How much initial timing is too much? Running hot on the highway.

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Downtime!

Downtime!

Better With A Big Block
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Nov 15, 2013
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Location
Keller, TX
Late model 440, older MP .484 cam. New Champion 26" radiator, 185 thermostat and dual 12" fans on a therm switch (on at 195, off at 180, I believe)

Now that's it finally gotten really hot here in Texas (we're in to multiple days over 100, yesterday it was 104), the Scamp is running hot after a drive on the highway. Around town, she'll get up to 195-200 and stay, but on the highway, she'll climb to 210-215 pretty quickly. Decided to check the timing finally, so I got out the old light, and it was dead. Damn, only got 30 years out of that old Craftsman. Couldn't locate a new bulb, so I bought a new light (Actron digital monster with tons of buttons). After finally figuring this thing out, I plug it up, pull the vacuum line off the can, and fire up the car. After pressing the advance button to get the mark back to zero, I look at the number on the screen and to my surprise, it reads 23.2. Assuming the marks on the car are correct, that seems a bit excessive for initial timing. Again, assuming the marks are correct, I adjusted initial back to about 12.5 and the car sounds a whole lot better. Idles better, seems to have a little more pep in her step at lower speeds too. Stayed about the same as far as temp around town, but I didn't get her on the highway yet.

So, does 12-14 sound about right for this combination? If not, where do y'all think she needs to be?
 
I wouldn't run that engine/camshaft combo at 12* initial. The 23* is closer to what I would run. If it starts when hot at 23, run it.

Initial timing should have zero effect on highway cruise temp. You're into the mechanical advance and total timing may be an issue.

Possible the shroud is packing air, restricting flow?

Could also be really lean. Does it surge at all on the highway? Hard to tell without reading a plug or having an A/F gauge installed.
 
crackedback said:
I wouldn't run that engine/camshaft combo at 12* initial. The 23* is closer to what I would run. If it starts when hot at 23, run it.

Initial timing should have zero effect on highway cruise temp. You're into the mechanical advance and total timing may be an issue.

Possible the shroud is packing air, restricting flow?

Could also be really lean. Does it surge at all on the highway? Hard to tell without reading a plug or having an A/F gauge installed.
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remember when 10* was the norm?.i agree ,if it runs good at 23 and starts, run it
 
crackedback said:
I wouldn't run that engine/camshaft combo at 12* initial. The 23* is closer to what I would run. If it starts when hot at 23, run it.

Initial timing should have zero effect on highway cruise temp. You're into the mechanical advance and total timing may be an issue.

Possible the shroud is packing air, restricting flow?

Could also be really lean. Does it surge at all on the highway? Hard to tell without reading a plug or having an A/F gauge installed.
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This would be my number 1 shot if it has a shroud, and even if it does I don't think 2-12 fans is enough for a big block. (not that it would matter on the freeway, but still)
 
The fans definitely don't seem to be keeping up very well, but I didn't really expect them too. They were included in the package though. BeCool has some serious 12" fans I may try on her, would be well over 3000 cfm with them. Their 1000 hp capable setup mounts the fans directly to the core, so I may try that too if nothing else works.

The shroud is not much of a shroud, more of a plate that covers the back of the radiator and provides a mounting point for the fans. There seems to be a pretty good flow of air when the fans are on.

The car starts fine at 23, cold or hot, and I've got the carb tuned pretty well too, so no real bogging or hesitations. It really does feel quite bit stronger in the low and mid range now with initial set at 14 (bumped it up a little bit from this morning).

Car has a new Milodon aluminum water pump (Mancini housing) too. Running out of things to replace of check to get this beast under control. Would really like to be able to enjoy her, even when it's 100 degrees outside.
 
Has anyone raised the back of the hood, or removed the seal back there, to help get hot air out from under the hood? It's pretty tightly packed under there with the big block in it, and it seems to hold a lot of hot air. Can't help but think helping it move some of that hot air out quicker would help some too.
 
Do you have the seal at the front of the hood? It keeps all the air going through the radiator.
 
Retarding the timing will actually make it run hotter. Jes sayin'.
 
I ran my 340 with the .484/284 cam at 17° initial and 36° total.
 
Downtime! said:
The shroud is not much of a shroud, more of a plate that covers the back of the radiator and provides a mounting point for the fans. There seems to be a pretty good flow of air when the fans are on.
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The fans do relatively little at cruise; they cool at low speed and idle, and should be rated to remove lower engine heat output than is generated at cruise conditions. My concern is how you describe the shroud above. If it is a flat or fairly flat plate with holes in it the size of your fans, that is very probably the issue, and is blocking a significant potion of the needed air flow at cruise. Can you please post a pix of that shroud? The only pix where I can a small edge of the shroud looks like a rather normal one, not like you descibe above. Is there a flat plate shroud inside a plastic shroud?

