I was wondering if anyone has had experience with putting blok fill in the LT1 blocks. I am having trouble keeping my engine cool in 85+ deg. weather, and have run out of options. I have heard both ways that blok fill helps the engine run cooler, and some say it would run hotter.
I have a custom built aluminum radiator, elec water pump, 160 thermo (have tried no thermo, and drilled holes in a different thermo also and didnt help) and everything has been cleaned and flushed (including engine block when re-built) factory fans are on manual all the time (both seem to work good), i run a 90 % distilled water mix with ethylene glycol, and 2 bottles of water wetter. Only thing i havent tried is a new radiator cap, block fill (might try when i pull the motor next) and aftermarket fans. The engine runs cool (about 185)driving around town but for long runs at 60 MPH (about 3200 RPM with the TH350 and 4.11's) it slowly climbs to 210-220 until i shut it down. Doesnt take but few mins with the fans running to cool back down to 170 or so (with engine off)
I have a pretty wild high RPM/compression, solid roller setup anyway, so i think the blok fill wouldnt hurt. I appreciate any opinions

Chad

 

LT1's from the factory run up to 210-220 before the secondary fans kick on. So thats not that hot, but if you have both fans on and a 160 degree thermostat it should run alot cooler. Are you sure you have all of the air out of the system? Are you getting good flow out of your Electric WP?

 

I am not positively sure what kind of flow im getting out of the water pump, i am no sure how I could tell exactly. The radiator gets Uniformly warm, and nopthing seems to be out of the ordinary when it heats up.
I have tried and tried to bleed the air out of the lines, probably for the past 2 years this car has been doing this.
210-220 isnt real hot compared to stock, but its not right either. DFI recommends the car run 180ish to work best with the Gen 7, and also with nearly all the coolant being water, it doesnt take much to start to boil over when it gets around 220 deg. Thanks for the suggestions though

Chad

 

I believe for every pound of pressure the radiator cap adds, the boiling point of the water is raised 3 degrees. Correct me if Im wrong but why not replace the darn thing? I'm actually fighting overheating problems my self out here in Vegas sitting on the freeway sucking exhaust fumes in 110 degree weather is a challenge

 

Air flow thru the radiator? Is the air dam still present?

 

That is next on the list...a radiator cap, but even if the cap was faulty, it would just boil over into the overflow resevoir sooner than it is supposed to....but really it should never get that hot with the custom AL radiator and everything else i have.
About the airflow through the radiator, i was going to experiment around with that idea. The air dam is present, but when the guy made the radiator for my car, he made a fan shroud out of a piece of aluminum sheet metal, cut holes in it for the fans, and mounted them to the shroud, then to the back of the radiator. When going down the highway at 50-60 MPH, could the fans being on actually RESTRICT airflow through (air speed coming through the radiator being faster then the fans are able to pull through)the radiator since there is no way for the air to bypass around the fans, like on a stock shroud. If you have noticed, the stock shroud is made of plastic, and has two rubber flaps under the fans....I am thinking that those flaps open up when going down the highway to allow more airflow through the radiator. and when at a stop, the flaps "close" to allow the fans to draw air through the whole radiator. What if i just used some of the plastic straps that go through the radiator, and mounted my fans directly on that way? OR what if i cut two rectangle holes in the aluminum shroud i have now and riveted the rubber flaps on the back to serve as a one way valve...kinda. any thoughts/suggestions on that?

Also, any body have any experience with the block fill and how it affected the cooling?
Thanks again

Chad

 

Block fill is not the answer.
If I where you I would get a stock shroud and fans as the F-body set up is prety darn good. Yes the fans runninjg at Hwy speed can abstruct air flow. My corvette has a very small margin for error so I have to have all of the front spoilers in place or I will have overheating problems. With an alum. radiator you should run a lot cooler and my guess is that fabed up fan shroud. My car started running hot in trafic this week but I found one of my fans was not running. Also does the F-body have a high and a low fan speed? The reason I ask is I installed a 95 fan/shroud assy into a LT1 swap project I did in my 84 corvette and the 96 corvette wiring used three relays that either applied power in series (Low speed) or parallel (High speed) acording to what the ECM signal was and I was using a 95 Z28 ECM.

 

ABout the block fill, i was just looking into it for future strengthening of the block, just didnt want it to affect anything cooling wise.

What sucks is that the factor fan shroud will not work with this custom radiator i have, there are no hooks on it, i can figure up something though....I would just mount the fans direct to the rad without a shroud, but then im afraid there may not be enough air flow when the car is stopped.

I believe they went to the low and high speed fans in late 95-96, mine is a 94 and they have fan 1 and 2 on at different temps, but only one speed.

 

Got ya, You can do what I did and break out the dremel. I had to do a bit of cutting to have it fit into the 84 with the stock corvette radiator and radiator housing. What I did was cut the shroud to fit flush then used zip ties, 3 up top 3 down low, and atached it to the stock radiator supports (I think its metal on your right) and it worked great.
I would still hold off on any block fill untill you get this isue resolved first it will just add one more variable to the equation.

 

Thats a good idea, ill try that and see what happens.
I didnt plan on doing any block fill until this winter when i pull the motor back out to put new bearings etc. anyway. Thanks man

Chad

 

Just to add a littl info By flush I kept the thing as whole as posible (Vent depth was the most I cut. I would think you would have to little if any triming just the ty wrap holes.

 

I can only tell you my experience from stock car racing that a shroud makes all the difference. WHen my shroud was missing it would overheat until we found a good shroud. We even tried making one out of a sheet of aluminum but it didnt work as well as figuring out a way to hang a plastic cheapy GM one on there.