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jmbjs 04-13-2006 09:32 PM

thrilling moment...
I started my first engine rebuild on its 20 minute break-in period. It started right up and that was a wonderful feeling. Anyway, I kept the engine above 2200 rpms, according to the cam card, and the 20 minute breakin is separated into 2 parts. As I finished the first session the radiator looked like it wanted to boil over. I had the cap off, filled with plain water, and no thermostat installed. The temp slowly climbed to about 210 degrees at the end of the first 10 min. session. I had advanced the timing to 38, Which was recomended to me by a bud. I must say that I had forgotten to install the vacuum hose from the carb to the distributor. Once I turned the engine off, the radiator did shoot water up and out of the radiator. It just seemed that the engine was on the way to getting too hot. I did not have enough time to finish the 2nd half of the break-in...besides, its supposed to cool down first before the 2nd half. Thats for the morning after a parts store run for the vacuum hose.

Here were the conditions:
It did get warm here today here in Tenn. and I was in a garage with not a lot of airflowing thru. I had switched on the electric fan the entire time. I do have a stock water pump. I have approximately 11:1 compression. I hope this provides enough info, now, my question: Am I right to assume it was running too hot, or well on the way to running too hot? How hot should I let it get before shutting it down? Is my stock water pump enough for this engine? Do you think my water pump might be out? I thank you in advance for any and all suggestions.


1972 Chevy Vega coupe:
Holley 600cfm carb, Holley street dominator intake
Brodix Ik 200 aluminum heads (.055 copper gaskets, appr. 11:1 comp.)
Howards cam (.410/410 lift, 288/288 duration) 1.6 roller rockers
HEI Petronix Flame-thrower 50,000v upgrade kit
8mm accel wires
350 bored .030 over, with flat-tops
3.562 offset grind crank
Moroso windage tray
Hooker headers
T-350 with shift kit/3200 ACC stall convertor
4:56 running gear, 26x8.5 slicks
Griffin radiator w/flex-lite Electric fan

curtis73 04-14-2006 02:36 AM

Having the cap off and only using water were the culprits. Use a 50/50 mix and a radiator cap. Left alone, water will boil at 212 which I'm sure the heads saw consistently. As soon as you shut it off, the water stopped moving and rested against the screaming hot metal of the engine. Bingo... boiling. Pressure also prevents boiling which wasn't there without the cap.

Mix 50/50, use a 15 lb cap, and you should be fine. If you're not, ditch that electric fan. A belt-driven fan takes as much as 10-15 hp to run. You can't replace that kind of airflow with a 3/4 hp electric motor, especially because it draws HP, too when the alternator tries to keep up.

Once you have all of that in place, don't worry about the actual temperature unless its going past 220 or 230. As long as you don't have boiling you're fine.

Jmark 04-14-2006 11:10 AM

Yep, I agree with Curtis. 210 is not "hot". Add some antifreeze and put the cap on!

On a side note, personally, i'd take the timing back down some for the breakin and would NOT hook up the advance until you can drive it and determine if you really do need more timing. Using more timing than you actually need, will cause the engine to run hotter than it needs to also.


curtis73 04-14-2006 11:32 AM

Agreed, and CONGRATS on your build! I forgot to say that in my original post. A thrilling moment indeed.

2wld4u 04-14-2006 12:10 PM

38 degrees might be too much, I would break it in with 32 Degrees total timing. then after you brake it in, then you might want to bump it up to 34, 36, then 38 to see where your combo likes it most. I never bump in that much timing on intial start up.. but I do have to admitt I do things a lil differnt.


scanman 04-14-2006 12:44 PM

re: thrilling moment
congrats on your startup. INMHO vacuum leaks cause lean mixtures which can cause overheating. check upper end for proper oiling. radiator cap is necessary for pressure needed to raise boiling point as previously mentioned. I agree about too much timing during break in. that leads to another point . heat is generated as parts seat in there for elevated temps early on may be normal. recheck what members have mentioned and best of luck w/ your project. per curtis 73: that hosrepower is consumed by the waterpump as well as the fan. turnung the fan wokt cost that much hp loss since you ars already spinning the pump.

xntrik 04-14-2006 07:28 PM

First, I never run without a thermostat.

Second, you have an airflow problem..... too small of a fan... ditch the electric and go to a fan clutch......

.. OR

Third, you have too small of a radiator.

Bulloney=== 210 degress at 2200 rpm is way-way-way too high. What are you gonna do when summer gets here??????? Running 250* in traffic will be no fun for you at all.

Your engine should never have gotten above 170 if you had a decent cooling system.

Rick WI 04-14-2006 10:11 PM

Ditto lucky number 7. Think of it this way, your rejecting about 15 HP running it up to 2200 with no load on it, if that. If the cooling system has an issue with that there is a problem. There is also no reason to not run a thermostat.

With your radiator it should have a hard time getting up to temp on break in not overheat.

There is a hiccup somewhere.

38 is a lot of timing for that setup. I'd be in the 35 or 34 range.

56Maynard 04-14-2006 10:51 PM

Got a fan shroud?????? If you dont, get one before you continue. If you do, fill er up with water and put the cap on and finish the break in. Personally, I wouldn't have anything but water in it until I knew everything was holding water. Coolant will kill your bearings if you have an internal leak.

jmbjs 04-14-2006 11:32 PM

Thanks folks,
Tommorow morning I will make adjustments on the timing to see how that works...I will post again tomorrow night to give ya'll a SITREP...Thanks very much for the suggestions and thanks for the patience!

Take care,

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