QuestionQUESTION: Hi Tom,
I need an education regarding timing. Here's the deal, I recently bought a 1951 Plymouth convertible hot rod with a rebuilt Chevy 350 engine. It's been running a bit hot so thinking timing might be a contributing factor, I had a local mechanic check it. He found it was close to 25' before adjusting so he brought it down to 8'. This did slow the idle some and seemed to help acceleration from a stop. No apparent effect on the temp issue so I'll be looking elsewhere for that solution. Now, it seems the engine runs a bit rough at driving speeds, not really "chugging", just kind of rough...not smooth if you know what I mean. I'm thinking 8' might be ok at idle, but the engine should be advanced for driving speeds. Nothing special about the rebuild, not high performance,just stock..Thanks VERY MUCH in advance for any thoughts you can share.
ANSWER: HI JOHN, I WOULD LEAVE THE TIMING AT 20 TO 30 DEGREES [ADVANCED] [[AS LONG AS IT IS NOT PINGING,]] BETTER MILEAGE AND BETTER PERFORMNACE AND RUNS SMOOTHER..DOES THIS HAVE A VACUUM ADVANCE HOOK UP TO THE DISTRIBUTOR ??? IF SO THEN LEAVE IT AT 8 DEGREES AND LET THE VACUUM ADVANCE TAKE CARE OF THAT. PROVIDING THE ADVANCE UNIT WORKS IN THE DIST ??? SHOULD HAVE VACUUM HOOKED TO A TIMED PORT.THIS MEANS NO VACUUM AT IDLE BUT OFF IDLE THERE SHOULD BE VACUUM. YOU SAY IT HAS BETTER ACCELERATION WITH THE TIMING BACKED DOWN..THIS SHOULD BE THE OTHER WAY AROUND. I KEEP MY RACE ENGINES AT 35 DEGREES ADVANCED,BUT I HAVE NO VACUUM ADVANCE UNIT IN MY DISTRIBUTOR .. NOW LETS TALK ABOUT THE TEMP PROBLEM,IS THE RADIATOR GOOD ?? BIG ENOUGH ?? DOES THIS HEAT UP ON THE OPEN ROAD OVER 30 MPH,IF SO THEN EITHER THE RAD IS PARTIALLY PLUGGED OR NOT LARGE ENOUGH OR NOT ENOUGH AIR GOING INTO IT. IF THIS OVERHEATS AROUND TOWN,SAY UNDER 35 MPH POSS THERMOSTAT PROBLEM,CK IT OUT, IF IT IS A 195 DEGREE, REPLACE IT WITH A 165 DEGREE.
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QUESTION: Thanks for the very quick reply Tom. I don't know if there is a vacuum advance or not. What would I see off the distributor is there is? I know a hose was plugged during the test and then re-connected after so I am thinking that might be the vacuum line you're referring to. As for performance, at around 20-30 mph it seems like the car runs like it has a manual tranny (it has a 700r4 automatic)and it was accidently shifted into 4th when it should have been shifted into second, doggy, sluggish. The temp runs about 195-210 on the highway without AC on. These temps aren't real bad. AC will bring it up a little more, maybe closer to 225. In town in stop and go traffic, it holds pretty steady at 210, maybe creeping up toward 225 at most. AC in town will send it closer to 250. Too hot. It does have a 195 stat, I've tried a 160 and a 180 with no noticeable change. The radiator is an aluminum two row and its clean. I am suspicious about the performance of the 16 inch Zirgo puller thats installed. I am thinking maybe a replacement fan might pull a greater amount of air. Air flow is the big player I guess, huh? Hey, thanks again for your help on this!!!
AnswerHI JOHN,YES THIS SOUNDS LIKE YOU GOT VACUUM ADVANCE. THERE WILL BE A VACUUM HOSE GOING TO THE DIST. IF THE TECH PLUGGED IT TO SET THE TIMING THAT WAS IT...I HOPE IT IS WORKING HOWEVER. WOULD HAVE HIM CK THAT TO BE SURE. IF NOT IT WILL NOT ADVANCE AND SATY AT 8 DEGREES. YES YOU ARE CORRECT THIS ENG IS RUNNING TO HOT..IF THE HEADGASKETS AND HEADS ARE OK ON THIS ENG TRY A LARGER FAN TO ALLOW FOR MORE COOL AIR GETTING TO THIS RADIATOR.IS THERE ENOUGH ROOM IN FRONT OF THIS RADIATOR ??? THIS COULD BE A PROBLEM AS WELL. YOU MAY WANT TO TRY A ELECTRIC FAN OR FANS INSTEAD....LET ME KNOW !!
