Overheating during cam break in - help

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mflynn

mflynn

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I've had all sorts of problems trying to do the 30 minute cam breakin recommended by Comp. 318 LA. Edelbrock Performer manifold. Comp Cam 262XE. Holley Street Avenger 670.

First, the Holley was flooding (secondary bowl) - I'd get it running for 10-15 seoconds, then it would flood - so I then tried another carb which also flooded, so I put a new secondary bowl on the Holley and put it back on and that fixed the flooding issue. All told - unfortunately - I had a bunch of starts and stops with the the flooding issue.

Finally, I got it to run for about 5 minutes then it got real hot so I shut it down. Put a new radiator on it today, got it to run for about 12-14 minutes, estimated at 2000-2500 rpm with a few times a little more, then it got hot again and shut itself down. Was running pretty nice for those 12-14 minutes. Tried to start a few more times, got some backfiring through the carb (a couple of fires even) so I let it sit. Checked a few things, found a leaky hose (which I fixed) and coolant level was down so I filled it up. Started it again, ran it for about 5-7 minutes (again at estimate 2000-2500 rpm) and the same thing happened - too hot, shut down, tried to get it going again, backfires, etc.

So I gave up for the night, then read a bunch of stuff on line that freaked me out, and now I'm hoping I didn't f*** up the cam.

I'm thinking about taking the thermostat out tomorrow for starters and trying to continue the break in procedure without it. I'm also thinking about spraying the radiator with water during my next attempt at the break in.

BTW: I have the stock fan, no shroud. And the temp sender (of course) isn't working so I'm not getting a true read on the actual termperature.

Looking for feedback on the following issues:

(1). Any suggestions on the overheating issue?
(2). Why the backfiring after the motor was warmed up and had been running nice?
(3). Did I f*** up the cam? How can I tell if I did?
(4). If I did not f*** the cam up already, can I continue the cam break in procedure? If so, do I need to run it for 30 minutes in a row, or am I good after enough 10-12 minutes?

One other thing - got some oil leaking someplace at the back, looking like it's coming either from the distributor to block gasket or (my worse fears) the rear rail of the intake manifold (thought I put enough RTV back there but maybe not).

Thanks in advance - I've read these forums 100s of times throughout my engine rebuild and am always amazed at how knowledgeable and brilliant - and willing to help - you guys are. And go easy on me - as I'm sure you can tell, I'm an amateur at this.
 
usually overheats cause the timing is retard.....did you use a timing light?

smell the oil..and see if it smell like gas....

rear bowl flooding...did you try to adjust float?
 
Thanks!

I have not checked timing. Do I need to be at idle to do so?

I tried to adjust the float on the bowl, and I replaced the needle. As it turns out Holley had a defect which caused the inner lining of the bowl to flake off, which was apparent when I took the bowl off. I put a new secondary bowl on and it's working fine now. I'm told Holley will give me a new carb if I return the one I got.
 
coolant low could be a head gasket, I mean where would it go if it didnt puke it out? popping could mean a valve is getting hung up or more likely you got a wire crossed, check 5-7. itll run decent at 2-3K on a crossed plug wire but wont idle for ****. Running hot could also be running lean. Are your floats set up correctly? Should just dribble out sight plugs when running (terrible way to check but thats the way). And take that Holley replacement carb! New is always better than defective. Hard to set idle when breaking in but you should be at about 34 BTDC at 2500, and then just let it return to wherever at idle. Get a timing light: beg-borrow-steal, then give back....
 
Generally you want it to start quickly and run at the recommended rpm 2000-2500 but you can do that more than once provided the rpm is achieved and its not sitting there idling. the backfire and heat issue could be caused by the timing being retarded , the heat issue could also be an air pocket but if you decide to pull the thermostat that will work , does the engine have a tick? usually when the cam is going it will start to tick and continue to get louder. Did you have the oil sending unit out? other than that it sounds like the leak at the back may be manifold related but look at everything you touched , clean the area and the leak will show itself. This stuff can be a source of frustration at times but with a little time and patience you will get through it. Did you change the valve springs?
 
