12 Last
Item Posts    Sort Order

400 scb running hot need help........

 
86montess3
I love my Chevy Chevette!
Posts: 6
Joined: 08/10
Posted: 08/15/10 01:45 AM

hi guys Im new to this forum but I been getting mags for years now..  any way, I recently built a 400 sbc 40 over(408) it has forged 5.7 rods, speed pro 10.5 to 1 compression pistons, cast crank, comp cams 268XFI (268 int.duration-280 exhaust. 520 intake lift-515 exhaust lift) with a pair of 165ss dart heads(72cc chamber), rpm ferformer intake and 650cfm doble pumper mechanical sec.(primary jets:70 sec. jets:78), also a high volume mechanical water pump... timing set at 34* full advance and 14* initial..
the problem is at idle it will hold the temp. at 160-170 but as I get on the hwy it climbs to about 200, but if I gas it and temp climbs up to 210-220 I cruise it again n it never drops the temp.    Im running a set of electric fans (not sure cfm rating)and a 160 stat. now I live in dallas tx and this happend at 100-104* ambient temp. I need help because I have put a new water pump, stat steel cored hoses and a 3 core all aluminum rad.  the car is an 86 monte carlo ss.
the only thing I havent changed is the fans but they feel like they are blowing pretty good.     could this be an air flow problem,water flow, timing, or carb running lean, or does the temp under the hood gets hot enough to fool the gauges?
Im running out of things to change lol...    by the way I have two temp gauges wich leads me to believe they are telling the truth... and also the heads have steam holes and the gaskets match I torqued them my self...
sorry for the long explanation, but any advice, thaughts or ideas will be highly appreciated... thanks ..  

Post Reply
gettnlarge01
I mow my lawn and find Chevys
Posts: 3330
Joined: 09/09
Posted: 08/15/10 06:43 AM

did you try a std.volume water pump?  
luck is when skill and opportunity meet

Post Reply
86montess3
I love my Chevy Chevette!
Posts: 6
Joined: 08/10
Posted: 08/15/10 08:37 AM

no, but I did had a 35gpm electric water pump on it wich it was the first thing I changed (to a mechanical) because it was my primary suspect.   would a std pump work better?  

Post Reply
gettnlarge01
I mow my lawn and find Chevys
Posts: 3330
Joined: 09/09
Posted: 08/15/10 04:09 PM

theres a theroy thats goes"if the coolant doesnt have time to remove heat from the engine because its flowing to fast then it wont".
I have a stock style waterpump,GM 4-core rad and clutch fan on my 406[450hp/500tq] that runs at 190-195  
luck is when skill and opportunity meet

Post Reply
86montess3
I love my Chevy Chevette!
Posts: 6
Joined: 08/10
Posted: 08/15/10 04:27 PM

so how could you slow the flow down with this pump? will a 180 or 190 stat slow the flow down vs a 160 what I have now? or the only solution to slowing the flow would be to put the factory water pump on wich I never tried on this motor?  

Post Reply
68scott385
I mow my lawn and find Chevys
Posts: 1994
Joined: 10/09
Posted: 08/15/10 04:45 PM

Have you changed pulley diameter on crank or waterpump?  
68scott385 68scott385 68scott385

Post Reply
idrivejunk
I mow my lawn and find Chevys
Posts: 5119
Joined: 12/09
Posted: 08/15/10 04:47 PM

A warmer thermostat will not change the speed of the coolant thru the intake at full operating temp. Open is open.  
idrivejunk

Post Reply
skyeking
I mow my lawn and find Chevys
Posts: 2738
Joined: 08/09
Posted: 08/15/10 05:14 PM

Hi there,
Have you overdriven the water pump pulley in relation to the crankshaft pulley??
With iron heads ..NO.. With Allo heads..Recommended...  
skyeking

Post Reply
86montess3
I love my Chevy Chevette!
Posts: 6
Joined: 08/10
Posted: 08/15/10 05:27 PM

all the pulleys are the stock ratio's...    and its an iron eagle headed 400.. Im starting to think is the fans, its a dual electric 10" or  11" not real sure I had them laying around thats why I just slap them on, but the plastic shroud that holds them together does not have the relief rubber flaps...   what kind of cfm rating fans do I need for this set up?
by the way I appreciate the reply's....  

