Redyota

I have a smog 455 with J heads that I have in a 67 Skylark. I put the motor in that car back in 93 and It has ALWAYS overheated at freeway speeds. Single core, 3 core and now a big 2 core aluminum with fans and shroud and it still overheats.

I recently rebuilt the entire car and one of my goals was to be able to run it on the freeway. It is hooked to a TH400 and 3.36 gears and tuns right around 2950 RPM at 65. It can idle all day long in any temp with the AC on and never overheat. Its always when I try and run it at a higher RPM, basically anything over 2400.

I currently have a Flowcooler water pump and a 2 core 1.25 tube Griffin Radiator. It also has twin 12" spal electic fans with a shroud. If I keep the speed under 50 it'll hold right at 200-205. Any faster and the temp starts to climb until I slow down to cool it off. I normally do that when I hit 230ish. Slow down to 50 and the temp drops to 200 and I pick up speed until it gets hot again. Takes about 15 minutes to climb back up. Faster if I have a long hill to climb. All in all, it runs great and has good power until I hit about 3000 RPM and then it seams to fall off. I've been blaming that on not have a good tune in the EFI at higher RPMS.

Lower hose didn't have a spring in it, so I added one. No Change.

Made sure I had burped all the air bubbles out. No Change.

16lb cap

pulled the cap and lowered the coolant level so I could watch flow and even at idle, its flows great.

I have a Holley Terminator EFI setup with a Hyperspark distributor. At cruise I'm running about 14.0 AFR and 44 degrees of timing. This is like 34 degrees of mechanical with 10 degrees of vacuum like I had set with the HEI. I know I should be able to lean it out a little more and put a little more timing into it, but I'm trying to be conservative to get the cooling right before I try and dial it in better. I'm seeing 30-35 kpa at idle and at cruise. It also has the AC pulleys on as well.

Checked a couple plugs to make sure I wasn't running too lean and they are nice brown color.

I replaced the head gaskets and tested the coolant for hydro carbons...everything looks good.

Only thing I haven't replaced is the exhaust. it has 2" true duals that I put on back in the mid 90's. I haven't replaced it because I have no leaks and it sounds ok. But on a whim I blocked each pipe with my hand and one bank has alot more volume and pressure than the other. After looking, there are some really crappy bends that are there. I'm scheduled to put a 2.5 inch true dual on it with Magnaflows next week.

Has anybody had this issue and it ended up being a restricted exhaust? I thought by running dual 2 inch that I might be losing out on power, but I didn't think it would contribute to an overheat at higher RPMS....

I'm just at my wits end with where I need to go next as I'm highly doubtful the exhaust is my issue...

Sugar Bear

Headers or exhaust manifolds? If manifolds does it have a heat riser/flapper on the drivers side at the exit of the exhaust manifold?

Good luck!!!

Vintage Chief

The first thing I always think of is the cycling of coolant. An engine turning at a higher RPM produces more heat. Engine heat is removed via coolant cycling by the coolant "system". There's the chance you aren't removing engine heat when at speed because something w/in the coolant system is restricting coolant flow. Least expensive & perhaps biggest bang for your buck might be to check the thermostat. It's basically the oldest road warrior issue when these beasts were new - everyone I knew carried an extra. The thermostat might not be opening all the way - restricting coolant flow when you need it as engine RPM increases and engine heat builds up.

EDIT: Oh yeah, sounds silly probably, but I'll say it anyways. Yes, there is a correct way and an incorrect way to install a thermostat. Installed the incorrect way causes a void just prior to the thermostat ring. It will fail to open properly since that void is comprised of air instead of fluid.

Redyota

It has the Repo W Z manifolds without the heat risers.

Redyota

Agreed, I've tried a Robertshaw, Stant, Super Stant and the old trick of not running a thermostat. Other than a defective stant I had, it runs the same temps whether I have one in or not. It just comes up to temp faster and holds 180 when I'm just cruising around town. If I pull the thermostat, it'll run about 155 around town. At freeway speeds, it'll climb up whether I have a thermostat in it or not.

Vintage Chief

At speed you aren't removing enough heat. Assuming the WP is moving the appropriate volume of water at the appropriate speed, the thermostat is opening, and the radiator has no blockage - I'd say you have an airflow issue over the radiator fins e.g. electric fans are not efficiently moving airflow across the core.

