[Jim Rockford]

no really good TBI mods other that ditch the heads and cam. sorry for the bad news.

[5_speed]

Originally Posted by 454C10

I would think shorties are worth around 10hp and 15 ftlbs on an otherwise stock 350. But can also lead to more exhaust leaks and certainly more exhaust noise.

I have Hedman Hedders Shorties on my carbureted 350 with a Magnaflow cat coming out Flowmaster American Thunder 3" it is kinda loud - but not unbearable.

http://www.youtube.com/watch?v=B0qBwOCbyTM

[65smallblock]

I will be replacing a 6 cyl motor with a 350 hp 327. Ive been thinking about going with a set of shorties just because they come with all the hardware and should flow pretty well. If I had a good set of stock manifolds though I wouldnt even think about headders. I beleive that headers and aftermarket intakes are the most overrated "performance" add ons on the planet, and yet they are very popular.

The truth is that a good performance set up is a well concieved combination and sometimes when you have a mismatch, the things that are supposed to make more power actually make it run weaker and less efficent. Too many people discount the fact that automakers spend a lot more hours and $$ on R&d than any aftermarket suppliers. Sometimes the automakers pull a boner though (like low compression and bad flowing heads) and that is mostly where the REAL bolt on improvements come into play.

[ap72]

Originally Posted by 65smallblock

I will be replacing a 6 cyl motor with a 350 hp 327. Ive been thinking about going with a set of shorties just because they come with all the hardware and should flow pretty well. If I had a good set of stock manifolds though I wouldnt even think about headders. I beleive that headers and aftermarket intakes are the most overrated "performance" add ons on the planet, and yet they are very popular.

The truth is that a good performance set up is a well concieved combination and sometimes when you have a mismatch, the things that are supposed to make more power actually make it run weaker and less efficent. Too many people discount the fact that automakers spend a lot more hours and $$ on R&d than any aftermarket suppliers. Sometimes the automakers pull a boner though (like low compression and bad flowing heads) and that is mostly where the REAL bolt on improvements come into play.

I'd be interested in knowing why you feel that intakes and headers are overrated- they're perhaps the most proven method to finding easy bolt of power, and in many cases better mpg's. The only thing that comes close would be a cam swap- and even those are less proven that intakes and headers.

[65smallblock]

Originally Posted by ap72

I'd be interested in knowing why you feel that intakes and headers are overrated- they're perhaps the most proven method to finding easy bolt of power, and in many cases better mpg's. The only thing that comes close would be a cam swap- and even those are less proven that intakes and headers.

Fair enough. Have you ever seen someone place a set of headders or aftermarket intake on an otherwise stock motor and and actually get worse performance? I have, many times. A lot of times it comes down to killing back pressure or booster signal. Especially the latter. Some aftermarket intakes work well on a stock motor but probably about half of them are simply a bad match because they are designed for WAY higher flow capacities than the average street rod will ever see. Even more often Ive seen guys spend their cash on a complete aftermarket exhaust to see very little or no gain when they could have had a really good set of heads for about the same $ and realized some huge gains. Of corse your mileage WILL vary, which is part of the reason I say this. I think a lot of suggestions are generalized and assume that the poster is building a balls to the wall beast, and therin lies the problem.

[ap72]

Originally Posted by 65smallblock

Fair enough. Have you ever seen someone place a set of headders or aftermarket intake on an otherwise stock motor and and actually get worse performance? I have, many times. A lot of times it comes down to killing back pressure or booster signal. Especially the latter. Some aftermarket intakes work well on a stock motor but probably about half of them are simply a bad match because they are designed for WAY higher flow capacities than the average street rod will ever see. Even more often Ive seen guys spend their cash on a complete aftermarket exhaust to see very little or no gain when they could have had a really good set of heads for about the same $ and realized some huge gains. Of corse your mileage WILL vary, which is part of the reason I say this. I think a lot of suggestions are generalized and assume that the poster is building a balls to the wall beast, and therin lies the problem.

I'll agree that some intakes are way overkill, most single planes fall into this catagory.

I just shake my head and sigh everytime I hear someone on the "not enough backpressure" bandwagon. Any backpressure is a bad thing, the reason they loose power isn't because of a loss of backpressure but because they have excessive ex. duration and it shows when you have a free flowing exhaust- when its choked down you need a little extra duration. The power loss isn't a result of a "lack of backpressure" but excessive ex duration- present on most stock cams and even a LOT of aftermarket ones. Stepping from a stock intake to a very mild dual plane is almost never a bad idea though. sure things like heads and a cam help too, but when it's about $1000 for a set of heads or $50 for a used intake... well you see the choice most people willt take. I do it all at once on my engines- pull it out and do heads, cam, intake, headers,pistons, the works- but for someone just wanting to go bit by bit the intake and exhaust are usually the best first step, then the cam, and finally the heads. (heads and cam together is the best bet, but most people do ehads last because of the price).

You can use a crap intake and get worse results- but the same is true for any part- it just takes a little bit of brainwork to make sure is all matched.

JMHO

[65smallblock]

Originally Posted by ap72

I'll agree that some intakes are way overkill, most single planes fall into this catagory.

I just shake my head and sigh everytime I hear someone on the "not enough backpressure" bandwagon. Any backpressure is a bad thing, the reason they loose power isn't because of a loss of backpressure but because they have excessive ex. duration and it shows when you have a free flowing exhaust- when its choked down you need a little extra duration. The power loss isn't a result of a "lack of backpressure" but excessive ex duration- present on most stock cams and even a LOT of aftermarket ones. Stepping from a stock intake to a very mild dual plane is almost never a bad idea though. sure things like heads and a cam help too, but when it's about $1000 for a set of heads or $50 for a used intake... well you see the choice most people willt take. I do it all at once on my engines- pull it out and do heads, cam, intake, headers,pistons, the works- but for someone just wanting to go bit by bit the intake and exhaust are usually the best first step, then the cam, and finally the heads. (heads and cam together is the best bet, but most people do ehads last because of the price).

You can use a crap intake and get worse results- but the same is true for any part- it just takes a little bit of brainwork to make sure is all matched.

JMHO

For the most part I would agree. I guess with the exhaust situation I should add that I am a stickler for efficency and where Ive seen drops by adding headders/bigger exhaust is mostly in MPG which is sometimes the price you pay for more power. Sometimes it is the other way around (better performance) and that is when it was a good add on, but that goes back to my take on the one size fits all reccomendations that dont always fit.. The other thing that I would add reguarding factory exhaust vs headders is that I think that way too many people jump on that bandwagon far too soon and that as long as a good flowing dual system is in place that a set of factory manifolds are capable of more power than most people realize.

As for intakes I kind of reguard them as a tuning device much like carb spacers. It is well known that velocity is more desirable for most street applications than sheer volume, and you would be hard pressed to find an aftermarket manifold that will beat out most factory intakes in that respect which is why they often produce minimal gains and are sometimes a step in the wrong direction.

The bottom line here to me is that for most otherwise stock motors, the gains by adding headders and an aftermarket intake are sometimes non-existant and often minimal. Especially with smaller cube engines.

I can also appreciate the need to work on a budget. Im one of those guys myself. That makes it all that more important to make informed decisions.