Teem66

1980 L48 Federal Auto

My car is pretty much original other than true dual exhausts which I've added (I've held on to the original set up). The vacuum operated Exhaust Heat Valve (heat riser) has been replaced with a mechanical, spring operated one. The vacuum line from the TVS which originally operated the EHV is blocked off. Would the engine perform better (faster warm ups, better fuel economy ) with the original EHV set up or is the mechanical, spring operated EHV a better option? I'm not trying to make a car suitable for judging, just trying to get the best performance out of the original set up.
Thanks

CaseyJones

I think that the original heat riser setup would be more efficient for your needs with an otherwise stock L-48. The best thing you can do at this point is to have the distributor curve optimized and the timing set to use it. A good carb setup by Lars (search for him on the Forum) will further increase your overall performance. After that, you start making significant changes such as headers, a performance intake manifold, camshaft, head work, etc. (in that basic order). Good luck!

7T1vette

Either system should work well enough to get the job done. But, both require some maintenance to make certain that they stay in working order. The 'spring' type that you presently have is prone to binding and not opening when the engine warms; and that condition can lead to engine damage. So, frequently check the freedom of that counterweight (when the engine is cold).

The vacuum-type system is more reliable (believe it or not) but still has its own limitations. That vacuum hose needs to be sealed off if not in use.

With either setup, those valves should be completely open within 1-2 minutes...even in relatively cold weather. Their purpose is to get some heat under the carb quickly, so the fuel can atomize better when cold. So, with that valve working, the engine will function better more quickly, but only for a minute or two more than if you didn't have the valve at all.