Looking for some help and experience. My 1970 SS 454 Chevelle likes to run hot. Going down the road in cool weather (for FL) it runs about 190 or 10 above thermostat. In the summer it's close to 210. If I have to stop and leave the engine running.. well it goes above 230 and lifts the cap. My SS 454 is a LS5 and I must keep it all stock looking. What I know about the system is:
4 core OEM radiator that looks very clean
15psi radiator cap that looks good
180 thermostat.
I run a 50/50 mix of water and green antifreeze
No collapsing radiator hoses
7 blade clutch fan
when cold med to light drag from clutch fan
OEM radiator shroud
Engine has a bit of a cam and I run more timing than stock maybe 35 total
Automatic and NO A/C
It's no fun to go to a car show when worrying about a boil over. HELP!!! I can post a picture of anything anyone wants to look at.

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Paul Schultz in Lake Worth FL
1970 SS 454 LS-5/M40
2000 Horton 7.23@182 in 1/4 mile dragster Oh-yeaa

[This message has been edited by pcs0snq (edited 01-11-2003).]

[This message has been edited by pcs0snq (edited 01-11-2003).]

Hi Paul,

Sounds like you've checked the usual things like thermo, hoses etc. If you have had it overhauled much of the silicone sealant is guilty of plugging cores on radiators. I'm a little surprised that you are having prob's with a 4-core on an LS5 W/O AirCond.? If all else fails and you just can't cool it down... do what I did on my LS5. Keep your tanks and install a 3-core dimple core radiator. They will drop it at least 20 degrees... or at least it did for me. Ask about them at your local reputable radiator shop.

--Jim


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Jim Morrison
71 SS 454
www.chevelles.com/showroom/MYLS51.jpg (http://www.chevelles.com/showroom/MYLS51.jpg)
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Try a non thermal fan clutch..it only works at idle/moderate cruising speeds,doesn't work on the highway.I have a 4 core in my 70 SS454 with this set-up,inlcluding the 7 blade fan/factory shroud,180 thermo,etc.Car nevergoes above 180-185 on the hottest days.The non thermal clutch can be had at any parts store,try a mid 70's truck application.

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My 70 SS396 (http://www.chevelles.com/showroom/mr4speed70SS1)
Engine pic (http://chevelles.com/showroom/mr4speed70SSengine2)
My Black Cherry 70 SS454 (http://www.chevelles.com/showroom/mr4speed/Picture025.jpg)
The launch (http://www.chevelles.com/showroom/CClaunch.jpg) 13.13 @ 101.490/1.92 60 ft. with radials,2.73's,and thru the mufflers
1.90 Best 60 ft.
101.84 Best MPH
My Drag Race page and combo (http://www.prestage.com/site/site_display.asp?SiteID=589)
1968 Oldsmobile Cutlass convertible
1973 GMC Sierra 454 p/u
1985 Cadillac Eldorado (daily driver)
Chris Corwel,TC Member # 785
Member # 141 AMCA

i assume you have the shroud on the radiator??

Paul,
The first thing I would do is to take the radiator to a good radiator shop and have them pull the tanks and clean it. I have seen quite a few radiators that "look" great but are all clogged up in the lower area. One way to check this is to run you hand over the front of the radiator while the car is running and see if you feel any cool spots. If so, the core is clogged up at that point. Also, you should be able to hear the factory fan "kick in" when it gets hot, there will be a pronounced difference in the sound and the amount of air blown through the radiator.
The fact that the car runs pretty much where it should (190) while driving down the road really sounds more like an air flow problem at idle. This would make the fan clutch more suspect than the radiator, but I would check both.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

1971 Heavy Chevy - original owner
Team Chevelle #100

Like the others said, check out your clutch again. You should hear it when it comes on, check your fluid leaking around the center of the clutch were the spring is. If the fluid is leaking out time for a new one

I don't have much experience with clutch fans, but if the engine is cold, should he be feeling "medium to light drag" on it? I was thinking that they should pretty much free spin. Not sure tho.
Also, see if you can get the radiator cap checked at a local parts store. That can cause some overheating problems, because it can't put enough pressure on the system, it will lower the boiling point of the liquid. You might even try going to a 16lb. cap. Just little things to think about.
I tend to agree with BillK, if you have a good temp going when you are driving, but don't when you are idling, then you don't have enough airflow across the radiator. ALSO, how close is the fan to the radiator. I'm not sure what the spec should be, but if it's very far away you might not have enough draw across the radiator. Hopefully someone can chime in as to the proper fan-to-radiator clearance. Good luck!

