I have a 350 Rocket in a Cutlass I’m just finishing restoring. Car is a 72, someone put a 69 in it at some point. We rebuilt engine, can’t seem to get it dialed in. Idles good, but gets hot very quickly. I installed electric fans and they kick on at 180 degrees with minutes. Paint at exhaust ports on heads has burned and discolored from heat and car has been drive any distance yet. Idles good, when I bring rpm’s up I’m getting flutter/miss. Checked timing, replaced plugs again. Readjusted quadrajet that was professionally rebuilt and tested. I used vacuum gauge while adjusting carb, notice needle fluctuating severely. Checked all hoses and carb mounting for leaks. I did install a Pertronics unit in distributor instead of one points. I’m at point I’ve exhausted my ideas, any input appreciated. In Cincinnati area, I’d take to a reputable shop if I can find one that will mess with old cars.

 

Static timing should be at 12-16⁰ idling, NOT 8-10 like a Chevy.
More details are needed

 

Did it overheat before the rebuild? Was the block dipped and cleaned? How many row radiator, what is its condition?

AC car? Fan shroud in place?

Thermostat boiled and watched to open?

Good luck!!!

 

What thermostat, fan, shroud and radiator are in the car? It sounds like it may have a vacuum leak. Stock iron intake? Is the carb stock to the motor? What was all done in the rebuild?

 

Sounds like you have 2 issues, valvetrain not set up correctly and an air pocket in the cooling system.

 

I didn't see where he said he had adjustable rockers.

 

Electric fans, eh? Some are much better than others, and you didn’t say which ones you have. Many overheating issues are due to electric fans that don’t move enough air.

 

Yeah, I reread, missed that. Not all electric fans are created equal, especially aftermarket ones.

 

I reworded my post.

 

It did not. Cam was worn, typical 125,000 engine. Ran ok, just tired.

 

Machine shop clean and check block and internals. Had to go .030 over on cylinders. Rebuilt rods, rebuilt heads, installed new cam bearings. I assembled engine. Sent carburetor out and had to reconditioned. Water pump was rebuilt. Installed 180 degree thermostat, installed new griffin 4 core aluminum radiator with twin Spal electric fans. The radiator has shroud that fans mount to.

 

Cooling system has been purged, performed compression check, compression was good and consistent across cylinders

 

Spall fans came with Griffin 4 core radiator. Engine builds heat very quickly, fans control heat well, pull temp down.

 

 

What is the temp at idle and going down the road? Do both heater hoses get hot? The paint burning off is normal IMO even early on.

Put a timing light on each plug wire, aim the flash at the dark firewall and watch for an erratic blink the same time as the flutter/miss. Try disconnecting the vacuum advance when it flutters/misses to see if it changes, this would indicate a problem as the breaker plate moves.

Triple check the firing order.

Good luck!!!

 

I’ll try the timing light on each cylinder. I check residence o. Plug wires, changed plugs… I honestly thought about pulling intake and resealing. Then installing new distributor and going hei.

 

If you have a vacuum gauge "needle fluctuating severely" I'm curious how installing a new distributor and going HEI is going to address a severely fluctuating vacuum needle reading and allow you to dial-in a steady vacuum reading. I believe, you have either weak valve springs &/or bad valve guides if what you stated is true and w/in the range identified by the chart I posted. A regular fluctuation (as noted in the chart) could indicate an intake manifold leak, but a severely and erratic reading (w/in the ranges identified on the chart) speaks to an incorrectly setup valve train somewhere (as noted by Eric). Pay attention to the range of Hg readings in the chart. Good Luck.

 

I completely missed the erratic vacuum readings, Eric and Norm are right that can be a valve spring or sticking valve.

Good luck!!!

 

Hmmm you still need to take into consideration what the total is too.

 

I’m wondering what valve springs would have to do with an overheat issue, hmmm.
Op, make sure you have flow in the radiator. Also don’t wait till 180* to turn on the fans, turn them on at 160*. In addition make sure you’re not running lean anywhere, that’ll add to your issue.

 

Doubt valve springs have anything to do w/ an overheat issue. OP states a severely fluctuating vacuum gauge needle & engine flutters & misses as RPM is increased. Engine shouldn't demonstrate a severely fluctuating vacuum gauge reading though.

