High Temp's with SL/6 (.060 oversize)

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mydart270

myDart270
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folks:

still trying to understand high temps w/ my Dodge Dart 270 SL-6/ rebuilt with 0.060 oversize pistons and rings. Motor sat for some 20+ years, fired right up, and w/ new carb, new distributor, and fuel pump, new water pump (NAPA), runs great. Timed at 0TDC, dwell at 42 deg, re-cored OEM rad, valves adj at 0.010 INT and 0.020 EXH. Spark plugs at 0.035 per spec. Stat is 180 dF. A/F screw set w/ vacuum gauge (highest reading 18 Hg at manifold).

Here is my problem. At idle and in driveway, TEMP meter will climb to about "P" on meter. I don't think this right. When driving I also see TEMP meter stay at about "P", sometimes just below HOT range on meter. It may come down a bit but it likes this area on gauge. Seems high too me.

I see a TEMP diff of about 20 deg on INLET and OUTLET of rad. This seems low. INLET at rad is 192 dF. No springs in bottom hose, will reinstall today plus pressure test although I don't see any 50/50 anti-freeze on ground or on frame. Will swap TEMP gauges also today, maybe OEM is reading HI. AMP meter is at "center"

Could 0.060 oversize be the culprit? Too much heat created? Sidewall thickness compromised?? Rust in the coolant passages? System drained and cleaned 2x with clean-out. Will try a "loaner" rad today from PRO that is almost a "look-a-like" to OEM. Car is totally restored and pretty w/ SL-6 but HIGH TEMPs bother me.

Any help appreciated. You guys are the best and know MOPARs. I am still new to old cars and love Dodge Darts. Thx again...
 
timing is retarded. specs are like 10-12 degrees. back in the day we used to "turn them all the way up" or, as far as the slot in the adjustment would allow.
 
Sounds like you are checking temp with a gun. Before I went into the dash I would want to confirm the actual temp by removing the sender and installing a mechanical guage.
 
Boost the timing.
The rad isn't losing enuff heat.
The rad should lose 30 - 50*+. Go check the inlet/outlets on your daily driver.
You said it was re-cored, was this recently, or a while ago?
Get he rad pressure flushed IMHO, then re-check temps
 
0.060" over size is not the issue. Especially at drive way idle.
Timing - as said before.
Radiator clogged- as said before or too much paint on fins? It takes a lot to over heat a /6/
Lower hose clasping (is no spring internally) When free revving in driveway does the lower hose suck together?
Engine running lean? possibly.
Fan belt slipping?
Exhaust clog? (stretch but has happened)
use an external gauge besides a heat gun. I've seen those fail as well. Especially Harbor Freight ones.
Not much more externally- you may have a bad thermostat. Chinese junk made for a lot of them; it could be stick at idle water flow but opens a bit when driving and more flow from water pump forcing it open.
Keep us posted on results.
Joe
 
0.060" over size is not the issue. Especially at drive way idle.
Timing - as said before.
Radiator clogged- as said before or too much paint on fins? It takes a lot to over heat a /6/
Lower hose clasping (is no spring internally) When free revving in driveway does the lower hose suck together?
Engine running lean? possibly.
Fan belt slipping?
Exhaust clog? (stretch but has happened)
use an external gauge besides a heat gun. I've seen those fail as well. Especially Harbor Freight ones.
Not much more externally- you may have a bad thermostat. Chinese junk made for a lot of them; it could be stick at idle water flow but opens a bit when driving and more flow from water pump forcing it open.
Keep us posted on results.
Joe
[SOLVED]...It's the Radiator
Early results show TEMP at mid-range and staying at this level after 30-45 mins driving at 40-50 mph plus stop and go traffic. I also installed a new t-stat (180 dF) from O'Reilly (MURRAY Ultra and made in Israel). Now some fine tuning on carb and back to org rad w/ OEM p/n. Rad on-board has been re-cored but a/t lines are totally realigned and lots of tension.....not good. Will ck temp's today at rad TOP and BOTTOM but return hose to water pump "icy cold"....this is good.

It could have been the t-stat but I have had 3 installed...all from NAPA. Dwell is at 41 deg, timing at 0 TDC, will adjust to 5 BTDC based on consensus of forum. Idle at 700 rpm, must ck a/f setting, plugs appear rather "rich", not healthy "light brown". Plugs are Autolite 66. Valve lash set right on at 0.010 IN and 0.020 EX when hot. Total mileage after rebuild less than 500 mi and engine started in 2014, built in 1995.

thx for recommendations, suggestions, and "things to try" for overheat issue. All were helpful. Long live SL-6s and Dodge Darts
 
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