Crank that timing up.... I run my 360 23 at idle and 35 all in by 2000rpm
Dont go over 34 unless you kno what your listning for
But sounds like you need more timing, if its retarted too much it will shoot fire down the headders and head up the water jackets in the head

If you already got timing square and still hott
Check clutch fan, or water pump (flowkooler pumps kick ***)
 
I always place a big fan in front of the radiator to aid the cooling system while I'm doing the first start up and cam break in. Another thing, the easiest way to prevent a air lock in the cooling system is to drill a 1/8" hole in the outer part of the thermostat. I was taught this trick by an old timer over 40 years ago. Finally, I keep a water hose with a spray nozzle on it to mist the radiator if need be to get the cam break in completed.
 
jay27 said:
, does the engine have a tick?
Click to expand...

No it does not. Does that mean the cam is still OK?

[/QUOTE] Did you have the oil sending unit out? [/QUOTE]

No

[/QUOTE] Did you change the valve springs?[/QUOTE]

Yes

Thanks for the help!
 
mflynn said:
Just by feel
Click to expand...

The cam will be fine.

What does that mean;"by feel"?And what do you mean"it shuts itself down?
-You know most guys cannot feel temps in excess of 135*F right?That is to say, we cannot keep our hand on that hot surface for more than a second or three; so I for one couldn't tell you if it was 130 or 180,or 220.You need to get an IR gun.Honestly tho, that's a pretty poor idea to not have a working temp gauge.
-The hole is just a bleeder. It can go anywhere on the flat disc,between the gasket ring and the pellet ring.You can accomplish the same thing, by filling up the engine through the stat house. When the liquid level comes up into the stat house, put it back together, and continue filling the rad until it is just above the core-tubes. Leave the cap off. Then as the engine comes up to temp,and when the stat opens, the liquid level in the rad will fall. Top it up again to cover the core tubes and watch for coolant circulation.

The backfiring during cranking is probably fuel related.
If it actually shuts itself off, and backfires, it either flooded itself to death, or ran out of fuel in the bowl, which could be the tank vent is not working, or the low-speed circuit dried up.
Well there is one other possibility, the valves ain't closing no more. With a cam change you always have to check the valve lash or lifter preload. If you bottomed the pushrods in the lifters, when cold, then as the engine warms up, it could, that is,could, happen that the valves no longer close. That will for sure cause stalling, and, backfiring during cranking.
And of course it could be electrical, but I doubt that.....
 
I leave the distributor loose enough to turn it by hand. When it's running, I turn the dizzy a little each way to see if it runs better so I can get through the cam break-in.
 
thanks for all the advice. I'll be back at it tonight. Based on the suggestion, here's the plan:

1). I'm going to take the stat out altogether for now, but drill the hole in it for when it goes back in after break in.
2). Fill the block through filler neck with coolant mixture, then the rad, then monitor during break in and fill as necessary
3). Get an IR gun at Harborfreight and use that to monitor heat (BTW: rewired the whole car as part of the build, having issues with the temp gauge - so I intend on having one, just not working as I had hoped right now - problem for another day, although I think it has someth to do Witt he instrument panel voltage resistor, so long as the IR gun gives me what I need for the break in which is my BIG concern right now)
4) mist the rad during break in
5). Set the idle jets a little richer and set the bowls a little higher, check bowls if I can during break in
6). Advance timing to 34 BTC at 2500 RPM (or thereabouts)

As to #6, although I have not checked timing while engine was running, I did rotate the crank just after we put the motor back in the car, and got #1 cylinder to TDC - at that point the timing mark was right at 10 BTC, which is exactly what the factory specs call for. I'm guessing that (a) the mark lining up at rest means little when it comes to actual timing and (b) the factory spec is worthless given the top end modifications? Comments/thoughts appreciated.
 
Sounds like a plan, hope it all works out. I'll be sitting on nins and peedles till I hear back from you.
 
