I got asked , "what makes a GOOD vs A poor engine combo?"
and without getting into specific combos , too deeply,
lets look at that question
the first few things I look for in most magazine engine builds, I read about is the use of fairly easy to locate parts, from several known manufacturer's , having a good reputation ,for supplying quality components, and a combo of components that has a semi- reasonable cost to power ratio, and one the average guy can afford to build with easily duplicated parts.
keep in mind theres a HUGE difference in the component selection process and basic goals when building a race engine, where peak power is your main concern, and rebuilds and parts replacement are EXPECTED on a regular basis, vs a high performance engine designed for street/strip use and at least occasional transportation use, where long term durability and rock solid dependability are your main concerns, and you expect to see 100K plus mileage out of any combo, you build
youll also want a parts list from a source that will be around for years, and have access to replacement parts.
Parts that won,t cost a great deal more, than similar components, from other sources, and parts that I can purchase and replace at a later date if necessary.
I also read carefully to see it the articles obviously designed to push or sell particular components , and compare the results to personal experience because , its common for those magazine engine builds to leave out or flat out lie about results at times
I also want to know that the combo will be durable over the long term, and I generally look for a combo that won,t require excessive or expensive custom machine work.A combo that will run on available pump octane fuel,and if the guys building the engine don,t concern themselves with building a stable valve train at the intended rpm range and building very effective lubrication system, and efficient exhaust scavenging , and effective cooling,the combos likely to lack durability!
youll generally find the better engine combos reach peak power about 1500rpm-2000rpm higher than peak torque, but have that peak power curve slightly below critical stress levels (generally under 4200fpm in a chevy V8) and maintain the fairly flat torque curve well over the useable rpm range thus gearing and tire size matching the intended use is also critical
I generally look at the combo , and calculate the peak and average piston speed as its a good indication of stress levels , as anything I'd suggest building should be durable over the long term, if you constantly need to replace components due to wear or parts failure, its not a well thought thru combo.
I want any American V8 I build or recommend duplicating to make or exceed at least 1.2 horse power per cubic inch of displacement, without power adders.
one of the first things youll want to look at is the basic engine block and rotating assembly strength, a bit of research , in the strengths and flaws of each engine family design,the extent of aftermarket parts support, may provide you with info that can save you a great deal of wasted effort
Any good combo should have a torque curve that will be useful in the applications intended rpm range.
On most muscle cars that will place the torque curve peak about 1000rpm-1500rpm lower than the power peak and the peak power a bit below 4200FPM in piston speed
a good many times I see guys build engines that might make very good power , but not in an rpm range that is really useful for their application.
it does little good to build an engine that makes killer power levels at 6500 plus rpms and then stick it in a car with 3.07:1 rear gears and an automatic transmission that shifts at 5500rpm, thus preventing the engine from operating at anywhere near its most efficient rpm band, most of the time!
I get lots of guys who have a 307-350-or 383 in their current car that have developed a taste for performance but want something a bit better that the mildly modified engine they currently have,and once you get serious you quickly find that the stock components won,t hold up, or allow you to produce the power levels you really want.
this almost always leads to the purchase of better quality aftermarket components and the frequent use of local machine shops and a rapid education in the costs involved in engine building, followed quickly by drive train and suspension upgrades.
you know I have similar discussions with the guys around here who want to upgrade from their current 383 sbc engines all the time and I usually break out a catalog and a legal pad and start listing a dream sheet with the required components the costs listed, the likely machine work, and by the time we get very far into it it usually becomes rather obvious that we will be some place in the $8K-$12K or higher dollar range by the time we get into a decent dart block,a decent quality forged rotating assembly,then heads from, afr, or brodix ,or profiler heads, and a decent induction system,rockers, etc.dependent of course on what you can use if anything from the current 383 sbc build.
at that point I generally point out that for the cost they can reasonably expect to have built a 505-650 hp engine.
I then point out that in most cases the combo is unlikely to be extremely street drive friendly, and its most likely going to require rear gears and average operational rpm ranges that will not be ideal for long term street use durability.
at that point I generally point out that a big block engine with significantly more displacement can be built for similar cash outlay , that can produce significantly better power per dollar spent.
think about what your doing before diving in and spending cash!
if a 383 sbc makes 1.2 hp-1.4 per cubic inch of displacement you can expect 460 hp-536hp
if a 540bbc makes 1.2 hp-1.4 per cubic inch of displacement you can expect 648 hp-756hp
HERES A FEW DECENT MAGAZINE BUILDS
SBC
http://www.airflowresearch.com/articles ... 5/A-P1.htm
http://www.airflowresearch.com/articles ... 9/A-P1.htm
http://www.airflowresearch.com/articles ... 8/A-P1.htm
viewtopic.php?f=69&t=4378
BBC
http://www.airflowresearch.com/articles ... /A-P1.html
http://www.airflowresearch.com/articles ... /A-P1.html
http://www.airflowresearch.com/articles ... /A-P1.html
http://www.airflowresearch.com/articles ... 3/A-P1.htm
http://www.airflowresearch.com/articles ... 6/A-P1.htm
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