I her people say all the time that so and so spent a bunch of money on a bunch of expensive parts, and got nowhere because "the combo' wasnt right.


Is this generally just a case of having either your heads, cam, or induction holding back the rest of your top end? Or is there more to it?

Obviousy, I guess you can get a cam meant to rev high and a motor/induction that's not, (TPI ), but this all seems so cryptic and vague to me.

IT seems to me that as long as you've got good parts all the way around, I dont know why you would be disappointed.

 

you have the general idea.. a good combo is parts that you choose that work best together and yield the most performance for what you have.. say you have a cam and intake that like the rpm range idle-5500rpm and you have stock heads that are idle-4500.. that will not be the best combo because the parts dont match each other.. your heads are going to hold you back, but if you get heads that are in the range you want, idle-5500, then you will come out with the most performance..

you also have alot of other thing to consider.. carb size, jetting, header size, exhaust, gearing, converter stall and tire size all come into play..

 

Spaghetti and meatballs.
Oreo's and milk.
Good combo's.

5678TA has it. You must build with a plan. Parts have to work well with each other or you'll not achieve optimum results.

 

The best way to learn is to find combos here that worked well, and see why they worked. What size cam worked well with a certain head; which carb worked best with what intake manifold and engine size?

For alot of parts out there - most of the important ones actually - there is no set powerband for them, like 'idle-5500' or whatever. Cylinder heads are a perfect example of this. I can almost guarantee none of the mainstream popular cylinder head mfg's will rate their heads like that. Stuff like that, you just have to look around and see what worked on what motor. For example - a 165cc Dart Iron Eagle head would be a great head for a stock-ish type rebuild, maybe 300hp or so (just assume we are using a carb here). Would work very well actually... but you want 400hp out of your 350? The 165cc heads will probably not get you there, because they just won't work with that big camshaft and high rise intake manifold you got, to get the most out of them. Now if you used the same Iron Eagle head with the 200cc ports, you will get alot more out of your big cam and high rise intake, because all the parts are now a well matched combo. The same goes for any other part out there.

Any part thats rated with a powerband like 'idle-5500' or '2500-6500' or something, don't ignore that, but just don't take it as written in stone either. There are so many variables within an engine combination that can alter that, it would make your head spin!

Use that rating more like the 'suggested serving' size on that box of pancake mix. This is how they suggest you use it, but thats all it is.

 

That's right, match the intended RPM range of the car (convertor, gears, weight, etc), and the cam and heads (duration and CC of ports), intake, carb etc etc.

It's not rocket science, if you match them up fairly well, you'll do well. Like 350 HP in a 350SBC. If you know some secrets, or match them up *perfectlly* then you'll get the 425HP 350 sorta thing. (and just bigger heads, bigger cam, etc).

I think the main reason people fall in the trap of poor performance is the "well I have this, so I may as well use it because it's free." (like a 305 block) Coupled with the big expensive parts you tacked on, make it a POS. Like:

"well, I got this intake from a friend of a friend of a guys dogs brother who..... and the guy went 11.5 in his (completely unrelated car), so it therefore must be a good intake!" - Torker2

"well these are vette heads, since all Vettes are fast, these will make my car fast" - 882 heads

"It's a race cam, (or 3/4 race cam), since race cars go fast, this will make my car go fast." - 234/244 duration summit cam.

"I've seen this air cleaner on so many show cars, and if it's good enough to be a show car, it's GOTTA be fast right?!" - Triangle of death

Or the obvious big cam, TPI, 4.11 geared 700R4 car. hooboy...

 

one more thing.. some people tend to think overkill will be good.. for example, too big carb, too big cam, single plane intake where dual will be fine, heads to big, etc..

not to mention names but myself.. take my cam for example.. it has ALOT (bolt italics and underline for a reason) of duration for a street/strip cam.. i had the one lower than this before and wanted more.. but instead of matching pieces together, i just put the cam in and didnt get a whole lot of extra power.. well the cam just gave me problems, high idle, weak lowend, lack of compression that lead to more money.. and just a more raspy sounding idle.. i had to buy a new carb that didnt have vacuum secondaries, an electric vacuum pump setup for my brakes, i milled the heads and wasted 2 sets of expensive head gaskets from leaking.. i tried a copper gasket and then a steel shim.. almost toasted my motor in the process from water..

so sad that i put myself down.. but if it helps others to make them think about what they are doing, then thats fine with me..

 

Hmm... some good stuff here... but then you have to pretty much delve into the voodoo that is cam selection to really put your combo together it seems.

It depends on what parts I can find ,but I'm looking at a flat tappet 350 with Vortec 906 heads, a 454 TBI unit, tuning hardware, and the cam is the big mystery. I thinking a Comp xe256 like this.

Pretty mild all in all, aiming for 300 at the flywheel, hoping for 350...

But it seems to me if I do the TBI right and the heads are fine, it's gonna just depend on how well I can match a cam to it.... But I may end up with some 083's... So it's hard ot nail anything down at this point, which is kind of why I asked the question.

Should be interesting, though.

 

Vortecs over the 083s, but if you can't get the vortecs, 083s are a good second.
You can't really go wrong with a mild XE series comp cam. That xe256 will make it good down low, don't plan on over 300HP, but the torque will make it a really solid daily driver. You'll be able to burn rubber really hard, no worries there. I might recommend the 262 instead, just to boost the HP a bit. It'll still be pretty easy to tune. (not sure how fussy TBI is, you might want to consider the XFI or the "computer compatible" version with the 114 LSA.