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Old 12-30-2003, 06:17 PM
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68 camaro RS w/ 454 overheating

I have posted here before about this problem but wanted to look for more info since some things have changed.

I have a 68 Camaro RS with a Vette (70-75') 454 in it.
Edelbrock 795 cfm carb on a performer intake
hooker headers
HEI

For some reason I keep overheating. From a cold engine on a cool day I overheat in about 20+ min at idle. since it isn't plated I can't drive it on the road so I dont' know how it does other than sitting still.

Replaced radiator with new Griffin Rad, possibly 6 core. (two 1.25" tubes)
Replaced thermostat w/ 180 thermo, tested and works
new hoses
replaced water pump
replaced fan (17" 7 blade no clutch)
universal shroud

I have tried timing her from 6 degrees mechanical to 18 degrees and still overheating.

I have tried revving to 3500 RPM with vacuum advance attached and timing for 36 degrees,

I have also timed it with a vacuum gauge for 20" of vacuum.

The latter two timings cause me to idle at over 1100 RPM and I am still overheating.

Both timing for vacuum and timing for total 36 degrees advance come out at the same idle RPM (1100).

I am running out of ideas. I was thinking of replacing the vacuum advance module, I have bought but not installed:

New electric temp gauge
New 160 degree thermostat
head gaskets (just in case)

I am wondering if anyone has any ideas on what I can look into before I pull the heads. I have heard of balancer slippage before but I can't imagine how that would happen along with things appear to be fine. I have tried a straight timing light and a dial back and all indications are I have the dist installed correctly and balancer is not slipped. I have pulled dist cover and set balancer to 0 and dist is firing on 1 so things look good. I have not (recently) pulled timing chain cover to line up dots so I am going by dist location and balancer location as well as feeling for compression on No. 1 cylinder's upstroke.

I do not know my cam, I didn't put it in but it is aftermarket.

I see some flow in radiator but I don't know what is considered "good". I have tested Radiator with one of those Rad thermometers you attach where the rad cap goes. It reads a good 30 degrees cooler on the cap side of that rad than on the engine side so that means to me I am getting flow and cooling.

When the engine overheats if I shoot water through the radiator it cools off so that also indicates to me I have flow. It starts to cool off almost immediately after shooting water through the rad so I think my flow is ok. At idle flow is constant and is a decent "dribble". I hope this is enough.

I do not have the rad overflow tank installed. It has been suggested this could cause overheating.


Main question: what are some steps I need to take BEFORE pulling the heads? I don't want to waste time if I don't need to.

Thanks
Rick

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Old 12-30-2003, 06:27 PM
STUPID is as STUPID does...
 
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It sounds like you have everything covered. I would suggest installing the overflow tank. Do you have it capped off right now? I would suspect you have some air trapped in the system and this is whats causing your problem. Hooking up the overflow will allow the system to burp itself and I'll bet you'll be putting in more fluid after it does .
Another thought... How much of the shroud is covering the fan and what kind of clearance is around it. The fan should stick 1/2 to 3/4's of the way into the shroud and should have about an inch clearance all around.
Mark
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Old 12-30-2003, 06:47 PM
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Going off of what Astro said, it sounds to me more like an AIR FLOW problem all together. What kind of fan are you running, and shroud as well. Also, where is your temp gauge at in the block? Having it in the head will give you a little higher of a reading. The reason I say this is because the water cools it down when you spray it over the rad...
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Old 12-30-2003, 06:54 PM
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The shroud is one of those "universal" shouds (that suck) that is basically a 5" wide piece of chromed tin that you bend in a half circle over the top half of the fan and secure with plastic screws ( I use zip ties) through the radiator.

The fan is about 3/4 of the way into the shroud and is about 1/2-3/4" away from the radiator and has around 1" clearance on top and sides but straightens out at the very bottom. It can't be bent more than that without damaging the radiator.

I am going to have to find a "burp" tank. also it is not capped at this time.

