ok I'm searching here.
my temp gage is saying its running hot 240 -250 after running for about 15min.

I started it up cold and watched the temp gage. at 170deg (what the thermostat is)the intake near the thermostat is still cold (it reached this temp very quickly 3min?).
at about 200 the fan kicked on, heck the radiator is still cold, and stat is closed.
around 220deg the thermostat opens and radiator gets some heat.
the temp still climbs to 240 slowly.
drove it around the block (first time on new motor wooohooo) temp got to 256deg.
I have checked the sending unit it the right head it is the one that controls the gage readout.
Is it possible that the TPIS headers are heating this sending unit up before the coolant does? and causing this excessive temp?

I thought that maybe it was a blown headgasket, but the radiator is not overflowing (only to the full hot mark, then sucks it back in when cold, normal I think).

info: 86 vette, 406ci (yes I drilled the steam holes in heads/gaskets), mini-ram, tpis headers, edelbrock waterpump, 170deg stat, griffin radiator,

one thing I didn't do , drill bypass holes in thermostat. guess I'll have to try that.

Has anyone else had this kind of problem???? what was the solution?
any ideas are welcome. thanks
RJ :confused:

 

I have a high flow edelbrock water pump, tapped and blocked the bypass in the block. I had drilled a few bypass holes in the thermostat and found that my temp was going way up-down a little then back up. It seems I had so much pressure that it was pushing the thermostat closed. The fix was to go to a high flow "balanced" thermostat. Now it opens at 160deg. no problem, but it does pass coolant even when closed, so in a real cold climate it may not warm enough. Hope this helps. :cheers:

 

thanks for the reply driveit,
I didn't plug the waterpump bypass. totally forgot about it, and the holes in the thermostat. I've never done that on older motors.
I will drill the thermostat and see if it helps. then if need be plug the bypass.
RJ

 

You have a thermostat problem for sure, just not sure what. Try a Robert Shaw high flow, there are some high flow pumps that require this stat (even with their own name on it). Check with your pump manufacturer and see what they recommend.

Sometimes the simple suggestions help - don't get pissed - make sure the stat is mounted in the correct position, or it would do exactly what you have going on.

Good Luck,

Pete

 

I had the same problem with my 86' 383. The wire that goes to the sensor started melting because of the header heat. A little shielding and the sensor worked fine again.
Good luck
Joe :yesnod:

 

thanks for the input guys,
this thing just has me scratching my head and looking at wiring diagrams. trying to find what temp sender does what. every book i have seems to be different (86 service manual says right head is fan turn on, well not on mine apparently :rolleys: ) one of the senders on the intake is listed as a cold start timer, I don't have a cold start injector with the miniram. wonder if I can pitch it? that is if I could figure out which one it is.

come to think of it the engine does get hot as I rev it. maybe the waterpump pressure is closing the thermostat.

this is getting to be like playing "were's waldo?" there he is! no wait thats not him. this one? nope :crazy:

 

thanks pete, I was wondering at one point if I might have the stat upside down. spring goes toward intake right? it wouldn't be the first stupid thing I ever did. :boxing

 

There a few things that should be checked/done.

I'm running a 415, auto, full length headers and stock radiator/water pump, etc.

I plugged the coolant by-pass hole in the passenger side of the water pump; drilled four holes in the 170 degree stat and completely eliminated the cold start injector on my 86. I found a 170 degree stat at AutoZone for $5 or so which was made for a foreign car. The OD was a little too large, so I just used my Mikita grinder and removed some of the metal from the OD.

I drilled the holes in the heads and block for steam release and also enlarged the center coolant holes in the block (between cylinders 4 & 6 and between 3 and 5 per Fel Pro Headgasket instructions.

Ignition timing is crucial too. Slightly retarded timing will make the engine run really hot in a hurry and will make the headers glow red too in short order.

Be sure to burp the coolant system to get all the air out. There's a packing procedure which I always use. Idle engine til it reaches 100 degrees or so, remove the radiator cap, grab the throttle lever and raise engine speed to 2000 or so and while keeping it there, pour in additional coolant mixture. Replace radiator cap wil engine is still being held at 2000 rpms. Voila, all air is gone.

I got confused too with the location of the two sensors in the heads since different manuals contradicated each other. The dash gauge sensor is in the passenger side head and the fan sensor is in the driver's side head.

BTW, I've got my fan coming on at 180.

In this Texas heat, at night I run in the 180s during the day 10 degrees more; A/C on in street traffic/100 degree day temps at 220. Can't let it idle for 20 minutes with A/C on though; temps climb to the 240/250 range. Gotta keep lots of air flowing through the radiator.

Hope this helps.

Jake

 

thanks for the reply JAKE.
good to know that someone is running cool with the 400 block. especially since your using the stock radiator!
grinders are wonderful things aren't they!
I have new confidence that this can be solved now, thanks again everyone.
RJ