Performance Engine Theory

 

 so in my working with my 4.3 project, i ended up re-using the factory roller camshaft. the lift on it at the valve during dial in was a .346 on intake and a .382 on exhaust with a 110 lobe center. this was a really mild spec, and my only estimation was that the factory is using hyd roller lifters for longevity more than anything else due to the lack of additives in modern engine oil. a high zinc content is necessary in engine oil for prolonged flat tappet camshaft life…..which has been removed from most engine oils due to both cost and emissions.

but i had to wonder about it cause it’s bugged me for years…..these camshaft specifications were ungodly similar to a specialty derby use cam someone conned me into buying years ago. so i re-visited an old project with a different perspective.

 so i dug through my archives…..and dammit if it wasn’t dead on within .003″ lift at a .050″ spec. the durations however were much different. the cam in question i got was a much shorter duration intake and a much wider duration on exhaust than this stock spec on this 4.3 cam i have now…..which also resulted in a tighter lobe center at 108 deg. lack of fuel: more exhaust- explains the lack of power while also giving you the illusion of having a performance cam due to the tight lobe center. overall result is a cooler operating temperature.  i don’t think the cam is very critical per say as far as the specs more so than the advantage is the roller valvetrain over a flat tappet..

 but the funny thing is, i think it is only a piece to a 3 way puzzle. i have come to the conclusion that reducing piston ring tensions is also key whether or not it is by running an extra .010″ of clearance on your piston to wall spec or using a set of low tension claimer rings. perhaps even omitting one of the compression rings and/or using a single total seal compression ring .  

the third piece to the puzzle is crankshaft clearances. Bill Trovato has justified the logic behind the extra clearance on the low end of the block due to flex in extreme conditions……such as drag racing. block flex is a major plague of big block olds engines. in the case of derby the extra clearance is moreso for heat expansion AND reducing friction. this is also explained obviously by the need for some builders to use ungodly thick oil additives with 20W50 motor oil.

now, this 3 way puzzle to a derby engine: have i actually done it to a gen 1 or 2 chevy v-8 yet and done any testing…..no. will i…..likely no. would it work….most likely. i do know that each of these three principles are in practical use by several reputable engine builders across several motorsports.

 i also researched a bit into the 5.3 and 6.0L iron block vortec/LS engines. most of the issues i listed above have already been remedied already from the factory as far as roller valve train, piston ring tensions, and block flex. not to mention an incredibly efficient oiling system. so that’s the direction i am going if i decide to spend money on another SBC build for myself.

Leave a Comment


NOTE - You can use these HTML tags and attributes:
<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>