SGBARRACUDA said:
I always place a big fan in front of the radiator to aid the cooling system while I'm doing the first start up and cam break in. Another thing, the easiest way to prevent a air lock in the cooling system is to drill a 1/8" hole in the outer part of the thermostat. I was taught this trick by an old timer over 40 years ago. Finally, I keep a water hose with a spray nozzle on it to mist the radiator if need be to get the cam break in completed.
Click to expand...

This is something i always do!! A big squirrel cage blower (set on high speed) up against the radiator even if you have a fan and a shroud. You want to keep the new motor as cool as possible since they usually run hot during "break in" because of the close tolerances. Spraying water (mist) on the radiator also helps as long as you can still tell if you have water leak. If you have a water leak it will allow pressure to drop in the cooling system and the water will boil easier.
I've broken an engine in 10/15 minutes at a time because of carb/water/timing issues. They all came out OK as long as you keep the RPM up!! Never start a new motor without an oil pressure gauge and a water temp gauge. Also, no open headers....you can't hear a bad rattle or knock with open exhaust.

treblig
 
I open my rad drain spout after it warms and the water has started to circulate, while it is still running I put the garden hose in the rad on low enough to hold the level, this little bit of cool water being constantly added has worked for me. Also timing is big as mentioned, retarded timing sometimes turns the headers cherry red during cam break in.
 
Heat gun - great idea. Don't get over worried if temperature spikes a little. Usually does Spike a little and then come back down especially during a break-in I mean don't let it overheat but I think it's a little over hot that's not out of the ordinary.
 
I also start it with the radiator cap off and usually it will go down when it circulates, then add as you go. I like another person there to look for leaks, watch the radiator level, and such.
 
The coolant dropping indicates you had air pockets. Some engines are difficult to purge out air, though haven't heard of that in Mopars. My M-B diesels are tricky and any air pockets make the temp sensor read much higher than normal since it is seeing hot vapor.
 
mflynn said:
thanks for all the advice. I'll be back at it tonight. Based on the suggestion, here's the plan:

1). I'm going to take the stat out altogether for now, but drill the hole in it for when it goes back in after break in.
2). Fill the block through filler neck with coolant mixture, then the rad, then monitor during break in and fill as necessary
3). Get an IR gun at Harborfreight and use that to monitor heat (BTW: rewired the whole car as part of the build, having issues with the temp gauge - so I intend on having one, just not working as I had hoped right now - problem for another day, although I think it has someth to do Witt he instrument panel voltage resistor, so long as the IR gun gives me what I need for the break in which is my BIG concern right now)
4) mist the rad during break in
5). Set the idle jets a little richer and set the bowls a little higher, check bowls if I can during break in
6). Advance timing to 34 BTC at 2500 RPM (or thereabouts)

As to #6, although I have not checked timing while engine was running, I did rotate the crank just after we put the motor back in the car, and got #1 cylinder to TDC - at that point the timing mark was right at 10 BTC, which is exactly what the factory specs call for. I'm guessing that (a) the mark lining up at rest means little when it comes to actual timing and (b) the factory spec is worthless given the top end modifications? Comments/thoughts appreciated.
Click to expand...

2 and 4 are not necessary, but having a garden hose ready nearby has saved my bacon a time or two.. 1) is an ok idea. 4) the IR gun is a great idea, 5a) there are no idle jets, 5b) the fuel level will be ok for break-in, anywhere in the bottom half of the window, or if no windows; at or near climbing out over the threads. For break-in this is not critical, so long as the float-valves control the fuel, and no flooding occurs, and 6) as earlier stated, just crank the dizzy to whatever she likes, soon after she fires up, this is not a panic. Leak checking is number one.
Then as to your last paragraph; this needs clarification. If you correctly determined the piston TDC with a piston stop, and the TDC mark truly was advanced 10*, then that damper is junk. Get rid of it before it comes apart. And you are correct, the factory timing barely applies to the factory engine. After the break-in is done, it will be up to you to determine how much timing the engine wants, and how to give it to her, and no more.
 
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