I have jacked up the rear of a the hood on a race car; it helped, especialy when things got slow after running hard and getting a lot of heat in the manifolds, etc. But you need to resolve what is likley a shroud problem first.
 
The shroud is the one that was included in the kit. Didn't really like the look of it from the start, but it's been a long time since I've dealt with a BB Mopar in Texas heat.

IMG_0089r.jpg
 
Hooked up the vacuum gauge and the timing light again after dinner. The highest vacuum reading I could get is 14", and that came with the mixture screws turned in all the way and backed out about 1/2 turn at each corner, and initial timing back up to 21 degrees. It's idling at 900 rpm like this, and actually sounds good, revs good, no bogs at all. Temp climbed to 200 degrees sitting in the driveway.
 
nm9stheham said:
The fans do relatively little at cruise; they cool at low speed and idle, and should be rated to remove lower engine heat output than is generated at cruise conditions. My concern is how you describe the shroud above. If it is a flat or fairly flat plate with holes in it the size of your fans, that is very probably the issue, and is blocking a significant potion of the needed air flow at cruise. Can you please post a pix of that shroud? The only pix where I can a small edge of the shroud looks like a rather normal one, not like you descibe above. Is there a flat plate shroud inside a plastic shroud?

I have jacked up the rear of a the hood on a race car; it helped, especialy when things got slow after running hard and getting a lot of heat in the manifolds, etc. But you need to resolve what is likley a shroud problem first.
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That is exactly what I was concerned about back when crackedback mentioned it, as that design sure would block a ton of hiway air.
 
I have 22 up front on my 340...but that's because that's what it likes. It shouldn't heat up on the highway regardless of fans...my fans are never on when the car is rolling at more than 15 for any period of time.

I have this Ford Contour fan setup on my car...I came up with it last year and several others have used them on small blocks with great luck. Haven't seen one on a big block but I'd guess it would be able to fit.

[ame]https://www.dropbox.com/s/wdvxqfd1tnhcpy3/Electric%20Fan%2026in%20Radiator.pdf[/ame]

There's also a typo. The fan connector is S827 not S287
 
Car has 3.89 gears and a 727 so it cruises at 3500 rpm at 60-65 mph. The last time I had it on the highway, I was still running the 22" stock 318 radiator and the 7 blade factory fan (no clutch).

The shroud is going to have to come off now. I see what y'all are talking about. It's a handy place to mount the fans though, so I might just skeleton cut that sucker and still use it for fan mounting. I had a bad experience before mounting the fans directly to the core using those plastic push through mounts and will not use them ever again.

I've seen the Contour fan setup before, how thick are they at the middle, where the water pump pulley is? I have severely limited room in that area.
 
69_340_GTS said:
215°F doesn't really seem that hot. Especially in 104° heat!
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I've wondered if I'm just overreacting too. Like I said, it's been 30 years since my last RB powered car, but I don't remember it ever running that hot. It was a 440 in a big B body though.
 
That shroud surely hinders airflow at higher speeds, but removing it will no doubt cause hot issues at idle and cruise speeds imo.
I would look into fabbing some one-way flaps in the shroud which open up when the airflow into the shroud demands it.
 
i read this here all the time.(overheating issues with elect.fans).ive personally never ran one,so no comments on that,ive always ran stock fans and never had an overheating issues with them.i realize with some you have no choice but to run one.
 
another thing i would be concerned about is climbing to 200 degrees sitting in the driveway.how is that with the fans on?
 
Just like with my rat truck. It's gonna have a mutilate your *** all to hell solid steel fan on it. A real OSHA nightmare. But it'll move some air.
 
The 'skeleton cut' on the shroud sounds good; it might needs some stiffening ribs on the remaining portions. My concern with higher temps is that there is less 'headroom' in the engine temp to go up and still not have a real issue.
 
BigBlockMopar said:
That shroud surely hinders airflow at higher speeds, but removing it will no doubt cause hot issues at idle and cruise speeds imo.
I would look into fabbing some one-way flaps in the shroud which open up when the airflow into the shroud demands it.
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this seems like a great idea. cut pieces out of the biggest areas in the shroud and install a small hinge or two on the top of the pieces so the swing open at speed.
 
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