Compression...
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
You worry too much 'bout that thing.
Compression numbers within 10% is ok Muddy and using the worst math to figure yours is still only 8% variation ([162-150]/150). Blocks under go distortion from years of thermal cycling - thats why seasoned blocks are great blocks once machined as most of the dimensional shifting is done.
But for a 6,200 vibration peak i would look elsewhere. Is it 6,200rpm each gear/speed? Can u swap in a different dist? Carb? Intake?
Myself rather than tear into a fresh rebuilt engine i would avoid 6,200rpm and just rev through it or shift at 6,100rpm. Could be something in the engine balance or just a harmonic that shakes the timing-set at 6,200rpm?
IMHO a compression imbalance large enough to vibrate the engine would vibrate at nearly all rpm and if was really bad enough worry about u would be able to identify it.
BTW try a Fluidampner/StreetDampner? Thats it's job to reduce crankshaft vibration onto the vlv train and i really like my StreetDampner.
cardo0
But for a 6,200 vibration peak i would look elsewhere. Is it 6,200rpm each gear/speed? Can u swap in a different dist? Carb? Intake?
Myself rather than tear into a fresh rebuilt engine i would avoid 6,200rpm and just rev through it or shift at 6,100rpm. Could be something in the engine balance or just a harmonic that shakes the timing-set at 6,200rpm?
IMHO a compression imbalance large enough to vibrate the engine would vibrate at nearly all rpm and if was really bad enough worry about u would be able to identify it.BTW try a Fluidampner/StreetDampner? Thats it's job to reduce crankshaft vibration onto the vlv train and i really like my StreetDampner.
cardo0
Thread Starter
Melting Slicks
Joined: Jan 2005
Posts: 3,347
Likes: 9
From: Salinas Ca.
Originally Posted by cardo0
Compression numbers within 10% is ok Muddy and using the worst math to figure yours is still only 8% variation ([162-150]/150). Blocks under go distortion from years of thermal cycling - thats why seasoned blocks are great blocks once machined as most of the dimensional shifting is done.
But for a 6,200 vibration peak i would look elsewhere. Is it 6,200rpm each gear/speed? Can u swap in a different dist? Carb? Intake?
Myself rather than tear into a fresh rebuilt engine i would avoid 6,200rpm and just rev through it or shift at 6,100rpm. Could be something in the engine balance or just a harmonic that shakes the timing-set at 6,200rpm? IMHO a compression imbalance large enough to vibrate the engine would vibrate at nearly all rpm and if was really bad enough worry about u would be able to identify it.
BTW try a Fluidampner/StreetDampner? Thats it's job to reduce crankshaft vibration onto the vlv train and i really like my StreetDampner.
cardo0
But for a 6,200 vibration peak i would look elsewhere. Is it 6,200rpm each gear/speed? Can u swap in a different dist? Carb? Intake?
Myself rather than tear into a fresh rebuilt engine i would avoid 6,200rpm and just rev through it or shift at 6,100rpm. Could be something in the engine balance or just a harmonic that shakes the timing-set at 6,200rpm?
IMHO a compression imbalance large enough to vibrate the engine would vibrate at nearly all rpm and if was really bad enough worry about u would be able to identify it.BTW try a Fluidampner/StreetDampner? Thats it's job to reduce crankshaft vibration onto the vlv train and i really like my StreetDampner.
cardo0
Thanks for the reply! I like the idea of the Streetdampner...I'll look into it In reference to the vib @ 6200... that's just where it starts... it increases as the RPM increases. I can also relate to, (within 10%) guide line for compression between cylinders. My concern is.. its basically all on one side of the engine. Muddy 