Quote:
Originally posted by gt2betubbed
Going off of what Astro said, it sounds to me more like an AIR FLOW problem all together. What kind of fan are you running, and shroud as well. Also, where is your temp gauge at in the block? Having it in the head will give you a little higher of a reading. The reason I say this is because the water cools it down when you spray it over the rad...
I have a 17" 7 blade firm flex aluminum fan with a spacer that places it around 1/2 - 3/4" from the radiator. The shroud is described above. I have been looking for a full shroud that would fit my griffin but I can't find one yet.

The temp gauge is installed in the intake manifold right before the return line to the radiator.

Rick

Here is alink to the fan I have:

http://store.summitracing.com/partde...art=FLX%2D1037

Here is a link to teh shroud I have:

http://store.summitracing.com/partde...art=FLX%2D1037
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Old 12-30-2003, 07:02 PM
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IMO, I think the shroud is your problem. If it's not pulling the air to it's best ability, that BB is gonna over heat. On my 69, it came with a 396 in it already, but the stock rad and shroud worked perfectly. The clearances around the fan were nice and tight, and the shroud covered the entire rad. The 454 I put in was pretty mild, and only overheated in traffic. Is the griffen a stock replacement, or a universal? And if it's a univers. does it have about the same dimensions as the stock rad? If so, I would look into getting a stock shroud and see if it helps. The burp tank will help out, and the rad definately needs to be capped...

BTW, the link to the shroud you posted is another link the fan.
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Old 12-30-2003, 07:05 PM
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With the "half shroud" that you are using you may as well not have one. It's not doing anything to promote air being pulled through the radiator. This is why it takes a while to over heat at an idle. Take your radiator measurements to a junk yard and do some scrounging. I bet a full size truck shroud will be pretty close or just get a big block Camaro shroud and make it work.
Once you get all of the air coming through the radiator you won't have a problem...
Mark
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Old 12-30-2003, 07:09 PM
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Here is the right link:

http://store.summitracing.com/partde...art=TRD%2D9454

the griffin is a universal so stock shroud won't work (don't have it anyhow)

I am wondering if I would be fine on the road and overheat in traffic. Problem is I live in Japan and it is ALL TRAFFIC, which means I wouldn't be able to drive anywhere.

It is 50 degrees daily now and sitting idle in the garage parking area I overheat, I would like to think I could sit in traffic for a few min without overheating. Especially since I am running no AC or anythinge else. Just waterpump, alternator, PS pump.

Should I replace the 180 thermostat with the 160? Would that help?

I could also adjust the carb mixture. I am already blowing just a bit of black smoke so I think i am kind of rich anyhow. It is hard to tell though because I can't take her out on the road so that just could be buildup of crappy base (87 octane) gas. I have started putting Japanese gas (96? Octane) in the car but it may take a while to work all the old cruddy base gas out.

Rick
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Old 12-30-2003, 07:10 PM
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The one thing you didn't mention is the temp sending unit. Chevys use at least two different sending units (probably more) and they differ mainly by the length of the probe. They probably differ between a gauge or idiot light as well.

I had a 350 in an 81 Vette and changed the heads from the thin wall castings to the earlier double hump heads and made the mistake of using my old sensor. Temps would go up to 220-230 after about 15 minutes of run time and wouldn't go down much while driving. When I felt the hoses the engine just didn't seem that hot. Did some checking and found I needed the longer sensor. A quick trip to the local auto parts store and $5.00 later engine temps were reading in the 160-180 range.

Good luck,

Centerline
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Old 12-30-2003, 07:18 PM
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Here is a link to my radiator:

http://store.summitracing.com/partde...D1%2D55242%2DX

I have had a hell of a tiem trying to find a full shroud to fit this monster.

Quote:
Originally posted by Centerline
The one thing you didn't mention is the temp sending unit. Chevys use at least two different sending units (probably more) and they differ mainly by the length of the probe. They probably differ between a gauge or idiot light as well.

