Engine Missing
Thread Starter
Melting Slicks
Joined: Sep 2000
Posts: 2,403
Likes: 416
From: Chester Virginia
Engine Missing
My engine, 1973 L-82 w/ automatic, has started running a little 'rough' and has less acceleration. I changed the rotor, cap spark plugs. The idle is 1000 rpm, the timing is 21deg & the dwell is 30deg. After installing the new items it still is running rough. I took the plug wire off the distributor one at a time. There was no speed change when #1 and #4 wires were removed. I put new wires in for these two cylinders. Even after the new wires there was no speed change when #1 & #4 wires were removed. I removed the valve cover on the drivers side and the valves for #1 cylinder were moving as the other three sets of valves. I checked the #1 cylinder for compression and it was 135, similiar to what was checked about three years ago.
Any ideas as to what is wrong or things to check/do???
Roger
Any ideas as to what is wrong or things to check/do???
Roger
Le Mans Master
Joined: Oct 2002
Posts: 7,098
Likes: 378
From: Las Vegas - Just stop perpetuating myths please.
Fuel press and filter ok?
Spark plug color may be key here. All should be light brown - suspect any black or oil soaked plugs/cyls. Good compression should be more like 180psi or higher. If u need to get a leakdown test from Chevy dealer to verify and ask to see results. Any old iron heads over 65k mi are eligable for vlv job. 'Bout $1k for a vlv job but if over 100k mi time for new cam too. I just did a top end and its a truck load of work (if u include headers) so don't be afraid to bring to the dealer - that way u'll have it back in just a week with a warrenty. 
My rough idle cam from a wiped cam lobe (#4 exh) but may not show on compression/leakdown test.
Hope this can help.
cardo0
My rough idle cam from a wiped cam lobe (#4 exh) but may not show on compression/leakdown test.
Hope this can help.
cardo0
Race Director
Joined: May 2000
Posts: 12,712
Likes: 2,264
No way a '73 L-82 with 9:1 CR and the 962 cam would make 180 psi cranking compression pressure. A check of the shop manual will likely yield a spec of less than 150 psi.
All cylinders should be compression checked. An old engine that has no more than 20 psi maximum variation is certainly not perfect, but okay for normal use.
A 1000 RPM idle and 21 degrees timing doesn't sound right.
Duke
All cylinders should be compression checked. An old engine that has no more than 20 psi maximum variation is certainly not perfect, but okay for normal use.
A 1000 RPM idle and 21 degrees timing doesn't sound right.
Duke
