| Taming the beast- cooling system |
Subject: Taming the beast- cooling system by dstaley on 2010/7/3 6:25:10 Hey guys, In case anyone is interested, I thought I'd post up my work trying to address my overheating issues. Maybe it will help someone out there somehow. I haven't posted much of anything lately because my family has been on a debt payoff blitz, and we haven't budgeted anything towards car projects or hobbies. Lately I've been able to sell a bunch of stuff around the house and decided to use some of the proceeds to attack my overheating problem. Background I put this 409 SBC in the car in late 2008. I only had a couple weeks to do quick tuning & basic debugging before putting it up for the winter. In the spring and summer of 2009 I rebuilt the front & rear suspension & differential and TIG welded a new exhaust system (starting with a Magnaflow kit for the raw materials) and resumed tuning in earnest. In-town tuning went fine, and when I was feeling comfortable I took it on a road trip to Kansas City from central Illinois. On the road trip, it became evident that I had a cooling problem that didn't show up in town. That's right, at slow speeds/idle/in town it didn't overheat at all. I had done all the right things that had always worked for me before- new engine, new GM water pump, new hoses (yes the lower hose has the spring), flushed radiator, new H/D fan clutch, original pulleys, 50/50 water/antifreeze mix, new 180* thermostat (brass high-flow), iron water neck, original shroud, original air dam in place & serviceable, etc etc etc. I experimented with timing and watched the fuel mixture on the laptop (using an Innovate wideband A/F gauge) although I didn't have a timing light with me- AutoZone was kind enough to let me use one in their parking lot once. When I got to KC I borrowed Dad's timing light and bought a vacuum gauge to monitor about everything there was to monitor, but nothing helped. At 60 MPH, the temperature was steady. Below 60 MPH, all was good. Above 60, the temperature rose without bounds- I couldn't stand to run it over 235* so I usually slowed down when it crept up to 225-230*. Anyway, after going through the carb (working with Cliff Ruggles), it is now running sufficiently rich that the mixture is ruled out as a root cause, and it's still getting hot at highway speeds. Digging for root cause I've been digging through tons of old CorvetteForum.com and DigitalCorvettes.com posts trying to figure out what to do. I'm convinced that the aluminum heads are conducting enough extra heat into the coolant that the stock radiator's heat dissipation capacity has been exceeded. 60MPH must be the tipping point beyond which the engine's heat generation is beyond what the radiator can handle. I think I've pretty much eliminated any other variable. Time to get to work I just pulled the car out of storage in early June. I had to fix the rear window first (it was actually falling out!) so I upgraded it to a removable one. I finished this (other than getting some new or used halo panels) last week. Now that the window is done, I can get to work on the cooling. This week I ordered a new DeWitts radiator. I also swapped the H/D fan clutch for a Hayden Severe Duty one (as came on the '73-74 big blocks). While the original radiator is out of the car and the new one is on order, I took the time to do a little engine compartment cleanup. I powder coated the hinges, radiator/shroud brackets, core support bracing rod, the lower 90 degree brackets, and some misc. bolts in semigloss black. I had the core support powder coated semigloss black at a local shop. I also made some brackets for a new transmission cooler out of aluminum tonight and plan to powder coat them semigloss black tomorrow. I bought some new blackened stainless bolts to mount all this stuff from Totally Stainless and ordered new core support/shroud seals, radiator cushions, and a replacement air dam from Dr. Rebuild. I also washed out the engine compartment with soap & water, painted the frame crossmember with semigloss black RustOleum and painted the inner wheelhouse walls with Eastwood underhood black using my airbrush. Here are some pictures of all that:        This weekend I need to drain the block, powder coat the transmission cooler brackets, make up some steel lines to plumb as much of the new cooler lines as possible with hard lines, and maybe start mounting the amplifiers (I never got around to it before we decided to get out of debt, I already had them) in the jack/storage compartment if I have time. I can't do a lot more until the radiator shows up. |
