What radiator options do I have for a v8 powered e30?
(cheapest to most expensive):
E28 535i radiator
This is the cheapest route to go. This will cool your v8 e30, however, your going to need a pretty decent sized front pull type radiator to keep you out of trouble on the track and in traffic. On a daily driver or street machine, these are bare minimum. The pros are that your car doesn't have to be hacked up too bad. The bottom e30 radiator mounts will need to be removed in order for the e28 radiator to fit. However, the e30s actual have holes from the factory that line up perfectly for an e30 radiator. You will need the clips and bolts from an e28 as well. The radiator is the thinnest of the three options we are showing you. The lower hose does not require much modification. However, for the upper hose you might need to get creative with, as it exits right into the oil filter housing. If you choose to use the m62 remote mount oil filter, this wont be a problem (or better yet get a remote mount oil filter housing and this wont be an issue). If you stick to the m60 filter housing which mounts to the upper driver side chain cover, then you will need to get either a custom hose or a custom pipe made that goes around the filter housing without kinking. We offer this radiator hose pipe, so please inquire if interested. These radiators are cheap and can still be found in junkyards or brand new for not too much money.
E34 540i V8 radiator (lela choice)
The logic was to stick exactly to what bmw initially had. It works with a bit more work. The bottom radiator mounts still need to be cut like the e28 option (look at pictures right above). However, it goes one step further, the front frame section needs to be expanded to fit the radiator. The frame at this front point of the car is not load bearing. When done correctly, the car wont suffer structurally. If this is an issue that concerns you, you can buy one of our x braces, as we have installed on Lela. The x brace holds the frames to the steering rack (a good upgrade to do anyway now that you have nearly 3 times the power the car initially came with from the factory). The factory e30 radiator mount is still used. This option is thicker than the e28 radiator and wider. A pull fan is still recommended. We track this car, sit in traffic in this car, did a Nevada test run in this car and guess where the temperature gauge stayed at. It stays half at all times with no issues whatsoever. The lower radiator hose exits near the area you took out of the frame so it needs to be a straight 90 degree angle. The upper radiator hose takes alot more effort than the e28 version because not only does it exit right into the m60 filter, but being that it is a thick radiator, it's even closer to the housing. We highly recommend that at this stage you go to the remote mount oil filter housing. If you don't, you will need to run a 45 degree straight from the exit of the radiator into a custom tube (stainless to keep it from rusting inside) into another 45 degree elbow. It can be done, but the headache can be avoided by getting a remote oil filter housing (some kits even offer an extra quart capacity).
Z3M Radiator (best choice)
This option uses a radiators from s54 powered Z3M models and S50B32 fitted Euro M3's. Part number is 17112227281. This is a 3 core radiator that will fit without modification and people who have used this in their swap have said nothing but great things. The great thing is that people who have a late model e30 (thats 1988+) will be able to use this radiator option without modification. Keep in mind, that the e36 radiator will fit as well but the M version will offer more cooling capacity.
Make it as wide as you can get into the frames (or cut into like the e34 radiator) and get it as thick as you can. You can make the radiator exits exactly where you want them. Keeping the m60 oil housing? Get the exit to come out of the side of the radiator. This is the most expensive option.
Other suggested modifications to your v8 swap cooling system
It should be no surprise that you will need a fan for your motor swap. We suggest that a "push" type fan is used in place of the stock AUX fan as there is no room for a "pull" type. Wiring is simple. Cut the harness that goes to your stock aux (not too short!). Then wire according to your new fan:
Chassis wiring has 3 wires: brown, green/black, and blue/black.
Based on SPAL 16" fan wiring.
brown -----> Ground on fan
green/black ------>Black wire on fan
blue/black ------> Red wire on fan
The thermoswitch on e30 cars is on the right side (most bmw radiator options we mentioned are also on the right side/pass side). This also has 3 wires. green/black, black, and black/brown.
Green/black wire= ground
Black wire = low fan speed
Black/brown = high fan speed
The e30 thermoswitch low speed turns on at around 196 degrees. High speed gets switched on at about 210 degrees. Its common e30 engine swap practice to actually switch the wiring around so that there is no low speed and the high speed is triggered at the original "low speed" setting of 196 degrees.
Suggestion: take this time to switch out your thermoswitch to part # 61318361787. It operates at 176 degrees at the low speed and 190 degrees at the high speed.