I had a 350 in an 81 Vette and changed the heads from the thin wall castings to the earlier double hump heads and made the mistake of using my old sensor. Temps would go up to 220-230 after about 15 minutes of run time and wouldn't go down much while driving. When I felt the hoses the engine just didn't seem that hot. Did some checking and found I needed the longer sensor. A quick trip to the local auto parts store and $5.00 later engine temps were reading in the 160-180 range.

Good luck,

Centerline
Well, I bought an aftermarket temp gauge and sensor (mechanical) since my camaro has no stock sensor (no gauge option).

My hoses also don't feel extremely hot, even when I am showing 220-250 degrees. Also, I don't always seem to overflow the Rad when I am showing an overheat condition on the gauge. I would imagine at 250 degree I should be dumping coolant all over the place but that isn't the case. It starts to bubble out a small bit at around 250 degrees.

To test I put a radiator cap thermometer in the cap side (non pressure side) of the radiator and when I am reading over 220 degrees on my car's gauge the thermometer on the cool side of the radiator shows around 170 so that indicates to me I am getting cooling but probably am running over 220 degrees.

One thing I didn't check is I put in a new heater core and hoses. I did have one hose at the core loose to shoot out some coolant but I have not "bled" the other hose at the intake manifold. Maybe I need to do that.

Also my "elbow" bypass hose is crimped about half way. I wouldn't imagine this would cause such an overheat condition though woudl it? It is basically just there to help the thermostat get temp to open. I have bought a new elbow bypass hose but have nto installed it yet.

Rick

Last edited by rakundig; 12-30-2003 at 07:18 PM.
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Old 12-30-2003, 07:33 PM
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rakundig, I have a 67 camaro with a 454 that I just installed. My buddy just put one in his 69. Im not having a problem yet but when summer gets here all bets are off. I am using the short water pump and a March Performance big lower pulley and smaller water pump pulley. They said the short water pump moves more water than the long pump and the pulley setup speeds up the waterpump and fan. I bought a derale clutch and a stock type fan with a stock big block shroud. I have the belt pretty tight but I still here a chirp when I rev the motor. I'm using a 4 row radiator right now but will probably upgrade to a Afco aluminum before summer.
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Old 12-30-2003, 07:34 PM
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Just thought of something that may contribute to my problem.

I am gonig to attach a picture of my engine. (old radiator but same setup) and if you look closely the radiator and engine are very very close to the same height and the engine "may" be slightly higher. I may have an air bubble as well in the engine that can't bleed out.

Now, would the overflow tank take care of this or is this a bigger problem?

Thanks
Rick
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Old 12-30-2003, 07:39 PM
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Here is the pic

Quote:
Originally posted by Full Throttle
rakundig, I have a 67 camaro with a 454 that I just installed. My buddy just put one in his 69. Im not having a problem yet but when summer gets here all bets are off. I am using the short water pump and a March Performance big lower pulley and smaller water pump pulley. They said the short water pump moves more water than the long pump and the pulley setup speeds up the waterpump and fan. I bought a derale clutch and a stock type fan with a stock big block shroud. I have the belt pretty tight but I still here a chirp when I rev the motor. I'm using a 4 row radiator right now but will probably upgrade to a Afco aluminum before summer.
Really, short water pumps push more water than long? I was thinking it was the other way around. I have a long pump. Maybe I need a short as well?

I had trouble opening the attached picture so here is a link to my gallery picture

http://hotrodders.com/gallery/showph...at=3031&page=1
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Old 12-31-2003, 05:34 AM
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You need to dump that wimpy flex fan , They are to flat and don't move much air at idle, find a stock GM 7 blade flex fan not a clutch type, it will move 10 times more air at idle. I have seen this same problem many times with the after market so called HP flex fans.
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Old 01-07-2004, 04:33 PM
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Did you ever solve this?
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Old 01-07-2004, 04:43 PM
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here's something: if the top inlet of the radiator is not higher than the engine, it will create an air pocket in the radiator and the engine will never cool. Check that out-

K
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