Which is more beneficial - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 06-21-2016, 07:24 AM Thread Starter
 
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Which is more beneficial

Hi all new here in the pontiac world couldnt find the answers i was looking for so thought id ask. First off is it true pontiac motors run hotter than your typical ford or chevy? Next how hot is too hot my wifes 68 catalina runs consistently at 220 with the temp sensor in the head not the intake until yesterday on her way home it got up to 240 stuck in traffic on a 95 day I had her get off the road and tow it home just to be safe. My next question how efficient is an electric fan setup going to be on a stock radiator? An aluminum is on the list of needs just trying to find a reasonable priced one with a good review. Oh and car is 68 catalina 400 auto mild cam and auxiliary trans cooler thanks in advance -mike
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post #2 of 4 (permalink) Old 06-21-2016, 03:29 PM
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Search the overheating threads on this forum. TONS of information. 220 is not overheating....240 is. How accurate is your gauge? If really 240, it should be puking coolant. 80-90% of the overheating Pontiacs I've seen in the past 40 years were not, in fact, overheating. Lectric Limited sells the right temp sender units for these cars. You need a properly clearanced water pump, a good radiator, a shroud, the fan positioned in the shroud correctly, and the right fan. Have never needed aftermarket anything to keep my Pontiacs cool since the 1970's.....but the system has to be in good shape.
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post #3 of 4 (permalink) Old 06-21-2016, 04:10 PM
 
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No truth to running hotter as a rule.

having noted the engine has a temp sending unit in a cyl head, what engine is in the Cat? What casting number cyl heads? have helped many locals sove their cooling issues over the years. Nearly everyone of them had cooling issues due to one on the following:

-engine rebuilt and block not decked. the absolute worst offenders are engines rebuilt with the multi valve relief cast pistons, often used in cheap engineoverhauls. These pistons will be down in the hole, then add the thickness of the head gasket. Result: NO quench. Have examined quite a few such builds, often the carburetion and ignition were thrown together years ago with a POS 1850 Holley or an Edelbrock 1406 or 1407 and either we're combined with a lazy advance curve smog era HEi or a Mallory or Accel Distrib from the '70's. Short timing and rich, long timing and lean, either will create heat problems. Just because Gratiot, or Stupid Shoppes sold it in the 80's and 90's, or Summit has sold it in their catalogue, CHEAP, for the last 25 years does not not make such cheap carbs a good fit.

-Wrong ratio pulleys. AC application PULLEYS when combined as a set, will give optimum cooling ratio. The factory engineers were not STUPID. With factory non AC applicationpulleys onthe engine, one cant just swap one pulley:

- if a '71+ pulley and PS bracket setup is being used, run the common 481038 and 481040 pulleys. PS pulley will be the same,mfactory AC or not. Can't find them priced right, drop me a PM. Have two sealed 55 gal barrels full of '71+ pulleys, do ship outs every week.
- If running an 11 bolt timing cover and tall 11 bolt pump, and the '67-70 PS set-up, run a "128" or "130" wp pulley and a "842" crank pulley. don't have AC with this height 11 bolt pump and with '67-70 PS set-up, can run an extra crank pulley rein ring behind the "842" crank pulley. Make sure, if running this setup, that the PS pump pulley is the large diam '67-70 pulley, not the smaller 5.5" diam non AC version.

Fan clutch...get the engine to operating temperature and warm, the fan clutch should lock up. With the engine warmed up and shutoff, grab the 19" factory 7 blade AC fan and see if it spins slightly. The fan shouldn't, the clutch should be locked up tight. If it spins, on a rel hot engine, need a new clutch. if factory non AC engine and it has a factory 5 blade flex fan, consider swapping on a 19" clutch style factory fan. Not that hard to find, I've personally seen a 25 degree improvement in cooling with just this mod!

In a thread i just read, Jim mentioned yesterday, running full manifold vacuum for the Distrib vac advance. Good advice, need a properly curved distributor utilizing vac advance. Lot of mpg goes out the window, as well as tune ability with straight advance and no vac advance.
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post #4 of 4 (permalink) Old 06-21-2016, 07:20 PM Thread Starter
 
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Thanks for the replies tons of info. I'll try to answer some of the questions as best I can. I have a good original radiator recently flushed motor is an original 400 that was done by a relatively respectable shop in my area makes 413hp at the crank has mallory pro billet hei distributor but unfortunately cheap edelbrock 1406 carb I will have to wait until my wife gets home for casting numbers on the head. As far as timing I will also have to double check that and see where its at my gauge is a new autometer gauge and sensor I do have a nice solid fan shroud no cracks or holes not flimsy at all fan is 18" 6 blade fixed mount sitting between 2 1/2" to 3" from the rad. I should note i changed the thermostat last night with a 180 and today in the same traffic but 103 outside temp the car stayed around 195 200 so im hoping it was just a sticky thermostat but would still like to go over all the possibillities and get this motor to its optimal performance. I did however order a griffin direct fit aluminum radiator because well it cant hurt anything again thank you for the response I hope I gave you the answers you were looking for -mike
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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