Redyota

That absolutely makes sense. I've tried an HD clutch fan with a shroud with the fan about and inch out and it ran hotter at lower speeds, but not what I'd consider hot. I put the electric fans on to see if it would help. With the clutch fan it wouldn't hold a piece of paper against the condenser at idle. The electric fans pull will hold several. Doesn't really mean anything at highways speeds though.... I also pulled the AC condenser to see if that would make a difference and it did not.. This is the setup that I currently have...

https://www.jegs.com/i/Griffin-Radia...70019/10002/-1

Sugar Bear

Use an infrared thermometer to check for cool spots in the rad indicating a blockage.

Any chance of an internal blockage in the cooling system or does it look really clean? Recently had incredible results with CRC ThemoCure on a car that was building heat on the highway, it took three applications but solved the problem.

What ratio coolant to water is in it?

Good luck!!!

Redyota

The Rad is pretty brand new, but I will absolutely take a look at that. All my coolant passages look good externally, but I can absolutely try that. I currently have a 50\50 mix with distilled water.

Sugar Bear

ThermoCure has to be used without any coolant, just water so planning/timing is required to prevent freezing. It works through chelation, (I cannot explain it) and can be left in the system for days to allow it to work. The manufacturer claims it to be non-toxic.

Good luck!!!

Vintage Chief

Chelators are rather simple to understand. It is a compound which is created to bind to a metal. Once the metal is bound to the compound (chelator), the compound is flushed from the system - along with the metal which is now bound to the chelator.

Redyota

That's easy enough to understand. When it binds and works its way through the system, should I be concerned with it clogging up my radiator passages, or are the particles pretty small?

Vintage Chief

I can’t speak to the ThremoCure compound as I’ve never used it. I’ve created chelators & employed chelators in advanced research settings far removed from any automobile applications. I suspect if the directions are followed explicitly there should be no compound(s) remaining in the system.

Greg Rogers

I put a hood scoop on a 65 Coronet I had years ago. Ran hot. I finally found that the scoop was pulling in air at highway speeds and causing air to not flow thru radiator at speed. Anything like that???

joe_padavano

What is the advance curve in the distributor? How is the carb jetted? Either or both can cause high speed heating problems. People always go for the cooling system. The reality is that low speed is nearly always the stressing case for cooling. If you're not overheating at low speeds, the problem is likely elsewhere.

matt69olds

He mentioned Holley EFI.

Which brings up a possible issue. I have the Holley Sniper EFI on my 69. There have been multiple posts on the Holley forums about inaccurate temp sending units. The particular sender in my car reads 15 degrees lower than actual engine temp. If you’re using the Holley temp senders, you may be trying to correct a problem that doesn’t exist. Put a mechanical gauge on just to verify the temp is really what you think it is.

matt69olds

Sounds like air is going AROUND the radiator instead of thru it.


Are all the baffles/shrouding/seals around the radiator installed and in good shape? What about the”chin spoiler” under the radiator support? It’s designed to create a low pressure area behind the radiator, encouraging air to go thru the radiator at speed. There are suppose to be rubber seals that fill the gap between the core support and the radiator, make sure they are in good shape. What about the tar paper in the bumper area, those are there to force air thru the radiator instead of the bumper.

Look at a service or assembly manual, make sure all the seals are there.

Redyota

My Skylark doesn't have a chin spoiler or rubber gaskets around the Radiator per the service manual. The radiator is super small at 28"x18" sized core and completely covers the hole in my radiator support.. I called Griffin and they said it should still be good out to 750 HP or so. Being a stock smog motor, I'd be shocked if I was half that.

I did take it by my local radiator shop to give it a look over. He thought the install looked good and checked the flow of the water pump at idle. He said all of that looked fine. He thought it maybe head gaskets that may only leak at higher RPM's or the maybe the 30 year old exhaust was clogged. I then ran it by the muffler shop that is going to be putting in a new full system next week. He had time to do a backpressure test similar to what he does for suspected clogged cats. He found that one side had 3 psi of positive pressure and the other had 4.5. He said that is WAY too much backpressure and he shoots for about 1.5 or so. He said he wasn't sure if that's the reason or not that it was overheating, but short term he recommedded that I drill a couple of 1/2 in holes before the mufflers and take it out on the free way. He said that should open up the exhaust enough that at least I'd know if that was my issue or not and since I was replacing everything next week, so why not?


