High pressure/overheat?

Hi guys, I know this is probably the wrong time of the year to ask this, since the car is pretty much put away for the season, but I will ask anyway...I have a '76 455 bored .030, 69 stage-1 heads, 9.25:1 comp. TA212 cam degreed in to specs, edelbrock perf intake, 74 q-jet by John Osborne, stock dist with petrinix unit. I am running about 35 degrees mechanical advance by 3000 rpm with 10 degrees additional vacuum advance. I have about 1200 to 1500 miles on the new motor and it seems to run a little hot, hasn't overheated as far as boiling over, but the upper radiator hose gets hard really fast and I have heat instantly from the heater(live in Michigan)I am using a 3-core radiator and have an electric fan that is adjustable to come in whenever desired, I have a 160 t-stat and have the system bled, took off the heater hose when filling it. The pressure seems to bug me the most. I am wondering if there are issues with running an older head on newer block, I think I used '76 gasket set. I drove the car on the highway, 3000 rpm for about a half hour, temp creeps up then, in town it is normal, am using the factory gauge, but have used an infra red temp gun when it was running hot before I purged out the air in the system. I was hoping to take it to Bowling Green, but am worried about the long highway trip. Any ideas? I have all winter to figure this one out before I rip and tear, but would like some solid leads before I start buying new parts, or tearing apart things. Thanks for any input.
Kevin

 

My 455 ran about 190 degrees stock. When I bored it .030" over and added a hotter cam, it ran up around 220. This is with a good 4 core radiator.

I added a Be Cool aluminum radiator, and that brought my tempreture down to about 190 again.

The only down side is the $600 the raditor cost. :shock:

 

Kevin-

maybe I missed it, but what's the max temp you're seeing? On a 15 psi system like is common with our engines, the boil over temp is 247*F. Is it possible you're seeing about 215*F and are getting needlessly worried?

Also, are you using an overflow tank?

 

you know, the correlation between an over bore and higher temperatures sounds like what i am seeing in my 430. i bored it.030, ran 190 stock now runs 205 in town,195 on the highway, with 4 row radiator. does gear selection play a role also? i have 3.73's in my car,(not changing gears, i LOVE the acceleration i get) weighs 3600 lb also do they run warmer until they are broken in? i have 195 miles on mine

 

I never saw any increase or decrease in my engine temps after break-in, and I put 50K miles on the motor.

205*F shouldn't bother the engine (or you) a bit, but the 205*F around town seems high. I never see higher temps than my t-stat rating until I get on the highway. Seems like an airflow throogh the radiator issue to me. If you use a clutch fan, I'd suspect it, or barring that, I wonder about your fan shroud being correct; on the 455 I didn't know for many years that there was a long snout and short snout water pump, which could affect your fan's ability to function properly with the shroud if you're suing the 'wrong' one

But I know that when my car ran hot at stop lights but fine on the highway it was 100% the fault of the fan clutch. I think that was my first succesful engine repair :laugh: I'm still waiting for #2

 

i am running a stock 430 water pump on mine,am using the shroud that came with the car(84 le sabre) i can extend it towards the engine if needed

 

462CID wrote:

Kevin-

maybe I missed it, but what's the max temp you're seeing? On a 15 psi system like is common with our engines, the boil over temp is 247*F. Is it possible you're seeing about 215*F and are getting needlessly worried?

Also, are you using an overflow tank?


I am using the stock overflow, and its level does rise and fall as temps do, so radiator cap is doing its job. I am using stock gauge cluster, in town it never seems to get up to 1/2 way point, but on the highway it just slowly crept up past it, but not to even 5/8ths, then I pulled off and it started to drop to under the 1/2 way point like normal, am not sure on the temps, but when it was overheating and boiling over before I burped out a ton of air, it was running over 230 at idle. I have not driven it more than 30 minutes on the highway at 3000 rpm or so, am leary about long trips yet, otherwise all seems great with the car.

Larry, thanks for the response, I am thinking about an alum radiator, no sense in messing around, get one and be done! I think I may go with one from summit racing, under $300 for a universal one, since I am using an electric fan with a stock shroud, and a 4-speed, I think I can make that work well without the exact oem fitting one for well over $500. Inputs would be appreciated,

Kevin

 

Hmmm. My overflow has burped a few times; probably because I just fill the radiator with the hoses on the engine.

