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proven engine combos, following a plan, and those deals...

PostPosted: February 6th, 2010, 3:21 am
by grumpyvette
proven engine combos, following a plan, and those deals.

theres an old saying about
"theres more than one way to skin a cat" well building engines is a bit like that in that if your goal is to produce a reasonable level of horsepower,for an engines displacement theres usually several fairly well known, combination's that can be built that will allow you to arrive, at that power level.
the difference in each engines parts list and machine work is usually a compromise in the engines cost, durability, or power range, and while almost everyone works within some budget restraints,most of us want to build the engines in our cars for the lowest possible cost in the least possible time, and in an ideal world have an almost indestructible and extremely durable combo.
Ive built enough engines, for my self and for other people, and given advice on, and worked on enough engine projects that were completed by other people that it became obvious that although, theres thousands of ways to build an engine for your average street/strip muscle car, theres also many more ways to take what potentially could be an excellent engine,and change just enough of the components, the machine work or the drive train its mated too, to make the intended results fall below your expectations.
One of the recurring reasons is that almost invariably, the person building that engine is presented with a (DEAL) on parts that cost less or that don,t match the rest of the engines components intended air or fuel flow rates, heat range,or power band or rpm range or the parts sacrifice some look thru the parts catalog and see the trickflow, air flow research or brodix heads listed in the component list cost lets say $1450 and about ten minutes later when you tell your friend he points out that you can purchase vortec heads for about 1/2 that cost...and while thats true, if you go for the less expensive heads your power potential takes a huge hit. the same thing happens when you point out the component list indicates you need a hydraulic roller cam and lifters and you friend quickly points out that
"there is a cheaper generic version or even worse that a flat tappet cam with a similar duration should work just fine"
the same thing applied to intakes, pistons, rods, etc.
lets assume your goal is to build the very common 383 sbc and your goal is a reasonable 425 flywheel horsepower, you can rarely pick up a handful of the current, corvette, hot rod,Chevy, muscle-car or exotic car magazines , without finding an article telling you exactly how they exceeded that goal, so how hard can it be?
well, that depends on your skills and budget, and your machine shops attention to detail,and the parts you select
and I can tell you from experience that theres a great many cars out there that have spend a good deal of time and effort trying to reach that goal that have yet to reach it.
If you look over this site you'll find a great deal of info on selecting & matching components, and calculating the results, and a fair number of proven confirmations that did in fact reach or exceed that goal.
you'll also find links to engine calculators and software that can be used to detect trends, point out potential flaws or predict results with some accuracy.






youll quickly find the combos are different as are the power produced, and it would seem that its just not all that difficult to build a decent 383 sbc, and while thats true to some extent, its also true that all those combos that produce a known and tested power level can be significantly reduced if you were to start swapping, a few key components.
drop the compression,ratio,go with a set of less expensive heads,use that old intake and carb of your current engine, use what you think is a similar cam, don,t use the rockers or headers or oil pan, and windage screen suggested in the original parts list and your results will frequently be lower than you might expect those changes to make.
and even if you do follow the component list exactly the machine shop you use and the care taken during the assembly and tuning can and will result in a different power curve.
but its the attention to details, care taken during the assembly process and following the know trends that allows you to build a decent Im not saying you can,t experiment or use a different component, but I am saying that any changes you make will have an effect on the results, that may or may not be to your benefit and the more changes you make to a well tested combo, the less likely that your get the result to match, the original planned results

Re: proven engine combos, following a plan, and those deals...

PostPosted: February 6th, 2010, 9:25 am
by grumpyvette
WHEN I started building engines many years ago, an older engine/machine shop owner and a Pontiac dealer mechanic took the time to answer many of my question, I remember the engine shop owner saying one day that building an engine correctly is a bit like baking and decorating a wedding cake, you use a component list on an engine build similar to a recipe, youll use to bake a cake and that recipe will list ingredients like flour,sugar , eggs, milk, baking powder,vanilla extract ,which ingredients get added at what stage,the amount of the ingredients used, the temperature you must bake it at, the pan size,etc
and an engine combo will in a similar way list the intake, carb,rotation assembly, compression ratio, etc.
now lets say your well into baking that wedding cake and the recipe, calls for 6 cups of white sugar, but youve only got 5 1/2 cups in your pantry,your on a strict budget , so looking around you notice that SALT LOOKS THE SAME, and the only other choice you have is dark brown sugar, which looks totally different,, because the salt looks like its a far more similar component you select the salt,and when you add it to the batter,to make up the difference, it BLENDS IN JUST FINE, and the cake looks identical once its baked, so whos going to now the difference?
I think you can grasp the significance, a small change will ruin the expected results, just like swapping some component in the proven engine package will also at times ruin the results, and if you had selected the brown sugar,when baking the cake, which appeared to be a total mismatch, you might have also ruined the cake but you might have improved the taste.
the same thing applies to engine building, some changes can improve the combo, but experience has a huge effect on making rational choices

Re: proven engine combos, following a plan, and those deals...

PostPosted: February 6th, 2010, 10:21 am
by bob
I can,t say enough about how valid that advice is!
I built a Pontiac 400 engine in a 1967 firebird back about in the early 1970s,
and I got the engine component list from a hot rod magazine ,I thought that I,d followed that magazine article almost exactly, and the results were extremely disappointing.
when, I was thru swapping parts, the engine ran like crap, I re-read the article several times and only then noticed that the car had already been fitted with headers and a low restriction exhaust and 3.73 rear gears, and traction bars,and it was only on the third or fourth time I read thru the article that I noticed the roller rockers,and carb spacer and Id ignored the combustion chamber shrouding clean up, pocket ported heads and port matched intake , and the back cut valves.
what Id done is basically blown thru the article, and noted the cam and intake and ignition that was used and jumped to the erroneous conclusion the other minor engine mods , and drive train components used might have been worth a few hp, but If I was using the same cam,and heads and intake I should make similar horsepower, it was only after Id installed the low restriction exhaust and rear gears , traction bars,that the engine responded correctly, and while it never did make the same horsepower the article claimed it was a very nice performance engine package once I took the time to follow the magazine article more closely.

just for your info, theres a good deal of useful pontiac info already posted on this site

viewtopic.php?f=74&t=2035 ... to_01.html


Re: proven engine combos, following a plan, and those deals...

PostPosted: March 12th, 2010, 12:02 pm
by grumpyvette