Re: 80 sporty engine noise/vibrationby luvzvintage » Mon Mar 04, 2013 10:01 am
Ok, jugs are off and i have bad scoring on low compression piston and some scoring (same fashion) on good compression cylinder piston. Scoring is present both intake and exhaust sides but worse on exhaust side, fair bit of blowby is evident on piston. Only common denominator is a new Parts Unlimited (deere) rings on top groove of both stock pistons as i had broke originals.
Sooooo........i replaced both pistons. One is an good original with good original rings. The other is an SPI. Prerun compression test gave me 138 per cylinder which is a bit lower than the 150 i got when i originally installed the engine - no big deal rt? Ran the engine with 35 - 1 premium gas/oil for "break-in" and followed break-in procedure (babied it). Actually made a 25 mile trip succesfully!!!!
The following morning i decided I'd do a compression test just to see how things were seating. 3 consecutive tests revealed 170 on stock piston and 135 on SPI !!
Was suppose to run the sled at a vintage display/lap at the Beausejour Ice Ovals that morning but decided against running the engine with such a huge discrepancy in compression.
Both pistons look good as far as wear/scoring goes with good lubrication. I'm going to replace the stock piston with another SPI and see what i get.
170 psi!?? really?!
Lloyd N.
Canadaluvzvintage
Posts: 82
Joined: Sat Mar 12, 2011 10:05 am
Location: Beausejour, Manitoba