Alright, I should be tearing up the streets at this point, but I haven't even made it out of the neighborhood.
My engine feels as though it is out of balance. I've tried a number of things to solve the issue, but I'm at a loss at this point. I'm all ears for suggestions, next steps, whatever. This post may be a bit long, but I want to include all the details in hopes someone can pick up on something I'm missing.
Here are the details-
383 stroker engine I purchased in person and we ran it on an engine stand to verify it ran good and all looked/sounded fine
Aluminum 64cc heads
Lunati hydraulic flat tappet cam-
https://www.summitracing.com/parts/lun-60105
Hyper pistons
5.7" rods
Aluminum roller rockers
Edlebrock Performer 2701 intake manifold (new)
Windage tray
7 qt oil pan
Full length headers
Summit Racing external balanced harmonic balancer (called Summit to verify this)
Energy Suspension poly motor and trans mounts (new)
93 octane fuel
Other pertinent parts-
MSD Street Fire ignition box (new)
MSD Billet distributor (new)
NGK BKR7E spark plugs- gapped to .040 (new)
Taylor 8mm plug wires (new)
Holley 4779 double pumper 750cfm carb (new)
McLeod 75224 clutch (new)
PRW external balance, 168 tooth flywheel (new)
New pilot bushing, new throwout bearing, new clutch fork
Muncie M21 4 speed transmission
Above is the current engine setup. When I bought the engine, I removed and replaced the following parts:
Single plane intake
Holley 9381 830cfm carb
Valve covers
SFI external balance flexplate
Electric water pump
When I initially got the engine home, I removed the oil pan to check out the bottom end, etc. Everything looked good. I could still see hone marks on the cylinder walls, windage tray was secure, oil pump looked good, etc. I put a new Fel Pro gasket on and reinstalled the oil pan.
Engine has always had strong oil pressure- about 65psi. It ran rich with the 830cfm carb and was carbon fouling plugs extremely fast. It had big jets, and some other mods done to it, so I replaced it with the 750cfm. The engine starts fine and seems ok at idle. Once you rev over 1000 rpms, you can begin to feel the excessive vibration and it sounds almost like the timing is out of order. I don't hear any weird valvetrain or other engine noise and have no exhaust smoke. I checked the plug wire routing a billion times. I also have a Bluetooth bore camera that I've used to look in all the cylinders and all looks fine.
The static compression ratio is about 11.5:1, but with the ABDC of my cam and our altitude, it calculates to 9.5:1 dynamic compression ratio.
I never removed the Summit harmonic balancer that was on the engine when I bought it. I thought I may have oriented the flywheel incorrectly. But today, I looked up through the bottom opening of the bellhousing and where the crankshaft dowel hole is in relation to the weight I can see on the flywheel, it seems that the flywheel is correctly oriented. I went back and looked at a photo of the flexplate that was on the engine when I bought it and before I removed it and the counterweight on the flexplate looks to be in the same orientation that is now on my flywheel. I've called Summit to verify the harmonic balancer is for an externally balanced engine and I can see/feel the counterweight on the backside.
Any help is greatly appreciated, I'm beyond frustrated at this point.
Daniel