using a balancer and flywheel for a 427 as that is what your engine will require. 454 units will throw the balance off as they are for externally balanced engines.

sparky77

Is the harmonic balancer for a internally balanced engine,just a thought.They are available both ways.


CanadaGrant you type faster than I do.

ddawson

Center Force clutch??

Everything I read shows it was balanced to within a gram and used a neutral flywheel and balancer.

Many people complain about the Center force causing a vibration.

Tiger Joe

I'm going to fully admit I was a total idiot once and accidentally put the wrong flywheel on a 454 and it did very similar.

I'd be checking flywheel and balancer

Big2Bird

Junk. No other words. Mc Leod, good stuff.

stephenmsweigart

What I would like to know is if anyone who has installed a 502 has used other that a 454 flywheel and balancer??


thanks
steve

Danish Shark

Maybe I misunderstand what you are saying but you can't use a 454 flywheel and balancer on your engine.

From the description (sounds like Skip White?):
"ENGINE IS INTERNAL BALANCED. USE NON WEIGHTED BALANCER AND NON WEIGHTED FLYWHEEL."

So the answer to your question would be "they all did".

427Hotrod

Normally a 502 as built by GM would use external balanced flywheel and balancer. But this one was assembled as an internal balanced motor...so if you used a 454 flywheel with the added weight on it.....you've found your problem...and need to fix it before you wound some bearings are crack a crankshaft.

JIM

forman

If the center force is not balenced with the motor you might have problems

Darinm

I used a centerforce clutch as well. When i told this to my engine builder, he requested i give it to him for the balancing phase. He balanced my engine without it, then added it on, had to add weight to the pressure plate until it was back in balance. So yeah, they don't seem to be very well balanced.

427Hotrod

I have to say I've run a Centerforce DF in my car with the 427 as well as through the 700+HP range on the 540 and I never had any vibration issues. The thing worked very well considering what I was throwing at it. I gave it to a buddy who's still running it behind his 7000 RPM 388"...and has been for years with no issues. Not saying folks didn't have troubles with some...but I don't think it's as widespread as it may seem.

I've never balanced a pressure plate to a motor.


JIM

forman

im just going by what my engine guy told me to do and i have no ,,no vibration problems what so ever ,,, he told me its a common problem