chevy BBC stroker: 496 High versus Low compression

I have a couple questions regarding two (2) articles in your Engine Masters magazine.  I have never rebuilt a BBC or stroked a motor; I’ve rebuilt two (2) SBC’s and have a 1986 454 BBC in a Suburban ready to go.

Anyway, back to the articles.  They are both relating to a Chevy 454 BBC stroker build (i.e. 496 ci), but I can’t seem to follow as to how they both make nearly the same horse power.  In the Howitzer article in your Winter 2007 Vol. 11 #4, the engine has a build that is so close to that of the Monster Mash in Summer 2008 Vol. 11 #2 issue.  The differences are so close until you start talking about compression.  Please note that I am comparing the naturally aspirated engine build and not the (awesome) supercharged version.

The Howitzer is running around 10.2:1 while the Monster Mash is at 8.25:1 CR, but the power curve numbers still don’t make sense to me.  Do I need a “lesson in compression”?  Yes, the carbs are a little different (i.e. 100 cfm), the rotating assemblies are from different manufacturers, and the heads and cam grinds are also slightly different in terms of flow, but does this warrant the same power?  In the end, around 6000 RPM we have the Howitzer running at 547 HP and 625 TQ, and the Monster Mash at 639 HP and 560 TQ.  On the strip the Howitzer would be ahead of the Monster Mash, but not by much going with the power numbers listed.

If these power numbers are correct, I would be more inclined to build the Monster Mash over the Howitzer just because I could tune it until it was solid and I had enough cash to throw on the Vortech Super Charger.

So, back to my original question, are these numbers correct and is the compression the only major difference here?  Am I missing something?  Please explain.

On another note, fuel supply.  I noted that the fuel pump was not noted in either article.  Mechanical vs. Electric is the question.  I want to run as little electrical as possible on this build; wires get in the way and are a hassle.  I will stick to the mechanical fuel pump setup if I can.

Another question regarding the Monster Mash build; roller rockers.  1.70:1?  1.71:1?  1.72:1?  It wasn’t noted in the article.  I have a full set of 1.72:1’s currently in the truck and I’d rather re-use them then buy a new set.

And last but not least, roller vs. flat-tapped lifters.  Why one over the other?


thanks and best regards,

Glenn  

is there anyone that can help me out with this one?

how about anyone from PHR?

anyone?

bueler?  

Will your bigblock be used for towing, or under no-load situations?  If under load, like towing, I'd suggest the lower compression, or aluminum heads to avoid detonation.

From what I have read, lower compression results in having to rev higher to get the power of a higher compression, but otherwise similiar, engine.  I don't have access to the two articles, so perhaps there is enough difference in airflow to compensate for the lower compression.

the MM engine recipe may be your better choice, but I think WHAT you are going to use it for, is also important.  A light vehicle with less traction, would probably do best w/ an engine that trades lower RPM torque for higher RPM power, in order to plant all that power you want the engine to make.  But a heavier car with bigger wheelwells in the rear (for bigger tires), maybe building for lower RPM power is your goal.  If this makes your RPM operating range into a limitation, then you don't have to worry so much about making a decision  It does it for you.

As for rollers versus flat-tappet, I'm going to take a guess--the Chevy BB has lifter bores smaller than, say, a 440 Mopar.  So, give it a radical cam with steep ramps, and they will try to push the side of the lifter rather than the bottom of the lifter, and you'll get a lifter sandwich, where the lifter gets caught between the wall of the lifter bore, and the side of the cam lobe.

The solution, is to run bigger heads (now an option, back in the day, not so much) to create more airflow, run rocker arms with increased ratio, or use roller lifters that applied a different surface area to the cam lobe, that didn't get caught in the 'sandwich.