I wonder if you installed a good mechanical aftermarket gauge, what temps would you see? Electrical stock gauges are inaccurate, especially after 35 years

 

That is exactly what I have planned. :TU: Summit has Griffin, 1 1/4" tube, 2 row universal aluminum radiators for $239.95--through December. I know what I want for Christmas. :Brow:

 

Larry and I have discussed this at length and there's no definate answer here. Each block is different and the water passages in the blocks and heads certainly "gunk up" over the years. My 455 is .040 over with a Modine stock 3-core replacement radiator and 160* T-stat and I run all day long at 190-195*. This summer in 95* heat I got stuck on the GW Bridge for 1 hour and it stayed just under 210* and quickly came down to 200* with a 10mph roll

.....Make sure your lower radiator hose isn't colapsing and has a spring in it. Makes sure your clutch fan is working correctly. Makse sure the T-stat opens up at the advertised temp by checking it in a pot of water on the stove. Make sure your water pump is in good working condiiton and the clearences are within spec - alot of waterpumps have been rebuilt over and either use incorrect or smaller vanes.

Im seeing about 10 degrees cooler temps with the current build than with the last and Im making ALOT more power now than then. Then, the block was .030 over with a stock set of S1 heads. Now, I have full race-ported S1's and am running more compression .....

Maybe the block or head passages were clogged up last time and now they arent ?? I dont have the definate "Smoking Gun" but I do feel that just slamming an aluminum Rad. up front , while a fix, is somewhat of a band-aid.

Check the easy stuff - like testing the T-stat. I put a new one in years ago that drove me crazy. Cant be the T-stat.....its brand new !! Someone told me about checking it in the pot of water with a cooking thermometer and sure enuf - it didn't even open when the water boiled !! I check them all now when I change one......

 

don't forget, you could tip your ignition timing down a bit for the highway then crank it back up at the track. just an idea.

 

Does anyone know a current part number for a lower rad hose with an internal spring? I cannot locate them anymore, they are all 'soft' hoses

 

Could you 'swipe' a spring out of a flex hose that would fit your formed hose?


Far as Kevins overheating goes, aside from the other potential problems mentioned, I wonder if there's an 'air-lock'?

Never happened before, but when I put fresh anti-freeze in my 462" BBB powered roadster a couple of days back, it acted like an air lock.
I let the engine get to 210* with a cool upper radiator hose before I shut it off.
Bled the air off by cracking open the temp sender fitting.

Next step is to do what I should have done before - drill a 1/8" hole in a flat area of the thermostat so air can bleed out of the block during the filling process.

(The 1/8" hole does not impinge on proper stat operation or create other problems.)

 

i'm running 14 initial, 20 centrifugal, 34 total. is street driven car, some highway driving. is this too much??

 

I was going to avoid that very thing, hopefully, by filling the radiator, then filling the water pump through a heater hose


As for the spring, I don't have one anymore. I suppose I could try to locate another hose that has the right size spring, but I don't know what hose that would be. o No: I haven't had an internal spring hose for a few years, and seen no change in temp, but it is scary to my way of thinking, because I can easily collapse that lower hose by hand. In fact, collapsing it makes it easier to install, I did that last night

 

I did have an "air lock" in it previously, then after installing a 160 t-stat and removing cooling fan sensor in the intake and burping out air, all was ok, I probably could go back to the 180 t-stat that was in there, since I know the air in the system was reaking havoc. Thanks for all the replies, I may reinstall the 180 t-stat with the 1/8 hole, have done that on previous non-Buick cars. I definatly am getting a better radiator, just found out that I can get a 4-core for $160, so am debating that and alum.
Kevin

 

One way to get air out of your system is run the engine in your driveway/shop without the radiator cap on. Get it up to temp. and let the coolant flow for a while. The flowing coolant will bring air to the radiator and let it out through the open filler neck. Do this for several minutes and top off the coolant as needed. This is also a good way to ensure that your system is full. I do this everytime I drain and refill a cooling system. Obviously you want to keep an eye on you temp. gauge because you will not have any system pressure to keep the coolant from boiling. But this proceedure only takes a few minutes and it shouldn't be a problem. :TU:

 

A total of 45* total advance. Sounds a little high to me. What does everyone else think? Is it possible that being this far advanced make an engine run a little hotter? o No: