[General Z]

My thread regarding the rebuild was getting pretty long, so I started a new one.

I rebuilt the engine again. I did the 421 mod, plugging the front two holes and drilling the other one.

Cast impeller water pump, with clearanced divider plate.

I had my heater core bypassed, but replaced it during the rebuild and am now using it.

I have all the AC baffles in place.

The engine is running hotter than ever. It was doing 210 tonight with just light driving.

I'm looking for ANY ideas. You can read my build specs below.

I do need to re-check my timing. I think I may need to advance it a bit more.

Thank you in advance.

My specs are below:

1967 Firebird Convertible

Engine: 1970 455 Block, bored .060
Bore: 4.2109, Stroke: 4.21

Crank: Pontiac factory crank, ground .010 on rods and mains

Pistons: Sealed Power forged pistons

Rods: RPM International forged rods

Heads: 1971 400 Heads, Code 96
Mildly Ported, Stainless Steel Valves, Dual Springs
96cc, Valves 2.11/1.77
Comp Cams roller rockers, Ratio: 1.52

Compression Ratio: 9.53:1

Intake: Edelbrock Performer, dual plane, port matched

Lifters: Summit Racing Hydraulic

Cam: Summit 2802

Carb: Holley 0-3310S 750cfm 4-bbl with manual choke. Using ½” carb spacer.

Rear End: 3.73 Gear ratio

Rear Tires: 216-65-15

Accessories: Power Steering, Power Brakes

Ignition: Performance Distributors HEI

Radiator: Aluminum 4 core, big block, with Mark 8 electric fan

Thermostat: Balanced 180 with extra holes drilled in it.

Water Pump: Cast impeller with clearanced divider plate

Transmission: 700R4

Torque Converter: Unknown

Exhaust: Hedman Headers, Dual 3” exhaust with H pipe

Oil: Rotella T 15W-40 + a bottle of Comp Cams 159 additive.

[torqjunki]

I had similar results and this is what I did. First I purchased a cheap manual style temp guage kit from local auto parts store. I hooked it up on the crossover near the autometer sensor. The spikes I was seeing with the electric auto meter guage was not seen on the other guage. I pulled the autometer sensor and used a different type of sealant on the threads. This took care of the spikes. It was still trying to over heat during moderate speeds. I have the 4 core alum radiator as well. If I done it again, I would go with the 2 core. To make the 4 core work, you need to get the 7 blade flex a lite flex fan or a stock 7 blade flex fan. The stock ones are hard to find. I believe the part number was 1818. It is very very quiet and pulls lots of air. I think the fan clutch set up stops pulling air too soon and free wheels before the car gets enough frontal air to properly cool. This is what worked for me. If you look at the flex a lite web site, it specifically says that this fan is designed for the four core radiators. I personally like the clutch arrangement, but with this car and radiator it does not work well enough. I could likely add some sort of air deflector in the front, but like the look as is. Good luck.

[David Jones]

Not lean at cruise rpm?
What is light driving?
What would it do during an extended idle?
The bottom hose is not collapsing?
Fan operates correctly, moves needed cfm of air.
Does you car run a shroud?

[dmac]

1970 455 .060 over will be fairly high compression. What kind of fuel are you using? Use at least 93 octane if available.

[cdrookie]

try a different size water pump pulley, might need to speed up coolant flow, might need to slow it down

[kyle_blake]

All I know is ... fire car up driveway... your tune is your tune.

let it idle up to operating temperature. idle temperature should be at or right around thermostat. so ok, yours probably will go up 20 + F past the thermostat temperature.

leave it idle for 30 mins or maybe hour, not sure what your temperature outside is? Maybe it is super hot there?

point being you are replicating sitting in traffic.

so once you've had enough beers sitting out there letting it idle... go in the car.

rev it up to 1500 rpm, if after 5 mins (or less) it drops +20 F then you have a flow problem

As cliff said, you can run 160F thermostat and that will buy you more time but if there is a problem with cooling system you are just masking it...

Some people run a higher idle, some people run a different water pump that spins faster at the RPM then run ( TUNE )..

Some people find a different pulley and start with that.

the mods to the stock water pump divider plate that come with stock water pumps is a good mod.. as featured in older PY news letter.