Post Reply
BigBlockBuck
V-6 Camaros rule!
Posts: 56
Joined: 09/09
Posted: 08/16/10 08:38 PM

Is there suppose to be an air dam to help direct air through the radiator? Do you have one on it? Those fans could flow a million cfm but if air has trouble getting in front of the rad the fans can't pull it through. At highway speeds there should be sufficent air flow that the fans arn't needed.  

Post Reply
tuffnuff
Moderator
Posts: 7841
Joined: 12/09
Posted: 08/16/10 09:59 PM

By and large, electric fans will create 40 MPH wind velocity, or air movement. They do NOT speed up with engine RPM's. A proper shroud is required so that the air has to go through the rad, into the shroud tunnel and then blow through,,, without the shroud, there is prop wash and half the air gets scattered out the sides
Smile  
When The Flag Drops.,.

tuffnuff

The Bull ***t Stops.,.
tuffnuff

P. Engineer, Engine Builder

Post Reply
Pontiacman2
Moderator
Posts: 8956
Joined: 09/08
Posted: 08/17/10 06:19 AM

Yep  
Pontiacman2
Pontiacman2

Professional Hi-performance engine builder

Post Reply
86montess3
I love my Chevy Chevette!
Posts: 6
Joined: 08/10
Posted: 08/17/10 07:47 PM

here are some before and after pics of the radiator gap that I did not pay attention to, its not in between the fan and the rad but its actually between the rad and the core support wich Im asuming when the outside air coming in is easier to go around the rad into the engine bay vs ramming straight through the rad and fans, or instead of pulling out fresh outside air is drawing engine bay hot air...  what I did, is stuffed some foam in between the gaps, the gaps on the side you could get your palm in between it and there was a small gap on the top of the rad about 1.5" wide so I stuff the *** out of it with foam for a temporary fix to see what its going to do it got dark on me so I didnt go for a drive today but tomorrow I will....
before:
http://i239.photobucket.com/albums/ff11/26scoupe/monte%20ss/SD531023.jpg
http://i239.photobucket.com/albums/ff11/26scoupe/monte%20ss/SD531024.jpg
http://i239.photobucket.com/albums/ff11/26scoupe/monte%20ss/SD531025.jpg
after:
http://i239.photobucket.com/albums/ff11/26scoupe/monte%20ss/SD531026.jpg
http://i239.photobucket.com/albums/ff11/26scoupe/monte%20ss/SD531029.jpg
http://i239.photobucket.com/albums/ff11/26scoupe/monte%20ss/SD531030.jpg
not really sure if you all can see what Im talking about but the gaps where pretty big..

also will  having no scoop increase pressure or create a restriction for the air thats tryng to come in?    like tryng to stuff 50 pounds of crap into a 40 pond sack...  just a thought.
as far as the air ram under neath no it did not come with one from the factory but I fabricated one with an actual scoop and all that was the secound thing I did after switching to a mechanical water pump, and didnt really notice much of a difference if any..  

Post Reply
68scott385
I mow my lawn and find Chevys
Posts: 1994
Joined: 10/09
Posted: 08/17/10 08:03 PM

Do you plan on putting the A/C back on?  
68scott385 68scott385 68scott385

Post Reply
86montess3
I love my Chevy Chevette!
Posts: 6
Joined: 08/10
Posted: 08/17/10 08:25 PM

I was planning to, but if I cant get her to cool down I guess I wont be able to.. I had a talk with a buddy of mine that said 400s always run a little warmer, but is that an old wives tale? or is it true?   if I can get it to stabilize at 200 or lower I think I would be cool with that but i cant bring 220 down after nailing it thats what scares me...  

Post Reply
12 Last
TO TOP