What just happened?

[Stewart G Griffin]

This morning i was running a little late so i kind of hammered it, not too much---i only went about 75-78ish.  i normally go 55-60 ish.  Towards the end, near work the engine, my 305, starting sounding funny---LOTS of pinging and sounded like a diesel.

i will have to say that i installed a grill block a few weeks ago which covers 80% of the grill which is probably too much but i'll discuss that in the other mpg thread.

To me, it sounds like overheating BUT my temp gauge read normal.

Then i thought it might be a tank of bad gas---i filled up recently at a faraway station.

But on the way home from work, it sounded and ran normal.

What just happened?

[fitz]

I'm guessing the 305 didn't like being pushed that hard.
How accurate is your temp gauge? 

[Stewart G Griffin]

i think it's pretty accurate---it's an autogage pt.# 2355.

A few weeks ago when i got on it hard AND the weather was warmer, the gauge did go up a little past normal.

[Stewart G Griffin]

UPDATE:
i was late again and the same thing happened;  This time i looked closer at the gauge and yes it was running at about 230 degrees vs. 195ish normally.  The grill block is too big.

[Stewart G Griffin]

Well.  i think i cooked it.   i was late again and hammered it and this time the engine said NO.

How hot is too hot for a chevy small block?

[VileZambonie]

Why in the world are you blocking off 80% of your radiator??? If you bring cylinder head temps up that high and detonation occurs it won't take long to annihilate your 305.

[Stewart G Griffin]

OK, here's my theory on what happened.

Remember this thread?
http://forum.73-87chevytrucks.com/smforum/index.php?topic=12865.msg240658#msg240658

Back last December-ish, i had to change waterpumps because the old one was leaking.   i could not get the old fan studs out of the old waterpump.  i was in a hurry and thought----it's cold i should be ok if i get stuck in a traffic jam without the fan and so i put everything back together without the fan.  i did get stuck in traffic and the temp was no problem at all.

Then we get to last summer and i got caught in another traffic jam.  This time it got REAL hot---like 260 on the gauge and the temp light came on.  i even had the heater on full.    So i quickly search for the next exit and do some driving at 45mph+.   It cooled down to normal and i thought i dodged a bullet.  The engine seemed to run just fine after this.   (incidentally, the summit mechanical temp gauge stopped working after this incident and i go ahead and get an autogauge electrical temp gauge)

After this i started getting more serious about putting the fan back on.  i have a 4.3 v-6 sitting in the garage (which i'm going to have to use now as you'll see in a sec) and decided it would be easiest to take the fan studs off the 6 and put it on the 305.   

So now i have a fan again, and i should be happy?    But no, i got stupid and put in a grill block in order to try to get more MPG.  This grill block was way to big and the radiator doesn't get enough air if you go above say 65mph ish. (i will show a picture in the other mpg thread)   But i figured i have a fan now, so it would be ok.  And i also have a temp gauge so if it gets too hot i'll just back off or pull over. 

So we get to a few weeks ago and i'm late for work so i really get on it---maybe 75-80mph.  Getting almost to work i sense the engine sounds different and we have pinging and almost sounding like a diesel.   But i hope for the best and sure enough after work it starts up and runs normal.   i decide a few days later it's probably best to remove the grill block completely for now.  (btw, the grill block seemed to have absolutely no effect on mpg.)

Then we get to last week and i'm late again.  This time on the highway, after a while the truck WILL NOT go faster than 65, and in fact starts slowing down even with my foot to the floor.   i do notice temp gauge getting to about 230 (engine normally runs at 195), but since the temp light didn't come on i figure it's ok even though i'm panicking because the engine is losing power and this has never happened before.   So i back off of it.

A few seconds later everything seems normal again and i'm able to accelerate to 75+ again.   Well, everything IS NOT normal because as i exit off the highway, the engine just shuts down.  i try to re-start it, but it won't even turn over---- i'm thinking it may be hydrolocked.    i had to get someone from work to pick me up and at night i had AAA tow me home.

i think what happened is last summer i did some damage and then a few weeks ago did some more damage and then it was only a matter of time.   i'm going to take it out soon and further inspect.

Well, perfect excuse to put in the v-6 i've been wanting to do for a while.

[VileZambonie]

So the moral of the story is while you may have save $1.00 in fuel economy you cost yourself a lot more $ in the long run.

You absolutely need a cooling fan and airflow. If it is winter time you might have gotten away with it but if you cannot get rid of the heat energy at the radiator it's going to get rid of it somewhere else.