| | | quote | Originally posted by Lambocountach:
I was wondering if it would be ok to block off both the lim and front timing cover coolant holes as I don’t want to run a heater core in my swap. I had read some we’re doing this causes thermostat to get crushed? Also was trying to find info on blocking the 2 holes in Lower intake for throttle body as well as I will be swapping to gen v supercharger. Thank you for any info or links.
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The factory alternator bracket that comes on Series 2 and 3 engines, as you probably already know, has both heater core lines from the LIM and water pump running thru it. What you may not know is this bracket ALSO has a coolant bypass passage that connects both of these coolant circuits inside of it. This is the engine's only means of a coolant bypass circuit. So if you aren't using the factory alternator bracket in a swap, you have no coolant bypass. Which may be fine as long as you are still using a heater core (in which case the heater core circuit would act as the bypass and that will be fine as long as it never becomes restricted). If you aren't going to use a heater core and are planning on plugging off the LIM and water pump passages, that could be a problem.
The way the cooling system works on pretty much ANY engine where the thermostat is located on the water outlet of the engine means there needs to be some kind of bypass that prevents pressure from building up against a closed thermostat. GM solved this issue in newer engines by placing the thermostat on the water pump inlet side of the system, however you can't simply do that on a 3800 engine because coolant must be allowed to flow past a closed thermostat on the inlet side of a system in order to permit it to open at the appropriate temperature. And GM achieved this in newer engines by routing the heater core coolant flow in such a way so that it would pass over the closed thermostat in a specially cast thermostat housing or water pump manifold.
You CAN plug off the heater core port on the LIM as well as the heater core port on the water pump housing so long as you run some kind of bypass in the system. You could use a modified stock Fiero t-stat housing and simply run a hose from the heater core outlet port of that housing over to the water pump inlet hose (or passenger's side coolant tube heater hose port if you have an 87-88 Fiero). This should allow coolant to circulate from the water outlet of the engine back to the water pump when the thermostat is closed.
If you don't install some kind of bypass and simply plug off all heater ports on the engine, you will likely collapse thermostats or worse - blow out gaskets due to excessive water pump head pressure.
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Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com[This message has been edited by Darth Fiero (edited 12-26-2017).]