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Justin Wray
Fathom Blue 1970 Malibu 1/8th mile best of 8.48 at "The Track that Time Forgot", George Ray's Wildcat Hot Rod Dragstrip

I KNOW that living in Florida is very hot and humid, and even in the winter, ambient temps can cause issues with a cooling systems if all is not up to snuff.

First, is your shroud (I think it is) the type that only covers about 65% of the radiator from behind....in other words only sucks air thru 2/3 of the surface of the radiator? If so, I have learned from other 69 or 70 Chevelle experiences that this may not be enough in your climate with the system not perfect. You could consider a 68 big block shroud (that covers the entire radiator) that will fit your application/radiator, however you will have to do some minor fitting, but will keep the stock look and feel. I have suggested this to several 69 and 70 owners with great success.

Secondly, the problem is definitely airflow across the radiator assuming the radiator is good. While taking the radiator out and cleaning, rodding and repainting is a good beginning....if it were mine I would seek out an identical aluminum model with large twin 1" tubes (crossflow models) from PRC (www.streetrodstuff.com) that will raise the efficiency over 35%! This would give you some insurance and margin when hotter temps arrive because if it's doing it now, it's gonna get worse in the summer!

When these cooling systems where brand new, they were on the fringe when perfect, so now with worn parts, age and so forth they are really at question. The clutch fans of yesterday where pretty good products and very consistent, but these days are not as good esp the aftermarket replacement parts. You cannot tell if they are failing! So, notwithstanding a new clutch and that's questionable in my opinion, I recommend the new technology flex fans that will produce more air at idle and slow speeds than your current set up, yet give up all their CFMs at higher RPMS and are very efficient...and quiet. Check out www.derale.com (http://www.derale.com) and go to the flex fan section. Look at the heavy duty 18" (17XXX) series only (yes, a 18" will fit)! These are worth their weight in gold and are about $50 from Summit Racing. While these are not stock, they do fit in the 19" shround nicely with the right spacer (2") and will produce an unbelieveable amount of air. We recently converted a 69 with air here in Hotanta that was suffering from the very same issues yours is and all of these changes produced profound and dramatic results.

Also, you can get buy with running 25% antifreeze and 75% water. This will help heat transfer whereas the more water the more heat gets carried.....you just have to get rid of it at the radiator.

On another final note, are you sure that the temperature gauge and sender are working correctly? I have found alot of these to be off as much as 30 degrees! I know the senders are in the head too. So, maybe testing your sender and gauge for calibration purposes is in order. It's easy to do with a pan of boiling water and taking the sender out, grounding the pan with boiling water and emersing the tip of the sending unit. Works for me.

For more on cooling go to Jack'Stands Cooling Forum (http://www.inccn.net/techforum.htm)

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Steve "Jack'stands" Jack
Tech forum at www.inccn.net/techforum.htm (http://www.inccn.net/techforum.htm)

[This message has been edited by HOTRODSRJ (edited 01-13-2003).]

Thanks for the support. I should get the NEW clutch for the FAN this week. You gave me a pretty long list of stuff to try.

Looks like the original water pump. Anyone know a pump rebuild shop.

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Paul Schultz in Lake Worth FL
1970 SS 454 LS-5/M40
2000 Horton 7.23@182 in 1/4 mile dragster Oh-yeaa

I would buy a high performance water pump from either TuffStuff, Edelbrock or Stewart Components.

Both of these pumps are very efficient, won't cavitate at higher rpms, out perform flow wise another 40% and take less hp doing it. It's a major improvement and step up in technology.....even the front support bearings are bigger for that fan and clutch. Rebuilds are okay, but it's like rebuilding a "286" computer, simply obsolete!

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Steve "Jack'stands" Jack
Tech forum at www.inccn.net/techforum.htm (http://www.inccn.net/techforum.htm)