i-rocket z28 86

i swapped out the 350 for a small block 400. had a performance shop in my area called k and s do a cam on it. largest we could fit. edelbrock heads, edelbrock intake, edelbrock carb. holley high performance 105 gph pump with reg set at 7 psi. 700 r4 syage 2 b and m shift kit. now the problems massive overheating. i know the 400 blocks had steam channels and im wondering if 350 head gaskets were used instead of the 400 with the steams holes punched out. i need to know what the biggest radiator and fan i can fit with the 400 in there. i wanna go as cool as possible. is a street and strip car when it wants to be. but not anymore just on a lift. i need help guys.. JUST SOMEONE WITH A BRAIN HELP ME!

n2deep22

this is a common issue witht the 400s if i was you i would put in a good aluminum radiator and use two electric fan setup having one fan pushing and one fan pulling maybey even go to an electric water pump.

n2deep22

also run the coolest thremostat you can DO NOT run without a thermostat this will actually make the car run hot because the coolant is continously flowing through the radiator and the radiator cant cool it fast enough

Horn0816

Just in case you haven't found out your problem yet, I'll throw in my . I'm also looking at putting heads on my 400 block truck. Now when you search on summit or jegs and places like that, it says "yes it's compatable with a 400." What that says is "Yes it will bolt up", but most of the time it's just another 350 head and you have to take it to a machine shop and have them drill out the steam holes. I went to a machine shop and he priced me out $40 if I bring in a set of 400 head gaskets. Hope it helps

-Horn

1BADRZ28

iTrader: (2)

Does it have the air dam under the car still? That is usually 90% of the over heating issues when it is missing. Ebay has cheap 200.00(I think) 3 core replacments in aluminim.

406c.i.RS

Fought this same issue forever... f-bodies hate 400s lol.... Get a big nasty fan!!! I dont know the part number right off hand but I found this ridiculous fan that came off a ford that will absolutely blow trees down!!! I will look at the part number when i get home.... Its actually a two speed fan with an awesome shroud setup too... I dont even have steam holes in my heads (brodix) and have no more cooling issues... I went through hi flow water pumps, and added rear cooling ports on my intake, 4 core aluminum radiators, played with differnt size thermostat restrictors, even had local machine shops stumped... I simply was not getting enuff air across the radiator..

TTOP350

iTrader: (8)

1st check the timming and fueling.
Also Sounds like the steam holes in the heads or gaskets maynot b there. Pull it apart and check heads and gaskets 4 the holes.
I run the OEM dual fan setup In my 89formula and have 0 cooling issues.
Also a 160 T-stat and a hypercrap fan switch to turn the 2nd fan on sooner.

406c.i.RS

I know this will prolley start a 10 page debate, But I talked to one of the local machine shop owners a couple year ago And he actually gave me a lil insight on the 400 steam holes.. He told me that the purpose of the steam holes were really only effective at or around idle.. He said anything above idle and the steam holes are rendered useless.... He even went as far as to say that if yer running a non-steam hole headed 400 and yer at a light and u start to get warm, simply putting the car in nuetral and revving the motor above idle will cool it back down... I still have my quirks with this theory but he is a very reputable man thats been in the go fast business for a loooong time... Some on here may know him.. His name is Gary Revis and he was the owner of HUNTSVILLE ENGINES for many years, back when summit-racing used to sell his motors..... I personally am not running steam holes in my heads but they are aluminum brodix heads and apparently the cooling passage design of them renders steam holes useless... BUT, I would still have to agree that if I was running an iron headed 400 I would be drilling the steam holes just becuz its too easy of a job for the extra insurance... 2 cents given :-) btw I'm new here, Nice to meet yall.

TTOP350

iTrader: (8)

This is very true. steam holes are for under 3k rpm Which most cars on here run at. if its a race motor over 3K rpm all day you wont have a prob..

cc 82Z-28

iTrader: (7)

I run a mildly built 406 in my Z-28 and before I went to the fan setup that is in the car now, I could not get the engine to run without overheating. I went with a 4th gen Z-28 or Trans Am cooling setup that has the dual fans and shroud that do a great job of keeping the car cool. I have run a Griffin radiator for over 10 years now along with a high flow aluminum water pump and a 160t-stat. My first go round was with the mechanical fan with the clutch from GM, it was ok but would overheat at idle, then I went with a fixed fan setup with the big ole' wide blades, same problem and I sounded like plane when reving the engine. Two years back I decided to try the 4th gen setup along with the Flexalite controller, I can sit in traffic without overheating issues whatsoever. Just make sure the air dam is on under the car as was stated above and I only did a little fabricating to make it all work and was the best 200.00 I spent on a cooling system. My car has overheated since the day I bought it back in 1984 when it was all stock, I couldn't run the a/c in traffic at all, and now I am finally going to put a/c back in next year.

cc 82Z-28

iTrader: (7)

I run a mildly built 406 in my Z-28 and before I went to the fan setup that is in the car now, I could not get the engine to run without overheating. I went with a 4th gen Z-28 or Trans Am cooling setup that has the dual fans and shroud that do a great job of keeping the car cool. I have run a Griffin radiator for over 10 years now along with a high flow aluminum water pump and a 160t-stat. My first go round was with the mechanical fan with the clutch from GM, it was ok but would overheat at idle, then I went with a fixed fan setup with the big ole' wide blades, same problem and I sounded like plane when reving the engine. Two years back I decided to try the 4th gen setup along with the Flexalite controller, I can sit in traffic without overheating issues whatsoever. Just make sure the air dam is on under the car as was stated above and I only did a little fabricating to make it all work and was the best 200.00 I spent on a cooling system. My car has overheated since the day I bought it back in 1984 when it was all stock, I couldn't run the a/c in traffic at all, and now I am finally going to put a/c back in next year. Here's a pic of my setup..

dencoIROC

I have a 1990 IROC that I just got I live in Aurora, CO. The car heats up after a 15 min drive and I have now idea what to do If anyone can help I would gladly appreciate it.