1969 Triumph Spitfire engine problems

IMNERT

MEMBER
1969 TRIUMPH SPITFIRE
4 CYL
2WD
MANUAL
100,000 MILES

My engine recently started rapidly losing power and knocking under the valve cover when under heavy uphill loads. Initially it would return to running fine when the terrain would flatten out. Now it knocks and runs erraticly all the time. I burrowed a compression tester from a friend and found these results. The numbers one and two cylinders were normal compression when tested dry at about 125 lbs. The number three cylinder had zero compression. The number four cylinder had very high compression at about 160 lbs. When tested dry. When tested wet the first two cylinders rose slightly as expected. The number three cylinder rose to just 15 lbs. And the number four cylinder maxed the tester out at 300 lbs. Any ideas?

1 Reply

HMAC300

MECHANIC
48,601 POSTS

You have your #3 cyclilder is bad either from a piston or valve problem. From the knocking you describe I'd say it' a piston problem. If it sounds low in the motor like oil pan it's a rod bearing if high it's probably piston. You can pull the plug wires one at a time to se which cylinder bu the compression on 3 is already bad so it's got to come apart anyhow. Check for scoring and what is called scuffing with #3 at low position if you see that do an engine overhaul