The Motor is in a 1967 Buick Skylark. Its a long story on why its there, but short story is that my neighbor had a 75 Tornado with 19k miles that he wanted the front wheel drive system for a Model T dual 455 with 4 Wheel steer he was building. Gave me(14 at the time) the 455 to learn how to tear a motor down since he was tired of watching me do body work every day. I catch a fair amount of grief that I don't have a Buick motor in it, but its part of the story if you know what I mean.

Redyota

My temp gauge apparently is off. It reads 10 degrees higher than my MAT sensor after sitting over night before first start. I have a spare Mechanical guage, so I'll throw that it and get a better number. I know it overheated however because my dummy light went off last week and it puked coolant at me.

Vintage Chief

Possible exorcism in the near future...

Redyota

If there are any EFI gurus out there, I'd love somebody to take a look at my tune. It says the Holley EFI is self learning, but it really isn't. It only self learns the fuel table, but the Timing Table, AFR Target Table as well as pile of other settings need to be tuned. I'm learning, but I have a long ways to go

Vintage Chief

What is that file for?

Vintage Chief

99.9999999999999999% certain 99.99999999999999% of the members cannot open a .TERX file extension.

droldsmorland

Two simple tests:
-Try a 192-195° Heavy duty stant T-Stat.
-Unhook the exhaust and run'er wide open and see if it improves.

What kind of hood are you running? Stock?

Redyota

Its the tune file for the Holley EFI. It includes besides other things the Fueling Map, Timing Map and Target AFR Map. I was hoping somebody other than I has been playing with EFI., LOL

Vintage Chief

There are several EFI guru members. They may or they may not see your request for tuning a Holley EFI. You might be better served to create a separate thread regarding Holley EFI tuning. Good Luck.

Redyota

I can't pull the exhaust loose or I'd lose the O2 sensor. Here's a pic for my hood..

Supernice88

You said you have a 2" exhaust on there now. That is probably the culprit right there. You're not getting enough heat out of the engine at the higher speeds. See how things are after you get the exhaust changed out.
Sharp looking car.

Meigzee71442

Meigzee71442

timing is your issue afr should be mid 12’s keep it around there 14 is for your family ECI / hybrid

matt69olds

At WOT an engine might make best power with 32 degrees of timing. At part throttle/light load the engine is much more efficient with another 10-15 degrees of timing.

Redyota

It seems to like 34 degrees at full throttle and at part throttle anything over 2500 RPM gets 8-10 additional for a total of 44 degrees at cruise. If I push the cruise timing, it'll start pinging at 53 degrees, I backed off to 44 just to insure that its not a contributor to the overheating issue. May not be as efficient, but I shouldn't be adding in more heat.

matt69olds

I have similar results. My engine likes 34 degrees at WOT, I have my cruise timing set at 47. Occasionally, when it’s really hot I can hear some faint pinging under light acceleration, crowd the throttle a little more and the ecm starts to pull timing and the rattling stops.

Redyota

Exhaust is in and the engine is much happier. Smoother idle, better power ect... Sounds awesome. Still gets hot on the freeway. I didn't really think it was gonna fix it, but it needed done anyways.

Tried to richen out the mixture to from 14.1 to 12.8. No change
Dropped timing from 44 down to 36. I figured if most circle track guys don't need the vacuum advance, then neither do I for testing. No change.
At the suggestion of the brother we pulled the hood off and it was rock solid at 180 running 75 mph and 3200 rpm. I would have figured that would actually heat it up worse as it wasn't forcing air through the radiator, but i guess not.

Put the hood back on and paid attention to my Manifold Air Temp and it was 165 degrees on the freeway and 105 on surface streets.
Maybe a Cold air intake or figure out how to get the air out of the engine compartment?

cfair

It took me 20 years to solve my wanting-to-overheat problem. Here’s what I learned:

1) Make sure you have or make front rubber curtains forcing air through the radiator core. They act like a front shroud. In case this is not Buick-normal, use masticated rubber sheets cut to fit or some other material to force air through the radiator core and not let incoming air around it. Olds-specialist Fusick will sell you sheets of masticated rubber that you can cut-to-fit and secure with hardware to block incoming air from going _around_ the radiator core.

2) Get a 4 core high-fin-density copper/brass radiator core. Or equivalent aluminum. I don’t want to get into that fight, but I’m traditional and using copper/brass. If in doubt, go for an HD or A/C radiator.

3) Flowkooler water pump - get the snout length you need. Olds had several lengths. Flowkooler invented/adapted a better impeller that helps keep things cool. I’ve found the longevity to be solid-to-good. Like 10 years or so with one water pump. Not crap.

