I’m having trouble keeping my car (77 vette) cool while cruising on the hwy. I’ve installed a stroked 454 now 496 into the car. The engine is a GM block with GM oval port heads, the heads have been ported and the block has had 4 bolt main caps installed to improve strength. The block has been bored .060 over and the rod length increased to yield 496 CI. I’m running a Lunati solid roller cam in the 260 duration, .700 lift with 112* sep. The engine has Ross pistons yielding 10:1 comp. The intake is a Holley strip dominator with a Holley 1000 CFM HP series carb. installed on it. I’m using a standard HEI with an Accel coil in the cap and a MSD high output digital module with RPM limiter. The base timing is set at 16* with centrifugal advance set to come in at 1000 rpm and full in at 2800 rpm. The vacuum advance is set to 10* max and is connected to a manifold vacuum source.
The cooling system consists of a Dewitt radiator (direct fit) two 11” Spal fans, a Stewart stage IV aluminum CCW rotation pump and a Stewart modified high flow 180* T-stat. I’ve removed the auto-trans oil cooler lines form the radiator cooling coil and added a separate external cooler with its own fan controlled by a thermostat mounted under the car away from the radiator. I’ve also installed a large engine oil cooler in front of the radiator to help with the cooling. I’m planning to move the oil cooler form in front of the radiator to the rear of the car and add its own fan to help control the oil temps. The radiator fans are controlled by a Spal PWM controller it will start the first fan at half speed when the temp reaches 160* and ramp the fan speed up to high when the temp reaches 190*, when the first fan goes to high the controller will start the second fan on high, both fans will be running at high speed until the temp drops below 190*
I’ve tried 3 different radiators the first being a brass replacement 4 core design with two 12” fans then a universal Tru-Kool aluminum radiator with an 18” Mark VIII fan as a puller and two 12” fans as pushers and the engine oil cooler in front of the two 12” fans and the third being the current set-up with the Dewitt aluminum radiator and the dual 11” Spal fans.
I’ve installed a Zoops serpentine drive system and originally tried the Zoops high flow pump that came with the drive system but I had temp issues form the time I installed the engine so I switched to the Stewart pump but this did not change my temp issues.
I have decent control of the temps while idling and at low speed but once on the hwy the temp starts climbing and will settle out at around 220* to 230*. Once I slow down or stop and idle the temps will slowly come down to around 180* to 190* but it takes a while.
I’m running 4:11 gears in the rear so my cruise rpm are around 3000 at 60 mph.
I’ve tried different T-stats to try and change the water flow rate but this does not seem to make a difference. It appears that when I installed a Stant 180* t-stat that had a 1” opening the temps did appear to take longer to climb to 220* while on the hwy but it could have been that it was cooler that day versus the day I tested the Stewart high flow T-stat. I’ve even tried running without the T-stat but the temps were the same.
I have verified the temps with an IR gun, I have two temp indicators installed, one on the outlet of the intake and one on the low pressure side or the radiator. Once the engine heats up after being on the hwy I stop an check the temps, the temp on the inlet and the outlet of the radiator are the same (no temp drop across the radiator) at around 220* to 230*.
Might you have any ideas as to what might be my issue?