 

Yet he has not posted any timing specs. It could be way too advanced or retarded. Timing was checked is not enough to go on.

 

Timing is at 16 degrees. I’ve checked every thing everyone has listed.

 

When you say it builds heat quickly, how hot in degrees is it getting? If the fans can control the heat what temp is it running at? The flutter could just be a timing curve issue. One or more of your new plugs could be bad. What is the vacuum gauge doing when you rev it till it flutters. As was mentioned before, does it have an adjustable valve train or the oem non adjustable?

 

Are the electric fans pulling the air through the radiator or pushing (mounted in front or behind the radiator)?
Are they wired up correctly so that the air moves in the driving direction and not the other way arround? Easy check with a piece of paper in front of the radiator when the fan is on.

 

Fans mounted on back side of radiator, the are wires correctly and pull air thru radiator.

 

Curious, are these cast or forged pistons in this rebuild? I would be looking at possibly pulling the intake and revealing it.

 

Wondering if one of those infrared pointer do-dad thermometer thingies would help you determine where the heat is originating from..

 

I’ve used one. Car isn’t overheating….just heats up freakishly fast. Fans kick on 3/4 minutes after starting her up. Still running bad. Haven’t had time to mess with it.

 

I would check the basics of the engine first with a cilinder leakage test on all cilinders to make sure the valves really close, check the valvelash if they are adjustable.
Then check if the TDC on the balancer is corresponding with the piston position using a piston-stop and rotating the engine in 2 ways, marking the balancer at the stop and dividing the middle, this should be 0 on the balancer.
To be 100% check the valve timing to make sure it has not been set wrong on the timing-set.
If OK then check the timing again (without the vacuum cannister attached!), the centrifugal advance for free movement of the weights and the vaccum cannister for leaks.
if still not OK check if the carb is squirting from the accelerator pumps if throttle is applied and if fuel is flowing in general, just to make sure as the carb has been rebuild.
A lean mixture or bad timing will make any engine run very hot and have no power.

 

Was it the 72 Qjet on this rebuilt 350? Was it just rebuilt or recalibated for this engine. Please post all the specs including compression ratio, camshaft used etc?

 

You still haven't mentioned any actual temperatures.

 

Sorry all, even busy with life and battle of the Olds.
Still having issues. Car is idling ok, vacuum gauge showing around 13-14 inches, but indicates late ignition timing. It is still jumping a bit.
timing is set at 12 degrees with advance disconnected. Replaced plugs, all looked consistent. Performed compression test, had 2 cylinders at 145, 2 at 150 and 4 at 160. Performed cylinder leak down test, at 60 psi all cylinders held 59# except one was at 57. Replaced plug wires. As soon as engine comes off idle it develops a miss. I am running stock distributor with Pertronix Ignitor 2 , very mild cam. Engine was rebuilt had has maybe 2 miles on it. Carb was professionally refurbished. Fuel pump, fuel lines and fuel tank are new. Was replaced during engine install. May try new hei style distributor and look at coil.

 

I put a new head on a 4 banger once and had the timing 180 out (TDC while exhaust valve is open) and it ran sorta ok and overheated. You said you check all but it may be worth pulling the valve cover to be sure?


Good Luck!

 

What cam? What pistons and compression ratio?You should have higher vacuum with something like the 204/214 cam, assuming this is the highest vacuum possible. Your timing should be within stock specs. There may be an issue with the Pertronix Ignitor 2 points conversion.

 

I’m not saying I know much of anything here, but a long, long time ago I had the outer ring on a stock harmonic balancer moving around, and the car did all kinds of awful things. It was super frustrating, as yours is, but was easy to fix.
Use one of those piston stop things in the spark plug hole of #1 cylinder-pull your plugs out, put the piston stop in, and rotate the engine until it stops. Mark it there aligned with the zero of the timing tab. Rotate the engine the other way and mark that when it stops. Halfway between those marks should be zero. If not, maybe change the balancer out.
It is pretty apparent that there is far more knowledge on this forum than I can contribute, so do this only if you run out of other things to try. I hope it helps.

 

yes