Overheating at idle

[Duke W.]

Re: Overheating at idle

Yes, and the Paragon 396 reproduction fan was a direct copy for the original on a long time NCRS member's car who specialized in 396 (Stewart).

The vac advance on my 396 is a '201 and it doesn't overheat at idle. Fan clutch is a Fred Oliva restoration. BTW, the last I talked to Fred, he'd made progress in his backlog and was quoting 6-month turnarounds.

On 396 rad cap, while the erratta sheet that came with the car says 15#, NCRS and the JG book say 13#--identical to the SB cars.

From later posts in this thread it doesn't sound like there's a bona fide overheating problem here. I see the concern is the temp gauge drifting above 180F during idle (no time period specified) and there is NO report of the rad cap 'popping' with coolant spewing out the overflow hose. So, I'm forced to conclude we don't have a case of 'overheating' to diagnose...

So is the L-78 ported or full time vacuum advance.\

Duke

[Duke W.]

Re: Overheating at idle

Duke,
My radiator part number is 3007436 date 65B. It has a harrison aluminum decal on right side on top. Carb is Holley 4150 list 3124 which is correct for the car. The cap on the expansion tank is a 15 lb RC26 which I believe is for the 327. I wonder if the cap is bad. The highest I have ever let the temp gauge go is half way between 180 and 240 so I guess about 210 but I don't have a IR heat gun yet to document this. While driving, the temp gauage stayed on 180 but after idleing for only about 2-3 minutes and watching the guage slowly build to 210 I shut down the engine and watched 2-3 qt of antifreeze boil out on to the floor. I recently installed a 180 thermostat and removed the 160 that was in there. I also put in G05 antifreeze. I can check the number on the VAC can but I'm not sure where to look. I plan to start the engine today and pull the vac hose off to test for engine RPM decrease and vac pull.
Stan

So your radiator is either the original or a DeWitts date coded repro. If original it could be clogged, but that usually causes overheating under all conditions.

Most auto parts stores have cap testers. It should hold close to 15 psi. With a 15 psi cap and 50/50 glycol-water mix it should not boil until 265F, so either the cap won't hold spec pressure or the temp gage/sender is way off. 210F is within the normal operating range in warm weather low speed driving/idling.

Get the correct fan blade test and make sure the fan clutch tightens when hot. When cold the fan should turn with little effort. After a hot shut down it should be require much more torque to turn it.

You may have to pop the dist. cap to see the number stamped on the VAC mounting bracket.

The best way to check for full time or ported vacuum advance is to tee into the VAC signal line with a vacuum gage. However, you can test by pulling off the vacuum hose and pinching it off. If idle revs don't change, it's ported. If the idle speed drops it's full time.

Either way, since that engine's idle characteristic is basically the same as L-72/71 (14" @ 900 with about 25-30 degrees total idle spark advance assuming full time vacuum advance) it doesn't have enough vacuum to pull a 15.5" VAC to the limit. This can cause idle instablility - loss of speed and stalling if idling a long time. I had this problem with my '63 L-76, which also had the 201 VAC, but only idled at about 12". Once I installed the ...236 8" VAC from the '64/'65 SHP/FI engines, the idle stability problem was solved.

Duke

[Stanley S.]

Re: Overheating at idle

I found the number on the VAC. It is B10. All I had to do was lift the dist cap about an 1". When I pulled the hose off of the VAC with engine running at idle, the engine RPM did drop some and there was significant suction on the hose. I can buy a vac guage to verify how much.

2 days ago when I boiled out about 2-3 qt antifreeze after shutting down the engine with temp gauge showing about 210, I had the impression that the temp would have continued to rise but I could be wrong. The air temp at that time was about 60 deg. Also, I spun the fan with the engine still hot and it seemed to turn at least as easy if not easier as when the engine was cold.

Sounds like I could have multiple factors working here.

I can have the radiator cap tested tomarrow.

Stan

[Duke W.]

Re: Overheating at idle

I don't have any data on the B10. For ten bucks buy and install a B20 or B26.

And I don't know if the L-78 is ported or non-ported vacuum advance until someone tests their L-78 and lets us know.

Duke

[Joe L.]

Re: Overheating at idle

I don't have any data on the B10. For ten bucks buy and install a B20 or B26.

And I don't know if the L-78 is ported or non-ported vacuum advance until someone tests their L-78 and lets us know.

Duke

Duke------


The B10 specs are as follows:

7" vacuum to start the plunger
12 crankshaft degrees @ 12" vacuum
12 maximum crankshaft degrees of advance.

The B10 is equivalent to the GM #1115360.

[Duke W.]

Re: Overheating at idle

Duke------


The B10 specs are as follows:

7" vacuum to start the plunger
12 crankshaft degrees @ 12" vacuum
12 maximum crankshaft degrees of advance.

The B10 is equivalent to the GM #1115360.

So B10 is the same as the OE VAC on L-72, and on Lar's list it's very close to the B30.

I still recommend the B20/B26, which has 4 degrees more advance at the 12" maximum. Since BBs with the original CR might need to run the initial timing at the low end of the recommended range, if not a little lower, four more degrees of vacuum advance will keep total idle timing in the proper 20-30 degree range.

Duke

[Stanley S.]

Re: Overheating at idle

I don't have any data on the B10. For ten bucks buy and install a B20 or B26.

And I don't know if the L-78 is ported or non-ported vacuum advance until someone tests their L-78 and lets us know.

Duke

Duke,
Let me know the proceedure to test for ported or full time and I will test mine.

[Duke W.]

Re: Overheating at idle

I specified the tests in post #17.

Duke

[Ronald L.]

Re: Overheating at idle

On the big block fan blade - have to differ, I have been there and looked at their part versus an original.

The Paragon part is not a direct copy, the rivets are rough and very noticeably different to a casual observer.

Then the issue of exact size - it is a little bigger than the original.

Put them side to side and you will not buy that part if you want to pass a knowledgeable NCRS judge.

There are usually any given week one or two on the flee and they do cost a pretty penny. If you want a good used one PM me.