[68blackbird]

I would look at pulley sizes. 8" crank pulley and a 6 1/2" water pump pulley.

Rich

[bullheimer]

i'll beat screaming chief to the punch and ask you How many eyebrows your pistons have. Hope you don't say "8"!

if they look like this you might have found your overheating cause (this is from ebay so may disappear in a few weeks):

[Squidward]

Pistons: Sealed Power forged pistons

Here ya go!

[steve25]

In all of this you have never mentioned how your motor runs?
What is the motors hot cranking compression and how much vacuum are you idling at?
If your stated temps readings are correct and your timing is at least 32 and your primary jetting is in the ball park then low cranking compression will tell you that your cam is in retarded which would be my guess at your issue with coolant temps!

[ta man]

Have any pictures of the fan and shroud?

[leeklm]

Originally Posted by steve25

In all of this you have never mentioned how your motor runs?
What is the motors hot cranking compression and how much vacuum are you idling at?
If your stated temps readings are correct and your timing is at least 32 and your primary jetting is in the ball park then low cranking compression will tell you that your cam is in retarded which would be my guess at your issue with coolant temps!

Speaking of timing... In an earlier thread I mentioned having an overheating issue when my vacuum advance was connected to a "partial" ported vacuum, which was not giving me enough advance at cruise speed. Make sure your advance is connected to a port that is providing full vacuum at cruise. Just something else to consider.

[Blued and Painted]

Once found the electric fans turning backwards. Wired wrong.

[77 TRASHCAN]

I bought one of those laser temperature guns. When they first came out, I could not affford one. I bought mine @ NAPA about 4 years ago, $59.95. You can find them all over for that price now, it takes the guess work out of engine temps, etc...

One of the dipsticks at my old job installed a long block in a 92 Chevrolet van. The intakes gaskets on those can only be installed one way. He had the gaskets installed so no coolant would circulate to the thermostat, essentially blocking all coolant flow. Boss checked w/ the thermal gun, told him to take the intake off...........asked him what he was thinking when he installed the gaskets.....drum roll..........I installed the new gaskets just like the old ones were..........we couldn't stop laughing.........sure ya did...

[mchell]

4 core aluminum radiator ?

Piddled around with mine for years....on a whim I replaced my high buck aluminum radiator and put in a 2 row 1.25 inch tube Griffin...wha la .....no more 200++ temps....two different engines, same cool results....in fact, it cools so well,I was able to get rid of all my "heavy duty" cooling garbage (fans, clutch etc....).....running standard duty fan,clutch and shroud...damn thing cools well!

[General Z]

It is 84 degrees outside. Just had it running for about an hour. Idling, resetting timing and going for a spirited test drive. During the long idle, it stayed under 210, perhaps 205. During the test drive, it got up to about 212 max and then came back down to about 205 when I let it idle again for awhile.

The electric fan has an integrated shroud.

My timing is set at 36 total, but I need to bring that down. I could hear pinging when I got on it. I also switched the vacuum advance to full manifold instead of ported.

I have a Thermocap on the radiator and it is showing about 180-190. Before the cam swap, the fan would hold the radiator at 160 all day.

The engine runs good, but I think I liked the old cam better than the new one.

Will a 7 blade clutch fan really work better than the Mark 8 fan?

[mnfatcat]

When you say Mark 8, are you talking Lincoln Mark 8 ? Is this a 2 speed fan ? I have a 2 speed Taurus fan running on the high side and it is the greatest fan I've ever used, cheap too.

[72LuxuryLeMansLa.]

When you degreed the cam where did you set the Intake Center Line?

[General Z]

Yes, the Lincoln Mark 8 fan.

I don't know how to degree a cam. I installed it straight up, with the dots at 6 and 12.

[72LuxuryLeMansLa.]

[QUOTE=General Z;5204300]Yes, the Lincoln Mark 8 fan.

I don't know how to degree a cam. I installed it straight up, with the dots at 6 and 12.[/QUOTE]

Well, there you go! It could be installed retarded and it will never perform correctly like that. You can not troubleshoot something if you don't know what you have to start with.