quote:
Originally posted by 74GTS:
... my understanding on dished pistons was that they are prone to failure ... and that they were performance zapping due to emissions of the day ...
The OEM pistons are not prone to failure at all. They are fairly sturdy for cast pistons, they have steel beams in the skirts, etc. But like any cast pistons they may crack their skirts when the engine is operated "vigorously". Cobra Jet engines were set-up to operate up to 6000 rpm; whereas the Boss 351, which had forged pistons, was set-up to operate up to 7000+ rpm.
The Ross pistons offer the advantage of having the durability of a forged piston, plus the compression afforded by flat top pistons. Other advantages include improving the cylinder wall durability due to their round skirts, plus the better sealing and lower friction afforded by thinner piston rings. Those last two things increase horsepower. Only you know how hard you plan to operate the engine in the future, or if the power improvements are worth the price of the pistons to you.
Lowering the compression of the engine did indeed zap its performance. The four basic schemes for raising compression are:
(1) flat top pistons, quench chamber heads, cams with IVC = ~70° ABDC
(2) dish top pistons, quench chamber heads, cams with IVC = ~60° ABDC
(3) flat top pistons, open chamber heads, cams with IVC = ~60° ABDC
(4) pop-up dome pistons, open chamber heads, cams with IVC = ~70° ABDC
Since you mentioned installing Edelbrock heads, the first or second schemes seem to be your choices. The second scheme saves having to purchase pistons.
quote:
Originally posted by 74GTS:
... Are rings, seals bearings etc important in your eyes as more preventative ...
Just being practical. Something to do while the engine is out of the car. You've already mentioned the compression readings were not consistent. The 40 year old crankshaft seals are bound to start leaking. I've never taken apart an OEM lower end without discovering worn bearings. The OEM timing set has nylon teeth on the cam gear. Service those things now, get them over with, and hopefully you'll never have to pull the engine again. Frankly I feel the maintenance is more necessary than Edelbrock heads ... the engine already has a decent set of heads on it.