Steam kit
Amazon.com: Gxencks AN4 Fuel Brake Line,LS Coolant Crossover Steam Vent Kit Fit for LS1, LS2, LS3, LS6, LS7, LS9, LSX : Automotive
Could buy some -4 AN to pipe fittings, hose/tube of your choice, fittings to match, along with a few Tee's...drill, tap, run how you like ?
https://th.bing.com/th/id/OPHS.lqeNo...r=1.1&pid=21.1
https://th.bing.com/th/id/OPHS.wUFH0...r=1.1&pid=21.1
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I used this one on eBay from FassterLLC & can confirm that it does work with FAST 102 & no issues
https://www.ebay.com/itm/132107718315
Last edited by 1QUIKWS6; Jan 5, 2026 at 03:21 PM.
https://www.ebay.com/itm/132107718315
Trick is to lightly apply fitting assembly lube to nipple & ID of hose & heat the end of the hose with heat gun = hose goes on EZ
(Pratt & Miller Engineering New Hudson Michigan) and Dr. Jamie Meyer (head of GM Performance) both say that the rear two should stay blocked off.
I used to advocate having fittings that went to -4an on all 4 steam vents feeding into a coolant swirl pot, which then drained back into the lower hose or return heater line... this is a setup that was used successfully by a few race teams, but it looks like this was a band-aid once I got 'real' information from REAL race teams.
The issue is not flow - the coolant passages flow plenty - it's pressure.* When driven hard, engines need coolant pressure to "scrape" the steam bubbles that form on hot spots in the head off the wall of the passage.* With all 4 ports open, there's not enough pressure locally (in the head) to promote proper heat transfer unless you run your overall coolant pressure extremely high (30psi or so).* Indy and F1 cars run MUCH higher than that, due to higher hp/liter (heat concentration).
The proper setup all my LSx racers are using is, assuming the top of your radiator is below the steam vent port:
*The rear vents blocked off, the front tee'd (LS6-style).
*Radiator cap replaced with "open" cap (free flow through radiator overflow port)
*Steam vent tee and radiator "overflow"/free flow feeding into coolant swirl pot (aka expansion tank)
*Swirl pot has pressurized radiator cap, bottom drains to non-thermostat-controlled water pump return