4) Rear shroud: make sure your shroud covers the entirety of your radiator. Be sure the fan sucks air through the whole core.

5) GM 7 blade fan & Hayden clutch. 7 blade fans pull lots of air and were common in the 70’s as heat loads went up due to emissions. Hayden clutches are heat triggered and work fine. See my posts here at C/O about my experiments. The keys are that the fan kicks in at the temp you want & length that fits your car. Aim at a fan close enough to the radiator core to really suck (1/2” or so), but not so close that it hits. Avoid having the fan >1” away from the radiator core. If you have the time & inclination, test different fans for noise vs. how much air they pull. You may be able to find a quiet one that pulls enough air on hot days to keep things cool.

6) Coolant Mix: I wound up at 1-2 bottles of water wetter / photoflow, and went with 70% distilled water and 30% antifreeze. 1966 Olds big car radiators use 17 quarts of coolant. If my math is right, that just over 4 gallons. I do water wetter first; then the 30% antifreeze (plus or minus); then top up with distilled water. Where I live, I don’t worry about subzero temps. Your experience may be different. Upshot is, in mild-to-hot climates, water cools better than antifreeze, but you still want the chemicals that antifreeze contains which lubricate & chemically preserve cooling system parts.

7) Heater core - make sure yours is sound (i.e. not leaking) & get a spare. Over a long enough time frame, these are service parts. Buying a spare now saves you pain in 2029 when you can’t get one & yours is leaking. If your car has a brace or bracket on the firewall to inhibit engine hose movement from bending the heater core inlet/outlet, use it/them. The less stress you put on the soft brass heater core tubes, the longer it will last.

8) Coolant Overflow (aka puke tank) + spring loaded radiator cap. In the 60’s they dealt with coolant expansion by somewhat under-filling the radiator & told you to check it hot. As emissions kicked in during the early 70’s, GM ran their engines hotter and cooling systems evolved to a full radiator with a spring-loaded radiator cap (for Olds often a 16 lb. cap) plus an external reservoir that would catch coolant that was forced out by expansion or hold reserve coolant that would get sucked in when needed. On my ‘66’s, I added a ‘74-75 Caddy puke tank that looks d*mn near factory. Can recommend.

9) Fuel mixture. To lean runs hot. One of the best tuning tools I ever found was an AFR (air/fuel ratio) gauge from Innovative Solutions. Once you can see the air/fuel mixture in real time, you can _really_ trace down the problem. Like observing AFR/Lambda on the freeway. For example, this week I deployed a new carb from SMI. The part throttle cruise was too lean and had a distinct flat spot until I tuned it richer using the Innovative Soluations AFR (lamba) gauge. Your freeway hot problem may just be part throttle cruise being too lean. It’ll idle great, accelerate fine, but at freeway cruise if it’s too lean, it’ll gradually heat up from the lean condition. With a qjet, this can be solved by raising the APT (adjustable part throttle), but I don’t know what carb you’re running. On a Holley, you might need a different power valve.

10) Timing. If it’s too retarded the engine will tend to run hot, too advanced and you’ll hear the knock/ping. If you’ve retarded the timing back to avoid cr*ppy gasoline, there’s a chance you’ve retarded it just far enough at cruise to cause it to heat up.

My $.02. Hope I didn’t go on too long and that this helps

Chris

cfair

In case it helps. I just dropped in a couple of Progression Ignitions Bluetooth distributors. They do away with the springs, vacuum advance cans and so on, in favor of a timing map you choose.l

I’m still adapting cold-startup to the new distributor, but am very happy with the precision of the spark timing. Great advance, assuming it lasts.

Chris

olds 307 and 403

Agree on the rubber curtain forcing air through the rad. My 88 Cutlass always ran hot on the highway. I finally added the GN rubber curtain surround, it dropped temps 20 degrees at least. My 88 was the exact same with the 403 as your Buick. Towing my boat, it would hit 240, the 2004R lower rpm no doubt helped it from constantly overheating at speed. The early Flowkooler water pumps are questionable. Leaking issues and the plate shoved on the open impeller leaves a lot of space between the impeller and housing compared to factory closed impeller pump. A defective Mr Gasket high flow, more like no flow thermostat, closed at highway speeds and under drive pulleys had me pulling out my hair. Replacing those helped but only somewhat. Tried mutiple rads, fans etc, didn't make much difference. Build a rubber surround!